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Galaxies: Formation, Evolution, Phenomena

Works Count: 88334

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This cluster of papers explores the formation and evolution of galaxies, including topics such as stellar populations, black holes, dark matter, cosmic evolution, quasars, and the extensive use of data from the Sloan Digital Sky Survey. It also includes discussions on astrophysical simulations to understand various aspects of galaxy formation.

Keywords

Galaxies; Cosmology; Black Holes; Stellar Populations; Star Formation; Dark Matter; Cosmic Evolution; Quasars; Sloan Digital Sky Survey; Astrophysical Simulations

Observational Evidence of Active Galactic Nuclei Feedback

2012-06-23

A. C. Fabian

Radiation, winds, and jets from the active nucleus of a massive galaxy can interact with its interstellar medium, and this can lead to ejection or heating of the gas. This … Radiation, winds, and jets from the active nucleus of a massive galaxy can interact with its interstellar medium, and this can lead to ejection or heating of the gas. This terminates star formation in the galaxy and stifles accretion onto the black hole. Such active galactic nuclei (AGN) feedback can account for the observed proportionality between the central black hole and the host galaxy mass. Direct observational evidence for the radiative or quasar mode of feedback, which occurs when AGN are very luminous, has been difficult to obtain but is accumulating from a few exceptional objects. Feedback from the kinetic or radio mode, which uses the mechanical energy of radio-emitting jets often seen when AGN are operating at a lower level, is common in massive elliptical galaxies. This mode is well observed directly through X-ray observations of the central galaxies of cool core clusters in the form of bubbles in the hot surrounding medium. The energy flow, which is roughly continuous, heats the hot intracluster gas and reduces radiative cooling and subsequent star formation by an order of magnitude. Feedback appears to maintain a long-lived heating/cooling balance. Powerful, jetted radio outbursts may represent a further mode of energy feedback that affects the cores of groups and subclusters. New telescopes and instruments from the radio to X-ray bands will come into operation over the next several years and lead to a rapid expansion in observational data on all modes of AGN feedback.

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The NRAO VLA Sky Survey

1998-05-01

J. J. Condon , W. D. Cotton , E. W. Greisen +4 more

The NRAO VLA Sky Survey (NVSS) covers the sky north of J2000.0 δ = -40° (82% of the celestial sphere) at 1.4 GHz. The principal data products are (1) a … The NRAO VLA Sky Survey (NVSS) covers the sky north of J2000.0 δ = -40° (82% of the celestial sphere) at 1.4 GHz. The principal data products are (1) a set of 2326 4° × 4° continuum "cubes" with three planes containing Stokes I, Q, and U images plus (2) a catalog of almost 2 × 106 discrete sources stronger than S ≈ 2.5 mJy. The images all have θ = 45'' FWHM resolution and nearly uniform sensitivity. Their rms brightness fluctuations are σ ≈ 0.45 mJy beam-1 ≈ 0.14 K (Stokes I) and σ ≈ 0.29 mJy beam-1 ≈ 0.09 K (Stokes Q and U). The rms uncertainties in right ascension and declination vary from ≲1'' for the N ≈ 4 × 105 sources stronger than 15 mJy to 7'' at the survey limit. The NVSS was made as a service to the astronomical community. All data products, user software, and updates are being released via the World Wide Web as soon as they are produced and verified.

Ultraluminous infrared galaxies and the origin of quasars

1988-02-01

D. B. Sanders , B. T. Soifer , J. H. Elias +4 more

An evolutionary connection between ultraluminous infrared galaxies and quasars is deduced from the observations of all 10 infrared galaxies with luminosities L(8-1000 µm) ~ 10 12 L 0 , taken … An evolutionary connection between ultraluminous infrared galaxies and quasars is deduced from the observations of all 10 infrared galaxies with luminosities L(8-1000 µm) ~ 10 12 L 0 , taken from a flux-limited sample of infrared bright galaxies.Images of the infrared galaxies show that nearly all are strongly interar•ing merger systems with exceptionally luminous nuclei.Millimeter-wave CO observations show that these objects typically contain 0.5-2 x 10 10 M 0 of H2 .Optical spectra indicate a mixture of starburst and active galactic nucleus (AGN) energy sources, both of which are apparently fueled by the tremendous reservoir of molecular gas.It is proposed that these ultraluminous infrared galaxies represent the initial, dust-enshrouded stages of quasars.Once these nuclei shed their obscuring dust, allowing the AGN to visually dominate the decaying starburst, they become optically selected quasars.The origin of quasars through the merger of molecular gasrich spiral galaxies can account for both the increased number of high-luminosity quasars at large redshift, when the universe was smaller and gas supplies less depleted, and the observed "redshift-cutoff" of quasars which represents the epoch after galaxy formation when the first collisions occur.

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TheGalaxy Evolution Explorer: A Space Ultraviolet Survey Mission

2005-01-17

D. Christopher Martin , James L. Fanson , David Schiminovich +7 more

We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, 2003. GALEX is performing the first space UV sky-survey, including imaging and … We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, 2003. GALEX is performing the first space UV sky-survey, including imaging and grism surveys in two bands (1350-1750 Angstroms and 1750-2750 Angstroms). The surveys include an all-sky imaging survey (m[AB] ~ 20.5), a medium imaging survey of 1000 square degrees (m[AB] ~ 23), a deep imaging survey of 100 square degrees (m[AB] ~ 25), and a nearby galaxy survey. Spectroscopic grism surveys (R=100-200) are underway with various depths and sky coverage. Many targets overlap existing or planned surveys. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0 < z < 1.5, and probe the physical drivers of star formation in galaxies. The GALEX mission includes a Guest Investigator program supporting the wide variety of programs made possible by the first UV sky survey.

Merger rates in hierarchical models of galaxy formation

1993-06-01

C. G. Lacey , Shaun Cole

We present an analytical description of the merging of virialized haloes which is applicable to any hierarchical model in which structure grows via gravitational instability. The formulae are an extension … We present an analytical description of the merging of virialized haloes which is applicable to any hierarchical model in which structure grows via gravitational instability. The formulae are an extension of the Press-Schechter model. The dependence of the merger rate on halo mass, epoch, the spectrum of initial density fluctuations and the density parameter Ω0 is explicitly quantified. We calculate the distribution of halo formation times and survival times. We also describe a Monte Carlo method for constructing representative histories of merger events leading to formation of haloes of a prescribed mass. Applying these results to the age distribution of rich clusters of galaxies, we infer that a high value of the density parameter (Ω0 ≳ 0.5) is required to reproduce the substantial fraction of rich clusters that exhibit significant substructure, if such substructure only persists for a time 0.2t0 after a merger, where t0 is the present age of the universe. We also investigate the rate of infall of satellite galaxies into galactic discs, by combining our Monte Carlo technique for halo mergers with an estimate of the time required for dynamical friction to erode the orbits of the baryonic cores of the accreted galaxies. We find that, even for Ω0 = 1, the infall rate is low (provided that the satellite orbits are not too eccentric), and that we would expect only a modest fraction of stellar discs to be thickened or disrupted by this process.

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Core condensation in heavy halos: a two-stage theory for galaxy formation and clustering

1978-07-01

Simon D. M. White , M. J. Rees

We suggest that most of the material in the Universe condensed at an early epoch into small ‘dark’ objects. Irrespective of their nature, these objects must subsequently have undergone hierarchical … We suggest that most of the material in the Universe condensed at an early epoch into small ‘dark’ objects. Irrespective of their nature, these objects must subsequently have undergone hierarchical clustering, whose present scale we infer from the large-scale distribution of galaxies. As each stage of the hierarchy forms and collapses, relaxation effects wipe out its substructure, leading to a self-similar distribution of bound masses of the type discussed by Press & Schechter. The entire luminous content of galaxies, however, results from the cooling and fragmentation of residual gas within the transient potential wells provided by the dark matter. Every galaxy thus forms as a concentrated luminous core embedded in an extensive dark halo. The observed sizes of galaxies and their survival through later stages of the hierarchy seem inexplicable without invoking substantial dissipation; this dissipation allows the galaxies to become sufficiently concentrated to survive the disruption of their halos in groups and clusters of galaxies. We propose a specific model in which |$\Omega \simeq 0.2$|⁠, the dark matter makes up 80 per cent of the total mass, and half the residual gas has been converted into luminous galaxies by the present time. This model is consistent with the inferred proportions of dark matter, luminous matter and gas in rich clusters, with the observed luminosity density of the Universe and with the observed radii of galaxies; further, it predicts the characteristic luminosities of bright galaxies and can give a luminosity function of the observed shape.

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How do galaxies get their gas?

2005-09-12

D. Kere , Neal Katz , David H. Weinberg +1 more

We examine the temperature history of gas accreted by forming galaxies in SPH simulations. About half the gas shock heats to roughly the virial temperature of the galaxy potential well … We examine the temperature history of gas accreted by forming galaxies in SPH simulations. About half the gas shock heats to roughly the virial temperature of the galaxy potential well before cooling, condensing, and forming stars, but the other half radiates its acquired gravitational energy at much lower temperatures, typically T<10^5 K, and the histogram of maximum gas temperatures is clearly bimodal. The "cold mode" of gas accretion dominates for low mass galaxies (M_baryon < 10^{10.3}Msun or M_halo < 10^{11.4}Msun), while the conventional "hot mode" dominates the growth of high mass systems. Cold accretion is often directed along filaments, allowing galaxies to efficiently draw gas from large distances, while hot accretion is quasi-spherical. The galaxy and halo mass dependence leads to redshift and environment dependence of cold and hot accretion rates, with cold mode dominating at high redshift and in low density regions today, and hot mode dominating in group and cluster environments at low redshift. Star formation rates closely track accretion rates, and we discuss the physics behind the observed environment and redshift dependence of galactic scale star formation. If we allowed hot accretion to be suppressed by conduction or AGN feedback, then the simulation predictions would change in interesting ways, perhaps resolving conflicts with the colors of ellipticals and the cutoff of the galaxy luminosity function. The transition between cold and hot accretion at M_h ~ 10^{11.4}Msun is similar to that found by Birnboim & Dekel (2003) using 1-d simulations and analytic arguments. The corresponding baryonic mass is tantalizingly close to the scale at which Kauffmann et al. (2003) find a marked shift in galaxy properties. We speculate on connections between these theoretical and observational transitions.

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The Demography of Massive Dark Objects in Galaxy Centers

1998-06-01

John Magorrian , Scott Tremaine , D. O. Richstone +7 more

We construct dynamical models for a sample of 36 nearby galaxies with Hubble Space Telescope (HST) photometry and ground-based kinematics. The models assume that each galaxy is axisymmetric, with a … We construct dynamical models for a sample of 36 nearby galaxies with Hubble Space Telescope (HST) photometry and ground-based kinematics. The models assume that each galaxy is axisymmetric, with a two-integral distribution function, arbitrary inclination angle, a position-independent stellar mass-to-light ratio Υ, and a central massive dark object (MDO) of arbitrary mass M•. They provide acceptable fits to 32 of the galaxies for some value of M• and Υ; the four galaxies that cannot be fitted have kinematically decoupled cores. The mass-to-light ratios inferred for the 32 well-fitted galaxies are consistent with the fundamental-plane correlation Υ ∝ L0.2, where L is galaxy luminosity. In all but six galaxies the models require at the 95% confidence level an MDO of mass M• ∼ 0.006Mbulge ≡ 0.006ΥL. Five of the six galaxies consistent with M• = 0 are also consistent with this correlation. The other (NGC 7332) has a much stronger upper limit on M•. We predict the second-moment profiles that should be observed at HST resolution for the 32 galaxies that our models describe well.

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Dark Matter Substructure within Galactic Halos

1999-10-10

Ben Moore , Sebastiano Ghigna , Fabio Governato +4 more

We use numerical simulations to examine the substructure within galactic and cluster mass halos that form within a hierarchical universe. Clusters are easily reproduced with a steep mass spectrum of … We use numerical simulations to examine the substructure within galactic and cluster mass halos that form within a hierarchical universe. Clusters are easily reproduced with a steep mass spectrum of thousands of substructure clumps that closely matches the observations. However, the survival of dark matter substructure also occurs on galactic scales, leading to the remarkable result that galaxy halos appear as scaled versions of galaxy clusters. The model predicts that the virialized extent of the Milky Way's halo should contain about 500 satellites with circular velocities larger than the Draco and Ursa Minor systems, i.e., bound masses ≳108 M☉ and tidally limited sizes ≳1 kpc. The substructure clumps are on orbits that take a large fraction of them through the stellar disk, leading to significant resonant and impulsive heating. Their abundance and singular density profiles have important implications for the existence of old thin disks, cold stellar streams, gravitational lensing, and indirect/direct detection experiments.

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Profiles of dark haloes: evolution, scatter and environment

2001-03-01

James S. Bullock , Tsafrir Kolatt , Yair Sigad +5 more

We study dark matter halo density profiles in a high-resolution N-body simulation of a ΛCDM cosmology. Our statistical sample contains ∼5000 haloes in the range 1011−1014 h−1 M⊙, and the … We study dark matter halo density profiles in a high-resolution N-body simulation of a ΛCDM cosmology. Our statistical sample contains ∼5000 haloes in the range 1011−1014 h−1 M⊙, and the resolution allows a study of subhaloes inside host haloes. The profiles are parametrized by an NFW form with two parameters, an inner radius rs and a virial radius Rvir, and we define the halo concentration cvir=Rvirrs. First, we find that, for a given halo mass, the redshift dependence of the median concentration is cvir∝(1+z)−1. This corresponds to rs(z)∼constant, and is contrary to earlier suspicions that cvir does not vary much with redshift. The implications are that high-redshift galaxies are predicted to be more extended and dimmer than expected before. Secondly, we find that the scatter in halo profiles is large, with a 1σ Δ(log cvir)=0.18 at a given mass, corresponding to a scatter in maximum rotation velocities of ΔVmaxVmax=0.12. We discuss implications for modelling the Tully—Fisher relation, which has a smaller reported intrinsic scatter. Thirdly, subhaloes and haloes in dense environments tend to be more concentrated than isolated haloes, and show a larger scatter. These results suggest that cvir is an essential parameter for the theory of galaxy modelling, and we briefly discuss implications for the universality of the Tully—Fisher relation, the formation of low surface brightness galaxies, and the origin of the Hubble sequence. We present an improved analytic treatment of halo formation that fits the measured relations between halo parameters and their redshift dependence, and can thus serve semi-analytic studies of galaxy formation.

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An analytical model for spherical galaxies and bulges

1990-06-01

Lars Hernquist

view Abstract Citations (2617) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Analytical Model for Spherical Galaxies and Bulges Hernquist, Lars Abstract A potential-density pair … view Abstract Citations (2617) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Analytical Model for Spherical Galaxies and Bulges Hernquist, Lars Abstract A potential-density pair which closely approximates the de Vaucouleurs R^1/4^ law for elliptical galaxies is presented. It is shown that the intrinsic properties and projected distributions of this model can be evaluated analytically. In particular, the distribution function, density of states, and projected surface brightness and velocity dispersion are expressible in terms of elementary functions. Publication: The Astrophysical Journal Pub Date: June 1990 DOI: 10.1086/168845 Bibcode: 1990ApJ...356..359H Keywords: Computational Astrophysics; Elliptical Galaxies; Galactic Bulge; Galactic Structure; Astronomical Models; Astronomical Photometry; Brightness Distribution; Distribution Functions; Astrophysics; GALAXIES: PHOTOMETRY; GALAXIES: STRUCTURE full text sources ADS |

The Origin of the Mass‐Metallicity Relation: Insights from 53,000 Star‐forming Galaxies in the Sloan Digital Sky Survey

2004-10-01

Christy Tremonti , Timothy M. Heckman , Guinevere Kauffmann +7 more

We utilize Sloan Digital Sky Survey imaging and spectroscopy of ~53,000 star-forming galaxies at z ~ 0.1 to study the relation between stellar mass and gas-phase metallicity. We derive gas-phase … We utilize Sloan Digital Sky Survey imaging and spectroscopy of ~53,000 star-forming galaxies at z ~ 0.1 to study the relation between stellar mass and gas-phase metallicity. We derive gas-phase oxygen abundances and stellar masses using new techniques that make use of the latest stellar evolutionary synthesis and photoionization models. We find a tight (±0.1 dex) correlation between stellar mass and metallicity spanning over 3 orders of magnitude in stellar mass and a factor of 10 in metallicity. The relation is relatively steep from 108.5 to 1010.5 M☉ h, in good accord with known trends between luminosity and metallicity, but flattens above 1010.5 M☉. We use indirect estimates of the gas mass based on the Hα luminosity to compare our data to predictions from simple closed box chemical evolution models. We show that metal loss is strongly anticorrelated with baryonic mass, with low-mass dwarf galaxies being 5 times more metal depleted than L* galaxies at z ~ 0.1. Evidence for metal depletion is not confined to dwarf galaxies but is found in galaxies with masses as high as 1010 M☉. We interpret this as strong evidence of both the ubiquity of galactic winds and their effectiveness in removing metals from galaxy potential wells.

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Detailed Structural Decomposition of Galaxy Images

2002-07-01

Chien Y. Peng , Luis C. Ho , Chris Impey +1 more

We present a two-dimensional fitting algorithm (GALFIT) designed to extract structural components from galaxy images, with emphasis on closely modeling light profiles of spatially well-resolved, nearby galaxies observed with the … We present a two-dimensional fitting algorithm (GALFIT) designed to extract structural components from galaxy images, with emphasis on closely modeling light profiles of spatially well-resolved, nearby galaxies observed with the Hubble Space Telescope. Our algorithm improves on previous techniques in two areas: by being able to simultaneously fit a galaxy with an arbitrary number of components and with optimization in computation speed, suited for working on large galaxy images. We use two-dimensional models such as the "Nuker" law, the Sérsic (de Vaucouleurs) profile, an exponential disk, and Gaussian or Moffat functions. The azimuthal shapes are generalized ellipses that can fit disky and boxy components. Some potential applications of our program include: standard modeling of global galaxy profiles; extracting bars, stellar disks, double nuclei, and compact nuclear sources; and measuring absolute dust extinction or surface brightness fluctuations after removing the galaxy model. When examined in detail, we find that even simple looking galaxies generally require at least three components to be modeled accurately, rather than the one or two components more often employed. Many galaxies with complex isophotes, ellipticity changes, and position angle twists can be modeled accurately in two dimensions. We illustrate this by way of 11 case studies, which include regular and barred spiral galaxies, highly disky lenticular galaxies, and elliptical galaxies displaying various levels of complexities. A useful extension of this algorithm is to accurately extract nuclear point sources in galaxies. We compare two-dimensional and one-dimensional extraction techniques on simulated images of galaxies having nuclear slopes with different degrees of cuspiness, and we then illustrate the application of the program to several examples of nearby galaxies with weak nuclei.

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Stellar masses and star formation histories for 105galaxies from the Sloan Digital Sky Survey

2003-05-01

Guinevere Kauffmann , Timothy M. Heckman , D. M. Simon White +7 more

We develop a new method to constrain the star formation histories, dust attenuation and stellar masses of galaxies. It is based on two stellar absorption-line indices, the 4000-Å break strength … We develop a new method to constrain the star formation histories, dust attenuation and stellar masses of galaxies. It is based on two stellar absorption-line indices, the 4000-Å break strength and the Balmer absorption-line index HδA. Together, these indices allow us to constrain the mean stellar ages of galaxies and the fractional stellar mass formed in bursts over the past few Gyr. A comparison with broad-band photometry then yields estimates of dust attenuation and of stellar mass. We generate a large library of Monte Carlo realizations of different star formation histories, including starbursts of varying strength and a range of metallicities. We use this library to generate median likelihood estimates of burst mass fractions, dust attenuation strengths, stellar masses and stellar mass-to-light ratios for a sample of 122 808 galaxies drawn from the Sloan Digital Sky Survey. The typical 95 per cent confidence range in our estimated stellar masses is ±40 per cent. We study how the stellar mass-to-light ratios of galaxies vary as a function of absolute magnitude, concentration index and photometric passband and how dust attenuation varies as a function of absolute magnitude and 4000-Å break strength. We also calculate how the total stellar mass of the present Universe is distributed over galaxies as a function of their mass, size, concentration, colour, burst mass fraction and surface mass density. We find that most of the stellar mass in the local Universe resides in galaxies that have, to within a factor of approximately 2, stellar masses ∼5× 1010 M⊙, half-light radii ∼3 kpc and half-light surface mass densities ∼109 M⊙ kpc−2. The distribution of Dn(4000) is strongly bimodal, showing a clear division between galaxies dominated by old stellar populations and galaxies with more recent star formation.

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Breaking the hierarchy of galaxy formation

2006-06-16

R. G. Bower , Andrew Benson , Rowena Katherine Malbon +5 more

Recent observations of the distant Universe suggest that much of the stellar mass of bright galaxies was already in place at z > 1. This presents a challenge for models … Recent observations of the distant Universe suggest that much of the stellar mass of bright galaxies was already in place at z > 1. This presents a challenge for models of galaxy formation because massive haloes are assembled late in the hierarchical clustering process intrinsic to the cold dark matter (CDM) cosmology. In this paper, we discuss a new implementation of the Durham semi-analytic model of galaxy formation in which feedback due to active galactic nuclei (AGN) is assumed to quench cooling flows in massive haloes. This mechanism naturally creates a break in the local galaxy luminosity function at bright magnitudes. The model is implemented within the Millennium N-body simulation. The accurate dark matter merger trees and large number of realizations of the galaxy formation process enabled by this simulation result in highly accurate statistics. After adjusting the values of the physical parameters in the model by reference to the properties of the local galaxy population, we investigate the evolution of the K-band luminosity and galaxy stellar mass functions. We calculate the volume-averaged star formation rate density of the Universe as a function of redshift and the way in which this is apportioned amongst galaxies of different mass. The model robustly predicts a substantial population of massive galaxies out to redshift z∼ 5 and a star formation rate density which rises at least out to z∼ 2 in objects of all masses. Although observational data on these properties have been cited as evidence for ‘antihierarchical’ galaxy formation, we find that when AGN feedback is taken into account, the fundamentally hierarchical CDM model provides a very good match to these observations.

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Energy input from quasars regulates the growth and activity of black holes and their host galaxies

2005-02-01

Tiziana Di Matteo , Volker Springel , Lars Hernquist

Modelling feedback from stars and black holes in galaxy mergers

2005-07-27

Volker Springel , Tiziana Di Matteo , Lars Hernquist

We describe techniques for incorporating feedback from star formation and black hole accretion into simulations of isolated and merging galaxies. At present, the details of these processes cannot be resolved … We describe techniques for incorporating feedback from star formation and black hole accretion into simulations of isolated and merging galaxies. At present, the details of these processes cannot be resolved in simulations on galactic scales. Our basic approach therefore involves forming coarse-grained representations of the properties of the interstellar medium and black hole accretion starting from basic physical assumptions, so that the impact of these effects can be included on resolved scales. We illustrate our method using a multiphase description of star-forming gas. Feedback from star formation pressurises highly overdense gas, altering its effective equation of state. We show that this allows the construction of stable galaxy models with much larger gas fractions than possible in earlier numerical work. We extend the model by including a treatment of gas accretion onto central supermassive black holes in galaxies. Assuming thermal coupling of a small fraction of the bolometric luminosity of accreting black holes to the surrounding gas, we show how this feedback regulates the growth of black holes. In gas-rich mergers of galaxies, we observe a complex interplay between starbursts and central AGN activity when the tidal interaction triggers intense nuclear inflows of gas. Once an accreting supermassive black hole has grown to a critical size, feedback terminates its further growth, and expels gas from the central region in a powerful quasar-driven wind. Our simulation methodology is therefore able to address the coupled processes of gas dynamics, star formation, and black hole accretion during the formation of galaxies.

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Cosmological smoothed particle hydrodynamics simulations: a hybrid multiphase model for star formation

2003-02-21

Volker Springel , Lars Hernquist

We present a model for star formation and supernova feedback that describes the multi-phase structure of star forming gas on scales that are typically not resolved in cosmological simulations. Our … We present a model for star formation and supernova feedback that describes the multi-phase structure of star forming gas on scales that are typically not resolved in cosmological simulations. Our approach includes radiative heating and cooling, the growth of cold clouds embedded in an ambient hot medium, star formation in these clouds, feedback from supernovae in the form of thermal heating and cloud evaporation, galactic winds and outflows, and metal enrichment. Implemented using SPH, our scheme is a significantly modified and extended version of the grid-based method of Yepes et al. (1997), and enables us to achieve high dynamic range in simulations of structure formation. We discuss properties of the feedback model in detail and show that it predicts a self-regulated, quiescent mode of star formation, which, in particular, stabilises the star forming gaseous layers of disk galaxies. The parameterisation of this mode can be reduced to a single free quantity which determines the overall timescale for star formation. We fix this parameter to match the observed rates of star formation in local disk galaxies. When normalised in this manner, cosmological simulations nevertheless overproduce the observed cosmic abundance of stellar material. We are thus motivated to extend our feedback model to include galactic winds associated with star formation. Using small-scale simulations of individual star-forming disk galaxies, we show that these winds produce either galactic fountains or outflows, depending on the depth of the gravitational potential. Moreover, outflows from galaxies in these simulations drive chemical enrichment of the intergalactic medium, in principle accounting for the presence of metals in the Lyman alpha forest. (abridged)

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The Optical and Near‐Infrared Properties of Galaxies. I. Luminosity and Stellar Mass Functions

2003-12-01

Eric F. Bell , Daniel H. McIntosh , Neal Katz +1 more

We use a large sample of galaxies from the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to calculate galaxy luminosity and stellar mass functions … We use a large sample of galaxies from the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to calculate galaxy luminosity and stellar mass functions in the local universe. We estimate corrections for passband shifting and galaxy evolution, as well as present-day stellar mass-to-light (M/L) ratios, by fitting the optical-near-infrared galaxy data with simple models. Accounting for the 8% galaxy overdensity in the SDSS early data release region, the optical and near-infrared luminosity functions we construct for this sample agree with most recent literature optical and near-infrared determinations within the uncertainties. We argue that 2MASS is biased against low surface brightness galaxies and use SDSS plus our knowledge of stellar populations to estimate the "true" K-band luminosity function. This has a steeper faint end slope and a slightly higher overall luminosity density than the direct estimate. Furthermore, assuming a universally applicable stellar initial mass function (IMF), we find good agreement between the stellar mass function we derive from the 2MASS/SDSS data and that derived by Cole et al. The faint end slope for the stellar mass function is steeper than -1.1, reflecting the low stellar M/L ratios characteristic of low-mass galaxies. We estimate an upper limit to the stellar mass density in the local universe Ω*h = 2.0 ± 0.6 × 10-3 by assuming an IMF as rich in low-mass stars as allowed by observations of galaxy dynamics in the local universe. The stellar mass density may be lower than this value if a different IMF with fewer low-mass stars is assumed. Finally, we examine type-dependence in the optical and near-infrared luminosity functions and the stellar mass function. In agreement with previous work, we find that the characteristic luminosity or mass of early-type galaxies is larger than for later types, and the faint end slope is steeper for later types than for earlier types. Accounting for typing uncertainties, we estimate that at least half, and perhaps as much as 3/4, of the stellar mass in the universe is in early-type galaxies. As an aid to workers in the field, we present in an Appendix the relationship between model stellar M/L ratios and colors in SDSS/2MASS passbands, an updated discussion of near-infrared stellar M/L ratio estimates, and the volume-corrected distribution of g- and K-band stellar M/L ratios as a function of stellar mass.

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Sloan Digital Sky Survey: Early Data Release

2002-01-01

Chris Stoughton , Robert H. Lupton , Mariangela Bernardi +7 more

The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of ≈106 galaxies, 100,000 quasars, … The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of ≈106 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R ≈ 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.

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A Direct Empirical Proof of the Existence of Dark Matter

2006-08-30

Douglas Clowe , Maruša Bradač , Anthony H. Gonzalez +4 more

We present new weak-lensing observations of 1E 0657-558 (z = 0.296), a unique cluster merger, that enable a direct detection of dark matter, independent of assumptions regarding the nature of … We present new weak-lensing observations of 1E 0657-558 (z = 0.296), a unique cluster merger, that enable a direct detection of dark matter, independent of assumptions regarding the nature of the gravitational force law. Due to the collision of two clusters, the dissipationless stellar component and the fluid-like X-ray-emitting plasma are spatially segregated. By using both wide-field ground-based images and HST/ACS images of the cluster cores, we create gravitational lensing maps showing that the gravitational potential does not trace the plasma distribution, the dominant baryonic mass component, but rather approximately traces the distribution of galaxies. An 8 σ significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law and thus proves that the majority of the matter in the system is unseen.

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The Global Schmidt Law in Star‐forming Galaxies

1998-05-10

Robert C. Kennicutt

Measurements of Hα, H I, and CO distributions in 61 normal spiral galaxies are combined with published far-infrared and CO observations of 36 infrared-selected starburst galaxies, in order to study … Measurements of Hα, H I, and CO distributions in 61 normal spiral galaxies are combined with published far-infrared and CO observations of 36 infrared-selected starburst galaxies, in order to study the form of the global star formation law over the full range of gas densities and star formation rates (SFRs) observed in galaxies. The disk-averaged SFRs and gas densities for the combined sample are well represented by a Schmidt law with index N = 1.4 ± 0.15. The Schmidt law provides a surprisingly tight parametrization of the global star formation law, extending over several orders of magnitude in SFR and gas density. An alternative formulation of the star formation law, in which the SFR is presumed to scale with the ratio of the gas density to the average orbital timescale, also fits the data very well. Both descriptions provide potentially useful "recipes" for modeling the SFR in numerical simulations of galaxy formation and evolution.

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The EAGLE project: simulating the evolution and assembly of galaxies and their environments

2014-11-11

Joop Schaye , Robert A. Crain , R. G. Bower +7 more

We introduce the Virgo Consortium's EAGLE project, a suite of hydrodynamical simulations that follow the formation of galaxies and black holes in representative volumes. We discuss the limitations of such … We introduce the Virgo Consortium's EAGLE project, a suite of hydrodynamical simulations that follow the formation of galaxies and black holes in representative volumes. We discuss the limitations of such simulations in light of their finite resolution and poorly constrained subgrid physics, and how these affect their predictive power. One major improvement is our treatment of feedback from massive stars and AGN in which thermal energy is injected into the gas without the need to turn off cooling or hydrodynamical forces, allowing winds to develop without predetermined speed or mass loading factors. Because the feedback efficiencies cannot be predicted from first principles, we calibrate them to the z~0 galaxy stellar mass function and the amplitude of the galaxy-central black hole mass relation, also taking galaxy sizes into account. The observed galaxy mass function is reproduced to $\lesssim 0.2$ dex over the full mass range, $10^8 < M_*/M_\odot \lesssim 10^{11}$, a level of agreement close to that attained by semi-analytic models, and unprecedented for hydrodynamical simulations. We compare our results to a representative set of low-redshift observables not considered in the calibration, and find good agreement with the observed galaxy specific star formation rates, passive fractions, Tully-Fisher relation, total stellar luminosities of galaxy clusters, and column density distributions of intergalactic CIV and OVI. While the mass-metallicity relations for gas and stars are consistent with observations for $M_* \gtrsim 10^9 M_\odot$, they are insufficiently steep at lower masses. The gas fractions and temperatures are too high for clusters of galaxies, but for groups these discrepancies can be resolved by adopting a higher heating temperature in the subgrid prescription for AGN feedback. EAGLE constitutes a valuable new resource for studies of galaxy formation.

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The 6dF Galaxy Survey: baryon acoustic oscillations and the local Hubble constant

2011-07-25

Florian Beutler , Chris Blake , Matthew Colless +6 more

We analyse the large-scale correlation function of the 6dF Galaxy Survey (6dFGS) and detect a Baryon Acoustic Oscillation (BAO) signal. The 6dFGS BAO detection allows us to constrain the distance-redshift … We analyse the large-scale correlation function of the 6dF Galaxy Survey (6dFGS) and detect a Baryon Acoustic Oscillation (BAO) signal. The 6dFGS BAO detection allows us to constrain the distance-redshift relation at z_{\rm eff} = 0.106. We achieve a distance measure of D_V(z_{\rm eff}) = 456\pm27 Mpc and a measurement of the distance ratio, r_s(z_d)/D_V(z_{\rm eff}) = 0.336\pm0.015 (4.5% precision), where r_s(z_d) is the sound horizon at the drag epoch z_d. The low effective redshift of 6dFGS makes it a competitive and independent alternative to Cepheids and low-z supernovae in constraining the Hubble constant. We find a Hubble constant of H_0 = 67\pm3.2 km s^{-1} Mpc^{-1} (4.8% precision) that depends only on the WMAP-7 calibration of the sound horizon and on the galaxy clustering in 6dFGS. Compared to earlier BAO studies at higher redshift, our analysis is less dependent on other cosmological parameters. The sensitivity to H_0 can be used to break the degeneracy between the dark energy equation of state parameter w and H_0 in the CMB data. We determine that w = -0.97\pm0.13, using only WMAP-7 and BAO data from both 6dFGS and \citet{Percival:2009xn}. We also discuss predictions for the large scale correlation function of two future wide-angle surveys: the WALLABY blind H{\sc I} survey (with the Australian SKA Pathfinder, ASKAP), and the proposed TAIPAN all-southern-sky optical galaxy survey with the UK Schmidt Telescope (UKST). We find that both surveys are very likely to yield detections of the BAO peak, making WALLABY the first radio galaxy survey to do so. We also predict that TAIPAN has the potential to constrain the Hubble constant with 3% precision.

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THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY

2009-05-18

Kevork N. Abazajian , Jennifer Adelman-McCarthy , Marcel A. Agüeros +7 more

This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase … This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg2 of imaging data, with most of the ∼2000 deg2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120° long, 25 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg2. The survey has completed spectroscopy over 9380 deg2; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.

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The host galaxies and classification of active galactic nuclei

2006-09-29

Lisa J. Kewley , Brent Groves , Guinevere Kauffmann +1 more

We present an analysis of the host properties of 85224 emission-line galaxies from the Sloan Digital Sky Survey. We show that Seyferts and LINERs form clearly separated branches on the … We present an analysis of the host properties of 85224 emission-line galaxies from the Sloan Digital Sky Survey. We show that Seyferts and LINERs form clearly separated branches on the standard optical diagnostic diagrams. We derive a new empirical classification scheme which cleanly separates star-forming galaxies, composite AGN-HII galaxies, Seyferts and LINERs and we study the host galaxy properties of these different classes of objects. LINERs are older, more massive, less dusty and more concentrated, and have higher velocity dispersions and lower [OIII] luminosities than Seyfert galaxies. We consider the quantity L[OIII]/sigma^4, which is an indicator of the black hole accretion rate relative to the Eddington rate. Remarkably, we find that at fixed L[OIII]/sigma^4, all differences between Seyfert and LINER host properties disappear. LINERs and Seyferts form a continuous sequence, with LINERs dominant at low L/L(EDD) and Seyferts dominant at high L/L(EDD). These results suggest that the majority of LINERs are AGN and that the Seyfert/LINER dichotomy is analogous to the high/low-state transition for X-ray binary systems. We apply theoretical photoionization models and show that pure LINERs require a harder ionizing radiation field with lower ionization parameter than Seyfert galaxies, consistent with the low and high X-ray binary states.

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Large-scale bias and the peak background split

1999-09-01

Ravi K. Sheth , G. Tormen

Dark matter haloes are biased tracers of the underlying dark matter distribution. We use a simple model to provide a relation between the abundance of dark matter haloes and their … Dark matter haloes are biased tracers of the underlying dark matter distribution. We use a simple model to provide a relation between the abundance of dark matter haloes and their spatial distribution on large scales. Our model shows that knowledge of the unconditional mass function alone is sufficient to provide an accurate estimate of the large-scale bias factor. We then use the mass function measured in numerical simulations of SCDM, OCDM and ΛCDM to compute this bias. Comparison with these simulations shows that this simple way of estimating the bias relation and its evolution is accurate for less massive haloes as well as massive ones. In particular, we show that haloes that are less/more massive than typical M* haloes at the time they form are more/less strongly clustered than is predicted by formulae based on the standard Press-Schechter mass function.

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Where Are the Missing Galactic Satellites?

1999-09-01

Anatoly Klypin , Andrey V. Kravtsov , O. Valenzuela +1 more

According to the hierarchical clustering scenario, galaxies are assembled by merging and accretion of numerous satellites of different sizes and masses. This ongoing process is not 100% efficient in destroying … According to the hierarchical clustering scenario, galaxies are assembled by merging and accretion of numerous satellites of different sizes and masses. This ongoing process is not 100% efficient in destroying all of the accreted satellites, as evidenced by the satellites of our Galaxy and of M31. Using published data, we have compiled the circular velocity (Vcirc) distribution function (VDF) of galaxy satellites in the Local Group. We find that within the volumes of radius of 570 kpc (400 h-1 kpc assuming the Hubble constant h = 0.7) centered on the Milky Way and Andromeda, the average VDF is roughly approximated as n(> Vcirc) ≈ 55 ± 11(Vcirc/10 km s-1)-1.4±0.4 h3 Mpc-3 for Vcirc in the range ≈10-70 km s-1. The observed VDF is compared with results of high-resolution cosmological simulations. We find that the VDF in models is very different from the observed one: n(> Vcirc) ≈ 1200(Vcirc/10 km s-1)-2.75 h3 Mpc-3. Cosmological models thus predict that a halo the size of our Galaxy should have about 50 dark matter satellites with circular velocity greater than 20 km s-1 and mass greater than 3 × 108 M☉ within a 570 kpc radius. This number is significantly higher than the approximately dozen satellites actually observed around our Galaxy. The difference is even larger if we consider the abundance of satellites in simulated galaxy groups similar to the Local Group. The models predict ~300 satellites inside a 1.5 Mpc radius, while only ~40 satellites are observed in the Local Group. The observed and predicted VDFs cross at ≈50 km s-1, indicating that the predicted abundance of satellites with Vcirc ≳ 50 km s-1 is in reasonably good agreement with observations. We conclude, therefore, that unless a large fraction of the Local Group satellites has been missed in observations, there is a dramatic discrepancy between observations and hierarchical models, regardless of the model parameters. We discuss several possible explanations for this discrepancy including identification of some satellites with the high-velocity clouds observed in the Local Group and the existence of dark satellites that failed to accrete gas and form stars either because of the expulsion of gas in the supernovae-driven winds or because of gas heating by the intergalactic ionizing background.

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Weak gravitational lensing

2001-01-01

Matthias Bartelmann , Peter Schneider

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Simulations of the formation, evolution and clustering of galaxies and quasars

2005-06-01

Volker Springel , Simon D. M. White , Adrian Jenkins +7 more

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The 2dF Galaxy Redshift Survey: power-spectrum analysis of the final data set and cosmological implications

2005-08-26

Shaun Cole , Will J. Percival , J. A. Peacock +7 more

We present a power-spectrum analysis of the final 2dF Galaxy Redshift Survey (2dFGRS), employing a direct Fourier method. The sample used comprises 221 414 galaxies with measured redshifts. We investigate … We present a power-spectrum analysis of the final 2dF Galaxy Redshift Survey (2dFGRS), employing a direct Fourier method. The sample used comprises 221 414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection, improving on previous treatments in a number of respects. A new angular mask is derived, based on revisions to the photometric calibration. The redshift selection function is determined by dividing the survey according to rest-frame colour, and deducing a self-consistent treatment of k-corrections and evolution for each population. The covariance matrix for the power-spectrum estimates is determined using two different approaches to the construction of mock surveys, which are used to demonstrate that the input cosmological model can be correctly recovered. We discuss in detail the possible differences between the galaxy and mass power spectra, and treat these using simulations, analytic models and a hybrid empirical approach. Based on these investigations, we are confident that the 2dFGRS power spectrum can be used to infer the matter content of the universe. On large scales, our estimated power spectrum shows evidence for the 'baryon oscillations' that are predicted in cold dark matter (CDM) models. Fitting to a CDM model, assuming a primordial ns= 1 spectrum, h= 0.72 and negligible neutrino mass, the preferred parameters are Ωmh= 0.168 ± 0.016 and a baryon fraction Ωb/Ωm= 0.185 ± 0.046 (1σ errors). The value of Ωmh is 1σ lower than the 0.20 ± 0.03 in our 2001 analysis of the partially complete 2dFGRS. This shift is largely due to the signal from the newly sampled regions of space, rather than the refinements in the treatment of observational selection. This analysis therefore implies a density significantly below the standard Ωm= 0.3: in combination with cosmic microwave background (CMB) data from the Wilkinson Microwave Anisotropy Probe (WMAP), we infer Ωm= 0.231 ± 0.021.

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The Dust Content and Opacity of Actively Star‐forming Galaxies

2000-04-20

Daniela Calzetti , L. Armus , R. C. Bohlin +3 more

(Abridged) We present far-infrared (FIR) photometry at 150 micron and 205 micron of eight low-redshift starburst galaxies obtained with the ISO Photometer. Five of the eight galaxies are detected in … (Abridged) We present far-infrared (FIR) photometry at 150 micron and 205 micron of eight low-redshift starburst galaxies obtained with the ISO Photometer. Five of the eight galaxies are detected in both wavebands and these data are used, in conjunction with IRAS archival photometry, to model the dust emission at lambda>40 micron. The FIR spectral energy distributions (SEDs) are best fitted by a combination of two modified Planck functions, with T~40-55 K (warm dust) and T~20-23 K (cool dust), and with a dust emissivity index epsilon=2. The cool dust can be a major contributor to the FIR emission of starburst galaxies, representing up to 60% of the total flux. This component is heated not only by the general interstellar radiation field, but also by the starburst itself. The cool dust mass is up to ~150 times larger than the warm dust mass, bringing the gas-to-dust ratios of the starbursts in our sample close to Milky Way values, once rescaled for the appropriate metallicity. The ratio between the total dust FIR emission in the range 1-1000 micron and the IRAS FIR emission in the range 40-120 micron is ~1.75, with small variations from galaxy to galaxy. The FIR emission predicted by the dust reddening of the UV-to-nearIR stellar emission is within a factor ~2 of the observed value in individual galaxies and within 20% when averaged over a large sample. If our sample of local starbursts is representative of high-redshift (z>1), UV-bright, star-forming galaxies, these galaxies' FIR emission will be generally undetected in sub-mm surveys, unless (1) their bolometric luminosity is comparable to or larger than that of ultraluminous FIR galaxies and (2) their FIR SED contains a cool dust component.

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CANDELS: THE COSMIC ASSEMBLY NEAR-INFRARED DEEP EXTRAGALACTIC LEGACY SURVEY

2011-12-01

Norman A. Grogin , Dale D. Kocevski , S. M. Faber +7 more

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, over the approximate redshift (z) range 8--1.5. It will image >250,000 … The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) is designed to document the first third of galactic evolution, over the approximate redshift (z) range 8--1.5. It will image >250,000 distant galaxies using three separate cameras on the Hubble Space Telescope, from the mid-ultraviolet to the near-infrared, and will find and measure Type Ia supernovae at z>1.5 to test their accuracy as standardizable candles for cosmology. Five premier multi-wavelength sky regions are selected, each with extensive ancillary data. The use of five widely separated fields mitigates cosmic variance and yields statistically robust and complete samples of galaxies down to a stellar mass of 10^9 M_\odot to z \approx 2, reaching the knee of the ultraviolet luminosity function (UVLF) of galaxies to z \approx 8. The survey covers approximately 800 arcmin^2 and is divided into two parts. The CANDELS/Deep survey (5\sigma\ point-source limit H=27.7 mag) covers \sim 125 arcmin^2 within GOODS-N and GOODS-S. The CANDELS/Wide survey includes GOODS and three additional fields (EGS, COSMOS, and UDS) and covers the full area to a 5\sigma\ point-source limit of H \gtrsim 27.0 mag. Together with the Hubble Ultra Deep Fields, the strategy creates a three-tiered "wedding cake" approach that has proven efficient for extragalactic surveys. Data from the survey are nonproprietary and are useful for a wide variety of science investigations. In this paper, we describe the basic motivations for the survey, the CANDELS team science goals and the resulting observational requirements, the field selection and geometry, and the observing design. The Hubble data processing and products are described in a companion paper.

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The Sloan Digital Sky Survey: Technical Summary

2000-09-01

Donald G. York , Jennifer Adelman , John E. Anderson +7 more

The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated … The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and nonluminous matter in the universe: a photometrically and astrometrically calibrated digital imaging survey of π sr above about Galactic latitude 30° in five broad optical bands to a depth of g' ∼ 23 mag, and a spectroscopic survey of the approximately 106 brightest galaxies and 105 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS and serves as an introduction to extensive technical on-line documentation.

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The host galaxies of active galactic nuclei

2003-12-01

Guinevere Kauffmann , Timothy M. Heckman , Christy Tremonti +7 more

We examine the properties of the host galaxies of 22,623 narrow-line AGN with 0.02 We examine the properties of the host galaxies of 22,623 narrow-line AGN with 0.02

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The physical properties of star-forming galaxies in the low-redshift Universe

2004-07-11

J. Brinchmann , S. Charlot , Simon D. M. White +4 more

Abstract We present a comprehensive study of the physical properties of ∼ 105 galaxies with measurable star formation in the Sloan Digital Sky Survey (SDSS). By comparing physical information extracted … Abstract We present a comprehensive study of the physical properties of ∼ 105 galaxies with measurable star formation in the Sloan Digital Sky Survey (SDSS). By comparing physical information extracted from the emission lines with continuum properties, we build up a picture of the nature of star-forming galaxies at z &lt; 0.2. We develop a method for aperture correction using resolved imaging and show that our method takes out essentially all aperture bias in the star formation rate (SFR) estimates, allowing an accurate estimate of the total SFRs in galaxies. We determine the SFR density to be 1.915+0.02−0.01 (random)+0.14−0.42 (systematic) h7010−2 M⊙ yr−1 Mpc−3 at z= 0.1 (for a Kroupa initial mass function) and we study the distribution of star formation as a function of various physical parameters. The majority of the star formation in the low-redshift Universe takes place in moderately massive galaxies (1010–1011 M⊙), typically in high surface brightness disc galaxies. Roughly 15 per cent of all star formation takes place in galaxies that show some sign of an active nucleus. About 20 per cent occurs in starburst galaxies. By focusing on the SFR per unit mass we show that the present to past average SFR, the Scalo b-parameter, is almost constant over almost three orders of magnitude in mass, declining only at M* &gt; 1010 M⊙. The volume averaged b parameter is 0.408+0.005−0.002 (random)+0.029−0.090 (systematic)h−170. We use this value to constrain the star formation history of the Universe. For the concordance cosmology the present-day Universe is forming stars at at least 1/3 of its past average rate. For an exponentially declining cosmic star formation history this corresponds to a time-scale of 7+0.7−1.5 Gyr. In agreement with other work we find a correlation between b and morphological type, as well as a tight correlation between the 4000-Å break (D4000) and b. We discuss how D4000 can be used to estimate b parameters for high-redshift galaxies.

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LUMINOUS INFRARED GALAXIES

1996-09-01

D. B. Sanders , I. F. Mirabel

▪ Abstract At luminosities above 10 11 [Formula: see text], infrared galaxies become the dominant population of extragalactic objects in the local Universe (z ≲ 0.3), being more numerous than … ▪ Abstract At luminosities above 10 11 [Formula: see text], infrared galaxies become the dominant population of extragalactic objects in the local Universe (z ≲ 0.3), being more numerous than optically selected starburst and Seyfert galaxies and quasi-stellar objects at comparable bolometric luminosity. The trigger for the intense infrared emission appears to be the strong interaction/merger of molecular gas-rich spirals, and the bulk of the infrared luminosity for all but the most luminous objects is due to dust heating from an intense starburst within giant molecular clouds. At the highest luminosities (L ir > 10 12 [Formula: see text]), nearly all objects appear to be advanced mergers powered by a mixture of circumnuclear starburst and active galactic nucleus energy sources, both of which are fueled by an enormous concentration of molecular gas that has been funneled into the merger nucleus. These ultraluminous infrared galaxies may represent an important stage in the formation of quasi-stellar objects and powerful radio galaxies. They may also represent a primary stage in the formation of elliptical galaxy cores, the formation of globular clusters, and the metal enrichment of the intergalactic medium.

The Slope of the Black Hole Mass versus Velocity Dispersion Correlation

2002-08-01

Scott Tremaine , Karl Gebhardt , R. Bender +7 more

Observations of nearby galaxies reveal a strong correlation between the mass of the central dark object M and the velocity dispersion sigma of the host galaxy, of the form log(M/M_sun) … Observations of nearby galaxies reveal a strong correlation between the mass of the central dark object M and the velocity dispersion sigma of the host galaxy, of the form log(M/M_sun) = a + b*log(sigma/sigma_0); however, published estimates of the slope b span a wide range (3.75 to 5.3). Merritt & Ferrarese have argued that low slopes (<4) arise because of neglect of random measurement errors in the dispersions and an incorrect choice for the dispersion of the Milky Way Galaxy. We show that these explanations account for at most a small part of the slope range. Instead, the range of slopes arises mostly because of systematic differences in the velocity dispersions used by different groups for the same galaxies. The origin of these differences remains unclear, but we suggest that one significant component of the difference results from Ferrarese & Merritt's extrapolation of central velocity dispersions to r_e/8 (r_e is the effective radius) using an empirical formula. Another component may arise from dispersion-dependent systematic errors in the measurements. A new determination of the slope using 31 galaxies yields b=4.02 +/- 0.32, a=8.13 +/- 0.06, for sigma_0=200 km/s. The M-sigma relation has an intrinsic dispersion in log M that is no larger than 0.3 dex. In an Appendix, we present a simple model for the velocity-dispersion profile of the Galactic bulge.

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The 2dF Galaxy Redshift Survey: spectra and redshifts

2001-12-01

Matthew Colless , Gavin Dalton , S. Maddox +7 more

The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for approximately 250-000 galaxies. This paper describes the survey design, the spectroscopic observations, the redshift measurements and the survey … The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for approximately 250-000 galaxies. This paper describes the survey design, the spectroscopic observations, the redshift measurements and the survey data base. The 2dFGRS uses the 2dF multifibre spectrograph on the Anglo-Australian Telescope, which is capable of observing 400 objects simultaneously over a 2° diameter field. The source catalogue for the survey is a revised and extended version of the APM galaxy catalogue, and the targets are galaxies with extinction-corrected magnitudes brighter than . The main survey regions are two declination strips, one in the southern Galactic hemisphere spanning around the SGP, and the other in the northern Galactic hemisphere spanning along the celestial equator; in addition, there are 99 fields spread over the southern Galactic cap. The survey covers 2000-deg2 and has a median depth of . Adaptive tiling is used to give a highly uniform sampling rate of 93 per cent over the whole survey region. Redshifts are measured from spectra covering at a two-pixel resolution of 9.0-Å and a median S/N of 13-pixel−1. All redshift identifications are visually checked and assigned a quality parameter Q in the range redshifts are 98.4 per cent reliable and have an rms uncertainty of 85-km-s−1. The overall redshift completeness for redshifts is 91.8 per cent, but this varies with magnitude from 99 per cent for the brightest galaxies to 90 per cent for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS.

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Introducing the Illustris Project: simulating the coevolution of dark and visible matter in the Universe

2014-08-29

Mark Vogelsberger , Shy Genel , Volker Springel +6 more

We introduce the Illustris Project, a series of large-scale hydrodynamical simulations of galaxy formation. The highest resolution simulation, Illustris-1, covers a volume of (106.5舁Mpc)3, has a dark mass resolution of … We introduce the Illustris Project, a series of large-scale hydrodynamical simulations of galaxy formation. The highest resolution simulation, Illustris-1, covers a volume of (106.5舁Mpc)3, has a dark mass resolution of 6.26 × 106舁M⊙, and an initial baryonic matter mass resolution of 1.26 × 106舁M⊙. At z = 0 gravitational forces are softened on scales of 710舁pc, and the smallest hydrodynamical gas cells have an extent of 48舁pc. We follow the dynamical evolution of 2 × 18203 resolution elements and in addition passively evolve 18203 Monte Carlo tracer particles reaching a total particle count of more than 18 billion. The galaxy formation model includes: primordial and metal-line cooling with self-shielding corrections, stellar evolution, stellar feedback, gas recycling, chemical enrichment, supermassive black hole growth, and feedback from active galactic nuclei. Here we describe the simulation suite, and contrast basic predictions of our model for the present-day galaxy population with observations of the local universe. At z = 0 our simulation volume contains about 40舁000 well-resolved galaxies covering a diverse range of morphologies and colours including early-type, late-type and irregular galaxies. The simulation reproduces reasonably well the cosmic star formation rate density, the galaxy luminosity function, and baryon conversion efficiency at z = 0. It also qualitatively captures the impact of galaxy environment on the red fractions of galaxies. The internal velocity structure of selected well-resolved disc galaxies obeys the stellar and baryonic Tully–Fisher relation together with flat circular velocity curves. In the well-resolved regime, the simulation reproduces the observed mix of early-type and late-type galaxies. Our model predicts a halo mass dependent impact of baryonic effects on the halo mass function and the masses of haloes caused by feedback from supernova and active galactic nuclei.

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The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological analysis of the DR12 galaxy sample

2017-03-24

Shadab Alam , M. Ata , S. Bailey +7 more

We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises … We present cosmological results from the final galaxy clustering data set of the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. Our combined galaxy sample comprises 1.2 million massive galaxies over an effective area of 9329 deg^2 and volume of 18.7 Gpc^3, divided into three partially overlapping redshift slices centred at effective redshifts 0.38, 0.51, and 0.61. We measure the angular diameter distance DM and Hubble parameter H from the baryon acoustic oscillation (BAO) method after applying reconstruction to reduce non-linear effects on the BAO feature. Using the anisotropic clustering of the pre-reconstruction density field, we measure the product DM*H from the Alcock-Paczynski (AP) effect and the growth of structure, quantified by f{\sigma}8(z), from redshift-space distortions (RSD). We combine measurements presented in seven companion papers into a set of consensus values and likelihoods, obtaining constraints that are tighter and more robust than those from any one method. Combined with Planck 2015 cosmic microwave background measurements, our distance scale measurements simultaneously imply curvature {\Omega}_K =0.0003+/-0.0026 and a dark energy equation of state parameter w = -1.01+/-0.06, in strong affirmation of the spatially flat cold dark matter model with a cosmological constant ({\Lambda}CDM). Our RSD measurements of f{\sigma}_8, at 6 per cent precision, are similarly consistent with this model. When combined with supernova Ia data, we find H0 = 67.3+/-1.0 km/s/Mpc even for our most general dark energy model, in tension with some direct measurements. Adding extra relativistic species as a degree of freedom loosens the constraint only slightly, to H0 = 67.8+/-1.2 km/s/Mpc. Assuming flat {\Lambda}CDM we find {\Omega}_m = 0.310+/-0.005 and H0 = 67.6+/-0.5 km/s/Mpc, and we find a 95% upper limit of 0.16 eV/c^2 on the neutrino mass sum.

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Detection of the Baryon Acoustic Peak in the Large‐Scale Correlation Function of SDSS Luminous Red Galaxies

2005-11-07

Daniel J. Eisenstein , Idit Zehavi , David W. Hogg +7 more

We present the large-scale correlation function measured from a spectroscopic sample of 46,748 luminous red galaxies from the Sloan Digital Sky Survey. The survey region covers 0.72 h-3 Gpc3 over … We present the large-scale correlation function measured from a spectroscopic sample of 46,748 luminous red galaxies from the Sloan Digital Sky Survey. The survey region covers 0.72 h-3 Gpc3 over 3816 deg2 and 0.16 < z < 0.47, making it the best sample yet for the study of large-scale structure. We find a well-detected peak in the correlation function at 100 h-1 Mpc separation that is an excellent match to the predicted shape and location of the imprint of the recombination-epoch acoustic oscillations on the low-redshift clustering of matter. This detection demonstrates the linear growth of structure by gravitational instability between z ≈ 1000 and the present and confirms a firm prediction of the standard cosmological theory. The acoustic peak provides a standard ruler by which we can measure the ratio of the distances to z = 0.35 and z = 1089 to 4% fractional accuracy and the absolute distance to z = 0.35 to 5% accuracy. From the overall shape of the correlation function, we measure the matter density Ωmh2 to 8% and find agreement with the value from cosmic microwave background (CMB) anisotropies. Independent of the constraints provided by the CMB acoustic scale, we find Ωm = 0.273 ± 0.025 + 0.123(1 + w0) + 0.137ΩK. Including the CMB acoustic scale, we find that the spatial curvature is ΩK = -0.010 ± 0.009 if the dark energy is a cosmological constant. More generally, our results provide a measurement of cosmological distance, and hence an argument for dark energy, based on a geometric method with the same simple physics as the microwave background anisotropies. The standard cosmological model convincingly passes these new and robust tests of its fundamental properties.

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A Universal Density Profile from Hierarchical Clustering

1997-12-01

Julio F. Navarro , Carlos S. Frenk , Simon D. M. White

We use high-resolution N-body simulations to study the equilibrium density profiles of dark matter halos in hierarchically clustering universes. We find that all such profiles have the same shape, independent … We use high-resolution N-body simulations to study the equilibrium density profiles of dark matter halos in hierarchically clustering universes. We find that all such profiles have the same shape, independent of the halo mass, the initial density fluctuation spectrum, and the values of the cosmological parameters. Spherically averaged equilibrium profiles are well fitted over two decades in radius by a simple formula originally proposed to describe the structure of galaxy clusters in a cold dark matter universe. In any particular cosmology, the two scale parameters of the fit, the halo mass and its characteristic density, are strongly correlated. Low-mass halos are significantly denser than more massive systems, a correlation that reflects the higher collapse redshift of small halos. The characteristic density of an equilibrium halo is proportional to the density of the universe at the time it was assembled. A suitable definition of this assembly time allows the same proportionality constant to be used for all the cosmologies that we have tested. We compare our results with previous work on halo density profiles and show that there is good agreement. We also provide a step-by-step analytic procedure, based on the Press-Schechter formalism, that allows accurate equilibrium profiles to be calculated as a function of mass in any hierarchical model.

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A Relationship between Nuclear Black Hole Mass and Galaxy Velocity Dispersion

2000-08-10

Karl Gebhardt , R. Bender , Gary Bower +7 more

We describe a correlation between the mass M_BH of a galaxy's central black hole and the luminosity-weighted line-of-sight velocity dispersion sigma_e within the half-light radius. The result is based on … We describe a correlation between the mass M_BH of a galaxy's central black hole and the luminosity-weighted line-of-sight velocity dispersion sigma_e within the half-light radius. The result is based on a sample of 26 galaxies, including 13 galaxies with new determinations of black hole masses from Hubble Space Telescope measurements of stellar kinematics. The best-fit correlation is M_BH = 1.2 (+-0.2) x 10^8 M_sun (sigma_e/200 km/s)^(3.75 (+-0.3))over almost three orders of magnitude in M_BH; the scatter in M_BH at fixed sigma_e is only 0.30 dex and most of this is due to observational errors. The M_BH-sigma_e relation is of interest not only for its strong predictive power but also because it implies that central black hole mass is constrained by and closely related to properties of the host galaxy's bulge.

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Final Results from theHubble Space TelescopeKey Project to Measure the Hubble Constant

2001-05-20

Wendy L. Freedman , Barry F. Madore , B. K. Gibson +7 more

We present here the final results of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant. We summarize our method, the results, and the uncertainties, tabulate our … We present here the final results of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant. We summarize our method, the results, and the uncertainties, tabulate our revised distances, and give the implications of these results for cosmology. Our results are based on a Cepheid calibration of several secondary distance methods applied over the range of about 60-400 Mpc. The analysis presented here benefits from a number of recent improvements and refinements, including (1) a larger LMC Cepheid sample to define the fiducial period-luminosity (PL) relations, (2) a more recent HST Wide Field and Planetary Camera 2 (WFPC2) photometric calibration, (3) a correction for Cepheid metallicity, and (4) a correction for incompleteness bias in the observed Cepheid PL samples. We adopt a distance modulus to the LMC (relative to which the more distant galaxies are measured) of μ0 = 18.50 ± 0.10 mag, or 50 kpc. New, revised distances are given for the 18 spiral galaxies for which Cepheids have been discovered as part of the Key Project, as well as for 13 additional galaxies with published Cepheid data. The new calibration results in a Cepheid distance to NGC 4258 in better agreement with the maser distance to this galaxy. Based on these revised Cepheid distances, we find values (in km s-1 Mpc-1) of H0 = 71 ± 2 ± 6 (systematic) (Type Ia supernovae), H0 = 71 ± 3 ± 7 (Tully-Fisher relation), H0 = 70 ± 5 ± 6 (surface brightness fluctuations), H0 = 72 ± 9 ± 7 (Type II supernovae), and H0 = 82 ± 6 ± 9 (fundamental plane). We combine these results for the different methods with three different weighting schemes, and find good agreement and consistency with H0 = 72 ± 8 km s-1 Mpc-1. Finally, we compare these results with other, global methods for measuring H0.

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STAR FORMATION IN GALAXIES ALONG THE HUBBLE SEQUENCE

1998-09-01

Robert C. Kennicutt

▪ Abstract Observations of star formation rates (SFRs) in galaxies provide vital clues to the physical nature of the Hubble sequence and are key probes of the evolutionary histories of … ▪ Abstract Observations of star formation rates (SFRs) in galaxies provide vital clues to the physical nature of the Hubble sequence and are key probes of the evolutionary histories of galaxies. The focus of this review is on the broad patterns in the star formation properties of galaxies along the Hubble sequence and their implications for understanding galaxy evolution and the physical processes that drive the evolution. Star formation in the disks and nuclear regions of galaxies are reviewed separately, then discussed within a common interpretive framework. The diagnostic methods used to measure SFRs are also reviewed, and a self-consistent set of SFR calibrations is presented as an aid to workers in the field.

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The Structure of Cold Dark Matter Halos

1996-05-01

Julio F. Navarro , Carlos S. Frenk , Simon D. M. White

view Abstract Citations (6847) References (69) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure of Cold Dark Matter Halos Navarro, Julio F. ; Frenk, Carlos S. … view Abstract Citations (6847) References (69) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure of Cold Dark Matter Halos Navarro, Julio F. ; Frenk, Carlos S. ; White, Simon D. M. Abstract We use N-body simulations to investigate the structure of dark halos in the standard cold dark matter cosmogony. Halos are excised from simulations of cosmologically representative regions and are resimulated individually at high resolution. We study objects with masses ranging from those of dwarf galaxy halos to those of rich galaxy clusters. The spherically averaged density profiles of all our halos can be fitted over two decades in radius by scaling a simple "universal" profile. The characteristic over- density of a halo, or equivalently its concentration, correlates strongly with halo mass in a way that reflects the mass dependence of the epoch of halo formation. Halo profiles are approximately isothermal over a large range in radii but are significantly shallower than r -2 near the center and steeper than r-2 near the virial radius. Matching the observed rotation curves of disk galaxies requires disk mass-to-light ratios to increase systematically with luminosity. Further, it suggests that the halos of bright galaxies depend only weakly on galaxy luminosity and have circular velocities significantly lower than the disk rotation speed. This may explain why luminosity and dynamics are uncorrelated in observed samples of binary galaxies and of satellite/spiral systems. For galaxy clusters, our halo models are consistent both with the presence of giant arcs and with the observed structure of the intracluster medium, and they suggest a simple explanation for the disparate estimates of cluster core radii found by previous authors. Our results also highlight two shortcomings of the CDM model. CDM halos are too concentrated to be consistent with the halo parameters inferred for dwarf irregulars, and the predicted abundance of galaxy halos is larger than the observed abundance of galaxies. The first problem may imply that the core structure of dwarf galaxies was altered by the galaxy formation process, and the second problem may imply that galaxies failed to form (or remain undetected) in many dark halos. Publication: The Astrophysical Journal Pub Date: May 1996 DOI: 10.1086/177173 arXiv: arXiv:astro-ph/9508025 Bibcode: 1996ApJ...462..563N Keywords: COSMOLOGY: THEORY; COSMOLOGY: DARK MATTER; GALAXIES: HALOS; METHODS: NUMERICAL; Astrophysics E-Print: compressed and uuencoded PS file. 22 pages including 14 figures. 447875 bytes. Submitted to ApJ on August 1, 1995 full text sources arXiv | ADS | data products SIMBAD (4)

Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies

2013-08-18

John Kormendy , Luis C. Ho

Supermassive black holes (BHs) have been found in 85 galaxies by dynamical modeling of spatially resolved kinematics. The Hubble Space Telescope revolutionized BH research by advancing the subject from its … Supermassive black holes (BHs) have been found in 85 galaxies by dynamical modeling of spatially resolved kinematics. The Hubble Space Telescope revolutionized BH research by advancing the subject from its proof-of-concept phase into quantitative studies of BH demographics. Most influential was the discovery of a tight correlation between BH mass [Formula: see text] and the velocity dispersion σ of the bulge component of the host galaxy. Together with similar correlations with bulge luminosity and mass, this led to the widespread belief that BHs and bulges coevolve by regulating each other's growth. Conclusions based on one set of correlations from [Formula: see text] in brightest cluster ellipticals to [Formula: see text] in the smallest galaxies dominated BH work for more than a decade. New results are now replacing this simple story with a richer and more plausible picture in which BHs correlate differently with different galaxy components. A reasonable aim is to use this progress to refine our understanding of BH-galaxy coevolution. BHs with masses of 10 5 −10 6 M ⊙ are found in many bulgeless galaxies. Therefore, classical (elliptical-galaxy-like) bulges are not necessary for BH formation. On the other hand, although they live in galaxy disks, BHs do not correlate with galaxy disks. Also, any [Formula: see text] correlations with the properties of disk-grown pseudobulges and dark matter halos are weak enough to imply no close coevolution. The above and other correlations of host-galaxy parameters with each other and with [Formula: see text] suggest that there are four regimes of BH feedback. (1) Local, secular, episodic, and stochastic feeding of small BHs in largely bulgeless galaxies involves too little energy to result in coevolution. (2) Global feeding in major, wet galaxy mergers rapidly grows giant BHs in short-duration, quasar-like events whose energy feedback does affect galaxy evolution. The resulting hosts are classical bulges and coreless-rotating-disky ellipticals. (3) After these AGN phases and at the highest galaxy masses, maintenance-mode BH feedback into X-ray-emitting gas has the primarily negative effect of helping to keep baryons locked up in hot gas and thereby keeping galaxy formation from going to completion. This happens in giant, core-nonrotating-boxy ellipticals. Their properties, including their tight correlations between [Formula: see text] and core parameters, support the conclusion that core ellipticals form by dissipationless major mergers. They inherit coevolution effects from smaller progenitor galaxies. Also, (4) independent of any feedback physics, in BH growth modes 2 and 3, the averaging that results from successive mergers plays a major role in decreasing the scatter in [Formula: see text] correlations from the large values observed in bulgeless and pseudobulge galaxies to the small values observed in giant elliptical galaxies.

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Cosmic Star-Formation History

2014-06-27

Piero Madau , Mark Dickinson

Over the past two decades, an avalanche of new data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Here we review the range … Over the past two decades, an avalanche of new data from multiwavelength imaging and spectroscopic surveys has revolutionized our view of galaxy formation and evolution. Here we review the range of complementary techniques and theoretical tools that allow astronomers to map the cosmic history of star formation, heavy element production, and reionization of the Universe from the cosmic “dark ages” to the present epoch. A consistent picture is emerging, whereby the star-formation rate density peaked approximately 3.5 Gyr after the Big Bang, at z≈1.9, and declined exponentially at later times, with an e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was formed before a redshift z = 1.3. About 25% formed before the peak of the cosmic star-formation rate density, and another 25% formed after z = 0.7. Less than ∼1% of today's stars formed during the epoch of reionization. Under the assumption of a universal initial mass function, the global stellar mass density inferred at any epoch matches reasonably well the time integral of all the preceding star-formation activity. The comoving rates of star formation and central black hole accretion follow a similar rise and fall, offering evidence for coevolution of black holes and their host galaxies. The rise of the mean metallicity of the Universe to about 0.001 solar by z = 6, one Gyr after the Big Bang, appears to have been accompanied by the production of fewer than ten hydrogen Lyman-continuum photons per baryon, a rather tight budget for cosmological reionization.

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The Host Galaxies of AGN

2003-04-14

Guinevere Kauffmann , Timothy M. Heckman , Christy Tremonti +7 more

We examine the properties of the host galaxies of 22,623 narrow-line AGN with 0.02<z<0.3 selected from a complete sample of 122,808 galaxies from the Sloan Digital Sky Survey. We focus … We examine the properties of the host galaxies of 22,623 narrow-line AGN with 0.02<z<0.3 selected from a complete sample of 122,808 galaxies from the Sloan Digital Sky Survey. We focus on the luminosity of the [OIII]$\lambda$5007 emission line as a tracer of the strength of activity in the nucleus. We study how AGN host properties compare to those of normal galaxies and how they depend on L[OIII]. We find that AGN of all luminosities reside almost exclusively in massive galaxies and have distributions of sizes, stellar surface mass densities and concentrations that are similar to those of ordinary early-type galaxies in our sample. The host galaxies of low-luminosity AGN have stellar populations similar to normal early-types. The hosts of high- luminosity AGN have much younger mean stellar ages. The young stars are not preferentially located near the nucleus of the galaxy, but are spread out over scales of at least several kiloparsecs. A significant fraction of high- luminosity AGN have strong H$\delta$ absorption-line equivalent widths, indicating that they experienced a burst of star formation in the recent past. We have also examined the stellar populations of the host galaxies of a sample of broad-line AGN. We conclude that there is no significant difference in stellar content between type 2 Seyfert hosts and QSOs with the same [OIII] luminosity and redshift. This establishes that a young stellar population is a general property of AGN with high [OIII] luminosities.

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Sample of 25 radio galaxies with highly unusual radio morphologies, selected from the LoTSS-DR2 survey at 144 MHz

2025-06-26

Gopal‐Krishna , Dusmanta Patra , Ravi Joshi | Journal of Astrophysics and Astronomy

Dissecting the Massive Pristine, Neutral Gas Reservoir of a Remarkably Bright Galaxy at z = 14.179

2025-06-23

K. E. Heintz , C L Pollock , Joris Witstok +6 more | The Astrophysical Journal Letters

Abstract At cosmic dawn, the first stars and galaxies are believed to form from and be deeply embedded in clouds of dense, pristine gas. Here we present a study of … Abstract At cosmic dawn, the first stars and galaxies are believed to form from and be deeply embedded in clouds of dense, pristine gas. Here we present a study of the James Webb Space Telescope/NIRSpec data of the most distant, spectroscopically confirmed galaxy observed to date, JADES-GS-z14-0 (GS-z14 for short), at z = 14.179, combined with recently reported far-infrared measurements of the [O iii ]-88 μ m and [C ii ]-158 μ m line transitions and underlying dust-continuum emission. Based on the observed prominent damped Ly α (DLA) absorption profile, we determine a substantial neutral atomic hydrogen (H i ) column density, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">HI</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>22.2</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , consistent with previous estimates though seemingly at odds with the dynamical and gas mass of the galaxy. Using various independent but complementary approaches, considering the implied neutral gas mass from the DLA measurement, the star formation rate surface density, and the metal abundance, we demonstrate that the total gas mass of GS-z14 is of the order M gas = 10 9.5 –10 9.8 M ⊙ . This implies a substantial gas mass fraction, f gas ≈ 0.7–0.9 and that the bulk of the interstellar medium (ISM) is in the form of H i , with mass ratios <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">HI</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:mn>3</mml:mn> </mml:math> . We show that the derived gas mass is fully consistent with the nondetection of [C ii ]-158 μ m, assuming an appropriate scaling to the neutral gas. The low dust-to-gas ratio, A V / N HI = (1.3 ± 0.6) × 10 −23 mag cm 2 , derived in the line of sight through the DLA further indicates that the absorbing gas is more pristine than the central, star-forming regions probed by the [O iii ]-88 μ m emission. These results highlight the implications for far-infrared line-detection searchers attainable with the Atacama Large Millimeter/submillimeter Array and demonstrate that the bright, relatively massive galaxy GS-z14 at z = 14.179 is deeply embedded in a substantial, pristine H i gas reservoir dominating its baryonic matter content.

A Pilot Method to Determine the High Mass End of the Stellar Initial Mass Function in Galaxies Using UVIT, Hα-MUSE Observations and Applied to NGC 628

2025-06-23

S Amrutha , Mousumi Das | The Astrophysical Journal

Abstract We present a pilot method to estimate the high-mass initial mass function (IMF) across the arm, interarm, and spur regions in galaxies and apply it to NGC 628. We … Abstract We present a pilot method to estimate the high-mass initial mass function (IMF) across the arm, interarm, and spur regions in galaxies and apply it to NGC 628. We extracted star-forming complexes (SFCs) from the H α Very Large Telescope/Multi Unit Spectroscopic Explorer and Ultraviolet Imaging Telescope (far-ultraviolet (FUV) and near-ultraviolet (NUV)) observations of NGC 628 and used Atacama Large Millimeter/submillimeter Array observations to define the molecular gas distribution. We find that the extinction-corrected H α and FUV luminosities correlate well. Using the fact that O stars have a shorter lifetime (10 7 yr) compared to B stars (10 8 yr), we estimated the approximate number of O stars from H α emission, and the number of B0 ( M * > 10 M ⊙ ), and B1 (10 M ⊙ ≥ M * ≥ 3 M ⊙ ) stars using FUV and NUV observations. We derived the IMF index ( α ) for different regions using O to B0 ( α 1 ) and B0 to B1 ( α 2 ) stellar ratios. Our findings indicate that if we assume H α arises only from O8-type stars, the resulting α 1 value is consistent with the canonical IMF index. It steepens when we assume O stars with masses up to 100 M ⊙ with mean α 1 = 3.16 ± 0.62. However, the α 2 does not change for large variations in the O-star population, and the mean α = 2.64 ± 0.14. When we include only blue SFCs (FUV − NUV ≤ 0.3), mean α 2 is 2.43 ± 0.06. The IMF variation for SFCs in arms and spurs is insignificant. We also find that α 2 correlates with different properties of the SFCs, the most prominent being the extinction-corrected UV color (FUV − NUV).

Microlensing at cosmological distances: Event rate predictions in the Warhol arc of MACS 0416

2025-06-23

J. M. Palencia , J.M. Diego , L. Dai +7 more | Astronomy and Astrophysics

Highly magnified stars (μ $>$ 100) are now routinely identified as transient events at cosmological distances thanks to microlensing by intra-cluster stars near the critical curves of galaxy clusters. Using … Highly magnified stars (μ $>$ 100) are now routinely identified as transient events at cosmological distances thanks to microlensing by intra-cluster stars near the critical curves of galaxy clusters. Using the James Webb Space Telescope (JWST) in combination with the Hubble Space Telescope, we outline here an analytical framework that is applied to the Warhol arc (at z=0.94) in the MACS 0416 galaxy cluster (at z=0.396), where over a dozen microlensed stars have been detected to date. This method is general and can be applied to other lensed arcs. Within this lensed galaxy, we fit the spatially resolved spectral energy distribution spanned by eight JWST-NIRCam filters combined with three ACS filters, for accurate lensed star predictions in 2D. With this tool we can generate 2D maps of microlensed stars for well-resolved arcs in general, incorporating wavelength dependence and limiting apparent magnitude. These maps can be directly compared with planned cadenced campaigns from JWST and Hubble, offering a means to constrain the initial mass function and the level of dark matter substructure.

Diffuse interstellar bands and ultraviolet extinction bump: A Milky Way perspective on distant galaxies

2025-06-23

R. Lallement | Astronomy and Astrophysics

The spectral width and the center wavelength of the ultraviolet (UV) absorption bump measured for at least two z≃7 galaxies were found to differ significantly from Milky Way (MW) values. … The spectral width and the center wavelength of the ultraviolet (UV) absorption bump measured for at least two z≃7 galaxies were found to differ significantly from Milky Way (MW) values. A decrease in the width by ∼ 45% and a positive shift of the center by ∼ 70-80 Å were measured. Within the MW, the bump amplitude and width do vary; however, such a narrow bump has never been observed and no variability of the peak position has been convincingly found. On the other hand, links have recently been detected between both the amplitude and the width of the bump and the strength of several diffuse interstellar absorption bands (DIBs). The links were found to be limited to the so-called σ-type DIBs and their detection to be strongly favored if the data were limited to monocloud-type lines of sight (LOSs), selected according to 3D maps of dust extinction. We aim to extend the study of the links between MW DIBs and UV bump parameters to the center wavelength of the bump and to the ratio between the bump amplitude and the underlying continuum, and to compare the characteristics of the MW variations in the bump parameters to values at a high redshift. We used published catalogs of cross-matched measurements of DIBs and reddening law parameters. We assigned monocloud flags to all LOSs. We focused on the strong σ-type DIBs at 5780 and 6284Å , and ζ-type DIBs at 5797 and 5850Å, and searched for trends linking the bump parameters to the DIB strength normalized to the reddening. Similarly to the case of the bump amplitude and width, the center wavelength of the bump is found to react to the abundance of σ-type DIB carriers and to be insensitive to the abundance of the ζ-type DIB carriers, which dominate in dense and UV-shielded cloud cores. A strong abundance of σ carriers induces a shift of the bump peak position to longer wavelengths and a decrease in its width. The variability range for these two parameters in the MW is about half the difference between average MW values and values in the distant galaxies. In the MW, an increase in the abundance of σ carriers also corresponds to an increase in the bump amplitude and in the ratio between the amplitude and the underlying continuum. In the case of the MW, these results reinforce the hypothesis of the existence of individual types of hydrocarbon molecules that are simultaneously responsible for DIBs and part of the UV bump. They show that the majority of species responsible for narrow and positively shifted bumps in distant galaxies have a link with (or are) those producing the σ DIBs and the long-wavelength part of the bump in the MW, and that, on the contrary, species producing the short-wavelength part of the bump in the MW are of a different nature and are absent along the paths to the regions of those distant galaxies that contribute most to the UV emission. These results are based on a limited number (≃ 95) of MW LOSs. More measurements of the reddening curve obtained with a space borne UV spectrograph and more massive DIB measurements with ground-based spectrographs would impose better constraints on the relationships between DIBs and UV bumps. Identifications of DIB carriers would shed light on their formation and the origin of the UV bump in the MW and distant galaxies.

On the Use of WGANs for Super Resolution in Dark-Matter Simulations

2025-06-23

John Brennan , Sreedhar Balu , Yuxiang Qin +2 more | The Open Journal of Astrophysics

Super-resolution techniques have the potential to reduce the computational cost of cosmological and astrophysical simulations. This can be achieved by enabling traditional simulation methods to run at lower resolution and … Super-resolution techniques have the potential to reduce the computational cost of cosmological and astrophysical simulations. This can be achieved by enabling traditional simulation methods to run at lower resolution and then efficiently computing high-resolution data corresponding to the simulated low-resolution data. In this work, we investigate the application of a Wasserstein Generative Adversarial Network (WGAN) model, previously proposed in the literature, to increase the particle resolution of dark-matter-only simulations. We reproduce prior results, showing the WGAN model successfully generates high-resolution data with summary statistics, including the power spectrum and halo mass function, that closely match those of true high-resolution simulations. However, we also identify a limitation of the WGAN model in the form of smeared features in generated high-resolution data, particularly in the shapes of dark-matter halos and filaments. This limitation points to a potential weakness of the proposed WGAN-based super-resolution method in capturing the detailed structure of halos, and underscores the need for further development in applying such models to cosmological data.

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Lens Modeling of STRIDES Strongly Lensed Quasars Using Neural Posterior Estimation

2025-06-23

Stephen W. Erickson , Sebastian Wagner-Carena , Philip J. Marshall +7 more | The Astronomical Journal

Abstract Strongly lensed quasars can be used to constrain cosmological parameters through time-delay cosmography. Models of the lens masses are a necessary component of this analysis. To enable time-delay cosmography … Abstract Strongly lensed quasars can be used to constrain cosmological parameters through time-delay cosmography. Models of the lens masses are a necessary component of this analysis. To enable time-delay cosmography from a sample of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> </mml:math> lenses, which will soon become available from surveys like the Rubin Observatory’s Legacy Survey of Space and Time and the Euclid Wide Survey, we require fast and standardizable modeling techniques. To address this need, we apply neural posterior estimation (NPE) for modeling galaxy-scale strongly lensed quasars from the Strong Lensing Insights into the Dark Energy Survey (STRIDES) sample. NPE brings two advantages: speed and the ability to implicitly marginalize over nuisance parameters. We extend this method by employing sequential NPE to increase precision of mass model posteriors. We then fold individual lens models into a hierarchical Bayesian inference to recover the population distribution of lens mass parameters, accounting for out-of-distribution shift. After verifying our method using simulated analogs of the STRIDES lens sample, we apply our method to 14 Hubble Space Telescope single-filter observations. We find the population mean of the power-law elliptical mass distribution slope, γ lens , to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">M</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>lens</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>2.13</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.06</mml:mn> </mml:math> . Our result represents the first population-level constraint for these systems. This population-level inference from fully automated modeling is an important stepping stone toward cosmological inference with large samples of strongly lensed quasars.

PANCAKE: A Python-based Numerical Color–Magnitude Diagram Analysis Package

2025-06-23

Yun Zheng , Yujiao Yang , Yongkun Zhang +7 more | The Astrophysical Journal Supplement Series

Abstract Stellar populations serve as a fossil record of galaxy formation and evolution, providing crucial information about the history of star formation and galaxy evolution. The color–magnitude diagram (CMD) stands … Abstract Stellar populations serve as a fossil record of galaxy formation and evolution, providing crucial information about the history of star formation and galaxy evolution. The color–magnitude diagram (CMD) stands out as the most accurate tool currently available for inferring the star formation histories (SFHs) of nearby galaxies with stellar-resolved multiband data. The launch of new space telescopes, including JWST, EUCLID, and the upcoming CSST and Roman, will significantly increase the number of stellar-resolved galaxies over the next decade. A user-friendly and customizable CMD-fitting package would be valuable for galaxy evolution studies with these data. We have developed the open-source Python-bAsed Numerical Color–magnitude diagram Analysis pacKagE ( pancake ), which is fast and accurate in determining SFHs and stellar population parameters for nearby galaxies. We have validated our method via a series of comprehensive tests. First, pancake performs well on mock data, while the random and systematic uncertainties are quantified. Second, pancake performs well on observational data containing a star cluster and 38 dwarf galaxies (50 fields). Third, the star formation rates (SFRs) from pancake are consistent with the SFRs determined with far-ultraviolet photometry. To ensure compatibility and accuracy, we have included isochrone libraries generated using PARSEC for most of the optical and near-infrared filters used by space telescopes such as the Hubble Space Telescope, JWST, and the upcoming CSST.

The Dependence of Dark Matter Halo Properties on the Morphology of Their Central Galaxies from Weak Lensing

2025-06-23

Zhenjie Liu , Kun Xu , Jun Zhang +2 more | The Astrophysical Journal

Abstract Xu & Jing reported a monotonic relationship between the host halo mass M h and the morphology of massive central galaxies, characterized by the Sérsic index n , at … Abstract Xu & Jing reported a monotonic relationship between the host halo mass M h and the morphology of massive central galaxies, characterized by the Sérsic index n , at fixed stellar mass, suggesting that morphology could serve as a good secondary proxy for the halo mass. Since their results were derived using the indirect abundance matching method, we further investigate the connection between the halo properties and central galaxy morphology using weak gravitational lensing. We apply galaxy–galaxy lensing to measure the excess surface density around CMASS central galaxies with stellar masses in the range of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>11.3</mml:mn> <mml:mo><</mml:mo> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo><</mml:mo> <mml:mn>11.7</mml:mn> </mml:math> , using the Hyper Suprime-Cam shear catalog processed through the Fourier_Quad pipeline. By dividing the sample based on n , we confirm a positive correlation between n and M h , and observe possible evidence of the positive correlation of n and halo concentration. After accounting for color, we find that neither color nor morphology alone can determine the halo mass, suggesting that a combination of both may serve as a better secondary proxy. In comparison to hydrodynamic simulations, we find that TNG300 produces much weaker correlations between M h and n . Furthermore, using SIMBA simulations with different feedback modes, we find that jet-mode active galactic nuclei feedback might be related to the relationship between the Sérsic index and halo mass.

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Bursts of Star Formation and Radiation-driven Outflows Produce Efficient LyC Leakage from Dense Compact Star Clusters

2025-06-23

Shyam H. Menon , Blakesley Burkhart , Rachel S. Somerville +2 more | The Astrophysical Journal

Abstract The escape of LyC photons emitted by massive stars from the dense interstellar medium (ISM) of galaxies is a key bottleneck for cosmological reionization. The escape fraction varies significantly … Abstract The escape of LyC photons emitted by massive stars from the dense interstellar medium (ISM) of galaxies is a key bottleneck for cosmological reionization. The escape fraction varies significantly across and within galaxies, motivating further study of the underlying physical factors responsible for these trends. We perform radiation hydrodynamic simulations of idealized clouds with different gas surface densities (compactness) Σ ∼ 10 2 –10 5 M ⊙ pc −2 , meant to emulate star cluster-forming clumps ranging from conditions typical of the local Universe to the high ISM-pressure conditions encountered at high redshift. We find that dense compact star clusters with Σ ≳ 10 4 M ⊙ pc −2 efficiently leak LyC photons, with cloud-scale luminosity-weighted average escape fractions ≳80% as opposed to ≲10% for Σ ∼ 100 M ⊙ pc −2 . This occurs due to higher star formation efficiencies and shorter dynamical timescales at higher Σ; the former results in higher intrinsic LyC emission, and the latter implies rapid evolution, with a burst of star formation followed by rapid gas dispersal, permitting high LyC escape well before the intrinsic LyC emission of stellar populations drop (∼4 Myr). LyC escape in dense clouds is primarily facilitated by highly ionized outflows driven by radiation pressure on dust with velocities ∼3 times the cloud escape velocity. We also vary the (assumed) dust abundances ( Z d ) and find a mild increase (∼10%) in the escape fraction for ∼100 lower Z d . Our results suggest a scenario in which localized compact bursts of star formation in galaxies are disproportionately productive sites of LyC leakage. We briefly discuss possible observational evidence for our predictions and implications for cosmic reionization.

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Weak lensing mass-richness relation of redMaPPer clusters in LSST DESC DC2 simulations

2025-06-20

Constantin Payerne , Michel Aguena , Céline Combet +7 more | Astronomy and Astrophysics

Cluster scaling relations are key ingredients in cluster abundance-based cosmological studies. In optical cluster cosmology, where clusters are detected through their richness, cluster-weak gravitational lensing has proven to be a … Cluster scaling relations are key ingredients in cluster abundance-based cosmological studies. In optical cluster cosmology, where clusters are detected through their richness, cluster-weak gravitational lensing has proven to be a powerful tool to constrain the cluster mass-richness relation. This work is conducted as part of the Dark Energy Science Collaboration (DESC), which aims to analyze the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory, starting in 2026. Cluster properties inferred from weak lensing, such as mass, suffer from several sources of bias. In this paper, we aim to test the impact of modeling choices and observational systematics in cluster lensing on the inference of the mass-richness relation. We constrained the mass-richness relation of 3,600 clusters detected by the redMaPPer algorithm in the cosmoDC2 extragalactic mock catalog of the LSST DESC DC2 simulation, covering $440$ deg^2, using number count measurements and either stacked weak lensing profiles or mean cluster masses in several intervals of richness ($20 ≤ λ ≤ 200$) and redshift ($0.2 ≤ z ≤ 1$). We provide the first constraints on the redMaPPer cluster mass-richness relation detected in cosmoDC2. We find that for an LSST-like source galaxy density, our constraints are robust to changes in the concentration-mass relation, as well as the dark matter density profile modeling choices, when source redshifts and shapes are perfectly known. We find that photometric redshift uncertainties can introduce bias at the $1σ$ level, which could be mitigated by an overall correction factor fitted jointly with the scaling parameters. We find that including positive shear–richness covariance in the fit shifts the results by up to $0.5σ$. Our constraints also offer a fair comparison to a fiducial mass-richness relation, obtained from matching cosmoDC2 halo masses to redMaPPer-detected cluster richness results.

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Probing cosmic voids with emission-line galaxies

2025-06-20

Yuka Yamada , Naoki Yoshida | Frontiers in Astronomy and Space Sciences

Introduction We aim to provide forecasts for future line intensity mapping (LIM) observations and galaxy redshift surveys, focusing on the physical properties of low-density region of the cosmic web (voids). … Introduction We aim to provide forecasts for future line intensity mapping (LIM) observations and galaxy redshift surveys, focusing on the physical properties of low-density region of the cosmic web (voids). We study how the measured physical properties depend on the observational methods for void detection and identification. Methods We generate mock intensity maps targeting the far-infrared CO(3–2) emission line by assigning the line luminosities to dark matter halos in cosmological simulations. The popular void-finding algorithm VIDE is applied to identify cosmic voids and quantify their properties. We analyze the voids detected in two different observation modes: (1) three-dimensional galaxy redshift surveys and (2) two-dimensional LIM observations corresponding to a single-frequency bin at 173 GHz. Results We find that the measured void size functions and radial density profiles differ depending on the observational method. These features exhibit characteristic signatures that reflect both the underlying cosmology and the nature of the emission-line galaxies. Discussion LIM-based void detection is a promising avenue for cosmological studies. We discuss the potential of combining LIM and galaxy survey data in a joint analysis to improve constraints on cosmological parameters and to better understand emission-line galaxy populations.

Measuring Scaling Relations: Fitting Technique Matters

2025-06-20

Bryanne McDonough , Olivia Curtis , Tereasa G. Brainerd | The Astrophysical Journal Letters

Abstract Scaling relationships, both integrated and spatially resolved, arise owing to the physical processes that govern galaxy evolution and are frequently measured in both observed and simulated data. However, the … Abstract Scaling relationships, both integrated and spatially resolved, arise owing to the physical processes that govern galaxy evolution and are frequently measured in both observed and simulated data. However, the accuracy and comparability of these measurements are hindered by various differences between studies such as spatial resolution, sample selection criteria, and fitting technique. In this Letter, we compare variations of standard least-squares techniques to the ridge line method for identifying spatially resolved scaling relations (Σ * −Σ SFR , Σ * −Σ gas , and Σ gas −Σ SFR ) for TNG100 galaxies. We find that using the ridge line technique to fit these scaling relations with a double linear function (in logarithmic space) results in significantly better fits than fitting with ordinary least squares. We further illustrate the utility of the ridge line technique with an investigation into the dependence of resolved star formation main-sequence (rSFMS) measurements on spatial resolution and smoothing scale. Specifically, we find that the slope of the rSFMS at low Σ * is independent (within 2 σ ) of spatial resolution and smoothing scale. Finally, we discuss the need for a consistent reanalysis of resolved scaling relations in the literature and physically motivate adoption of the ridge line technique over other fitting methods.

Probabilistic estimators of Lagrangian shape biases: Universal relations and physical insights

2025-06-20

Francisco Germano Maion , Jens Stücker , Raúl E. Angulo | Astronomy and Astrophysics

The intrinsic alignment of galaxies can provide valuable information for cosmological and astrophysical studies and is crucial for interpreting weak-lensing observations. Modeling intrinsic alignments requires understanding how galaxies acquire their … The intrinsic alignment of galaxies can provide valuable information for cosmological and astrophysical studies and is crucial for interpreting weak-lensing observations. Modeling intrinsic alignments requires understanding how galaxies acquire their shapes in relation to the large-scale gravitational field, which is typically encoded in the value of large-scale shape-bias parameters. In this article we contribute to this topic in three ways: (i) developing new estimators of Lagrangian shape biases, (ii) applying them to measure the shape biases of dark-matter halos, and (iii) interpreting these measurements to gain insight into the process of halo-shape formation. Our estimators yield measurements consistent with previous literature values and offer advantages over earlier methods; for example, our bias measurements are independent of other bias parameters, and we can define bias parameters for each individual object. We measure universal relations between shape-bias parameters and peak height, ν. For the first-order shape-bias parameter, this relation is close to linear at high ν and approaches zero at low ν, which provides evidence against the proposed scenario that galaxy shapes arise due to post-formation interaction with the large-scale tidal field. We anticipate that our estimators will be very useful for analyzing hydrodynamical simulations, and thereby enhance our understanding of galaxy shape formation, and for establishing priors on the values of intrinsic alignment biases.

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Investigating the Hi distribution and kinematics of ESO444-G084 and [KKS2000]23: New insights from the MHONGOOSE survey

2025-06-20

B. Namumba , R. Ianjamasimanana , B. Koribalski +7 more | Astronomy and Astrophysics

We present the neutral atomic hydrogen ( distribution, kinematics, mass modelling, and gravitational stability of the dwarf irregular galaxies ESO444--G084 and KKS2000 23 using high spatial, spectral, and column density … We present the neutral atomic hydrogen ( distribution, kinematics, mass modelling, and gravitational stability of the dwarf irregular galaxies ESO444--G084 and KKS2000 23 using high spatial, spectral, and column density sensitivity data from the MeerKAT observations of nearby galactic objects: Observing Southern Emitters (MHONGOOSE) survey obtained with MeerKAT. ESO444--G084 exhibits centrally concentrated emission, while KKS2000 23 has irregularly distributed high-density pockets. The total fluxes measured down to column density thresholds of cm ) and cm ) are nearly the same, suggesting that the increase in the diameter at lower column densities is primarily due to the larger beam size, and that no significant additional emission is detected. The total masses are ((1.1 ± 0.1) ⊙ ) for ESO444--G084 and ((6.1 ± 0.3) ⊙ ) for KKS2000 23. We derived rotation curves using 3D kinematic modelling tools Python fully automated TiRiFiC (PyFAT) and tilted ring fitting code (TiRiFiC), which allow us to fully capture the gas kinematics. Both galaxies exhibit disk-like rotation, with ESO444--G084 showing a kinematic warp beyond (∼1.8) kpc. Its relatively fast-rising rotation curve suggests a more centrally concentrated dark matter distribution, whereas KKS2000 3.4,μ m = 0.20) for ESO444--G084 and (0.18) for KKS2000 gas /Σ_ crit ), linking these with recent star formation traced by hydrogen-alpha (H(α)) and far-ultraviolet (FUV) emission. ESO444--G084 supports localised star formation despite global stability, while KKS2000 23 is gravitationally unstable yet lacks strong H(α) emission, suggesting that turbulence, gas depletion, or past feedback suppresses star formation. The absence of detectable inflows or outflows implies that internal processes regulate star formation. This study highlights the interplay between morphology, kinematics, dark matter distribution, and disk stability, demonstrating how internal mechanisms shape dwarf galaxy evolution.

A New Framework for Interstellar Medium Emission Line Models: Connecting Multiscale Simulations across Cosmological Volumes

2025-06-20

Shengqi Yang , Adam Lidz , Andrew Benson +7 more | The Astrophysical Journal

Abstract The James Webb Space Telescope (JWST) and Atacama Large Millimeter/submillimeter Array have detected emission lines from the ionized interstellar medium (ISM) in some of the first galaxies at z … Abstract The James Webb Space Telescope (JWST) and Atacama Large Millimeter/submillimeter Array have detected emission lines from the ionized interstellar medium (ISM) in some of the first galaxies at z ≳ 6. These measurements present an opportunity to better understand galaxy assembly histories and may allow important tests of state-of-the-art galaxy formation simulations. It is challenging, however, to model these lines in their proper cosmological context. In order to meet this challenge, we introduce a novel subgrid line emission modeling framework. The framework uses the high- z zoom-in simulation suite from the Feedback in Realistic Environments (FIRE) collaboration. The line emission signals from H ii regions within each simulated FIRE galaxy are modeled using the semianalytic HIIL ines code. A machine learning approach is then used to determine the conditional probability distribution for the line luminosity to stellar-mass ratio from the H ii regions around each simulated stellar particle. This conditional probability distribution can then be applied to predict the line luminosities around stellar particles in lower-resolution, yet larger volume cosmological simulations. As an example, we apply this approach to the IllustrisTNG simulations at z = 6. The resulting predictions for the [O ii ], [O iii ], and Balmer line luminosities as a function of star formation rate agree well with current observations. Our predictions differ, however, from related works in the literature, which lack detailed subgrid ISM models. This highlights the importance of our multiscale simulation modeling framework. Finally, we provide forecasts for future line luminosity function measurements from the JWST and quantify the cosmic variance in such surveys.

Intermediate Mass Ratio Inspirals in Milky Way Galaxies

2025-06-19

Jillian Bellovary , Y. Luo , Thomas Quinn +3 more | The Astrophysical Journal

Abstract A consequence of a nonzero occupation fraction of massive black holes (MBHs) in dwarf galaxies is that these MBHs can become residents of larger galaxy halos via hierarchical merging … Abstract A consequence of a nonzero occupation fraction of massive black holes (MBHs) in dwarf galaxies is that these MBHs can become residents of larger galaxy halos via hierarchical merging and tidal stripping. Depending on the parameters of their orbits and original hosts, some of these MBHs will merge with the central supermassive black hole in the larger galaxy. We examine four cosmological zoom-in simulations of Milky Way-like galaxies to study the demographics of the black hole mergers that originate from dwarf galaxies. Approximately half of these mergers have mass ratios less than 0.04, which we categorize as intermediate mass ratio inspirals, or IMRIs. Inspiral durations range from 0.5–8 Gyr, depending on the compactness of the dwarf galaxy. Approximately half of the inspirals may become more circular with time, while the eccentricity of the remainder does not evolve. Overall, IMRIs in Milky Way-like galaxies are a significant class of black hole mergers that can be detected by LISA, and must be prioritized for waveform modeling.

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Strong Correlation between Galactic HI-to-stellar Mass Ratio And Halo Spin Explored by HI-rich Galaxies

2025-06-19

Shihong Liu , Yu Rong , Zichen Hua +1 more | Research in Astronomy and Astrophysics

Abstract Using a semi-analytic approach, we estimate halo spins for a large sample of HI-rich galaxies from the Arecibo Legacy Fast Alfa Survey and examine the correlation between HI mass … Abstract Using a semi-analytic approach, we estimate halo spins for a large sample of HI-rich galaxies from the Arecibo Legacy Fast Alfa Survey and examine the correlation between HI mass fractions and halo spins. Our analysis reveals a strong correlation between halo spin and the HI-to-stellar mass ratio in both low-mass and massive galaxy samples. This finding suggests a universal formation scenario: higher halo spin reduces angular momentum loss and gas condensation, leading to lower star formation rates and weaker feedback, which in turn helps retain gas within dark matter halos.

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DAWN JWST Archive: Morphology from profile fitting of over 340,000 galaxies in major JWST fields. Morphology evolution with redshift and galaxy type

2025-06-19

Aurélien Genin , Marko Shuntov , Gabriel Brammer +7 more | Astronomy and Astrophysics

Understanding how galaxies assemble their structure and evolve morphologically over cosmic time is a central goal of galaxy evolution studies. In particular, the morphological evolution of quiescent and star-forming galaxies … Understanding how galaxies assemble their structure and evolve morphologically over cosmic time is a central goal of galaxy evolution studies. In particular, the morphological evolution of quiescent and star-forming galaxies provides key insights into the mechanisms that regulate star formation and quenching. We present a new catalog of morphological measurements for more than 340,000 sources spanning $0 < z < 12$, derived from deep NIRCam imaging across four major extragalactic fields (CEERS, PRIMER–UDS, PRIMER–COSMOS, GOODS) compiled in the DAWN Archive (DJA). We performed two-dimensional surface brightness fitting for all galaxies in a uniform, flux-limited sample. Each galaxy was modeled with both a Sérsic profile and a two-component (bulge and disk) decomposition, yielding consistent structural parameters, including effective radius, Sérsic index (n_S), axis ratio, and bulge-to-total ratio (B/T). To demonstrate the scientific application of our morphology catalogs, we combined these measurements with DJA photometric redshifts, physical parameters and rest-frame colors, and investigated the relation between total, bulge, and disk sizes, n_S , star formation activity, and redshift. Bulge-dominated galaxies (high n_S and B/T) predominantly occupy the quiescent region of the UVJ diagram, while disk-dominated galaxies are mostly star-forming. A significant bimodality persists, with quiescent disks and compact, bulge-dominated star-forming galaxies observed out to z > 3. Quiescent galaxies also show significantly higher stellar mass surface densities, nearly an order of magnitude greater at z ∼ 4 than at z ∼ 1. Our results confirm a strong and evolving link between morphology and star formation activity and support a scenario in which bulge growth and quenching are closely connected. This work is a highly valuable addition to the DJA, adding a morphological dimension to this rich dataset and thus enabling a wider scientific application.

The vertical structure of the stellar disk in NGC 551

2025-06-19

Harshal Raut , Narendra Nath Patra , Prerana Biswas +6 more | Astronomy and Astrophysics

This paper aims to self-consistently determine the 3D density distribution of the stellar disk in NGC 551 and to utilize it to study the observational signatures of two-component stellar disks … This paper aims to self-consistently determine the 3D density distribution of the stellar disk in NGC 551 and to utilize it to study the observational signatures of two-component stellar disks (thin and thick) in galaxies. Assuming that the baryonic disks are in hydrostatic equilibrium, we solved the Poisson-Boltzmann equation to estimate the 3D density distribution in the stellar disk of NGC 551. Unlike in previous studies, we used integral-field spectroscopic observations to estimate the stellar velocity dispersion. A 3D dynamical model of the stellar disk was built using these density solutions and the observed rotation curve. Using this model, we generated simulated surface brightness maps and compared them with observations to verify the consistency of our modeling. Furthermore, the dynamical model was inclined to $90^∘$ to produce an edge-on surface density map of the galaxy. We further investigated this map by fitting different 2D functions and plotting vertical cuts in a logarithmic scale to infer observational signatures of two-component disks in galaxies. We estimated the vertical stellar velocity dispersion in NGC 551 using an iterative method and obtained results consistent with the formalism employed in the Disk Mass Survey. Through dynamical modeling of the stellar disk in NGC 551, we produced moment maps, which reasonably matched the observations, indicating consistent modeling. We examined the simulated edge-on model by taking vertical cuts and decomposing them into multiple Gaussian components. We find that an artificial double Gaussian component arises due to the line-of-sight integration effect, even for a single-component disk. This indicates that decomposing vertical intensity cuts into multiple Gaussian components is an unreliable method for identifying multicomponent disks. Instead, an up-bending break, visible in the plot of the vertical cuts in the logarithmic scale for a two-component disk, serves as a more reliable indicator, which is absent in the case of a single-component disk. We performed 2D fitting on the edge-on surface density map using the product of a scaled modified Bessel function (for the radial profile) and a rm sech^2 function (for the vertical profile) to estimate the stellar disk’s structural parameters. We find that these traditional methods systematically underestimate the scale length and flattening ratio of the stellar disk. Therefore, we suggest using detailed modeling to accurately deduce the structural parameters of stellar disks in galaxies.

The Sagittarius stellar stream embedded in a fermionic dark matter halo

2025-06-19

Santiago Collazo , Martín F. Mestre , C. R. Argüelles | Astronomy and Astrophysics

Stellar streams are essential tracers of the gravitational potential of the Milky Way, with key implications for the problem of dark matter model distributions, either within or beyond phenomenological ΛCDM … Stellar streams are essential tracers of the gravitational potential of the Milky Way, with key implications for the problem of dark matter model distributions, either within or beyond phenomenological ΛCDM halos. For the first time in the literature, a dark matter (DM) halo model based on first physical principles such as (quantum) statistical mechanics and thermodynamics is used to try to reproduce the $6$D observations of the Sagittarius (Sgr) stream. Thus, we aim to extract quantitative and qualitative conclusions on how well our assumptions stand with respect to the observations. We model both DM halos, the one of the Sgr dwarf and the one of its host, with a spherical self-gravitating system of neutral fermions that accounts for the effects of particle escape and fermion degeneracy (due to the Pauli exclusion principle), the latter causing a high-density core at the center of the halo. Full baryonic components for each galaxy are also considered. We used a spray algorithm with ∼10^5 particles to generate the Sgr tidal debris, which evolves in the combined gravitational potential of the host-progenitor system, to then make a direct comparison with the full phase-space data of the stream. We repeated this kind of simulation for different parameter setups of the fermionic model including the particle mass, with special attention to testing different DM halo morphologies allowed by the physics, including polytropic density tails as well as power-law-like trends. We find that the fermionic halo models considered can only reproduce the trailing arm of the Sgr stream. Within the observationally allowed span of enclosed masses where the stream moves, neither the power-law-like nor the polytropic behavior of the fermionic halo models can answer for the observed trend of the leading tail — a conclusion that is shared by former analyses using other types of spherically symmetric halos. Thus, we conclude that further model improvements, such as abandoning spherical symmetry and including the Large Magellanic Cloud perturber, are needed for the proper modeling of the overall Milky Way potential within this kind of first-principle halo model.

Luminosity and Stellar Mass Functions of Faint Photometric Satellites around Spectroscopic Central Galaxies from DESI Year-1 Bright Galaxy Survey

2025-06-19

Wenting Wang , Xiaohu Yang , Y. P. Jing +7 more | The Astrophysical Journal

Abstract We measure the luminosity functions (LFs) and stellar mass functions (SMFs) of photometric satellite galaxies around spectroscopically identified isolated central galaxies (ICGs). The photometric satellites are from the DESI … Abstract We measure the luminosity functions (LFs) and stellar mass functions (SMFs) of photometric satellite galaxies around spectroscopically identified isolated central galaxies (ICGs). The photometric satellites are from the DESI Legacy Imaging Surveys (DR9), while the spectroscopic ICGs are selected from the DESI Year-1 BGS sample. We can measure satellite LFs down to r -band absolute magnitudes of M r ,sat ∼ −7, around ICGs as small as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>7.1</mml:mn> <mml:mo><</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mo>,</mml:mo> <mml:mrow> <mml:mi mathvariant="normal">ICG</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo><</mml:mo> <mml:mn>7.8</mml:mn> </mml:math> , with the stellar mass of ICGs measured by the DESI F astspecfit pipeline. The satellite SMF can be measured down to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mo>,</mml:mo> <mml:mrow> <mml:mi mathvariant="normal">sat</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>5.5</mml:mn> </mml:math> . Interestingly, we discover that the faint/low-mass end slopes of satellite LFs/SMFs become steeper with the decrease in the stellar masses of host ICGs, with smaller and nearby host ICGs capable of being used to probe their fainter satellites. The steepest slopes can be −2.298 ± 0.656 and −2.888 ± 0.916 for satellite LF and SMF, respectively. Detailed comparisons are performed between the satellite LFs around ICGs selected from DESI BGS or from the SDSS NYU-VAGC spectroscopic Main galaxies over <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>7.1</mml:mn> <mml:mo><</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mo>,</mml:mo> <mml:mrow> <mml:mi mathvariant="normal">ICG</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo><</mml:mo> <mml:mn>11.7</mml:mn> </mml:math> , showing reasonable agreement, but we show that differences between DESI and SDSS stellar masses for ICGs play a role to affect the results. We also compare measurements based on DESI F astspecfit and C igale stellar masses used to bin ICGs, with the latter including the modeling of active galactic nuclei based on Wide-field Infrared Survey Explorer photometry, and we find good agreements in the measured satellite LFs by using either of the DESI stellar mass catalogs.

Understanding Stellar Mass–Metallicity and Size Relations in Simulated Ultrafaint Dwarf Galaxies

2025-06-19

Minsung Go , Myoungwon Jeon , Yumi Choi +7 more | The Astrophysical Journal

Abstract Reproducing the physical characteristics of ultrafaint dwarf galaxies (UFDs) in cosmological simulations is challenging, particularly with respect to stellar metallicity and galaxy size. To investigate these difficulties in detail, … Abstract Reproducing the physical characteristics of ultrafaint dwarf galaxies (UFDs) in cosmological simulations is challenging, particularly with respect to stellar metallicity and galaxy size. To investigate these difficulties in detail, we conduct high-resolution simulations ( M gas ∼ 60 M ⊙ , M DM ∼ 300 M ⊙ ) on six UFD analogs ( M vir ∼ 10 8 –10 9 M ⊙ , M ⋆ ∼ 10 3 –2.1 × 10 4 M ⊙ at z = 0). Our findings reveal that the stellar properties of the UFD analogs are shaped by diverse star-forming environments from multiple progenitor halos in the early Universe. Notably, our UFD analogs exhibit a better match to the observed mass–metallicity relation, showing higher average metallicity compared to other theoretical models, though our results remain 0.5–1 dex lower than for observed UFDs. The metallicity distribution functions (MDFs) of our simulated UFDs lack high-metallicity stars ([Fe/H]≥ −2.0) while containing low-metallicity stars ([Fe/H] < −4.0). Excluding these low-metallicity stars, our results align well with the MDFs of observed UFDs. However, forming stars with higher metallicity (−2.0 ≤ [Fe/H] max ≤ −1.5) remains a challenge, due to the difficulty of sustaining metal enrichment during the brief star formation period before cosmic reionization. Additionally, our simulations show extended outer structures in UFDs, similar to recent Milky Way UFD observations, resulting from dry mergers between progenitor halos. To ensure consistency, we adopt the same fitting method commonly used in observations to derive the half-light radius. We find that this method tends to produce lower values compared to direct calculations and struggles to accurately describe the extended outer structures.

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Invisible spiral arms in Milky Way-like galaxies

2025-06-19

Bokyoung Kim | Nature Astronomy

Black in galaxy astrophysics

2025-06-19

Devontae C. Baxter , Arianna S. Long , Sinclaire M. Manning +3 more | Nature Astronomy

Spatially Resolved Galaxy–Dust Modeling with Coupled Data-driven Priors

2025-06-19

Jared Siegel , P. Melchior | The Astrophysical Journal

Abstract A notorious problem in astronomy is the recovery of the true shape and spectral energy distribution (SED) of a galaxy despite attenuation by interstellar dust embedded in the same … Abstract A notorious problem in astronomy is the recovery of the true shape and spectral energy distribution (SED) of a galaxy despite attenuation by interstellar dust embedded in the same galaxy. This problem has been solved for a few hundred nearby galaxies with exquisite data coverage, but these techniques are not scalable to the billions of galaxies soon to be observed by large wide-field surveys like the Legacy Survey of Space and Time, Euclid, and Roman. We present a method for jointly modeling the spatially resolved stellar and dust properties of galaxies from multiband images. To capture the diverse geometries of galaxies, we consider nonparametric morphologies, stabilized by two neural networks that act as data-driven priors: the first informs our inference of the galaxy’s underlying morphology, while the second constrains the galaxy’s dust morphology conditioned on our current estimate of the galaxy morphology. We demonstrate with realistic simulations of z ∼ 0 galaxies that we can recover galaxy host and dust properties over a wide range of attenuation levels and geometries. We apply our joint galaxy–dust model to three local galaxies observed by the Sloan Digital Sky Survey and find qualitatively good results. In addition to improving estimates of unattenuated galaxy SEDs, our inferred dust maps will facilitate the study of dust production, transport, and destruction. However, without informed priors on the inferred host spectrum, our method is vulnerable to the thin-screen limit; future work will need to address this degeneracy with stellar population synthesis modeling.

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The effect of measurement uncertainties on the inferred stability of planes of satellite galaxies

2025-06-18

Prem Kumar , Marcel S. Pawlowski , Kosuke Jamie Kanehisa +3 more | Astronomy and Astrophysics

Observations have revealed that the Milky Way, Andromeda, Centaurus A, and possibly other galaxies host spatially thin and kinematically coherent planes of satellites. Such structures are highly improbable within the … Observations have revealed that the Milky Way, Andromeda, Centaurus A, and possibly other galaxies host spatially thin and kinematically coherent planes of satellites. Such structures are highly improbable within the standard ΛCDM cosmological model, and the dynamical stability of these planes has long been debated. Accurately determining their stability requires a thorough understanding of orbital parameters such as proper motion, distance, and line-of-sight velocity, in addition to as the gravitational potential of the host galaxy. However, many of these parameters remain poorly constrained, leading to significant uncertainties in analyses. This study explores the impact of measurement errors in the proper motions and distances of the satellite galaxies and in the adopted host halo mass on the inferred stability of satellite planes in Milky Way-like potentials. We simulated mock-observed test satellite galaxies orbiting a host galaxy by adding various degrees and types of observational errors, and then backward-integrated the orbits. We analyzed trends and correlations between the initial conditions and the uncertainties applied on the inferred orbital stability of the satellite systems. We also considered the effects of adopting incorrect potentials and the impact of different orbital eccentricities. Uncertainties in proper motions lead to an apparent widening of an intrinsically stable satellite plane, with its width increasing linearly with the uncertainties in the adopted proper motion. Even uncertainties at the level of Gaia systematics strongly affect the plane's inferred past width. Moreover, the potential with a low halo mass has a significant impact on the stability of these planes, whereas the remaining two host models show similar effects. Uncertainties in satellite distance also contribute noticeably to the inferred instability.

Delving into the depths of NGC 3783 with XRISM. I. Kinematic and ionization structure of the highly ionized outflows

2025-06-18

M. Mehdipour , J. S. Kaastra , Megan E. Eckart +7 more | Astronomy and Astrophysics

We present our study of the X-Ray Imaging and Spectroscopy Mission (XRISM) observation of the Seyfert-1 galaxy NGC 3783. XRISM’s Resolve microcalorimeter has enabled, for the first time, a detailed … We present our study of the X-Ray Imaging and Spectroscopy Mission (XRISM) observation of the Seyfert-1 galaxy NGC 3783. XRISM’s Resolve microcalorimeter has enabled, for the first time, a detailed characterization of the highly ionized outflows in this active galactic nucleus. Our analysis constrains their outflow and turbulent velocities, along with their ionization parameter (ξ) and column density ( The high-resolution Resolve spectrum reveals a distinct series of Fe absorption lines between 6.4 and 7.8 keV, ranging from Fe xviii to Fe xxvi . At lower energies (1.8--3.3 keV), absorption features from Si, S, and Ar are also detected. Our spectroscopy and photoionization modeling of the time-averaged Resolve spectrum uncovers six outflow components, five of which exhibit relatively narrow absorption lines with outflow velocities ranging from 560 to 1170 km s^-1. In addition, a broad absorption feature is detected, which is consistent with Fe xxvi outflowing at 14,300 (0.05 c). The kinetic luminosity of this component is 0.8--3% of the bolometric luminosity. Our analysis of the Resolve spectrum shows that more highly ionized absorption lines are intrinsically broader than those of lower-ionization species, indicating that the turbulent velocity of the six outflow components (ranging from 0 to 3500 increases with ξ. Furthermore, we find that the column density ( of the outflows generally declines with the ionization parameter up to logxi = 3.2 but rises beyond this point, suggesting a complex ionization structure. The absorption profile of the Fe xxv resonance line is intriguingly similar to UV absorption lines ( and C iv ) observed by the Hubble Space Telescope, from which we infer that the outflows are clumpy in nature. Our results from lower- and higher-ionization regimes support a ``hybrid wind'' scenario in which the observed outflows have multiple origins and driving mechanisms. We explore various interpretations of our findings within active galactic nucleus wind models.

Intermediate-mass-ratio Inspirals with General Dynamical Friction in Dark Matter Minispikes

2025-06-18

Yu-Chen Zhou , Hong-Bo Jin , Cong‐Feng Qiao +1 more | The Astrophysical Journal

Abstract Intermediate-mass-ratio inspirals (IMRIs) may be surrounded by dark matter (DM) minispikes. The dynamical friction from these DM minispike structures can affect the dynamics and the gravitational-wave (GW) emission of … Abstract Intermediate-mass-ratio inspirals (IMRIs) may be surrounded by dark matter (DM) minispikes. The dynamical friction from these DM minispike structures can affect the dynamics and the gravitational-wave (GW) emission of the IMRIs. We analyze the effects of general dynamical friction, with a particular contribution from DM particles moving faster than the stellar-mass black hole in an eccentric IMRI. Our calculations show that these DM particles tend to increase the eccentricity of the orbit; therefore, the evolution of the eccentricity depends on the competition between the fast-moving DM particles and the slow-moving DM particles. The results show that the dynamical friction enhances the eccentricity when γ sp ≲ 2.0, and the general dynamical friction is able to increase the eccentricity. We also analyze the effects of general dynamical friction on the GW characteristic strain. The results indicate that the characteristic strain is suppressed at lower frequencies, and the peak value of the characteristic strain occurs at higher frequencies as the power-law index of the DM minispike γ sp increases. For the first time, a relation between the frequency peak value of the characteristic strain of GWs and γ sp is established. Using this analytical relation, the presence of DM and its halo density may potentially be determined from future GW data.

Describing the Nonuniversal Galaxy Merger Timescales in IllustrisTNG: Effects of Host Halo Mass, Baryons, and Sample Selection

2025-06-18

Kun Xu , Y. P. Jing | The Astrophysical Journal

Abstract Galaxy merger timescales are crucial for understanding and modeling galaxy formation in our hierarchically structured Universe. However, previous studies have reported widely varying dependencies of merger timescales on initial … Abstract Galaxy merger timescales are crucial for understanding and modeling galaxy formation in our hierarchically structured Universe. However, previous studies have reported widely varying dependencies of merger timescales on initial orbital parameters and mass ratios at the first crossing of r vir . Using IllustrisTNG simulations, we find that these dependencies vary with host halo mass, suggesting that discrepancies in prior studies may arise from differences in the systems analyzed. Specifically, in low-mass halos, merger timescales show a stronger dependence on initial orbital parameters, while, in high-mass halos, this dependence weakens. To account for these variations, we present a fitting formula that incorporates host mass dependence, achieving a logarithmic scatter smaller than 0.15 dex. Comparing dark-matter-only and baryonic simulations, we observe similar merger timescales for circular orbits but notable differences for radial orbits. In halos with M host < 10 12.5 h −1 M ⊙ , mergers in dark-matter-only runs take longer than in baryonic runs, whereas the trend reverses in more massive halos. We attribute these differences to the competing effects of tidal disruption by central galaxy disks and the resistance of baryonic satellites to tidal stripping. Finally, we extend our model to predict merger timescales from any starting radius within the halo. By fitting the extended model to the entire infall sample, we find that using only the merger sample can underestimate merger timescales, particularly for low mass ratios. Our model provides a valuable tool for improving semianalytical and empirical models of galaxy formation.

The M BH–M ∗ Relation of the Hyperluminous Dust-obscured Quasars up to z ∼ 4

2025-06-18

Yibin 毅彬 Luo 罗 , Lulu Fan , Weibin 卫斌 Sun 孙 +6 more | The Astrophysical Journal

Abstract Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyperluminous dust-obscured quasars discovered by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. The heavy circumnuclear dust obscuration allows … Abstract Hot dust-obscured galaxies (Hot DOGs) are a rare population of hyperluminous dust-obscured quasars discovered by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. The heavy circumnuclear dust obscuration allows only a small amount of scattered light from the obscured quasar to escape, enabling the decomposition of the stellar component from the total flux. The presence of scattered light enables the redshift of the source and the properties of the black hole to be obtained from the Sloan Digital Sky Survey (SDSS) and SDSS-related literature. From WISE and SDSS data, we select 11 hyperluminous Hot DOGs at z = 1.5–3.7 with bolometric luminosities L bol ≳ 10 47 erg s −1 . We investigate the M BH – M ⋆ relation in these sources using Bayesian spectral energy distribution fitting or with extra constraints from Hubble Space Telescope image decomposition. Stellar masses are successfully derived for eight Hot DOGs. We find high Eddington ratios λ Edd in these Hot DOGs, with the median value of 1.05 and the maximum value close to 3. The super-Eddington accretion may be associated with the overdense environments of Hot DOGs. We find no significant differences in the M BH / M ⋆ of these Hot DOGs compared to the local relation, suggesting that these dust-obscured quasars are the progenitors of massive early-type galaxies. We speculate that the subsequent evolution of Hot DOGs may be significantly influenced by active galactic nucleus feedback and remain on the local relation.

The Physical Origin of Positive Metallicity Radial Gradients in High-redshift Galaxies: Insights from the FIRE-2 Cosmological Hydrodynamic Simulations

2025-06-17

Xunda Sun , Xin Wang , Xiangcheng Ma +7 more | The Astrophysical Journal

Abstract Using the FIRE-2 cosmological zoom-in simulations, we investigate the temporal evolution of gas-phase metallicity radial gradients of Milky Way–mass progenitors in the redshift range of 0.4 < z < … Abstract Using the FIRE-2 cosmological zoom-in simulations, we investigate the temporal evolution of gas-phase metallicity radial gradients of Milky Way–mass progenitors in the redshift range of 0.4 < z < 3. We pay special attention to the occurrence of positive (i.e., inverted) metallicity gradients—where metallicity increases with galactocentric radius. This trend, contrary to the more commonly observed negative radial gradients, has been frequently seen in recent spatially resolved grism observations. The rate of occurrence of positive gradients in FIRE-2 is about ∼7% for 0.4 < z < 3 and ∼13% at higher redshifts (1.5 < z < 3), broadly consistent with observations. Moreover, we investigate the correlations among galaxy metallicity gradient, stellar mass, star formation rate (SFR), and degree of rotational support. Metallicity gradients show a strong correlation with both sSFR and the rotational-to-dispersion velocity ratio ( v c / σ ), implying that starbursts and kinematic morphology of galaxies play significant roles in shaping these gradients. The FIRE-2 simulations indicate that galaxies with high sSFR ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">sSFR</mml:mi> <mml:mspace width="1em"/> <mml:mo stretchy="false">[</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">yr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">]</mml:mo> <mml:mo stretchy="false">)</mml:mo> <mml:mo>≳</mml:mo> <mml:mo>−</mml:mo> <mml:mn>9.2</mml:mn> </mml:math> ) and weak rotational support ( v c / σ ≲ 1) are more likely—by ∼15%—to develop positive metallicity gradients. This trend is attributed to galaxy-scale gas flows driven by stellar feedback, which effectively redistribute metals within the interstellar medium. Our results support the important role of stellar feedback in governing the chemo-structural evolution and disk formation of Milky Way–mass galaxies at the cosmic noon epoch.

Mapping the Excitation Mechanisms in the LINER I Active Galactic Nucleus NGC 5005: Positive Feedback and a Thin LINER Cocoon

2025-06-17

Anna Trindade Falcão , G. Fabbiano , M. Elvis +5 more | The Astrophysical Journal

Abstract We present a spatially resolved Baldwin–Phillips–Terlevich analysis of the narrow-line region (NLR) in the low-ionization nuclear emission-line region (LINER) I galaxy NGC 5005 using Hubble Space Telescope narrowband imaging … Abstract We present a spatially resolved Baldwin–Phillips–Terlevich analysis of the narrow-line region (NLR) in the low-ionization nuclear emission-line region (LINER) I galaxy NGC 5005 using Hubble Space Telescope narrowband imaging of [O iii ] λ 5007, H β , H α , and [S ii ] λλ 6717,6731. With a resolution of ≲0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>″</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 1 (≲10 pc at z = 0.003), we dissect the NLR into H ii (star-forming), Seyfert, and LINERs across spatial scales extending up to r ∼ 8 kpc from the nucleus. Our results reveal a compact nuclear region exhibiting Seyfert-like emission, consistent with photoionization by a low-luminosity active galactic nucleus (AGN). Surrounding this Seyfert-like nucleus is a thin (∼20 pc thick) higher-excitation LINER-like cocoon, likely arising from shock-excited gas in the interstellar medium (ISM). Beyond this cocoon, a centrally localized extended ( r ∼ 1 kpc) LINER-like region surrounds the Seyfert-like nucleus and cocoon, likely ionized by the AGN, while a more extended ( r ≳ 2 kpc) LINER-like zone may be ionized by a combination of post-AGB stars and shocks from gas inflows. We also detect H ii –like regions at both small and large scales. In the inner 500 pc, these regions may be triggered by jet–ISM interactions, potentially inducing localized star formation. At r ∼ 4 kpc, we identify an outer H ii –like region tracing a large-scale star-forming ring, where ionization is dominated by young stars.

Potential-driven Metal Cycling: JADES Census of Gas-phase Metallicity for Galaxies at 1 < z < 7

2025-06-17

Jia Cheng , Enci Wang , Cheqiu Lyu +7 more | The Astrophysical Journal Letters

Abstract The gravitational potential is established as a critical determinant of gas-phase metallicity (12+log(O/H)) in low-redshift galaxies, whereas its influence remains unconfirmed at high redshifts. We investigate the correlation between … Abstract The gravitational potential is established as a critical determinant of gas-phase metallicity (12+log(O/H)) in low-redshift galaxies, whereas its influence remains unconfirmed at high redshifts. We investigate the correlation between gas-phase metallicity and effective radius ( R e ) for a sample of galaxies with redshifts ranging from 1 to 7, drawn from JWST Advanced Deep Extragalactic Survey Data Release 3. We calculate the metallicities using four strong-line methods: N2S2H α , R23, N2, and O3N2. After taking out the evolution of size, we find that the offsets of the mass–size relation ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo mathvariant="normal">Δ</mml:mo> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">e</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) are significantly negatively correlated with the offset of the mass–metallicity relation ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo mathvariant="normal">Δ</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">O</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:math> ) for the four metallicity tracers. Regardless of the metallicity tracer used, we obtain Spearman rank p- values much less than 0.01, rejecting the null hypothesis that the observed correlation is statistically nonsignificant and attributable to random chance. This is also true for galaxies with z > 3, with p- values less than 0.05 for the four metallicity tracers. We for the first time find evidence of size playing a key role in determining gas-phase metallicity toward cosmic dawn, suggesting that the gravitational potential influences galaxies' material-exchange processes with the surrounding environment in the very early Universe.

Impact of the Cosmic Web on the Properties of Galaxies in IllustrisTNG Simulations

2025-06-17

Guangyao Yu , Weishan Zhu , Qi-Rui Yang +3 more | The Astrophysical Journal

Abstract We investigate the influence of the cosmic web on galaxy properties in the IllustrisTNG simulations. To disentangle the effects of galaxy groups and cosmic filaments, we divide the cosmic … Abstract We investigate the influence of the cosmic web on galaxy properties in the IllustrisTNG simulations. To disentangle the effects of galaxy groups and cosmic filaments, we divide the cosmic web environment into four categories: group, group-dominated region, filament-dominated region, and field. By controlling for stellar mass, we reveal evident differences in specific star formation rates (sSFRs), quenched fraction, gas fractions, local density, and stellar ages among central galaxies in different cosmic web environments, particularly for lower-mass galaxies. However, these differences largely diminish when the effect of local overdensity is further accounted for, indicating its dominant role. Additionally, we observe distinct differences in these properties among satellite galaxies across environments, mainly driven by stellar mass, halo mass, and overdensity. Notably, residual differences between satellites in field and filament-dominated regions persist even after controlling for these factors, suggesting a stronger susceptibility of satellite galaxies to filaments compared to central galaxies. Our findings highlight the importance of differentiating between central and satellite to accurately assess the environmental effects of the cosmic web. Our analysis suggests that the relationship between galaxy properties and their distance from filaments arises from a combination of factors, including stellar and halo mass, groups, overdensity, and the intrinsic influence of the cosmic web. Additionally, we find that the effect of the cosmic web on galaxy properties is reduced at z = 0.5, compared to z = 0. Furthermore, central galaxies near thick filaments tend to exhibit slightly to moderately lower sSFR and cold gas fractions compared to those near thin filaments.

Spatially Resolved Circumgalactic Medium around a Star-forming Galaxy Driving a Galactic Outflow at z ≈ 0.8

2025-06-17

Ahmed Shaban , Rongmon Bordoloi , John M. O’Meara +6 more | The Astrophysical Journal

Abstract We report the small-scale spatial variation in cool ( T ∼ 10 4 K) Mg ii absorption detected in the circumgalactic medium (CGM) of a star-forming galaxy at z … Abstract We report the small-scale spatial variation in cool ( T ∼ 10 4 K) Mg ii absorption detected in the circumgalactic medium (CGM) of a star-forming galaxy at z ≈ 0.8. The CGM of this galaxy is probed by a spatially extended bright background gravitationally lensed arc at z = 2.76. The background arc continuously samples the CGM of the foreground galaxy at a range of impact parameters between 54 and 66 kpc. The Mg ii absorption strengths vary by more than a factor of 2 within these ranges. A power-law fit to the fractional variation of absorption strengths yields a coherence length of 5.8 kpc within this range of impact parameters. This suggests a high degree of spatial coherence in the CGM of this galaxy. The host galaxy is driving a strong galactic outflow with a mean outflow velocity ≈ −179 km s −1 and mass outflow rate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mover accent="true"> <mml:mi>M</mml:mi> <mml:mo>̇</mml:mo> </mml:mover> <mml:mi>out</mml:mi> </mml:msub> <mml:mspace width="0.25em"/> <mml:mo>≥</mml:mo> <mml:mspace width="0.25em"/> <mml:mn>6</mml:mn> <mml:msubsup> <mml:mn>4</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>27</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>31</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ yr −1 traced by blueshifted Mg ii and Fe ii absorption lines. The galaxy itself has a spatially extended emission halo with a maximum spatial extent of ≈33 kpc traced by [O ii ], [O iii ], and H β emission lines. The extended emission halo shows kinematic signatures of corotating halo gas with solar metallicity. Taken together, these observations suggest evidence of a baryon cycle that is recycling the outflowing gas to form the next generation of stars.

Gas outflows in two recently quenched galaxies at z=4 and 7

2025-06-16

Francesco Valentino , K. E. Heintz , G. Brammer +7 more | Astronomy and Astrophysics

Outflows are a key element in the baryon cycle of galaxies, impacting their evolution by extracting gas, momentum, and energy and then injecting them into the surrounding medium. The properties … Outflows are a key element in the baryon cycle of galaxies, impacting their evolution by extracting gas, momentum, and energy and then injecting them into the surrounding medium. The properties of gas outflows provide a fundamental test for our models of how galaxies transition from a phase of active star formation to quiescence. Here we report the detection of outflowing gas signatures in two recently quenched, massive (M_⋆ ∼ 10^ M_⊙) galaxies at z=4.106 ( and z=7.276 ( observed at rest-frame ultraviolet to near-infrared wavelengths with JWST/NIRSpec. The outflows are traced by blueshifted magnesium (MgII) absorption lines, and in the case of the z=4.1 system, also by iron (FeII) and sodium (NaI) features. Together, these transitions broadly trace the chemically enriched neutral phase of the gaseous medium. The rest-frame optical spectra of the two sources are similar to those of local post-starburst galaxies, showing deep Balmer stellar features, a relatively low D_n4000 index, and minimal ongoing star formation on 10 Myr timescales, as traced by the lack of bright nebular and recombination emission lines. This also suggests the absence of strong and radiatively efficient active galactic nucleus activity. The galaxies' star formation histories are consistent with a recent and abrupt quenching, prior to which the average star formation rate was ∼15 over the last 100 Myr of their lives. In the case of dedicated millimeter observations allowed us to also strongly constrain the dust obscured star formation rate to $<12myr, unambiguously confirming its quiescence. Under simple geometrical assumptions, we derive mass loading factors η= M out SFR_ 100,Myr and $>10$ for the z=4.1 and z=7.3 systems, respectively, and a similarly pronounced difference in the energy carried by the outflows. Supernova feedback could account for the mass and energy of the outflow in However, the low mass loading factor and average gas velocity (∼180 which is lower than the stellar velocity dispersion) suggest that the observed outflow is likely not the primary factor behind the quenching of but it might represent a relic of the star formation process winding down. Star-formation-related processes seem to also be insufficient to explain the extreme mass outflow rate of which would require an additional ejective mechanism such as an undetected active galactic nucleus. Finally, the average outflow velocities per unit stellar mass, the star formation rate, and the surface area are consistent with those of lower-redshift post-starburst galaxies, suggesting that outflows in rapidly quenched galaxies might occur similarly across cosmic time. Our findings hint at the existence of a rich tapestry of galaxy quenching pathways at high redshifts, and they highlight the importance of using large spectroscopic samples that map different spectral features to account for the different timescales on which different mechanisms contribute to this process.

Broad-line AGNs at 3.5 < z < 6: The Black Hole Mass Function and a Connection with Little Red Dots

2025-06-16

Anthony J. Taylor , Steven L. Finkelstein , Dale D. Kocevski +7 more | The Astrophysical Journal

Abstract We present a sample of 62 H α detected broad-line active galactic nuclei (BLAGNs) at redshifts 3.5 < z < 6.8 using data from the CEERS and RUBIES surveys. … Abstract We present a sample of 62 H α detected broad-line active galactic nuclei (BLAGNs) at redshifts 3.5 < z < 6.8 using data from the CEERS and RUBIES surveys. We select these sources directly from JWST/NIRSpec G395M/F290LP spectra. We use a multistep pre-selection and Bayesian fitting to ensure a high-quality sample of sources with broad Balmer lines and narrow forbidden lines. We compute rest-frame ultraviolet and optical spectral slopes for these objects, and determine that 21 BLAGNs in our sample are also little red dots (LRDs). These LRD BLAGNs, when examined in aggregate, show broader H α line profiles and a higher fraction of broad-to-narrow component H α emission than non-LRD BLAGNs. We find that ∼90% of LRD BLAGNs are intrinsically reddened ( β opt > 0), independent of contributions from emission lines to the broadband photometry. We construct the black hole (BH) mass function at 3.5 < z < 6 after computing robust completeness corrections. This BH mass function shows agreement with recent JWST-based BH mass functions, though we extend these earlier results to log ( M BH / M ⊙ ) < 7. The derived BH mass function is consistent with theoretical models, indicating that the observed abundance of BHs in the early Universe may not be discrepant with physically motivated predictions. The BH mass function shape resembles a largely featureless power law, suggesting that signatures from BH seeding have been lost by redshift z ∼ 5–6. Finally, we compute the BLAGN UV luminosity function and find agreement with JWST-detected BLAGN samples from recent works, finding that BLAGN hosts constitute ≲10% of the total observed UV luminosity at all but the brightest luminosities.

Unveiling the Aromatic and Aliphatic Universe at Redshifts z ∼ 0.2–0.5 with JWST NIRCam/WFSS

2025-06-16

Jianwei Lyu , Xuejuan Yang , Aigen Li +4 more | The Astrophysical Journal

Abstract Utilizing deep NIRCam/WFSS data from JWST’s FRESCO program, we spectroscopically survey the 3.3 μ m aromatic and 3.4 μ m aliphatic C–H stretching emission bands of polycyclic aromatic hydrocarbon … Abstract Utilizing deep NIRCam/WFSS data from JWST’s FRESCO program, we spectroscopically survey the 3.3 μ m aromatic and 3.4 μ m aliphatic C–H stretching emission bands of polycyclic aromatic hydrocarbon (PAH) molecules in galaxies at redshifts z ∼ 0.2–0.5. Unlike pre-JWST studies, largely limited to infrared (IR)-bright galaxies ( L IR ≳ 10 11 L ⊙ ) at z ≲ 0.1, we probe 200 galaxies down to L IR ∼ 10 8.5 –10 10 L ⊙ , well beyond the local Universe. The 3.3 μ m emission is detected at ≥3 σ in 88 out of 187 galaxies, correlating tightly with galaxy IR luminosity and star formation rate (SFR) and confirming the 3.3 μ m PAH as a viable SFR tracer. Despite a large scatter, the 3.3 μ m–to–IR luminosity ratio ( L 3.3 / L IR ) exhibits a strong metallicity dependence with a drop of L 3.3 / L IR by a factor of ≳10 at 12+log(O/H) ∼ 8.4–8.5 toward lower metallicities. The 3.4 μ m emission is detected in 37 out of 159 galaxies, with the 3.4 μ m–to–3.3 μ m luminosity ratio ( L 3.4 / L 3.3 ) spanning from ∼0.05 to ∼0.58 (median ∼0.19), corresponding to PAH aliphatic fractions of ∼0.78%–8.3% (median ∼2.9%) in terms of fractional carbon atoms in aliphatic units. While L 3.4 / L 3.3 does not depend significantly on redshift, stellar mass, metallicity, or galaxy morphology, it does decrease with various SFR tracers, suggesting that ultraviolet photons in active star-forming regions may strip aliphatic side groups from PAH molecules. Our study showcases the unique power of JWST’s NIRCam/WFSS to systematically map PAH aromatic and aliphatic content in statistically significant, less biased galaxy samples, providing critical insights into PAH chemistry and its connection to galaxy properties.

A Systematic Search for Galaxies with Extended Emission Lines and Potential Outflows in JADES Medium-band Images

2025-06-16

Yongda Zhu , Marcia Rieke , Zhiyuan Ji +7 more | The Astrophysical Journal

Abstract For the first time, we present a systematic search for galaxies with extended emission lines and potential outflow features using JWST medium-band images in the GOODS South field. This … Abstract For the first time, we present a systematic search for galaxies with extended emission lines and potential outflow features using JWST medium-band images in the GOODS South field. This is done by comparing the morphology in medium-band images to adjacent continuum and UV bands. We look for galaxies that have a maximum extent 50% larger, an excess area 30% greater, or an axis ratio difference of more than 0.3 in the medium band compared to the reference bands. After visual inspection, we find 326 candidate galaxies at 1.4 < z < 8.4, with a peak in the population near cosmic noon, benefiting from the good coverage of the medium-band filters. By fitting their spectral energy distributions, we find that the candidate galaxies are at least 20% more bursty in their star-forming activity and have 50% more young stellar populations compared to a control sample selected based on the continuum band flux. Additionally, these candidates exhibit a significantly higher production rate of ionizing photons. We further find that candidates hosting known active galactic nuclei (AGN) produce extended emission that is more anisotropic compared to non-AGN candidates. A few of our candidates have been spectroscopically confirmed to have prominent outflow signatures through NIRSpec observations, showcasing the robustness of the photometric selection. Future spectroscopic follow-up will better help verify and characterize the kinematics and chemical properties of these systems.

A gas-rich cosmic web revealed by the partitioning of the missing baryons

2025-06-16

Liam Connor , Vikram Ravi , Kritti Sharma +7 more | Nature Astronomy

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Tracing galaxy evolution in infalling galaxies of Abell 496: from starburst to quenching

2025-06-14

M M López-Gutiérrez , H. Bravo–Alfaro , P. T. Rahna +4 more | Monthly Notices of the Royal Astronomical Society

ABSTRACT During the fall of late-type galaxies into clusters, they can experiment a variety of evolutionary mechanisms according to their local environment. Consequently, studying the ultraviolet (UV) emission and the … ABSTRACT During the fall of late-type galaxies into clusters, they can experiment a variety of evolutionary mechanisms according to their local environment. Consequently, studying the ultraviolet (UV) emission and the cold gas of late-type galaxies provide key insights in the evolution of short-lived starburst and galaxy quenching. In this work, we conducted a study of two 28 arcmin fields observed with Ultra Violet Imaging Telescope-AstroSat in the central region of the Abell cluster A496 ($z=0.033$), including H i data from National Radio Astronomy Observatory (NRAO) Very Large Array (VLA). We reported 22 cluster members detected in far-ultraviolet (FUV); all of them are detected in H i, or have upper limits for the H i-mass. We find our FUV detected galaxies generally have higher specific star formation rates (sSFRs) than other star-forming galaxies. Most of the FUV galaxies with masses above 10$^9$$\mathrm{M}_{\odot }$ and showing high sSFR have no close neighbours, pointing at RPS as the dominant mechanism affecting them. In contrast, most of the low-mass FUV objects present at least one companion, suggesting that tidal interactions also play an important role in the triggering of infalling galaxies. Combining the FUV–SFR with the H i properties of the observed galaxies in A496, we identify an evolutionary sequence consisting of five stages: (1) Pre-triggering, (2) Initial SF-triggering, (3) Peak of star-formation, (4) SF-fading, and (5) SF-quenching. During this path, normal gas-rich objects reach a gas-deficiency phase with SFR well below the main sequence. This process, prior to becoming a full passive galaxy, can be accomplished within a few 10$^{8}$ yr.

Gravitational Redshift as a Measure of Rapid Mass Increase

2025-06-14

David L. Berkahn , James M. Chappell , Derek Abbott | Universe

We begin by reviewing the special relativistic properties of a rotating system of coordinates. These were considered by Einstein in the spinning disk thought experiment during his initial considerations of … We begin by reviewing the special relativistic properties of a rotating system of coordinates. These were considered by Einstein in the spinning disk thought experiment during his initial considerations of time and length changes in gravity. Using a novel extension of this approach, we identify a variation in an object’s internal energy within a gravitational field, through employing the equivalence principle. We then find an additional gravitational lensing and redshift prediction over and above current theory from the Schwarzschild metric. Implications for rapid clumping in the early universe and ultramassive blackhole formation are also considered. Correlations to recent James Webb findings are also discussed. Experiments to test this principle in the terrestrial domain are also proposed.

Cosmology with One Galaxy: Autoencoding the Galaxy Properties Manifold

2025-06-12

Amanda Lue , Shy Genel , Marc Huertas-Company +2 more | The Astrophysical Journal

Abstract Cosmological simulations like CAMELS and IllustrisTNG characterize hundreds of thousands of galaxies using various internal properties. Previous studies have demonstrated that machine learning can be used to infer the … Abstract Cosmological simulations like CAMELS and IllustrisTNG characterize hundreds of thousands of galaxies using various internal properties. Previous studies have demonstrated that machine learning can be used to infer the cosmological parameter Ω m from the internal properties of even a single randomly selected simulated galaxy. This ability was hypothesized to originate from galaxies occupying a low-dimensional manifold within a higher-dimensional galaxy property space, which shifts with variations in Ω m . In this work, we investigate how galaxies occupy the high-dimensional galaxy property space, particularly the effect of Ω m and other cosmological and astrophysical parameters on the putative manifold. We achieve this by using an autoencoder with an information-ordered bottleneck, a neural layer with adaptive compression, to perform dimensionality reduction on individual galaxy properties from CAMELS simulations, which are run with various combinations of cosmological and astrophysical parameters. We find that for an autoencoder trained on the fiducial set of parameters, the reconstruction error increases significantly when the test set deviates from fiducial values of Ω m and A SN1 , indicating that these parameters shift galaxies off the fiducial manifold. In contrast, variations in other parameters such as σ 8 cause negligible error changes, suggesting galaxies shift along the manifold. These findings provide direct evidence that the ability to infer Ω m from individual galaxies is tied to the way Ω m shifts the manifold. Physically, this implies that parameters like σ 8 produce galaxy property changes resembling natural scatter, while parameters like Ω m and A SN1 create unsampled properties, extending beyond the natural scatter in the fiducial model.

DIISC-V: Variations in Hα-to-FUV Star Formation Rate Ratios Across Star-forming Regions in Nearby Galaxies

2025-06-12

Mansi Padave , Sanchayeeta Borthakur , Rolf A. Jansen +3 more | The Astrophysical Journal

Abstract We present the variations in far-ultraviolet (FUV) and H α star formation rates (SFR), SFR UV and SFR H α , respectively, at subkiloparsec scales in 11 galaxies as … Abstract We present the variations in far-ultraviolet (FUV) and H α star formation rates (SFR), SFR UV and SFR H α , respectively, at subkiloparsec scales in 11 galaxies as part of the Deciphering the Interplay between the Interstellar Medium, Stars, and the Circumgalactic medium survey. Using archival GALEX FUV imagery and H α +[N ii ] narrowband images obtained with the Vatican Advanced Technology Telescope, we detect a total of 1335 (FUV-selected) and 1474 (H α -selected) regions of recent high-mass star formation, respectively. We find the H α -to-FUV SFR ratios tend to be lower primarily for FUV-selected regions, where SFR H α generally underestimates the SFR by an average factor of 2–3, for SFR < 10 −4 M ⊙ yr −1 . In contrast, the SFRs are generally observed to be consistent for H α -selected regions. This discrepancy arises from morphological differences between the two indicators. Extended FUV morphologies and larger areas covered by FUV-only regions, along with decreasing overlap between FUV clumps and compact H ii regions with R / R 25 suggest that stochastic sampling of the initial mass function may be more pronounced in the outer regions of galaxies. Our observed H α -to-FUV SFR ratios are also consistent with stochastic star formation model predictions. However, using larger apertures that include diffuse FUV emission results in an offset of 1 dex between SFR H α and SFR UV , suggesting that the observed low H α -to-FUV SFR ratios in galaxies are likely caused by diffuse FUV emission, which can contribute ∼60%–90% to the total FUV flux.

Spatially Resolved Star Formation Rate and Dust Attenuation of Nearby Galaxies from CALIFA, GALEX, and WISE Data

2025-06-12

Jong Chul Lee , Joon Hyeop Lee , Hyunjin Jeong +2 more | The Astrophysical Journal

Abstract We study star formation rate (SFR) indicators and dust attenuation of 74 nearby star-forming galaxies on kiloparsec scales, based on GALEX far-ultraviolet (FUV) and WISE mid-infrared (MIR) images with … Abstract We study star formation rate (SFR) indicators and dust attenuation of 74 nearby star-forming galaxies on kiloparsec scales, based on GALEX far-ultraviolet (FUV) and WISE mid-infrared (MIR) images with CALIFA optical integral field spectroscopic data. We obtain hybrid SFR indicators by combining the observed FUV and MIR luminosities and calibrate them using the dust-corrected H α luminosity as a reference SFR. The simple linear combination appears to follow well the reference SFR, but the calibration residual shows a significant dependence on the specific SFR (sSFR), which can be removed by employing the combination coefficient or conversion offset that varies with the sSFR. In the plane of gas versus stellar attenuation, the median trend line’s slope (≈stellar-to-gas attenuation ratio) changes from 0.44 to 1.0 with increasing attenuation. The differential attenuation, defined as the deviation of stellar attenuation from the median trend line, is strongly correlated with the SFR surface density and sSFR, compatible with the two-component dust model. The differential attenuation seems to be affected by both local and global factors.

On the minimum number of radiation field parameters to specify gas cooling and heating functions

2024-06-27

David Robinson , Camille Avestruz , Nickolay Y. Gnedin

Fast and accurate approximations of gas cooling and heating functions are needed for hydrodynamic galaxy simulations. We use machine learning to analyze atomic gas cooling and heating functions in the … Fast and accurate approximations of gas cooling and heating functions are needed for hydrodynamic galaxy simulations. We use machine learning to analyze atomic gas cooling and heating functions in the presence of a generalized incident local radiation field computed by Cloudy. We characterize the radiation field through binned radiation field intensities instead of the photoionization rates used in our previous work. We find a set of 6 energy bins whose intensities exhibit relatively low correlation. We use these bins as features to train machine learning models to predict Cloudy cooling and heating functions at fixed metallicity. We compare the relative SHAP importance of the features. From the SHAP analysis, we identify a feature subset of 3 energy bins ($0.5-1, 1-4$, and $13-16 \, \mathrm{Ry}$) with the largest importance and train additional models on this subset. We compare the mean squared errors and distribution of errors on both the entire training data table and a randomly selected 20% test set withheld from model training. The machine learning models trained with 3 and 6 bins, as well as 3 and 4 photoionization rates, have comparable accuracy everywhere. We conclude that 3 energy bins (or 3 analogous photoionization rates: molecular hydrogen photodissociation, neutral hydrogen HI, and fully ionized carbon CVI) are sufficient to characterize the dependence of the gas cooling and heating functions on our assumed incident radiation field model.

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