The significant contribution of supersoft X-ray Sources to the nebular
HeII line emission
The significant contribution of supersoft X-ray Sources to the nebular
HeII line emission
Nebular spectral lines provide insight into the properties of the interstellar medium and the ionizing radiation within galaxies. The presence of high-energy ionization lines, such as He II, indicates the existence of hard ionizing photons, because the second ionization energy of helium is high (54 eV). The enigma surrounding the …