Differential Rotation and Turbulence in Extended H<scp>i</scp>Disks
Differential Rotation and Turbulence in Extended H<scp>i</scp>Disks
When present, extended disks of neutral hydrogen around spiral galaxies show a remarkably uniform velocity dispersion of approx 6 km/s. Since stellar winds and supernovae are largely absent in such regions, neither the magnitude nor the constancy of this number can be accounted for in the classical picture in which …