The width (Doppler broadening)of the 21-cm line in a spiral galaxy is NOT related to which property of the galaxy?

Question

Quizplus · Accepted Answer

The width of the 21-cm line is primarily related to the rotation rate and mass of a galaxy, as they affect the motion of the emitting hydrogen gas. Luminosity may also have a secondary effect on the line width, as more luminous galaxies tend to have more massive and faster rotating gas. Age, however, is not directly related to the line width.

The Width (Doppler Broadening)of the 21-Cm Line in a Spiral