The width (Doppler broadening) of the 21-cm line in a spiral galaxy is NOT related to which one of these properties of the galaxy?
A) rotation rate
B) mass
C) luminosity
D) age

Question

Quizplus · Accepted Answer

The width of the 21-cm line is primarily related to the rotation rate and mass of the galaxy, as these affect the Doppler broadening due to the motion of hydrogen gas. Luminosity can be indirectly related through mass-luminosity relations. However, the age of the galaxy does not directly affect the Doppler broadening of the 21-cm line.

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