If a galaxy contains a great deal of dark matter, then, compared to the mass-to-light ratio of the inner part, the mass-to-light ratio of the whole galaxy will be
A) less
B) more
C) the same
D) it depends on the type of galaxy
E) it depends on the galaxy's red-shift
Section 26.4: The Extragalactic Distance Scale

Question

Quizplus · Accepted Answer

The mass-to-light ratio of the whole galaxy will be more if it contains a great deal of dark matter. This is because dark matter contributes to the mass but not to the light output, increasing the mass-to-light ratio especially in the outer parts where dark matter is more prevalent.

If a Galaxy Contains a Great Deal of Dark Matter