Question

There is a typical elliptical galaxy that has a velocity dispersion that is high.

a. relatively, what's its stellar mass?

b. Compared this galaxy to a galaxy with a lower velocity dispersion but the same half light radius. How does the surface brightness of this high σ galaxy differ?

Answer 1

Stellar mass is a phrase that is used by astronomers to describe the mass of a star. It is usually enumerated in terms of the Sun's mass as a proportion of a solar mass. It turns out that the only (good) way to measure stellar masses is to measure the properties of stars in binary systems. And the most useful such binaries are those in which the two stars take turns passing in front of each other, the eclipsing binary systems.

At late times (low redshift), star formation continues in galaxies with lower velocity dispersion, while the nearly all of galaxies with the highest velocity dispersions are already quiescent. Further, since velocity dispersion correlates with the mass of a galaxy’s supermassive black hole, the fixed high velocity dispersion end of the VDF suggests that the most massive black holes had already formed

Almost all galaxies in our sample have central surface brightness in the range 20 .galaxies rely critically on high-quality observations with perfect sky conditions . Theoretically, σ2, together with Aiso, can constrain the SB profile of the image