Observations of Elliptical Galaxies. II

Astronomy 626: Spring 1995

Correlations between the global parameters of elliptical galaxies lead to a variety of useful relationships, the most important being the fundamental plane. Correlations between core parameters imply that ellipticals are similar to the bulges of disk galaxies, but that both are different from dwarf spheroidal galaxies.


Color & Line-Strength Gradients

Global Parameter Correlations

The Fundamental Plane of Elliptical Galaxies

Core Parameters & Galaxy Families


Homework

Due date: 2/2/95

6. Suppose that all galaxies are actually extremely thin disks, aligned randomly to our line of sight. What distribution of axial ratios would we expect to see in this case?

7. Using Eq. 4, the definition of the mass-to-light ratio (M/L), and the assumption that all elliptical galaxies have similar forms, derive Eq. 5.

8. How could you use the correlation between central surface brightness I_0 and core radius r_c (see Eq. 7) as a tool for measuring distances? What kind of accuracy could you achieve, assuming all the scatter shown in Fig. 6 of K87 is intrinsic?


References


Joshua E. Barnes (barnes@zeno.ifa.hawaii.edu)

Last modified: January 24, 1995