Extragalactic Astronomy -
Fall 2012
Homework #6 - due October 15
1. Can the virial theorem
be used to make a good estimate of the mass of the local group? Explain.
2. Why does the Abell catalog include entries that are not true
clusters?
3. What is a typical mass to light ratio for a rich cluster?
4. Which types of galaxies are least common in regions of high density
of galaxies?
5. What two processes produce X-ray emission from gas at a temperature
of 108 K?
6. How does the emissivity of line emission scale with temperature and
density?
7. Is the low temperature gas predicted by cooling flow models observed?
8. Show how the Sunyaev-Zeldovich effect can be used to determine the
distance to a cluster.
9. How does the mass of a cluster scale with its temperature?
10. What is the Butcher-Oemler effect?