Review Questions

1. When we speak of an "absorber," or of an "absorption system," we are referring to a gas structure that has been observed to give rise to absorption lines, and it could give rise to anywhere from one to a dozen lines from multiple transitions and ions.  When we say the phrase "MgII-selected" absorbers, "CIV-selected" absorbers, etc., what is our meaning?

2. In your own words, what is the hypothesis that Lanzetta & Bowen adopted in 1992 that codifies the key underlying assumption of all quasar absorption line CGM studies? For this hypothesis to hold true, what are the underlying assumptions about the physical nature of the CGM of galaxies? When we put this hypothesis into practice, what are the implications for our scientific inferences/deductions?

3. In a classic survey, explain why a uniform minimum equivalent width cut off in the measured sample of absorbers and/or a minimum equivalent width detection threshold in all quasar spectra is necessary if one aims to measure the true evolution in a population of absorbers.

4. Briefly summarize the twelve key quantities that are commonly measured from a classic quasar absorption line survey of a population of absorbers. What are some real world issues that one must account for (or correct for) in order to make unbiased measurements of the key quantities?

5. Briefly describe the first documented used of a double line of sight (DLOS) experiment.  What was goal of this experiment (what motivated it) and what was the astrophysical conclusion? 

6. Qualitatively describe the Alcock-Paczynski test. 

7. What is meant by tomography of the IGM or the CGM?  Describe the essence of a "tomography" experiment, including the design of the observations and the analysis of the observations. 

8. Qualitatively describe what spectrum stacking is. What are some advantages of stacking?  What are some possible disadvantages of stacking? 

9. Qualitatively describe what a "down the barrel" experiment is.

10. For GRBs, what is the quantity T90? In terms of this quantity, what are the classes of GRBs that have been observed? Describe the physical scenarios thought to be the progenitors of each.

Problems

There are no quantitative problems for this chapter.