Review Questions

1. List the eight epochs of the Universe. For each. give its  (i) approximate redshift range, (ii) cosmic age range, and (iii) defining properties. 

2. From Figure 2.2(d), give the approximate year when we could first study quasar absorption lines for (i) z ≥ 1, (ii) z ≥ 2, (iii) z ≥ 3, (iv) z ≥ 4, (v) z ≥ 5, (vi) z ≥ 6, and (vii) z ≥ 7.

3. In 1981, Ray Weymann et al. proposed an update to Bahcall's two-population classification scheme of absorption lines. Briefly describe the types proposed by Weymann et al. and how they relate to Bahcall's classification scheme.

4. What does it mean when we say an ion is "lithium-like" or "sodium-like"?  List at least three reasons why the transitions from the six ions presented in Figure 2.4 are so commonly studied in quasar absorption line science.

5. Using Figure 2.6, create a table with the four columns, (1) gas phase label, (2) range of hydrogen number density, (3) range of temperature, and (4) range of size. Now consider the regions of overlapping phases, IGM/CGM, CGM/ISM, WHIM/IGM, and WHIM/CGM. Create a second table for the overlapping phases with columns (1) labels of the overlapping phases, (2) range of hydrogen number density, and (3) range of temperature.

6. Qualitatively (in words). (i) What is photoionization? (ii) What is collisional ionization? (iii) Describe what Figure 2.9(a) is telling you. (iv) Describe what Figure 2.9(b) is telling you (focus on CIE only).

Problems

1. Consider Figure 2.5 and the relationship given by Equation 1.1.  (i) Say you aim to observe CIV 1548 absorption spanning all of Cosmic Noon. Compute the spectral wavelength range you would need to target/observe.  Does this require UV, optical, and/or IR spectra? (ii) Say you aim to observe MgII 2796 absorption spanning all of Cosmic Noon. Compute the spectral wavelength range you would need to target/observe. Does this require UV, optical, and/or IR spectra?

2. Repeat Problem 1 for OI 1302 and MgII 2796 for the Epoch of Reionization (z ≥ 5.2, but limited to z ≤ 7).

3. Examining Figure 2.8, the phase diagram of MgII, CIV, and OVI absorbers, identify the range of gas phases (density, temperature ranges) in which photoionized MgII, CIV, and OVI absorption arises. Do the same for collisionally ionized MgII, CIV, and OVI.  For the next part of this questions, a copy of Figure 2.6 is provided (see below).  On this figure, using your findings from Figure 2.8, identify which gaseous media (ISM, IGM, CGM, WHIM, etc.) you expect to observe photoionized MgII, CIV, and OVI absorption. Using a color scheme, like green for MgII, blue for CIV, and red for OVI, outline each of these regions on the provided copy of Figure 2.6. Repeat for collisionally ionized MgII, CIV, and OVI.