Astr/Phys 328/428 Final Exam Study Questions (2016 edition)

The final exam is Tuesday, December 13th, 8:00am-11:00am. It is closed notes, no calculators, just you, your brain, a pencil or pen, and a blue book.

It will consist of 5-6 questions taken from this list. You should plan on spending ~ 2-3 blue book pages answering each one. Remember to always answer with a "what" (i.e., describe the object/effect/concept in question) and a "why" (i.e. explain physically why it behaves the way it does).


  1. Describe and sketch the Press-Schecter relationship for collapsed dark matter halos. Why does it have the shape it does? How and why does Press-Schecter evolve with redshift?
  2. Describe the Sunyaev-Zeldovich Effect, and how we can use it to constrain cosmological parameters. What data is needed for this test?
  3. Describe Big Bang Nucleosynthesis (BBN). Observationally, how can we constrain OmegaB from BBN arguments? What is the best estimate for OmegaB from these arguments?
  4. Describe the physics behind the microwave background, and explain how the CMB constrains models for structure formation in the universe.
  5. Why is "classical standard CDM" cosmology (i.e., OmegaM=1, OmegaL=0) dead? Give me several well described arguments.
  6. How and why does structure form differently under hot dark matter and cold dark matter models? 
  7. Observations suggest that OmegaM ~ 0.3. Why couldn't the dark matter all be baryonic? Give several reasons why.
  8. Explain the Lyman break technique and how we use it to identify high redshift galaxies. Describe the properties of Lyman Break Galaxies.
  9. Describe how the growth of structure is different (both to z=0 and in the future) under these two cosmologies:
  10. Make sure you explain why structure evolves differently in these different universes. Based on these arguments (only), and the observed structure in the universe what value or ranges of values are acceptable for OmegaL and OmegaM? Why?
  11. Explain what is meant by the "Radiation-Dominated Era", "Matter-Dominated Era", and "Lambda-dominated Era". How does the expansion of the universe behave during these eras? What determines when transitions between these eras happen?
  12. Describe how we can use peculiar velocities to measure the matter content of the Universe? How do we derive those peculiar velocities? In this context, what is the Great Attractor?
  13. Why do we currently believe that the cosmological constant (or "dark energy" in general) is real? Give several lines of evidence.
  14. Describe how globular clusters are age dated, and how these ages can be used to constrain cosmological parameters (ie OmegaM, OmegaL, H0). Be specific!
  15. Describe what the two point correlation function (2pt CF) measures. How is it parameterized for galaxies, and what is the meaning of the different parameters? How do observational effects distort our measurement of the 2pt CF? Describe how different kinds of galaxies are clustered.
  16. What do we mean by "reionization in the early universe"? How do we measure this, and at what redshift did it happen? What are possible sources of this reionization?
  17. Describe several reasons (both physical and observational) why high redshift galaxies might look different from galaxies in the local universe.
  18. It is said that in a universe with cold dark matter (CDM), structure (galaxies and galaxy clusters) grows hierarchically. Describe this process, and explain why the properties of CDM mandate that growth must be hierarchical.  Describe how different kinds of galaxies (i.e., spirals and ellipticals) grow with time -- think about and discuss merger trees. From observational evidence, why is it said that cluster ellipticals formed at high redshift (z>2), and why is even that statement ambiguous?
  19. Write down the Friedmann equation and describe each term. In today's "concordance cosmology" (i.e., using the current best values of the cosmological parameters), show how the scale factor of the universe will change with time in the far future (longer than a few more Hubble times). How will large scale structure evolve in the universe at these late times, and how will our ability to study large scale structure change? Describe, in general, the evolution of the universe of the next 10 Hubble times or so.
  20. This plot shows the joint constraints on the cosmological parameters OmegaM and OmegaL from three different techniques: the microwave background (CMB), studies of supernovae at high redshift (SNe), and measurements of large scale structure at z~0 (BAO). BAO has the strongest sensitivity to the matter density parameter, which is why its constraint is mostly vertical. Describe qualitatively why the other contraints have the shape they do -- that is, why do the CMB constraints follow a "downward" diagonal, and the SNe constrains follow an "upward" diagonal?
  21. Why do we need to study relatively distant galaxies to get a get a measure of the Hubble constant? Why can't we just use distances to nearby galaxies, where Cepheids give us good distances, to measure H0? Why are Cepheid distances so important for measuring H0?
  22. Explain how "supernova cosmology" projects work, the cosmological test they make, and the results from these projects.
  23. Explain and compare the two galaxy dynamical distance indicators discussed in class. What kinds of galaxies do they work on? What are the advantages and disadvantages to each one?
  24. Describe the star formation history of the universe. How do we measure it? How has it changed with time?
  25. For a OmegaM=1 universe, work out mathematically how the proper horizon distance changes with time, and solve for its value (in Gpc) at z=0.
  26. Describe what baryonic acoustic oscillations are, how they evolve, and how we measure their effect observationally.