The Astrophysics Seminar (ASTR 6000) is offered each semester and counts toward the (four-seminar) PhD requirement in APS. The goal is to show graduate students how to critically read, evaluate, write, and referee scientific papers. Students will become familiar with frontiers of research and gain experience in making effective oral presentations at conferences, Comps-2 defenses, and other professional venues. You are not expected to become cosmological experts, but you will gain a broad overview of an important field in modern astronomy.

Seminar Format and Expectations:

This seminar will meet 15 times during the term each Thursday from 4:00-5:00 pm, starting Aug 25 and ending Dec 8. The first two seminars (Aug 25 and Sept 1) provide an overview of the "standard cosmological model" based on material in review papers (see list below). The next 13 sessions will be devoted to discussing scientific papers. We will organize teams (3 students each) to lead the discussions of the "paper of the week". These teams will be responsible for several discussions throughout the semester, but all students are responsible for reading the weekly paper and being prepared to discuss the major results.

All students must read the weekly papers and participate in the class discussion. Before each seminar, students will be asked to write down (and hand in) one or two questions about the main points in the article, at a level appropriate for a non-expert in the field of Cosmology.

The Topic: Precision Measurements in Cosmology

ASTR 6000 is the graduate astrophysics seminar (Fall 2016) on the topic of "Precision Measurements in Cosmology". We will explore how cosmological measurements have become more accurate, bringing this field into a testable science. Illustrative examples are the claimed measurements of the Hubble expansion rate (H_0) to better than 4% accuracy with the Hubble Space Telescope (HST), in statistical tension with inferences from the Cosmic Microwave Background (CMB). Is the Hubble constant (H_0) = 67-68 km/s/Mpc (inferred from Planck CMB measurements) or 72-73 km/s/Mpc (from HST studies of Cepheids and Type Ia supernovae)? The latest HST measurement (Riess et al. 2016) claims 2.4% accuracy (H_0 = 73.24 +/- 1.74 km/s/Mpc), in disagreement (at 3.4 sigma) with the value (H_0 = 66.93 +/- 0.62 km/s/Mpc) from the 2016 Planck Collaboration (CMB). We will discuss the assumptions behind each of these techniques, including "distance anchors" in the Milky Way, Large Magellanic Cloud, and water maser disk (NGC 4258) used to calibrate the "standard candles" (Cepheids and Type Ia supernovae). We will examine the parameters of the standard "Lambda-CDM model" used in CMB studies to infer cosmological densities of baryonic matter, dark matter, and dark energy, the number (and masses) of neutrinos, and properties of inflationary fields in the early universe. These parameters have been inferred to good accuracy from CMB temperature fluctuations measured by the WMAP and Planck satellites and through detection of Baryon Acoustic Oscillations (BAO) in the large-scale structure of galaxies. Studies of galaxy clusters in X-ray emission, in (Sunyaev-Zeldovich) distortions of the CMB, and by gravitational lensing provide key insights into the properties of dark matter, dark energy, and baryon content. Other precision cosmological studies include probing the evolution of the dark-energy equation of state, Big Bang nucleosynthesis of the light elements (H, D, He, Li), and probes of the Hydrogen Reionization Epoch (at redshifts z > 7) observed in galaxies, quasars, and the redshifted 21-cm line of hydrogen during the period when the first galaxies and black holes were formed.

After an introduction to the topic by the instructor, students will read, present, and discuss scientific papers on various aspects of "Precision Measurements in Cosmology". For those who want additional background reading about these topics, the following list gives several review papers, followed by websites with general background. Just click on the underlined links.