Talks & Events
Astronomy and Astrophysics Colloquia - Usually Wednesdays, 3 PM, BSLC 115, unless otherwise specified. Reception starts at 4 PM in TAAC 71; persons with a disability who believe they may need assistance, please call the departmental secretary in advance at 773-702-8203 or email deptsecoddjob.uchicago.edu. See also the list of KICP Wednesday Colloquia which alternate with the Astronomy and Astrophysics Colloquia.
Current & Future Astronomy Colloquia
Past Astronomy Colloquia
Dwarf Galaxies: The Nexus of Dark Matter and Chemical Evolution
The Local Group's dwarf galaxies are near enough for exquisitely detailed, resolved stellar spectroscopy and diverse enough to conduct experiments on dark matter and chemical evolution. I have collected medium-resolution spectra for thousands of stars in many dwarf galaxies in the Local Group. Innovative techniques applied to these spectra recover velocities precise to a few km/s and detailed abundances precise to 0.1 dex. Although Milky Way satellites and field dwarf galaxies are different in many ways, their velocity dispersions show that both types of galaxy pose a serious challenge to cold dark matter. Both types also obey the same mass-metallicity relation despite the large diversity of star formation histories and detailed abundance ratios.
From Reionization to Dark Matter with the Lyman-alpha Forest
Absorption lines in the spectra of distant quasars offer one of the most powerful probes of cosmic structure. The Lyman-alpha forest traces the baryons in the intergalactic medium (IGM) over several decades in scale. The properties of the baryons, in turn, reflect the ongoing interaction between luminous objects and the IGM, as well as the nature of dark matter itself. I will present recent results from a suite of projects focused on determining some of the most basic properties of the high-redshift IGM, including its temperature, ionization state, and small-scale density structure. These measurements are providing new insights into when and how the IGM was reionized, the properties of high-redshift galaxies, as well as the viability of warm dark matter. I will also discuss how upcoming IGM studies with current and next-generation facilities will advance our understanding of these and other topics.
To Build an Elliptical Galaxy
I will discuss two essential aspects of elliptical galaxy formation: how they get their stars, and how they lose their gas. For the former, I use integral-field observations of local massive galaxies to study the stellar populations and kinematics of stars at large radius, to understand the origin of the size growth of elliptical galaxies. Then I focus on black hole feedback as a means of clearing gas from massive galaxies. I show that luminous obscured quasars have ubiquitous, round ionized outflows with very high gas dispersions of nearly 1000 km/s out to 20 kpc. Finally, if time permits I will combine these two themes and present our recent search for sub-pc supermassive black hole binaries.
Direct Imaging of Extrasolar Planets
With current technology, young (<100 Myr) planets can be directly imaged - resolved from their parent star - in the near-infrared with adaptive optics. I will discuss the first system of extrasolar planets to be imaged - the four planets orbiting the young F0 star HR8799. The outer two planets have been characterized spectroscopically using adaptive optics on the Keck telescope, showing non-equilibrium chemistry as well as evidence of composition enhanced in C/O from the original stellar nebula.
The supply of young stars in the solar neighborhood suitable for such searches has been essentially exhausted. Providing a statistically significant sample of planets, and accessing Jupiter-like masses and separations, will require dedicated instruments. The Gemini Planet Imager is one such facility, combining advanced adaptive optics with a coronagraph and near-infrared integral field spectrosgraph. Designed to be an order of magnitude more sensitive than current instruments, GPI had first light in November 2013. I will present results here.
The role of ultra-luminous galaxies in galaxy formation and evolution
I will provide an overview of ultra-luminous galaxies (L_IR>10^12 Lsun) at high redshift, and the different roles and properties they appear to exhibit as a function of their luminosity. I will focus on the molecular gas properties of the galaxies as the crucial fuel available for star formation, emphasizing our recent work with ALMA and the IRAM Plateau-de-Bure, where we have studied galaxies preselected at various wavelengths, and conducted blind surveys for CO gas. I will conclude with wide field surveys that are uncovering the most extreme specimens of star forming galaxies in the universe, and point to future facilities which will push the field to a new level of understanding.
Rest-frame Optical Spectra: A Window into Galaxy Formation at z~2
Rest-frame optical spectroscopy provides basic insight into the stellar and gaseous contents of galaxies. Until now, our knowledge of the rest-frame optical spectroscopic properties of galaxies at 1.5<=z<=3.5 has been extremely limited, despite the critical importance of this cosmic epoch for the assembly of galaxies and the growth of black holes. The recent commissioning of the MOSFIRE spectrograph on the Keck I telescope represents a major development for the study of the rest-frame optical properties of high-redshift galaxies. The MOSFIRE Deep Evolution Field (MOSDEF) Survey fully exploits the new capabilities of MOSFIRE, charting the evolution of the rest-frame optical spectra for ~2000 galaxies in three distinct redshift intervals spanning 1.5<=z<=3.5 -- more than an order of magnitude improvement over existing surveys. With MOSDEF, we address key questions including: What are the physical processes driving star formation in individual galaxies? How do galaxies exchange gas and heavy elements with the intergalactic medium? How are stellar mass and structure assembled in galaxies (in situ star formation vs. mergers)? What is the nature of the co-evolution of black holes and stellar populations? In this talk I will present early science results from the MOSDEF survey.
The GMT Project: Science and Status
In this talk, I will give an overview of the GMT project and the science cases and goals that are driving its design. I will also describe the current status of the project and the first generation instruments that are now under development.
Asteroseismology and Exoplanets: A Kepler Success Story
Asteroseismology - the study of stellar oscillations - is a powerful observational tool to probe the structure and evolution of stars. In addition to the large number of newly discovered exoplanets, the Kepler space telescope has revolutionized asteroseismology by detecting oscillations in thousands of stars from the main-sequence to the red-giant branch. In this talk I will highlight recent asteroseismic discoveries by Kepler, focusing in particular on studies of exoplanet host stars and the application of asteroseismology to measure stellar spin-orbit inclinations. I will furthermore discuss current efforts to improve fundamental properties (such as temperatures, masses, and radii) of Kepler targets, and their importance for deriving accurate planet occurrence rates using the Kepler sample. Finally, I will give a brief overview on first results by Kepler's ecliptic plane follow-up mission, K2.