Two talks: Unraveling the history of the Milky Way (speaker: Yuan-Sen Ting, Harvard); High-Redshift Astrophysics Using Every Photon (speaker: Patrick Breysse, Johns Hopkins)

Monday, September 26, 12:00pm
33-116 (plesae note location)

Speaker 1:  Yuan-Sen Ting, Harvard

Unraveling the history of the Milky Way
Abstract:  Understanding physical processes responsible for the formation and evolution of galaxies like the Milky Way is a fundamental problem in astrophysics. However, a key challenge is that the properties and orbits of the stars can only be observed at present: in order to understand what happened in the Milky Way at earlier epochs, one must explore “archeological” techniques. One idea, "chemical tagging”, aims to probe the history of the Milky Way via the unique imprint in chemical abundance space of long-disrupted star clusters. I will discuss the opportunities and challenges associated with chemical tagging, including a first constraint on the disrupted cluster mass function in the Milky Way. I will also describe a new set of tools for efficient fitting large quantities of stellar spectra and opportunities for extracting many stellar parameters from low-resolution data.
Speaker 2:  Patrick Breysse, Johns Hopkins
High-Redshift Astrophysics Using Every Photon
Abstract:  Large galaxy surveys have dramatically improved our understanding of the complex processes which govern gas dynamics and star formation in the nearby universe.  However, we know far less about the most distant galaxies, as existing high-redshift observations can only detect the very brightest sources.  Intensity mapping surveys provide a promising tool to access this poorly-studied population.  By observing emission lines with low angular resolution, these surveys can make use of every photon in a target line to study faint emitters which are inaccessible using traditional techniques.  With upcoming carbon monoxide experiments in mind, I will demonstrate how an intensity map can be used to measure the luminosity function of a galaxy population, and in turn how these measurements will allow us to place robust constraints on the cosmic star formation history.  I will then show how cross-correlating CO isotopologue lines will make it possible to study gas dynamics within the earliest galaxies in unprecedented detail.