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Chris Churchill
"QSO Absorption Lines and Cosmological Simulations: The Quest to Understand Galaxies"
June 20, 2011

June's speaker will be Chris Churchill, Associate Professor of Astronomy at New Mexico State University and head of the NMSU Quasar Absorption Line Group (http://astronomy.nmsu.edu/cwc/).

The title of his talk is "QSO Absorption Lines and Cosmological Simulations: The Quest to Understand Galaxies".

Slides and Movies from his talk can be found here: http://astronomy.nmsu.edu/cwc/Group/QALsims

There are more information available at:http://astronomy.nmsu.edu/cwc/Research/interests.html

The primary challenge for contemporary studies of galaxy formation and evolution is to establish detailed models in which the physical processes deep within galaxies are unified and made consistent with the observed universe of galaxies on much larger scales. The small scale processes include stellar formation and stellar feedback on the galaxy in which they are embedded. Stellar feedback encompasses all of the effects that stars exert on their home galaxies -- the effects of the radiation stars emit, the effects of novae, and the chemical enrichment that results as stars produce more complex elements from their hydrogen fuel. The large scale physics includes accretion of primordial gas from the intergalactic medium, merging of galaxies, and most interestingly the influence of stellar driven superwinds that develop into huge chemically-enriched gas halos many times the sizes of the galaxies themselves.

Absorption lines seen in the spectra of distance QSOs have historically proven to be the most powerful tool for understanding the role of gas in the universe on all spatial scales and over the majority of the age of the universe. Simply stated, "QSO absorption lines" are one of astronomy's most powerful observational windows on the universe. In addition to observing these phenomena in real world data, we also use fluid-dynamic cosmological simulations to develop and refine our understanding of stellar feedback physics and its role in governing the gas physics that regulates the evolution of galaxies and the intergalactic medium.

In this presentation, he will summarize the method known as "QSO absorption lines" and discuss how it works in practice. He will then describe experiments in which he compares observational data to cosmological simulations and presents his current best view of how galaxies evolve in the cosmic web.

Chris Churchill is an Associate Professor of Astronomy at New Mexico State University in Las Cruces, NM. He heads the NMSU Quasar Absorption Line Group. Chris specializes in observational spectroscopic techniques and analysis, including long slit and echelle formats. He has taught many introductory classes in Astronomy and Physics at UC Santa Cruz, Penn State, and New Mexico State University. He is currently working hard to complete a graduate level text book entitled "Absorption Line Spectroscopy of Cosmological Sources" to be published in the Astrophysics Series of Cambridge University Press. His favorite topics in the class room are "Life in the Universe" and "Human Space Flight".

His research group studies galaxy evolution in the "inverse" using the technique of quasar absorption lines. We use the Keck, Subaru, and Very Large Telescopes to obtain the high resolution spectra of the quasars. We decode the complex and beautiful patterns of missing light (absorption lines) in these spectra and then go out and find the intervening galaxies hosting the absorbing gas. We then study the morphology and sky orientations of these galaxies out to redshifts of 0.5-1.0 in detail with the Hubble Space Telescope. We are testing to see if the large extended halos around galaxies, which can be 10 times larger than the stellar disks, are dynamically coupled to the galaxies or are an interface with the cosmic web structures of the intergalactic medium.

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