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Theoretical Astrophysics and General Relativity Seminar: Measurement of the extragalactic gamma-ray background with the Fermi-LAT / Searching for satellite galaxies of the Milky Way in the Dark Energy Survey

Event Type
Department of Physics
464 Loomis
Feb 12, 2014   12:00 pm  
Keith Bechtol (U of Chicago)
Milton Ruiz
Originating Calendar
Physics - Astrophysics, Gravitation, and Cosmology Seminar

Two topics. First, I will discuss an updated measurement of the extragalactic gamma-ray background (EGB) intensity with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). The EGB is the superposition of all sources of high-energy radiation from the edge of our Galaxy to the edge of the observable Universe. Only a fraction of the total EGB intensity has been resolved into individual sources --- the remaining extragalactic emissions that are either too faint or too diffuse to be individually resolved are blurred together into a quasi-isotropic component. Improvements in event selection and particle background characterization, better understanding of diffuse Galactic foreground emission, and a longer data accumulation of 50 months allow for a measurement of the total EGB spectrum (resolved extragalactic sources + isotropic component) now covering the energy range from 0.1 to 820 GeV.

The second theme is the search for ultra-faint satellite galaxies of the Milky Way in the Dark Energy Survey (DES). Ultra-faint galaxies are exceptional their large mass-to-light ratios (>1000 within the half-light radius in some cases) and old, metal-poor stellar populations. The DES is an ongoing optical imaging survey in 5 photometric filters which will cover 5000 square degrees of the relatively unexplored southern hemisphere over the next 5 years. I will describe a matched-filter maximum-likelihood algorithm to identify and characterize ultra-faint galaxies in the DES footprint, and the implications of finding new Milky Way satellites as targets for indirect dark matter searches.

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