University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Thursday, September 17th 2015
Speaker: Betsey Adams, Astronomy, NL
Subject: Probing the extreme edges of galaxy formation with ALFALFA

The ALFALFA HI survey has detected rare but extremely interesting HI sources that probe the extreme limits of systems that are able to form stars. These sources include the ultra-compact high velocity clouds (UCHVCs), some of which may represent gas-rich but (nearly) starless Local Group galaxies; the low-mass gas-rich SHIELD dwarf galaxies; and the "Almost-Dark" HI sources, which are clearly extragalactic HI detections that have no discernible optical counterpart in extant optical surveys. I will discuss these different source populations and how they are interconnected, highlighting one system, AGC 226067, that bridges the three categories. I will also focus in particular on the UCHVCs as candidate Local Group galaxies, highlighting one particular source, AGC 198606, for which HI observations with WSRT and deep WIYN/ODI optical imaging strongly support the hypothesis that it represents gas in a nearby dark matter halo.

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