PI: Yujin Yang, University of Arizona, email@example.com
Address: Steward Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA
CoI: Ann Zabludoff, University of Arizona
CoI: Romeel Dav\mathrm\acutee, University of Arizona
CoI: Daniel Eisenstein, University of Arizona
Title: How Do Galaxies Get Their Baryons?
Abstract: Galaxies obtain material to form their stars from the intergalactic medium, but direct observations of such accretion do not yet exist. Motivated by our theoretical work, we propose to search for two major cooling lines (\lya and \heii) from the gas surrounding forming galaxies at z=2.3 to identify and study the process of gas accretion. The best candidates for gas-accreting galaxies are extended \lya\ sources, the so-called \lya blobs. However, there is controversy over their true origin(s) because 1) there is no large, spectroscopic sample of \lya blobs and 2) there are many intrinsic ambiguities in interpreting \lya emission. To resolve these issues, we plan a two- stage program. First, we propose to obtain a new sample of \lya blobs from very deep narrow-band imaging using KPNO 4m+MOSAIC and our custom- made filter. Second, having identified these \lya blobs, we will propose to target them again to make the first detection of \heha, a line better suited than \lya to distinguish gas-accreting forming galaxies from other sources of extended \lya emission such as superwinds, AGNs, and star formation. A blind search for \lya blobs is risky (as noted by the 2006B TAC), but the blank field survey we propose will provide the first \emphunbiased constraints on the number density and environments of \lya blobs at z ~ 2. Combined with the survey time awarded us in the 2006B semester, the additional allocation discussed here will allow us to complete our survey of the Chandra Deep Fields with meaningful statistics.
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