Background Fluctuations and Galaxy Counts with HST
Johns Hopkins University
The sum total of the energy released by the earliest era of star formation should show up today within the diffuse extragalactic background light (EBL), its signature peaking in the near-infrared. There is considerable controversy over estimates of the average EBL per steradian at wavelengths longward of 1µm, over measurements of background fluctuations, and over the interpretation of the measurements. Resolving this controversy is important because the EBL constrains the history of galaxy evolution, and because the near-infrared fluctuations may contain important information about Population III stars and the earliest era of star formation. We compare number counts from recent galaxy surveys, correcting for their differing passbands. With some assumptions about galaxy sizes and surface-brightness profiles, we account for the light missed in standard photometric estimates, integrating the resulting corrected counts to estimate the total EBL due to resolved galaxies. We then present an analysis of background fluctuations in observations of the UDF fields obtained with WFC3. The fluctuation signal provides a constraint on the slope of galaxy counts fainter than the levels of individual detection.
Date: Friday, 11 March 2011 Time: 12:00 Where: Université Laval Pavillon Alexandre-Vachon, local 1661 Contact: Serge Pinault