Optical and infrared backgrounds from the Hubble Space Telescope.

摘要

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 optical and infrared wavelengths, 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. The fluctuations and their colors may also 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 as well as undetected galaxies. We then present an analysis of background fluctuations in observations of the HUDF, the GOODS field, and the CANDELS fields obtained with WFC3. The fluctuation signal provides a constraint on the slope of galaxy counts fainter than the levels of individual detection, as well as their typical angular sizes. The color dependence of the fluctuations provides a constraint on the redshift distribution of these very faint sources. The spatial and spectral information from these anisotropies, even in their non-detection, provide valuable information about the era of reionization, when the first stars and galaxies formed. Via various analysis tools such as power spectra and P(D) fitting, best-fit models to faint sources can be obtained.