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Session 3 - Source Surveys, Galaxy Surveys, Distance Scale I.
Display session, Wednesday, January 07
Statistical analysis of the unresolved light in the Hubble Deep Field (HDF) strongly constrains possible sources of the optical Extragalactic Background Light (EBL). We estimate the auto, cross, and color correlations of the ``sky'' that remains after masking I<30 objects detected in the HDF. Auto and cross correlations in the F606W and F814W bandpasses are well fitted by a power law ømega(\theta)=C(\theta)/øverlinemu^2\sim 10^-6(\theta/1'')^-0.6. This measurement yields the most stringent limits to date on small-scale structure in the night sky; analysis of shallower imaging would be dominated by galaxies now detected by the HDF. If we treat the HDF correlations as a firm upper limit on the true EBL fluctuations, then we obtain a constraint on possible populations of undetected objects, by requiring that their surface brightness profiles not overproduce correlations in the unresolved sky. With this constraint, only a confusion-limited population of extremely low surface brightness objects could make a contribution to the EBL comparable to the flux contributed by detected faint galaxies. Diffuse intergalactic light clustered similarly to faint galaxies could explain some of the observed signal. These results suggest that we have already detected the sources of the majority of the optical EBL.
Program listing for Wednesday