Contribution to Unresolved Infrared Fluctuations from Dwarf Galaxies at Redshifts of 2-3
Abstract
In order to understand the origin of clustered anisotropies detected in Spitzer IRAC images, we stack the Spitzer IRAC/Great Observatories Origins Deep Survey (GOODS) images at pixel locations corresponding to faint, z_{AB}~27 mag, optical sources with no obvious IR counterparts. We obtain a stacked median flux of 130+/-5 nJy at 3.6 microns. We also use the wealth of multi-wavelength data in GOODS to measure the stacked spectrum of these sources from the ultraviolet to near-infrared bands. The median flux spectrum is consistent with a L<0.03 L_{*,UV} galaxy population at z~2.5. They produce a 3.6 micron absolute background intensity between 0.1 and 0.35 nW m^{-2} sr^{-1} and the clustered IR light could account for ~30-50% of fluctuation power in the IR background at 4 arcminute angular scales. Although the redshift distribution of these sources is unknown, they appear to contain between 5-20% of the co-moving stellar mass density at z~2.5.Keywords
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