Detecting Faint Galaxies by Stacking at 24 m
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We stack Spitzer 24 m images for 7000 galaxies with 0.1 z < 1 in the Chandra Deep Field South to probe the thermal dust emission in low-luminosity galaxies over this redshift range. Through stacking, we can detect mean 24 m fluxes that are more than an order of magnitude below the individual detection limit. We find that the correlations for low- and moderate-luminosity galaxies between the average LIR/LUV and rest-frame B-band luminosity, and between the star formation rate (SFR) and LIR/LUV, are similar to those in the local universe. This verifies that oft-used assumption in deep UV/optical surveys that the dust obscuration - SFR relation for galaxies with SFR 20 M yr-1 varies little with epoch. We have used this relation to derive the cosmic IR luminosity density from z = 1 to z = 0.1. The results also demonstrate directly that little of the bolometric luminosity of the galaxy population arises from the faint end of the luminosity function, indicating a relatively flat faint-end slope of the IR luminosity function with a power-law index of 1.2 0.3. 2006. The American Astronomical Society. All rights reserved.