2010ApJ...719..483G

Using the 330 hr ESO-MPG 870 µm survey of the Extended Chandra Deep Field South (ECDF-S) obtained with the Large Apex BOlometer CAmera (LABOCA) on the Atacama Pathfinder EXperiment (APEX), we have carried out a stacking analysis at submillimeter (submm) wavelengths of a sample of 8266 near-infra-red (near-IR) selected (K_vega≤ 20) galaxies, including 893 BzK galaxies, 1253 extremely red objects (EROs), and 737 distant red galaxies (DRGs), selected from the Multi-wavelength Survey by Yale-Chile (MUSYC). We measure average 870 µm fluxes of 0.22±0.01 mJy (22.0σ), 0.48±0.04 mJy (12.0σ), 0.39±0.03 mJy (13.0σ), and 0.43±0.04 mJy (10.8σ) for the K_vega≤ 20, BzK, ERO, and DRG samples, respectively. For the BzK, ERO, and DRG sub-samples, which overlap to some degree and are likely to be at z =~ 1-2, this implies an average far-IR luminosity of ~(1-5)x10¹¹ L_☉ and star formation rate (SFR) of ∼20-90 M_☉. Splitting the BzK galaxies into star-forming (sBzK) and passive (pBzK) galaxies, the former is significantly detected (0.50±0.04 mJy, 12.5σ) while the latter is only marginally detected (0.34±0.10 mJy, 3.4σ), thus confirming that the sBzK and pBzK criteria to some extent select obscured, star-forming, and truly passive galaxies, respectively. The K_vega≤ 20 galaxies are found to contribute 7.27±0.34 Jy/deg2 (16.5%±5.7%) to the 870 µm extragalactic background light (EBL). sBzK and pBzK galaxies contribute 1.49 ±0.22 Jy/deg2 (3.4%±1.3%) and 0.20±0.14 Jy/deg2 (0.5%±0.3%) to the EBL. We present the first delineation of the average submm signal from the K_vega≤ 20 selected galaxies and their contribution to the submm EBL as a function of (photometric) redshift, and find a decline in the average submm signal (and therefore IR luminosity and SFR) by a factor ∼2-3 from z ∼ 2 to z ∼ 0. This is in line with a cosmic star formation history in which the star formation activity in galaxies increases significantly at z ≳ 1. A linear correlation between the average 24 µm and 870 µm flux densities is found for the K_vega≤ 20 galaxies with 24 µm fluxes ≲350 µJy (corresponding to L_IR=~ 1.5x10¹² L_☉at z =~ 2), while at higher 24 µm fluxes there is no correlation. This behavior suggests that star formation, and not active galactic nuclei (AGNs), is in general responsible for the bulk of the mid-IR emission of L_IR≲ 1.5x10¹² L_☉systems, while in more luminous systems the AGN makes a significant contribution to the 24 µm emission. By mapping the stacked 870 µm signal across the B - z versus z - K diagram we have confirmed the ability of the sBzK selection criterion to select star-forming galaxies at z > 1, although our analysis suggests that the subset of sBzK galaxies which are also EROs are responsible for >80% of the submm emission from the entire sBzK population.