The large apex bolometer camera survey of the extended Chandra deep field south

Abstract

We present a sensitive 870 μm survey of the Extended Chandra Deep Field South (ECDFS) combining 310 hr of observing time with the Large Apex BOlometer Camera (LABOCA) on the APEX telescope. The LABOCA ECDFS Submillimetre Survey (LESS) covers the full 30′ × 30′ field size of the ECDFS and has a uniform noise level of σ870 μm ≈ 1.2 mJy beam -1. LESS is thus the largest contiguous deep submillimeter survey undertaken to date. The noise properties of our map show clear evidence that we are beginning to be affected by confusion noise. We present a catalog of 126 submillimeter galaxies (SMGs) detected with a significance level above 3.7σ, at which level we expect five false detections given our map area of 1260 arcmin2. The ECDFS exhibits a deficit of bright SMGs relative to previously studied blank fields but not of normal star-forming galaxies that dominate the extragalactic background light (EBL). This is in line with the underdensities observed for optically defined high redshift source populations in the ECDFS (BzKs, DRGs, optically bright active galactic nucleus, and massive K-band-selected galaxies). The differential source counts in the full field are well described by a power law with a slope of α = -3.2, comparable to the results from other fields. We show that the shape of the source counts is not uniform across the field. Instead, it steepens in regions with low SMG density. Towards the highest overdensities we measure a source-count shape consistent with previous surveys. The integrated 870 μm flux densities of our source-count models down to S 870 μm = 0.5 mJy account for >65% of the estimated EBL from COBE measurements. We have investigated the clustering of SMGs in the ECDFS by means of a two-point correlation function and find evidence for strong clustering on angular scales <1′ with a significance of 3.4σ. Assuming a power-law dependence for the correlation function and a typical redshift distribution for the SMGs we derive a characteristic angular clustering scale of θ0 = 14″ ± 7″ and a spatial correlation length of r 0 = 13 ± 6 h -1 Mpc. © 2009. The American Astronomical Society. All rights reserved.