Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts

Abstract

We present the first results from a confusion‐limited map of the Great Observatories Origins Deep Survey‐South (GOODS‐S) taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment. We imaged a field to a 1σ depth of 0.48–0.73 mJy beam−1, making this one of the deepest blank‐field surveys at mm‐wavelengths ever achieved. Although by traditional standards our GOODS‐S map is extremely confused due to a sea of faint underlying sources, we demonstrate through simulations that our source identification and number counts analyses are robust, and the techniques discussed in this paper are relevant for other deeply confused surveys. We find a total of 41 dusty starburst galaxies with signal‐to‐noise ratios S/N ≥ 3. 5 within this uniformly covered region, where only two are expected to be false detections, and an additional seven robust source candidates located in the noisier (1σ≈ 1 mJy beam−1) outer region of the map. We derive the 1.1 mm number counts from this field using two different methods: a fluctuation or “P(d)” analysis and a semi‐Bayesian technique and find that both methods give consistent results. Our data are well fit by a Schechter function model with . Given the depth of this survey, we put the first tight constraints on the 1.1 mm number counts at S1.1 mm= 0.5 mJy, and we find evidence that the faint end of the number counts at from various SCUBA surveys towards lensing clusters are biased high. In contrast to the 870 μm survey of this field with the LABOCA camera, we find no apparent underdensity of sources compared to previous surveys at 1.1 mm; the estimates of the number counts of SMGs at flux densities >1 mJy determined here are consistent with those measured from the AzTEC/SHADES survey. Additionally, we find a significant number of SMGs not identified in the LABOCA catalogue. We find that in contrast to observations at λ≤ 500 μm, MIPS 24 μm sources do not resolve the total energy density in the cosmic infrared background at 1.1 mm, demonstrating that a population of z≳ 3 dust‐obscured galaxies that are unaccounted for at these shorter wavelengths potentially contribute to a large fraction (∼2/3) of the infrared background at 1.1 mm.

ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: THE INFRARED EXCESS OF UV-SELECTED z = 2–10 GALAXIES AS A FUNCTION OF UV-CONTINUUM SLOPE AND STELLAR MASS

“…There are also five sources out of 122 (4%) followed up by the ALESS survey with ALMA (da Cunha et al 2015) with estimated stellar masses <10 9.75 M e which nevertheless show moderately high IR luminosities of ∼10 10.5 to ∼10 11.6 L e . Likewise, seven sources out of the 48 sources (15%) from the AzTEC/ASTE survey (Scott et al 2010), also identified based on their IR properties, have stellar masses below 10 9.75 M e . Additionally, from the Capak et al (2015) sample of ∼10 z = 5-6 galaxies, there is one source (HZ4) below our 10 9.75 M e threshold (stellar mass of  10 9.67 0.21 M e ), which nonetheless has a moderately high IR luminosity (10 11.13 L e ).…”

An Alma Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Source Catalog and Multiplicity

“…Even with the limited capabilities offered in Cycle 0, it has the resolution and sensitivity necessary to double the total number of interferometrically observed submillimeter sources in a matter of hours. We therefore used ALMA in Cycle 0 to observe a large sample of submillimeter galaxies in the Extended Chandra Deep Field South (ECDFS), a 30 × 30 field with deep, multi-wavelength coverage from the radio to the X-ray (Giacconi et al 2001;Giavalisco et al 2004;Lehmer et al 2005;Beckwith et al 2006;Luo et al 2008;Miller et al 2008;Weiß et al 2009;Devlin et al 2009;Scott et al 2010;Ivison et al 2010a;Miller et al 2013). The 126 submillimeter sources we target were previously detected in the LABOCA ECDFS Submillimeter Survey (LESS; Weiß et al 2009), the largest, most homogenous, and most sensitive blind 870 μm survey to date.…”

Multiple-component Decomposition from Millimeter Single-channel Data

“…The AzTEC/ASTE GOODS-S observations reported a 1σ depth of about 0.48−0.73 mJy beam −1 , which is below the estimated confusion background limit of 2 mJy beam −1 (Scott et al 2010). The confusion background is the sea of faint unresolved sources in the sky, creating an extended emission that can potentially bias detections below the confusion background limit (Hogg 2001).…”

“…For that, we revisit the AzTEC/ASTE GOODS-S survey, which is considered to be a blank field. For that reason, this survey has been extensively studied and used as a trial data set for extensions to the AzTEC pipeline (Scott et al 2010;Scott et al 2012;Downes et al 2012;Yun et al 2012). Although astrophysical foregrounds are not expected, these observations were certainly contaminated by bright atmospheric foregrounds.…”