ALMA CENSUS OF FAINT 1.2 mm SOURCES DOWN TO ∼ 0.02 mJy: EXTRAGALACTIC BACKGROUND LIGHT AND DUST-POOR, HIGH-z GALAXIES

Abstract

We present statistics of 133 faint 1.2mm continuum sources detected in about 120 deep Atacama Large Millimeter/submillimeter Array (ALMA) pointing data that include all the archival deep data available by 2015 June. We derive number counts of 1.2 mm continuum sources down to 0.02 mJy partly with the assistance of gravitational lensing, and find that the total integrated 1.2 mm flux of the securely identified sources is 22.9 5.6 6.7 -+ Jy deg−2 whichcorresponds to 104 % 25 31 -+ of the extragalactic background light (EBL) measured by Cosmic Background Explorer observations. These results suggest that the major 1.2 mm EBL contributors are sources with 0.02 mJy, and that very faint 1.2 mm sources with 0.02 mJy contribute negligibly to the EBL with the possible flattening and/or truncation of number counts in this very faint flux regime. To understand the physical origin of our faint ALMA sources, we measure the galaxy bias b g by the counts-in-cells technique, and place a stringent upper limit of b g <3.5 that is not similar to b g values of massive distant red galaxies and submillimeter galaxies but comparable to those of UV-bright, star-forming BzK galaxies (sBzKs) and Lymanbreak galaxies (LBGs). Moreover, in the optical and near-infrared (NIR) deep fields, we identify optical-NIR counterparts for 59% of our faint ALMA sources, the majority of which have luminosities, colors, and the IRX-β relation the same as sBzKs and LBGs. We thus conclude that about a half of our faint ALMA sources are dust-poor, high-z galaxies as known as sBzKs and LBGs in optical studies, and that these faint ALMA sources are not miniature (U)LIRGs simply scaled down with the infrared brightness.

SXDF–ALMA 2-arcmin2 deep survey: 1.1-mm number counts

“…The best-fit parameters are summarized in Table 2. The power law slopes are consistent with those of Fujimoto et al (2016). Table 2.…”

“…We also do not use the faint end of number counts (S < 0.1 mJy) by Fujimoto et al (2016), where the counts are derived by including gravitationally lensed sources to avoid uncertainty from the magnification correction. The best-fit parameters are summarized in Table 2.…”

“…Atacama Large Millimeter/submillimeter Array (ALMA) enables us to explore the flux regime more than an order of magnitude fainter than those detected in previous single-dish surveys because of its high sensitivity and high angular resolution. ALMA has probed the faint end of the number counts and more than half of the EBL has been resolved in previous studies (Hatsukade et al 2013;Ono et al 2014;Carniani et al 2015;Fujimoto et al 2016). However, these studies are based on the ensemble of serendipitously-detected sources in fields originally targeting different sources, and the number counts obtained in those fields could be biased due to the clustering of sources around the targets or sidelobes caused by bright targets.…”

Faint Submillimeter Galaxies Identified Through Their Optical/Near-Infrared Colors. I. Spatial Clustering and Halo Masses

“…Deep ALMA imaging taken for the primary targets of interestare sometimes deep enough to make serendipitous faint SMG detections (Hatsukade et al 2013;Hodge et al 2013;Ono et al 2014;Carniani et al 2015;Oteo et al 2015;Simpson et al 2015;Fujimoto et al 2016). However, so far, such studies have only surveyed relatively small areas and the clustering properties of faint SMGs are neither well constrained nor unbiased (Ono et al 2014;Fujimoto et al 2016).…”

The Hawaii SCUBA-2 Lensing Cluster Survey: Radio-detected Submillimeter Galaxies in the HST Frontier Fields

“…Imaging of massive galaxy cluster fields is one way to reach fainter detection limits because background sources are gravitationally magnified. Previous studies have constructed number counts (e.g., Smail et al 1997Smail et al , 2002Cowie et al 2002;Knudsen et al 2008;Johansson et al 2011;Chen et al 2013aChen et al , 2013bFujimoto et al 2016;Hsu et al 2016) or detected individual sources (Watson et al 2015;González-López et al 2017) using submillimeter/millimeter observations of cluster fields.…”