SXDF-ALMA 2 arcmin$^2$ Deep Survey: 1.1-mm Number Counts

TL;DR

This study uses ALMA to measure faint 1.1-mm galaxy counts in the SXDF, confirming previous results and estimating that about 40% of the background light at this wavelength is resolved into individual sources.

Contribution

First ALMA-based measurement of 1.1-mm number counts in the SXDF, reducing bias from source clustering and serendipitous detection methods.

Findings

Number counts are consistent with previous studies within errors.

Approximately 40% of the 1.1-mm background light is resolved at fluxes > 0.2 mJy.

Serendipitous detections do not significantly bias number counts.

Abstract

We report 1.1 mm number counts revealed with the Atacama Large Millimeter/submillimeter Array (ALMA) in the Subaru/XMM-Newton Deep Survey Field (SXDF). The advent of ALMA enables us to reveal millimeter-wavelength number counts down to the faint end without source confusion. However, previous studies are based on the ensemble of serendipitously-detected sources in fields originally targeting different sources and could be biased due to the clustering of sources around the targets. We derive number counts in the flux range of 0.2-2 mJy by using 23 (>=4sigma) sources detected in a continuous 2.0 arcmin$^2$ area of the SXDF. The number counts are consistent with previous results within errors, suggesting that the counts derived from serendipitously-detected sources are not significantly biased, although there could be field-to-field variation due to the small survey area. By using the best-fit function of the number counts, we find that ~40% of the extragalactic background light at 1.1 mm is resolved at S(1.1mm) > 0.2 mJy.