Evidence for a Population of High-Redshift Submillimeter Galaxies from Interferometric Imaging

TL;DR

This study used interferometric imaging to identify and analyze a sample of high-redshift submillimeter galaxies, revealing distinct properties of radio-dim sources indicating they are very dusty starbursts at higher redshifts.

Contribution

First high-resolution interferometric imaging of a flux-limited submillimeter galaxy sample, revealing differences between radio-bright and radio-dim populations and their likely high-redshift, dusty starburst nature.

Findings

Radio-dim sources have higher submillimeter-to-radio flux ratios.

Radio-dim sources have lower IRAC fluxes and are undetected at 24um.

Size constraints suggest they are similar to local ultraluminous infrared galaxies.

Abstract

We have used the Submillimeter Array to image a flux limited sample of seven submillimeter galaxies, selected by the AzTEC camera on the JCMT at 1.1 mm, in the COSMOS field at 890um with 2" resolution. All of the sources - two radio-bright and five radio-dim - are detected as single point-sources at high significance (> 6\sigma), with positions accurate to 0.2" that enable counterpart identification at other wavelengths observed with similarly high angular resolution. All seven have IRAC counterparts, but only two have secure counterparts in deep HST/ACS imaging. As compared to the two radio-bright sources in the sample, and those in previous studies, the five radio-dim sources in the sample (1) have systematically higher submillimeter-to-radio flux ratios, (2) have lower IRAC 3.6-8.0um fluxes, and (3) are not detected at 24um. These properties, combined with size constraints at 890um (\theta < 1.2"), suggest that the radio-dim submillimeter galaxies represent a population of very dusty starbursts, with physical scales similar to local ultraluminous infrared galaxies, and an average redshift higher than radio-bright sources.