Submillimeter Galaxy Number Counts and Magnification by Galaxy Clusters

TL;DR

This paper introduces an analytical model that explains galaxy number counts in submillimeter and millimeter surveys by considering a high-redshift galaxy population magnified by galaxy clusters, matching observed data.

Contribution

The model uniquely combines a single high-redshift galaxy population with gravitational lensing effects to reproduce observed number counts across multiple surveys.

Findings

The model successfully reproduces observed counts from BLAST, SCUBA, AzTEC, and SPT surveys.

High magnifications by galaxy clusters explain the most luminous galaxies detected.

Most submillimeter galaxies at wavelengths >500 micron are at redshifts >2.

Abstract

We present an analytical model which reproduces measured galaxy number counts from surveys in the wavelength range of 500 micron to 2 mm. The model involves a single high-redshift galaxy population with a Schechter luminosity function which has been gravitationally lensed by galaxy clusters in the mass range 10^13 to 10^15 Msun. This simple model reproduces both the low flux and the high flux end of the number counts reported by the BLAST, SCUBA, AzTEC and the SPT surveys. In particular, our model accounts for the most luminous galaxies detected by SPT as the result of high magnifications by galaxy clusters (magnification factors of 10-30). This interpretation implies that submillimeter and millimeter surveys of this population may prove to be a useful addition to ongoing cluster detection surveys. The model also implies that the bulk of submillimeter galaxies detected at wavelengths larger than 500 micron lie at redshifts greater than 2.