The Herschel-ATLAS: a sample of 500{\mu}m-selected lensed galaxies over 600 square degrees

TL;DR

This paper presents a catalog of 80 candidate strongly lensed galaxies selected at 500μm over 600 square degrees, confirming 20 cases and analyzing their properties to facilitate detailed follow-up studies of high-redshift star-forming galaxies.

Contribution

It provides the first large sample of 500μm-selected lensed galaxy candidates with confirmed lensing status and redshift estimates, enabling new insights into galaxy evolution.

Findings

Confirmed 20 strong lensing cases among 80 candidates.

Median redshifts are z_L=0.6 for lenses and z_S=2.5 for sources.

Number counts agree with theoretical models for magnification 10-20.

Abstract

We present a sample of 80 candidate strongly lensed galaxies with flux density above 100mJy at 500{\mu}m extracted from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), over an area of 600 square degrees. Available imaging and spectroscopic data allow us to confirm the strong lensing in 20 cases and to reject it in one case. For other 8 objects the lensing scenario is strongly supported by the presence of two sources along the same line of sight with distinct photometric redshifts. The remaining objects await more follow-up observations to confirm their nature. The lenses and the background sources have median redshifts z_L = 0.6 and z_S = 2.5, respectively, and are observed out to z_L = 1.2 and z_S = 4.2. We measure the number counts of candidate lensed galaxies at 500{\mu}m and compare them with theoretical predictions, finding a good agreement for a maximum magnification of the background sources in the range 10-20. These values are consistent with the magnification factors derived from the lens modelling of individual systems. The catalogue presented here provides sub- mm bright targets for follow-up observations aimed at exploiting gravitational lensing to study with un-precedented details the morphological and dynamical properties of dusty star forming regions in z >~ 1.5 galaxies.