The Herschel-ATLAS Data Release 1 Paper I: Maps, Catalogues and Number Counts

TL;DR

This paper presents the first major data release from the Herschel-ATLAS survey, including maps and catalogues of over 120,000 sources across five infrared bands, with detailed analysis of source detection, completeness, and counts.

Contribution

It provides the first large-area Herschel survey data release with comprehensive source catalogues, noise estimates, and a novel method for true source count determination.

Findings

Catalogues include over 120,000 sources detected at >4-sigma in SPIRE bands.

Survey noise levels are 7.4-10.2 mJy at 250-500 um.

H-ATLAS source counts are consistent with the deeper HerMES survey.

Abstract

We present the first major data release of the largest single key-project in area carried out in open time with the Herschel Space Observatory. The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 600 deg^2 in five photometric bands - 100, 160, 250, 350 and 500 um - with the PACS and SPIRE cameras. In this paper and a companion paper (Bourne et al. 2016) we present the survey of three fields on the celestial equator, covering a total area of 161.6 deg^2 and previously observed in the Galaxy and Mass Assembly (GAMA) spectroscopic survey. This paper describes the Herschel images and catalogues of the sources detected on the SPIRE 250 um images. The 1-sigma noise for source detection, including both confusion and instrumental noise, is 7.4, 9.4 and 10.2 mJy at 250, 350 and 500 um. Our catalogue includes 120230 sources in total, with 113995, 46209 and 11011 sources detected at >4-sigma at 250, 350 and 500 um. The catalogue contains detections at >3-sigma at 100 and 160 um for 4650 and 5685 sources, and the typical noise at these wavelengths is 44 and 49 mJy. We include estimates of the completeness of the survey and of the effects of flux bias and also describe a novel method for determining the true source counts. The H-ATLAS source counts are very similar to the source counts from the deeper HerMES survey at 250 and 350 um, with a small difference at 500 um. Appendix A provides a quick start in using the released datasets, including instructions and cautions on how to use them.