The<i>Herschel</i> -ATLAS data release 1 – I. Maps, catalogues and number counts

Abstract

We present the first major data release of the largest single key-project in area car- ried out in open time with the Herschel Space Observatory. The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 600 deg2 in five photometric bands - 100, 160, 250, 350 and 500 μm - 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 deg2 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 μm images. The 1 noise for source detection, including both confusion and instrumental noise, is 7.4, 9.4 and 10.2mJy at 250, 350 and 500 μm. Our catalogue includes 120230 sources in total, with 113995, 46209 and 11011 sources detected at &gt; 4 at 250, 350 and 500 μm. The catalogue contains detections at &gt; 3 at 100 and 160 μm for 4650 and 5685 sources, and the typical noise at these wavelengths is 44 and 49mJy. 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 μm, with a small difference at 500 μm. Appendix A provides a quick start in using the released datasets, including instructions and cautions on how to use them.