TheHerschel -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 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 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 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 µm images. The 1σ noise for source detection, including both confusion and instrumental noise, is 7.4, 9.4 and 10.2 mJy at 250, 350 and 500 µm. Our catalogue includes 120230 sources in total, with 113995, 46209 and 11011 sources detected at > 4σ at 250, 350 and 500 µm. The catalogue contains detections at > 3σ at 100 and 160 µm 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 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.

The Herschel Bright Sources (HerBS): sample definition and SCUBA-2 observations

“…The H-ATLAS survey used the PACS (Poglitsch et al 2010) and SPIRE (Griffin et al 2010) instruments on the Herschel Space Observatory to observe the North and South Galactic Pole Fields and three equatorial fields to a 1σ sensitivity of 5.2 mJy at 250 µm to 6.8 mJy at 500 µm, although the noise varies per source (Valiante et al 2016). The three equatorial fields overlap with the Galaxy And Mass Assembly (GAMA) fields 9, 12 and 15 hours, and from here on we adopt this naming convention for the equatorial fields (Driver et al 2011;Liske et al 2015).…”

“…We initially selected the HerBS sample from the H-ATLAS point-source catalogues (Valiante et al 2016), who extracted the flux densities at the 250 µm position, and used this position for flux extraction at 350 and 500 µm. The flux densities in the catalogues are not de-boosted, however the flux boosting is negligible compared to the flux uncertainty; around 1 per cent at 80 mJy, and diminishing for increasing flux density, as can be seen in Table 6 of Valiante et al (2016).…”

“…The flux densities in the catalogues are not de-boosted, however the flux boosting is negligible compared to the flux uncertainty; around 1 per cent at 80 mJy, and diminishing for increasing flux density, as can be seen in Table 6 of Valiante et al (2016). We estimated the redshift of each source by fitting a source template to the 250, 350 and 500 µm flux densities (Pearson et al 2013).…”

“…Flat-fields probe the responsivity of individual bolometers, and are derived from the bolometer's response to the resistance heaters, which are located next to each bolometer. Reading from the left, the columns are: Column 1 -name of field; Column 2 and 3 -The location of the centre of the field; Column 4 and 5 -The approximate dimensions of the field; Column 6 -The surface area from the final maps (Valiante et al 2016); Column 7 -The number of final HerBS sources in each field; Column 8 -The surface density of HerBS sources per field.…”

“…The H-ATLAS survey (Herschel Astrophysical Terahertz Large Area Survey - Eales et al 2010;Valiante et al 2016) is one of the largest legacies of Herschel. This survey observed a total of 616.4 square degrees over five fields in five wavebands.…”