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Register a new userThe Herschel-ATLAS Data Release 1 Paper I: Maps, Catalogues and Number Counts
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Elisabetta Valiante
Publication date
2016
fields
Physics
and research's language is
English
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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.
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This paper is the second in a pair of articles presenting data release 1 (DR1) of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS), the largest single open-time key project carried out with the Herschel Space Observatory. The H-ATLAS is a wide-area imaging survey carried out in five photometric bands at 100, 160, 250, 350 and 500$mu$m covering a total area of 600deg$^2$. In this paper we describe the identification of optical counterparts to submillimetre sources in DR1, comprising an area of 161 deg$^2$ over three equatorial fields of roughly 12$^circ$x4.5$^circ$ centred at 9$^h$, 12$^h$ and 14.5$^h$ respectively. Of all the H-ATLAS fields, the equatorial regions benefit from the greatest overlap with current multi-wavelength surveys spanning ultraviolet (UV) to mid-infrared regimes, as well as extensive spectroscopic coverage. We use a likelihood-ratio technique to identify SDSS counterparts at r<22.4 for 250-$mu$m-selected sources detected at $geq$ 4$sigma$ ($approx$28mJy). We find `reliable counterparts (reliability R$geq$0.8) for 44,835 sources (39 per cent), with an estimated completeness of 73.0 per cent and contamination rate of 4.7 per cent. Using redshifts and multi-wavelength photometry from GAMA and other public catalogues, we show that H-ATLAS-selected galaxies at $z<0.5$ span a wide range of optical colours, total infrared (IR) luminosities, and IR/UV ratios, with no strong disposition towards mid-IR-classified AGN in comparison with optical selection. The data described herein, together with all maps and catalogues described in the companion paper (Valiante et al. 2016), are available from the H-ATLAS website at www.h-atlas.org.
We present a catalogue of nearly 3,000 submillimetre sources detected at 850um over ~5 square degrees surveyed as part of the James Clerk Maxwell Telescope (JCMT) SCUBA-2 Cosmology Legacy Survey (S2CLS). This is the largest survey of its kind at 850um, probing a meaningful cosmic volume at the peak of star formation activity and increasing the sample size of submillimetre galaxies selected at 850um by an order of magnitude. We describe the wide 850um survey component of S2CLS, which covers the key extragalactic survey fields: UKIDSS-UDS, COSMOS, Akari-NEP, Extended Groth Strip, Lockman Hole North, SSA22 and GOODS-North. The average 1-sigma depth of S2CLS is 1.2 mJy/beam, approaching the SCUBA-2 850um confusion limit, which we determine to be ~0.8 mJy/beam. We measure the single dish 850um number counts to unprecedented accuracy, reducing the Poisson errors on the differential counts to approximately 4% at S_850~3mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5-1 degree scales are generally within 50% of the S2CLS mean for S_850>3mJy, with scatter consistent with the Poisson and estimated cosmic variance uncertainties, although there is a marginal (2-sigma) density enhancement in the GOODS-North field. The observed number counts are in reasonable agreement with recent phenomenological and semi-analytic models. Finally, the large solid angle of S2CLS allows us to measure the bright-end counts: at S_850>10mJy there are approximately ten sources per square degree, and we detect the distinctive up-turn in the number counts indicative of the detection of local sources of 850um emission and strongly lensed high-redshift galaxies. Here we describe the data collection and reduction procedures and present calibrated maps and a catalogue of sources; these are made publicly available.
The {it Herschel} Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 660 deg$^2$ with the PACS and SPIRE cameras in five photometric bands: 100, 160, 250, 350 and 500mic. This is the second of three papers describing the data release for the large fields at the south and north Galactic poles (NGP and SGP). In this paper we describe the catalogues of far-infrared and submillimetre sources for the NGP and SGP, which cover 177 deg$^2$ and 303 deg$^2$, respectively. The catalogues contain 153,367 sources for the NGP field and 193,527 sources for the SGP field detected at more than 4$sigma$ significance in any of the 250, 350 or 500mic bands. The source detection is based on the 250mic map, and we present photometry in all five bands for each source, including aperture photometry for sources known to be extended. The rms positional accuracy for the faintest sources is about 2.4 arc seconds in both right ascension and declination. We present a statistical analysis of the catalogues and discuss the practical issues -- completeness, reliability, flux boosting, accuracy of positions, accuracy of flux measurements -- necessary to use the catalogues for astronomical projects.
We present the largest submillimeter images that have been made of the extragalactic sky. The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 660 deg$^2$ with the PACS and SPIRE cameras in five photometric bands: 100, 160, 250, 350, and 500{mu}m. In this paper we present the images from our two largest fields which account for ~75% of the survey. The first field is 180.1 deg$^2$ in size centered on the North Galactic Pole (NGP) and the second field is 317.6 deg$^2$ in size centered on the South Galactic Pole. The NGP field serendipitously contains the Coma cluster. Over most (~80%) of the images, the pixel noise, including both instrumental noise and confusion noise, is approximately 3.6, and 3.5 mJy/pix at 100 and 160{mu}m, and 11.0, 11.1 and 12.3 mJy/beam at 250, 350 and 500{mu}m, respectively, but reaches lower values in some parts of the images. If a matched filter is applied to optimize point-source detection, our total 1{sigma} map sensitivity is 5.7, 6.0, and 7.3 mJy at 250, 350, and 500{mu}m, respectively. We describe the results of an investigation of the noise properties of the images. We make the most precise estimate of confusion in SPIRE maps to date finding values of 3.12+/-0.07, 4.13+/-0.02 and 4.45+/-0.04 mJy/beam at 250, 350, and 500{mu}m in our un-convolved maps. For PACS we find an estimate of the confusion noise in our fast-parallel observations of 4.23 and 4.62 mJy/beam at 100 and 160{mu}m. Finally, we give recipes for using these images to carry out photometry, both for unresolved and extended sources.
We describe data release 3 (DR3) of the Galaxy And Mass Assembly (GAMA) survey. The GAMA survey is a spectroscopic redshift and multi-wavelength photometric survey in three equatorial regions each of 60.0 deg^2 (G09, G12, G15), and two southern regions of 55.7 deg^2 (G02) and 50.6 deg^2 (G23). DR3 consists of: the first release of data covering the G02 region and of data on H-ATLAS sources in the equatorial regions; and updates to data on sources released in DR2. DR3 includes 154809 sources with secure redshifts across four regions. A subset of the G02 region is 95.5% redshift complete to r<19.8 over an area of 19.5 deg^2, with 20086 galaxy redshifts, that overlaps substantially with the XXL survey (X-ray) and VIPERS (redshift survey). In the equatorial regions, the main survey has even higher completeness (98.5%), and spectra for about 75% of H-ATLAS filler targets were also obtained. This filler sample extends spectroscopic redshifts, for probable optical counterparts to H-ATLAS sub-mm sources, to 0.8 mag deeper (r<20.6) than the GAMA main survey. There are 25814 galaxy redshifts for H-ATLAS sources from the GAMA main or filler surveys. GAMA DR3 is available at the survey website (www.gama-survey.org/dr3/).
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