Editorial

Monthly Notices of the Royal Astronomical Society

Maddox

et al. 2011

115

131

We present a technique to identify optical counterparts of 250‐μm‐selected sources from the Herschel–ATLAS survey. Of the 6621 250 μm > 32‐mJy sources in our science demonstration catalogue we find that ∼60 per cent have counterparts brighter than r = 22.4 mag in the Sloan Digital Sky Survey. Applying a likelihood ratio technique we are able to identify 2423 of the counterparts with a reliability R > 0.8. This is approximately 37 per cent of the full 250‐μm catalogue. We have estimated photometric redshifts for each of these 2423 reliable counterparts, while 1099 also have spectroscopic redshifts collated from several different sources, including the GAMA survey. We estimate the completeness of identifying counterparts as a function of redshift, and present evidence that 250‐μm‐selected Herschel–ATLAS galaxies have a bimodal redshift distribution. Those with reliable optical identifications have a redshift distribution peaking at z ≈ 0.25 ± 0.05, while submillimetre colours suggest that a significant fraction with no counterpart above the r‐band limit have z > 1. We also suggest a method for selecting populations of strongly lensed high‐redshift galaxies. Our identifications are matched to UV–NIR photometry from the GAMA survey, and these data are available as part of the Herschel–ATLAS public data release.

Section: Calculating the Likelihood Ratiomentioning

confidence: 80%

“…Studying these objects in detail is beyond the scope of this paper, but see e.g. Thompson et al, (2010) for a discussion of stellar sources in the Herschel –ATLAS and the identification of two candidate debris discs.…”

Section: Resultsmentioning

confidence: 99%

Herschel-ATLAS: counterparts from the ultraviolet-near-infrared in the science demonstration phase catalogue★

Smith

Monthly Notices of the Royal Astronomical Society

Maddox

et al. 2011

115

131

“…It is unlikely that stars are detected with SPIRE, unless they are post‐asymptotic giant branch, shrouded in dust or have debris discs (e.g. Thompson et al 2010). We have matched 12 SPIRE sources reliably to point‐like objects.…”

Section: Resultsmentioning

confidence: 99%

Herschel-ATLAS: VISTA VIKING near-infrared counterparts in the Phase 1 GAMA 9-h data^★

Fleuren

Sutherland

Monthly Notices of the Royal Astronomical Society

et al. 2012

We identify near‐infrared Ks‐band counterparts to Herschel Astrophysical Terahertz Large Area Survey (H‐ATLAS) submillimetre (submm) sources, using a preliminary object catalogue from the VISTA Kilo‐degree Infrared Galaxy (VIKING) survey. The submm sources are selected from the H‐ATLAS Phase 1 catalogue of the Galaxy and Mass Assembly 9‐h field, which includes all objects detected at 250, 350 or with the instrument. We apply and discuss a likelihood ratio method for VIKING candidates within a search radius of 10 arcsec of the 22 000 SPIRE sources with a 5σ detection at . We estimate the fraction of SPIRE sources with a counterpart above the magnitude limit of the VIKING survey to be Q0≈ 0.73. We find that 11 294 (51 per cent) of the SPIRE sources have a best VIKING counterpart with a reliability R≥ 0.8, and the false identification rate of these is estimated to be 4.2 per cent. We expect to miss ∼5 per cent of true VIKING counterparts. There is evidence from Z−J and J−Ks colours that the reliable counterparts to SPIRE galaxies are marginally redder than the field population. We obtain photometric redshifts for ∼68 per cent of all (non‐stellar) VIKING candidates with a median redshift of . We have spectroscopic redshifts for 3147 (∼28 per cent) of the reliable counterparts from existing redshift surveys. Comparing to the results of the optical identifications supplied with the Phase 1 catalogue, we find that the use of medium‐deep near‐infrared data improves the identification rate of reliable counterparts from 36 to 51 per cent.

“…This paper presents the 250 μm selected source catalogue created from the initial H‐ATLAS Science Demonstration Phase (SDP) observations. Eight papers based on this catalogue have already been published in the Astronomy and Astrophysics Herschel Special Issue ranging from the identification of blazars (González‐Nuevo et al 2010) and debris discs (Thompson et al 2010) in the SDP field, to determinations of the colours (Amblard et al 2010), source counts (Clements et al 2010), clustering (Maddox et al 2010) and 250 μm luminosity function evolution (Dye et al 2010) of the submillimetre population, as well as the star formation history of quasar host galaxies (Serjeant et al 2010) and the dust energy balance of a nearby spiral galaxy (Baes et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Herschel-ATLAS: first data release of the Science Demonstration Phase source catalogues

Rigby

Maddox

Monthly Notices of the Royal Astronomical Society

et al. 2011

122

112

The definitive version can be found at : http://onlinelibrary.wiley.com/ Copyright Royal Astronomical SocietyThe Herschel Astrophysical Terahertz LargeArea Survey (Herschel-ATLAS) is a survey of 550 deg(2) with the Herschel Space Observatory in five far-infrared and submillimetre bands. The first data for the survey, observations of a field 4 x 4 deg(2) in size, were taken during the Science Demonstration Phase (SDP), and reach a 5s noise level of 33.5 mJy beam(-1) at 250 mu m. This paper describes the source extraction methods used to create the corresponding SDP catalogue, which contains 6876 sources, selected at 250 mu m, within similar to 14 deg(2). Spectral and Photometric Imaging REciever (SPIRE) sources are extracted using a new method specifically developed for Herschel data and Photodetector Array Camera and Spectrometer (PACS) counterparts of these sources are identified using circular apertures placed at the SPIRE positions. Aperture flux densities are measured for sources identified as extended after matching to optical wavelengths. The reliability of this catalogue is also discussed, using full simulated maps at the three SPIRE bands. These show that a significant number of sources at 350 and 500 mu m have undergone flux density enhancements of up to a factor of similar to 2, due mainly to source confusion. Correction factors are determined for these effects. The SDP data set and corresponding catalogue will be available from www.h-atlas.org