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Published November 2010 | Accepted Version + Published
Journal Article Open

The Herschel Multi-Tiered Extragalactic Survey: source extraction and cross-identifications in confusion-dominated SPIRE images


We present the cross-identification and source photometry techniques used to process Herschel SPIRE imaging taken as part of the Herschel Multi-Tiered Extragalactic Survey (HerMES). Cross-identifications are performed in map-space so as to minimize source-blending effects. We make use of a combination of linear inversion and model selection techniques to produce reliable cross-identification catalogues based on Spitzer MIPS 24-μm source positions. Testing on simulations and real Herschel observations shows that this approach gives robust results for even the faintest sources (S_(250) ~10 mJy). We apply our new technique to HerMES SPIRE observations taken as part of the science demonstration phase of Herschel. For our real SPIRE observations, we show that, for bright unconfused sources, our flux density estimates are in good agreement with those produced via more traditional point source detection methods (SUSSEXtractor) by Smith et al. When compared to the measured number density of sources in the SPIRE bands, we show that our method allows the recovery of a larger fraction of faint sources than these traditional methods. However, this completeness is heavily dependent on the relative depth of the existing 24-μm catalogues and SPIRE imaging. Using our deepest multiwavelength data set in the GOODS-N, we estimate that the use of shallow 24-μm catalogues in our other fields introduces an incompleteness at faint levels of between 20–40 per cent at 250 μm.

Additional Information

© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 September 3. Received 2010 September 2; in original form 2010 June 1. Article first published online: 21 Oct. 2010. We thank the anonymous referee for many suggestions, which greatly enhanced the clarity of this paper. IGR and LW were supported by the Science and Technology Facilities Council (grant number ST/F002858/1). The SPIRE Consortium includes participants from eight countries (Canada, China, France, Italy, Spain, Sweden, UK, USA). The following institutes have provided hardware and software elements to the instrument programme: Cardiff University, UK; Commissariat l'nergie Atomique (CEA), Saclay, France; CEA, Grenoble, France; Imperial College, London, UK; Instituto de Astrofisica de Canarias (IAC), Tenerife, Spain; Infrared Processing and Analysis Centre (IPAC), Pasadena, USA; Istituto di Fisica dello Spazio Interplanetario (IFSI), Rome, Italy; University College London's Mullard Space Science Laboratory (MSSL), Surrey, UK; NASA Goddard Space Flight Centre (GSFC), Maryland, USA; NASA Jet Propulsion Laboratory (JPL) and Caltech, Pasadena, USA; National Astronomical Observatories, Chinese Academy of Sciences (NAOC), Beijing, China; Observatoire Astronomique de Marseille Provence (OAMP), France; Rutherford Appleton Laboratory (RAL), Oxfordshire, UK; Stockholm Observatory, Sweden; UK Astronomy Technology Centre (UK ATC) Edinburgh; University of Colorado, USA; University of Lethbridge, Canada; University of Padua, Italy; and the University of Sussex, UK. Funding for SPIRE has been provided by the national agencies of the participating countries and by internal institute funding: the Canadian Space Agency (CSA); NAOC in China; Centre National d'tudes Spatiales (CNES), Centre National de la Recherche Scientifique (CNRS), and CEA in France; Agenzia Spaziale Italiana (ASI) in Italy; Ministerio de Educacin y Ciencia (MEC) in Spain, Stockholm Observatory in Sweden; the Science and Technology Facilities Council (STFC) in the UK; and NASA in the USA. Additional funding support for some instrument activities has been provided by ESA.

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Published - Roseboom2010p12118Mon_Not_R_Astron_Soc.pdf

Accepted Version - 1009.1658.pdf


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