Probing the submillimetre number counts at f850 μm < 2 mJy |
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| Authors: | K K Knudsen P P van der Werf J-P Kneib |
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| Institution: | Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany;Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands;Observatoire Midi-Pyrénées, UMR5572, 14 Avenue Edouard Belin, 31000 Toulouse, France;Caltech, Astronomy, 105-24, Pasadena, CA 91125, USA;OAMP, Laboratoire d'Astrophysique de Marseille, traverse du Siphon, 13012 Marseille, France |
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| Abstract: | We have conducted a submillimetre mapping survey of faint, gravitationally lensed sources, where we have targeted 12 galaxy clusters and additionally the New Technology Telescope (NTT) Deep Field. The total area surveyed is 71.5 arcmin2 in the image plane; correcting for gravitational lensing, the total area surveyed is 40 arcmin2 in the source plane for a typical source redshift z ≈ 2.5. In the deepest maps, an image plane depth of 1σ rms ∼0.8 mJy is reached. This survey is the largest survey to date to reach such depths. In total 59 sources were detected, including three multiply imaged sources. The gravitational lensing makes it possible to detect sources with flux density below the blank field confusion limit. The lensing-corrected fluxes range from 0.11 to 19 mJy. After correcting for multiplicity, there are 10 sources with fluxes <2 mJy of which seven have submJy fluxes, doubling the number of such sources known. Number counts are determined below the confusion limit. At 1 mJy, the integrated number count is ∼104 deg−2 , and at 0.5 mJy it is ∼2 × 104 deg−2 . Based on the number counts, at a source plan flux limit of 0.1 mJy, essentially all of the 850-μm background emission has been resolved. The dominant contribution (>50 per cent) to the integrated background arises from sources with fluxes S 850 between 0.4 and 2.5 mJy, while the bright sources S 850 > 6 mJy contribute only 10 per cent. |
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| Keywords: | surveys galaxies: evolution galaxies: high-redshift galaxies: starburst submillimetre |
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