Abstract
A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich (Mdust≃ 9 × 108M⊙), luminous (LFIR≃ 2 × 1012L⊙) star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of ≃400 M⊙ yr−1. We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N350(>25 mJy) ∼ 200–500 deg−2.
Highlights
The Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES; Mortier et al 2005; Coppin et al 2006) mapped ≃0.25 deg2 of sky with an rms of 2 mJy at 850 μm with SCUBA (Holland et al 1999)
We estimate a lower limit of N(>S) 200 deg−2, given a SHARC-II detection success rate of 7/24 and a total of 120 Submillimetre HAlf Degree Extragalactic Survey (SHADES) sources found in ≃720 arcmin2
Large surveys planned with the Balloonborne Large Aperture Subillimetre Telescope (BLAST; Devlin et al 2004), Herschel (Pilbratt 2003), SCUBA-2 (Holland et al 2006) and Planck (Tauber 2004) will be able to provide further constraints on the source counts at shorter submm wavelengths and over a wider dynamic range of flux densities
Summary
The Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES; Mortier et al 2005; Coppin et al 2006) mapped ≃0.25 deg of sky with an rms of 2 mJy at 850 μm with SCUBA (Holland et al 1999). The survey uncovered 120 submillimetre galaxies (SMGs) with a median deboosted flux density of ∼5 mJy (Coppin et al 2006). The SHADES programme was designed to study the nature and evolution of high star formation rate (SFR) SMGs via a systematic study of a well-characterized and statistically meaningful sample. The programme includes an effort to identify members of the source list at other wavelengths using deep follow-up data from the radio (Ivison et al 2007) to X-ray, in order to characterize the SHADES population and to probe the variation in the star formation and clustering with redshift. The relatively precise positions available from the radio data greatly aid in identifying secure counterparts at other wavelengths, which can be used to provide spectroscopic or photometric redshifts (Aretxaga et al 2007) and to categorize the sources
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