1302.2619 (Caitlin M. Casey et al.)

Characterisation of SCUBA-2 450um and 850um-selected Galaxies in the COSMOS Field    [PDF]

Caitlin M. Casey, Chian-Chou Chen, Lennox Cowie, Amy Barger, Peter Capak, Olivier Ilbert, Michael Koss, Nicholas Lee, Emeric Le Floc'h, David B. Sanders, Jonathan P. Williams

We present deep 450um and 850um observations of a large, uniformly covered 394arcmin^2 area in the COSMOS field obtained with the SCUBA-2 instrument (with RMS values 4.13mJy at 450um and 0.80mJy at 850um). This region of COSMOS is found to have a counts deficit at both wavelengths. Seventy-eight point sources are identified at 450um and 99 at 850um at >3.6sigma, with S_450=13-37mJy and S_850=2-16mJy. Approximately half of both samples are detected at both wavelengths. Since the positional uncertainties at 450um are small (1-2.5"), this allows a precise identification of multiwavelength counterparts without reliance on detection at 24um or radio wavelengths; we find that only 40% of 450um-sources have 24um or radio counterparts and conclude that other submm work reliant on such counterparts could be significantly biased. The redshift distributions peak at =2.0+-1.1 for 450um-selected galaxies and =2.2+-1.6 for 850um-selected galaxies. The primary difference between 450 and 850um populations is their far-infrared S_850/S_450 colour, although this colour does not show any redshift evolution. All SCUBA-2 sources have UV/optical/near-infrared-derived star formation rates which underpredict their infrared-based SFR by factors ~>10; this has implications of how and if infrared-luminous systems sitting along the "main sequence" can be interpreted. The total contribution of these submillimeter sources (both 450um and 850um) to the cosmic star formation rate density is measured as roughly flat at ~0.01Msun/yr h^3 Mpc^-3 across 0View original: http://arxiv.org/abs/1302.2619