Abstract
Determining an accurate position for a submillimetre (submm) galaxy
(SMG) is the crucial step that enables us to move from the basic
properties of an SMG sample - source counts and 2D clustering - to an
assessment of their detailed, multiwavelength properties, their
contribution to the history of cosmic star formation and their links
with present-day galaxy populations. In this paper, we identify robust
radio and/or infrared (IR) counterparts, and hence accurate positions,
for over two-thirds of the SCUBA HAlf-Degree Extragalactic Survey
(SHADES) Source Catalogue, presenting optical, 24-μm and radio images
of each SMG. Observed trends in identification rate have given no strong
rationale for pruning the sample. Uncertainties in submm position are
found to be consistent with theoretical expectations, with no evidence
for significant additional sources of error. Employing the submm/radio
redshift indicator, via a parametrization appropriate for
radio-identified SMGs with spectroscopic redshifts, yields a median
redshift of 2.8 for the radio-identified subset of SHADES, somewhat
higher than the median spectroscopic redshift. We present a diagnostic
colour-colour plot, exploiting Spitzer photometry, in which we identify
regions commensurate with SMGs at very high redshift. Finally, we find
that significantly more SMGs have multiple robust counterparts than
would be expected by chance, indicative of physical associations. These
multiple systems are most common amongst the brightest SMGs and are
typically separated by 2-6arcsec, at z ~ 2, consistent with early bursts
seen in merger simulations.
Original language | English |
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Pages (from-to) | 199-228 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 380 |
DOIs | |
Publication status | Published - 1 Sep 2007 |