Optical and near-IR properties of submillimetre galaxies in the GOODS-North field

1
Optical and near-IR properties of submillimetre
galaxies in the GOODS-North field
Alexandra Pope, D. Scott (UBC), C. Borys, C.
Conselice (Caltech), M. Dickinson (NOAO), B.
Mobasher (STScI)
Figure 1 JCMT SCUBA 850?m S/N map 42
sources Integration time1300 ksec
Figure 2 HST ACS bviz colour image 32 000
sources Integration time500 ksec
ABSTRACT We present a new sub-mm 'Super-map' in
the GOODS-North field containing 42 statistically
robust sources at 850 ?m. This map contains new
data, and several new sources (including the
brightest one in the survey). We have used the
ACS HST images and ground-based near-IR
observations from GOODS to study these sources.
With the depth achieved by this survey, optical
counterparts have been found for all the
radio-detected sub-mm sources. We have used the
colours, morphologies and photometric redshifts
of these secure identifications to help identify
counterparts to the radio-undetected sources,
finding that certain combinations of optical
properties can be used to successfully identify
the counterpart to a sub-mm source. 75 of our
sources have a unique optical counterpart using
our new techniques for counterpart
identification, and an additional 15 have more
than one possibility that meet our criteria in
the ACS images. Thus only 10 of our sources
lack a plausible counterpart, meaning that we
have the first sample of SCUBA sources which is
nearly completely identified. We have found a
higher ERO rate than other sub-mm surveys, due to
the increased depth in the optical images. The
median redshift from optical photometric
redshifts for the bright radio-detected sources
is around 2, and rises to 2.6 for the bright
radio-undetected sources. While the quantitative
morphologies span a range of values, in general
the sub-mm galaxies show larger sizes and a
higher degree of asymmetry than other galaxy
populations at the same redshifts. With the
current and upcoming GOODS-North data from
Spitzer, we will be able test our counterpart
selection techniques and use the additional IR
photometric points to study the optical/IR SEDs
of an sample of sub-mm galaxies.
Redshifts
Colours
Morphologies
Figure 4 Near-IR colour-colour plot. Dusty EROs
with 1ltzlt2 should lie in top-right corner.
Figure 3 Photometric redshift distribution.
Figure 5 Size at all redshifts.
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