TY - JOUR

T1 - The SCUBA 8-mJy survey - I. Submillimetre maps, sources and number counts

AU - Scott, S. E.

AU - Fox, M. J.

AU - Dunlop, J. S.

AU - Serjeant, S.

AU - Peacock, John

AU - Ivison, R. J.

AU - Oliver, S.

AU - Mann, R. G.

AU - Lawrence, A.

AU - Efstathiou, A.

AU - Rowan-Robinson, M.

AU - Hughes, D. H.

AU - Archibald, E. N.

AU - Blain, A.

AU - Longair, M.

PY - 2002/4/1

Y1 - 2002/4/1

N2 - We present maps, source lists and derived number counts from the
largest, unbiased, extragalactic submillimetre (submm) survey so far
undertaken with the SCUBA camera on the James Clerk Maxwell Telescope
(JCMT). Our maps are located in two regions of sky (ELAIS N2 and
Lockman-Hole E) and cover 260arcmin2 , to a typical rms noise
level of σ 850 ~=2.5mJybeam-1 . We have
reduced the data using both the standard JCMT surf procedures, and our
own IDL -based pipeline which produces zero-footprint maps and noise
images. The uncorrelated noise maps produced by the latter approach have
enabled us to apply a maximum likelihood method to measure the
statistical significance of each peak in our maps, leading to properly
quantified errors on the flux density of all potential sources. We
detect 19 sources with signal-to-noise ratios (S/N)>4, and 38 with
S/N>3.5. To assess both the completeness of this survey and the
impact of source confusion as a function of flux density, we have
applied our source-extraction algorithm to a series of simulated images.
The result is a new estimate of the submm source counts over the
flux-density range S 850 ~=5-15mJy, which we compare with
estimates derived by other workers, and with the predictions of a number
of models. Our best estimate of the cumulative source count at S
850 >8mJy is per square degree. Assuming that the majority
of sources lie at z >1.5, this result implies that the comoving
number density of high-redshift galaxies forming stars at a rate in
excess of 1000Msolar yr-1 is ~=10-5
Mpc-3 , with only a weak dependence on the precise redshift
distribution. This number density corresponds to the number density of
massive ellipticals with L >3-4L * in the present-day Universe , and
is also the same as the comoving number density of comparably massive,
passively evolving objects in the redshift band 1

AB - We present maps, source lists and derived number counts from the
largest, unbiased, extragalactic submillimetre (submm) survey so far
undertaken with the SCUBA camera on the James Clerk Maxwell Telescope
(JCMT). Our maps are located in two regions of sky (ELAIS N2 and
Lockman-Hole E) and cover 260arcmin2 , to a typical rms noise
level of σ 850 ~=2.5mJybeam-1 . We have
reduced the data using both the standard JCMT surf procedures, and our
own IDL -based pipeline which produces zero-footprint maps and noise
images. The uncorrelated noise maps produced by the latter approach have
enabled us to apply a maximum likelihood method to measure the
statistical significance of each peak in our maps, leading to properly
quantified errors on the flux density of all potential sources. We
detect 19 sources with signal-to-noise ratios (S/N)>4, and 38 with
S/N>3.5. To assess both the completeness of this survey and the
impact of source confusion as a function of flux density, we have
applied our source-extraction algorithm to a series of simulated images.
The result is a new estimate of the submm source counts over the
flux-density range S 850 ~=5-15mJy, which we compare with
estimates derived by other workers, and with the predictions of a number
of models. Our best estimate of the cumulative source count at S
850 >8mJy is per square degree. Assuming that the majority
of sources lie at z >1.5, this result implies that the comoving
number density of high-redshift galaxies forming stars at a rate in
excess of 1000Msolar yr-1 is ~=10-5
Mpc-3 , with only a weak dependence on the precise redshift
distribution. This number density corresponds to the number density of
massive ellipticals with L >3-4L * in the present-day Universe , and
is also the same as the comoving number density of comparably massive,
passively evolving objects in the redshift band 1

U2 - 10.1046/j.1365-8711.2002.05193.x

DO - 10.1046/j.1365-8711.2002.05193.x

M3 - Article

SN - 1365-2966

VL - 331

SP - 817

EP - 838

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

ER -