J/MNRAS/495/3409 SCUBA-2-COSMOS field brightest sub-mm sources (Simpson+, 2020)
An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2-COSMOS
field.
Simpson J.M., Smail I., Dudzeviciute U., Matsuda Y., Hsieh B.-C.,
Wang W.-H., Swinbank A.M., Stach S.M., An F.X., Birkin J.E., Ao Y.,
Bunker A.J., Chapman S.C., Chen C.-C., Coppin K.E.K., Ikarashi S.,
Ivison R.J., Mitsuhashi I., Saito T., Umehata H., Wang R., Zhao Y.
<Mon. Not. R. Astron. Soc., 495, 3409-3430 (2020)>
=2020MNRAS.495.3409S 2020MNRAS.495.3409S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Millimetric/submm sources ; Interferometry ;
Positional data ; Cross identifications
Keywords: galaxies: evolution - galaxies: formation - galaxies: high-redshift -
sub-millimetre: galaxies
Abstract:
We present an ALMA study of the ∼180 brightest sources in the SCUBA-2
850-µm map of the COSMOS field from the S2COSMOS survey, as a pilot
study for AS2COSMOS - a full survey of the ∼1000 sources in this
field. In this pilot study, we have obtained 870-µm continuum maps
of an essentially complete sample of the brightest 182 sub-millimetre
sources (S850µm>6.2mJy) in COSMOS. Our ALMA maps detect 260
sub-millimetre galaxies (SMGs) spanning a range in flux density of
S870µm=0.7-19.2mJy. We detect more than one SMG counterpart in
34±2 per cent of sub-millimetre sources, increasing to 53±8 per
cent for SCUBA-2 sources brighter than S850µm>12mJy. We estimate
that approximately one-third of these SMG-SMG pairs are physically
associated (with a higher rate for the brighter secondary SMGs,
S870µm≳3mJy), and illustrate this with the serendipitous
detection of bright [CII] 157.74-µm line emission in two SMGs,
AS2COS 0001.1 and 0001.2 at z=4.63, associated with the highest
significance single-dish source. Using our source catalogue, we
construct the interferometric 870-µm number counts at
S870µm>6.2mJy. We use the extensive archival data of this field
to construct the multiwavelength spectral energy distribution of each
AS2COSMOS SMG, and subsequently model this emission with MAGPHYS to
estimate their photometric redshifts. We find a median photometric
redshift for the S870µm>6.2mJy AS2COSMOS sample of z=2.87±0.08,
and clear evidence for an increase in the median redshift with
870-µm flux density suggesting strong evolution in the bright end
of the 870-µm luminosity function.
Description:
The parent sample for our work is selected from a sensitive 850-µm
map of the COSMOS field obtained with SCUBA-2 (Holland et al.
2013MNRAS.430.2513H 2013MNRAS.430.2513H) at the James Clerk Maxwell Telescope (JCMT). This
SCUBA-2-COSMOS (S2COSMOS; Simpson et al. 2019ApJ...880...43S 2019ApJ...880...43S) survey
is comprised of two tiers: a main region that reaches a median
sensitivity of 1.2mJy/beam over the 1.6-deg2 Hubble Space
Telescope/Advanced Camera for Surveys footprint (Koekemoer et al.
2007ApJS..172..196K 2007ApJS..172..196K) and a supplementary region that provides an
additional 1deg2 of coverage at a median sensitivity of 1.7mJy/beam.
In this paper, we only consider the 1020 single-dish-identified
sources (S850µm=2-20mJy) that were detected at the >4σ
significance level in the S2COSMOS main survey.
Between 2018 May 15 and 21, we obtained ALMA Band 7 observations of
160 S2COSMOS sources, under project ID: 2016.1.00463.S (PI: Y.
Matsuda). Observations were undertaken with a standard correlator
set-up for continuum, with four basebands providing 7.5-GHz bandwidth
at a central frequency of 343GHz (870µm). For each target, the ALMA
pointing centre was fixed to the S2COSMOS source position and, at our
observing frequency, the ALMA primary beam (FWHM=17.3arcsec) is
well-matched to the SCUBA-2/JCMT beam (effective FWHM=14.6arcsec;
Dempsey et al. 2013MNRAS.430.2534D 2013MNRAS.430.2534D).
Overall, our pilot survey of 182 S2COSMOS sources yields a sample of
260 AS2COSMOS sub-millimetre galaxies (SMGs) with a median detection
significance of 24σ. In Table 1, we provide the basic observable
properties for each AS2COSMOS source as well as cross-matched
identifications for the 69 AS2COSMOS SMGs that have been detected at
∼1arcsec resolution in prior sub-/millimetre interferometric
observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 276 260 AS2COSMOS source catalogue
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Source name (AS2COSNNNN.N)
14- 31 F18.14 deg RAdeg Right ascension (J2000)
33- 50 F18.16 deg DEdeg Declination (J2000)
52- 70 F19.16 mJy Sscuba2 SCUBA-2 flux density
72- 89 F18.16 mJy e_Sscuba2 Lower error on Sscuba2
91- 108 F18.16 mJy E_Sscuba2 Upper error on Sscuba2
110- 128 F19.17 mJy/beam RMS 1σ sensitivity of the
non-primary-beam-corrected ALMA map
130- 147 F18.16 arcsec Beammaj Beam size, major axis
149- 166 F18.16 arcsec Beammin Beam size, minor axis
168- 187 F20.16 --- SNR Signal to noise ratio
189- 207 F19.16 mJy SALMA Total flux density, corrected for the ALMA
primary beam response
209- 227 F19.17 mJy e_SALMA Lower error on SALMA
229- 247 F19.17 mJy E_SALMA Upper error on SALMA
249- 276 A28 --- OName Alternative names (1)
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Note (1): Cross-matched identifications for AS2COSMOS SMGs that have been
detected in prior sub-/mm interferometric observations (see
Younger et al. 2007ApJ...671.1531Y 2007ApJ...671.1531Y, 2009ApJ...704..803Y 2009ApJ...704..803Y;
Aravena et al. 2010ApJ...719L..15A 2010ApJ...719L..15A; Smolcic et al.
2012A&A...548A...4S 2012A&A...548A...4S; Bussmann et al. 2015ApJ...812...43B 2015ApJ...812...43B,
Cat. J/ApJ/812/43; Wang et al. 2016ApJ...828...56W 2016ApJ...828...56W;
Brisbin et al. 2017A&A...608A..15B 2017A&A...608A..15B, Cat. J/A+A/608/A15;
Hill et al. 2018MNRAS.477.2042H 2018MNRAS.477.2042H)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 20-Jun-2023