J/MNRAS/436/1919 SCUBA observations of COSMOS galaxies (Casey+, 2013)
Characterization of Scuba-2 450µm and 850µm selected galaxies in
the COSMOS field.
Casey C.M., Chen C.-C., Cowie L.L., Barger A.J., Capak P., Ilbert O.,
Koss M., Lee N., Le Floc'h E., Sanders D.B., Williams J.P.
<Mon. Not. R. Astron. Soc., 436, 1919-1954 (2013)>
=2013MNRAS.436.1919C 2013MNRAS.436.1919C
ADC_Keywords: Galaxies, IR ; Millimetric/submm sources
Keywords: galaxies: evolution - galaxies: high-redshift - galaxies: starbursts -
infrared: galaxies
Abstract:
We present deep 450µm and 850µm observations of a large,
uniformly covered 394arcmin2 area in the Cosmic Evolution Survey
(COSMOS) field obtained with the Scuba-2 instrument on the James Clerk
Maxwell Telescope (JCMT). We achieve root-mean-square noise values of
σ450=4.13mJy and σ850=0.80mJy. The differential and
cumulative number counts are presented and compared to similar
previous works. Individual point sources are identified at >3.6σ
significance, a threshold corresponding to a 3-5% sample contamination
rate. We identify 78 sources at 450µm and 99 at 850µm, with flux
densities S450=13-37mJy and S850=2-16mJy. Only 62-76% of 450µm
sources are 850µm detected and 61-81% of 850µm sources are
450µm detected. The positional uncertainties at 450µm are small
(1-2.5 arcsec) and therefore allow a precise identification of
multiwavelength counterparts without reliance on detection at 24µm
or radio wavelengths; we find that only 44% of 450µm sources and
60% of 850µm sources have 24µm or radio counterparts. 450µm
selected galaxies peak at =1.95±0.19 and 850µm selected
galaxies peak at =2.16±0.11. The two samples occupy similar
parameter space in redshift and luminosity, while their median SED
peak wavelengths differ by ∼20-50µm (translating to
ΔTdust=8-12K, where 450µm selected galaxies are warmer).
The similarities of the 450µm and 850µm populations, yet lack of
direct overlap between them, suggests that submillimetre surveys
conducted at any single far-infrared wavelength will be significantly
incomplete (≳30%) at censusing infrared-luminous star formation at
high z.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 121 78 *450um sources identified >3.6σ point sources
in COSMOS field
table2.dat 123 99 *850um sources identified >3.6σ point sources
in COSMOS field
table4.dat 119 24 *Marginal 3<σ<3.6 450um identified sources
with 850um >3σ counterparts
table5.dat 151 144 *Counterpart identifications and multiwavelength
properties for Scuba-2 450um detected sources
table6.dat 151 65 Counterpart identifications and multiwavelength
properties for marginal Scuba-2 450um and
850um detected sources
table7.dat 151 151 *Counterpart identifications and multiwavelength
properties for Scuba-2 850um detected sources
table8.dat 96 52 *Identification of Scuba-2 sources at 870um-1.2mm
table9.dat 135 130 Physical characteristics of Scuba-2 selected
galaxies
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Note on table1.dat, table2.dat: sources detected within the central
394-arcmin2 of our COSMOS map. The 3.6σ detection threshold is
chosen based on an estimated 3-5% contamination rate.
Note on table4.dat: Sources extracted down to 3σ in the 450um map using
850um>3σ positional priors. The 450um>3σ list (with 274 sources)
was checked against the 850um>3σ list (with 164 sources) and 25 sources
were found.
Note on table5.dat: All possible counterparts (24um, radio and optical/near-IR)
for Scuba-2 450um identified >3.6σ sources. The best-guess counterpart is
the source with the lowest p-value of any within the search radius (see text
for details). Sources with a p-value >0.50 are excluded from this table since
they are more likely a random coincident source than a true counterpart.
Note on table7.dat: Sources which have 450um counterparts are excluded from this
table as their 450um positional uncertainty is smaller than their 850um
uncertainty; the former is used to determine their counterparts which are given
in either Table 5 or Table 6
Note on table8.dat: Counterparts of Scuba-2 sources at 870um-1.2mm as identified
by LABOCA, PdBI, AzTEC, SMA and MAMBO with given references.
Sources are divided into 450um>3.6σ and 850um>3.6σ samples. None of
the marginal 3<σ<3.6 450um/850um sources was reported as detections in
the given references. Sources are searched within a 10 arcsec (450um sources)
or 12 arcsec (850um sources) search radius; this is approximately one beamsize
at ∼850um-1.2mm and represents a regime where chance coincidence between submm
sources is very low (p-value<0.01).
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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- 3 A3 --- --- [SMM]
5- 20 A16 --- SMM SMM name (JHHMMSS.s+DDMMSS)
22- 27 A6 --- N450 Short name for source at 450um (450.NN)
29- 30 I2 h RAh Right ascension at 450um (J2000)
32- 33 I2 min RAm Right ascension at 450um (J2000)
35- 38 F4.1 s RAs Right ascension at 450um (J2000)
40 A1 --- DE- Declination sign at 450um (J2000)
41- 42 I2 deg DEd Declination at 450um (J2000)
44- 45 I2 arcmin DEm Declination at 450um (J2000)
47- 48 I2 arcsec DEs Declination at 450um (J2000)
50- 53 F4.2 --- S/N [3.6/7.8] Signal-to-noise ratio at 450um
55- 59 F5.2 mJy S450r Raw 450um flux density (G1)
61- 64 F4.2 mJy e_S450r rms uncertainty on S450r
66- 70 F5.2 mJy S450d Deboosted 450um flux density (G2)
72- 75 F4.2 mJy e_S450d rms uncertainty on S450d
77- 80 F4.2 arcsec ePos 90% confidence interval for positional
uncertainty
82 A1 --- l_Pcont Limit flag on Pcont
83- 86 F4.2 --- Pcont [0/0.11] Probability of contamination (G3)
88 A1 --- u_N850 [(] Uncertainty flag on 850um
cross-identification
89- 95 A7 --- N850 Short name for 850um counterpart (850.NN) (G4)
97- 99 F3.1 arcsec Off ? Offset between 450 and 850um sources
101-105 F5.2 mJy S850r ? Raw flux density at 850um (G1)
107-110 F4.2 mJy e_S850r ? rms uncertainty on S850r
112-116 F5.2 mJy S850d ? Deboosted flux density at 850um (G2)
118-121 F4.2 mJy e_S850d ? rms uncertainty on S850d
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [SMM]
5- 20 A16 --- SMM SMM name (JHHMMSS.s+DDMMSS)
22- 27 A6 --- N850 Short name for source at 850um (850.NN)
29- 30 I2 h RAh Right ascension at 850um (J2000)
32- 33 I2 min RAm Right ascension at 850um (J2000)
35- 38 F4.1 s RAs Right ascension at 850um (J2000)
40 A1 --- DE- Declination sign at 850um (J2000)
41- 42 I2 deg DEd Declination at 850um (J2000)
44- 45 I2 arcmin DEm Declination at 850um (J2000)
47- 48 I2 arcsec DEs Declination at 850um (J2000)
50- 54 F5.2 --- S/N [3.6/21] Signal-to-noise ratio at 850um
56- 60 F5.2 mJy S850r Raw 850um flux density (G1)
62- 65 F4.2 mJy e_S850r rms uncertainty on S850r
67- 71 F5.2 mJy S850d Deboosted 850um flux density (G2)
73- 76 F4.2 mJy e_S850d rms uncertainty on S850d
78- 81 F4.2 arcsec ePos 90% confidence interval for positional
uncertainty
83 A1 --- l_Pcont Limit flag on Pcont
84- 87 F4.2 --- Pcont [0/0.15] Probability of contamination (G3)
89 A1 --- u_N450 [(] Uncertainty flag on 450um
cross-identification
90- 96 A7 --- N450 Short name for 450um counterpart (450.NN) (G4)
98-100 F3.1 arcsec Off ? Offset between 450 and 850um sources
102-106 F5.2 mJy S450r ? Raw flux density at 450um (G1)
108-111 F4.2 mJy e_S450r ? rms uncertainty on S450r
113 A1 --- l_S450d Limit flag on S450d
114-118 F5.2 mJy S450d ? Deboosted flux density at 450um (G2)
120-123 F4.2 mJy e_S450d ? rms uncertainty on S450d
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [SMM]
5- 20 A16 --- SMM SMM name (JHHMMSS.s+DDMMSS)
22- 28 A7 --- N850 Short name for source at 850um (850.NNN) (1)
30- 36 A7 --- N450 Short name for source at 450um (450.NNN) (1)
38- 41 F4.1 arcsec Off Offset between 450 and 850um centroids
43- 44 I2 h RAh Right ascension at 450um (J2000)
46- 47 I2 min RAm Right ascension at 450um (J2000)
49- 52 F4.1 s RAs Right ascension at 450um (J2000)
54 A1 --- DE- Declination sign at 450um (J2000)
55- 56 I2 deg DEd Declination at 450um (J2000)
58- 59 I2 arcmin DEm Declination at 450um (J2000)
61- 62 I2 arcsec DEs Declination at 450um (J2000)
64- 67 F4.2 --- S/N850 Signal-to-noise ratio at 850um
69- 72 F4.2 --- S/N450 Signal-to-noise ratio at 450um
74- 78 F5.2 mJy S450r Raw 450um flux density (G1)
80- 83 F4.2 mJy e_S450r rms uncertainty on S450r
85- 89 F5.2 mJy S450d Deboosted 450um flux density (G2)
91- 94 F4.2 mJy e_S450d rms uncertainty on S450d
96- 99 F4.2 mJy S850r Raw 850um flux density (G1)
101-104 F4.2 mJy e_S850r rms uncertainty on S850r
106-109 F4.2 mJy S850d Deboosted 850um flux density (G2)
111-114 F4.2 mJy e_S850d rms uncertainty on S850d
116-119 F4.2 arcsec ePos 90% confidence interval for positional
uncertainty
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Note (1): The short names are numbered in order of decreasing S/N for all
sources extracted in the map, e.g. from 450.00 at S/N=7.80 to 450.273 with
S/N=3.00, hence the high, non-sequential numbers given at both 450um and
850um.
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Byte-by-byte Description of file: table5.dat table6.dat table7.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- N450 Short name N450
8 A1 --- --- [/]
9- 15 A7 --- N850 Short name N850 (table6)
16 A1 --- n_N850 [*] multiple possible counterparts (1)
17- 19 A3 --- m_N850 Conterpart number/total (NA for not analysed)
21- 27 F7.5 --- pvalue [0/0.5]? Probability of non-association
29- 30 I2 h RA24h ? Right ascension at 24um (J2000)
32- 33 I2 min RA24m ? Right ascension at 24um (J2000)
35- 39 F5.2 s RA24s ? Right ascension at 24um (J2000)
41 A1 --- DE24- Declination sign at 24um (J2000)
42- 43 I2 deg DE24d ? Declination at 24um (J2000)
45- 46 I2 arcmin DE24m ? Declination at 24um (J2000)
48- 51 F4.1 arcsec DE24s ? Declination at 24um (J2000)
53- 56 F4.2 arcsec d24 [0/3.2]? Offset of 24um source with respect to
the Scuba-2 450um or 850um position
58- 61 I4 uJy S24 ? Spitzer/MIPS Flux density at 24um
63- 65 I3 uJy e_S24 ? rms uncertainty on S24um
66 A1 --- n_S24 [*] Note on 24um flux (2)
67- 68 I2 h RA1h ? Right ascension at 1.4GHz (J2000)
70- 71 I2 min RA1m ? Right ascension at 1.4GHz (J2000)
73- 77 F5.2 s RA1s ? Right ascension at 1.4GHz (J2000)
79 A1 --- DE1- Declination sign at 1.4GHz (J2000)
80- 81 I2 deg DE1d ? Declination at 1.4GHz (J2000)
83- 84 I2 arcmin DE1m ? Declination at 1.4GHz (J2000)
86- 89 F4.1 arcsec DE1s ? Declination at 1.4GHz (J2000)
91- 94 F4.2 arcsec d1.4 [0/2.7]? Offset of 1.4GHz source with respect
to the Scuba-2 450um or 850um position
96- 99 I4 uJy S1.4GHz ? Flux density at 1.4GHz
101-102 I2 uJy e_S1.4GHz ? rms uncertainty on S1.4GHz
104 A1 --- Opt [*] Note on optical counterpart (3)
105-106 I2 h RAOh ? Optical Right ascension (J2000)
108-109 I2 min RAOm ? Optical Right ascension (J2000)
111-115 F5.2 s RAOs ? Optical Right ascension (J2000)
117 A1 --- DEO- Optical Declination sign (J2000)
118-119 I2 deg DEOd ? Optical Declination (J2000)
121-122 I2 arcmin DEOm ? Optical Declination (J2000)
124-128 F5.2 arcsec DEOs ? Optical Declination (J2000)
129-132 F4.2 arcsec dOpt [0/6.8]? Offset of optical source with respect
to the Scuba-2 450um or 850um position
134-138 F5.2 mag imag ? i magnitude (AB) (4)
139 A1 --- n_imag [*] Note on imag (5)
141-145 F5.2 mag [3.6] ? 3.6um magnitude (AB) (4)
146 A1 --- n_[3.6] [*] Note on [3.6] (5)
148-151 F4.2 --- zph ? Photometric redshift
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Note (1): Source 850.22 was interferometrically observed by Smolcic et al.
(2012A&A...548A...4S 2012A&A...548A...4S); however no source was detected; it is likely that
the reason for this is that the submillimetre emission emanates from multiple
possible counterparts.
Note (2): * : the 24um flux density for 450.07 is originally measured as 1.3mJy;
this is an obvious blend with a nearby bright source. We have approximated the
contribution from 450.07 to be ∼38%, thus we arrive at 467uJy.
Note (3): * indicates that counterparts are submillimetre sources which have
been observed interferometrically in the literature, therefore the correct
counterpart is known as the source at the given position. See the text
(Section 3.5) for details on reliability of counterpart identifications.
Note (4): Sources without optical magnitudes are dropouts and the position is
measured from the Spitzer-IRAC 3.6um.
Note (5): * indicates that the i-band and 3.6um magnitudes for 450.03/850.00 is
measured from the HST imaging, where it can be decoupled from the bright
elliptical nearby (1.6-arcsec).
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- N450 450um name
9- 15 A7 --- N850 850um name
17- 41 A25 --- AName Alternate name
42 A1 --- n_AName [*] * indicates sources that correspond to
multiple Scuba-2 sources (1)
44- 47 F4.2 mm lam Observed wavelength λ
49- 53 F5.2 mJy Slam ?=- Deboosted flux density at λ
55- 58 F4.2 mJy e_Slam ?=- rms uncertainty on Slam
60 A1 --- Int [Y] Interferometric observation?
62- 67 A6 --- Inst Instrument
70- 99 A30 --- Ref Reference (2)
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Note (1): i.e. 450.16, 450.28 and 850.05 all correspond to COSBO3/AzTEC/C6.
Note (2): References as follows:
Aretxaga et al. (2011MNRAS.415.3831A 2011MNRAS.415.3831A, Cat. J/MNRAS/415/3831)
Bertoldi et al. (2007ApJS..172..132B 2007ApJS..172..132B)
Navarette et al., in prep
Scott et al. (2008MNRAS.385.2225S 2008MNRAS.385.2225S, Cat. J/MNRAS/385/2225)
Smolcic et al. (2012A&A...548A...4S 2012A&A...548A...4S)
Younger et al. (2007ApJ...671.1531Y 2007ApJ...671.1531Y, 2009MNRAS.394.1685Y 2009MNRAS.394.1685Y)
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- N450 Short name for source at 450um (450.NNN)
9- 15 A7 --- N850 Short name for source at 850um (850.NNN)
17- 20 F4.2 --- zph Photometric redshift
22- 25 F4.2 --- E_zph Error on zph (upper value)
27- 30 F4.2 --- e_zph Error on zph (lower value)
32- 35 F4.1 --- chi2 Fit chi2 value
37- 43 E7.2 Lsun LIR Infrared luminosity (1)
45- 52 E8.3 Lsun E_LIR Error on LIR (upper value)
54- 60 E7.2 Lsun e_LIR Error on LIR (lower value)
63- 65 F3.1 [Msun/yr] logSFR1 Infrared star formation rate (1)
67- 69 F3.1 [Msun/yr] e_logSFR1 rms uncertainty on logSFR1
71 A1 --- n_lam.p [f] f for fixed value (2)
72- 74 F3.1 um lam.p Peak wavelength (1)
76- 78 F3.1 um e_lam.p ? rms uncertainty on lam.p
81- 85 E5.1 Msun Mdust ?=- Dust mass (1)
87- 92 E6.1 Msun E_Mdust ?=- Error on Mdust (upper value)
94- 98 E5.1 Msun e_Mdust ?=- Error on Mdust (lower value)
100-104 F5.2 [Msun/yr] logSFR2 Ultraviolet star formation rate
(Le Phare properties)
106-109 F4.2 [Msun/yr] E_logSFR2 Error on logSFR2 (upper value)
111-114 F4.2 [Msun/yr] e_logSFR2 Error on logSFR2 (lower value)
116-120 E5.1 Msun M* Stellar mass (Le Phare properties)
122-127 E6.1 Msun E_M* Error on M* (upper value)
129-135 E7.3 Msun e_M* Error on M* (lower value)
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Note (1): Parameter estimated from infrared SED fillting.
Some basic derived properties of 450um sources using the infrared SED
fitting described in Section 4.2. The sources' optical/NIR photometric
redshifts are given by zph. Their integrated 8-1000um infrared luminosity,
LIR, infrared star formation rates SFRIR (calculated via the relation given in
Kennicutt, 1998ARA&A..36..189K 1998ARA&A..36..189K), SED peak wavelength, and approximated dust
masses Mdust are calculated assuming SEDs as described in Section 4.2.
Note (2): Sources with fewer than three IR photometric points have the SED peak
wavelength (or dust temperature) fixed to the mean of the remainder of the
sample, measured to be <log(λpeak/um)≥2.05±0.04 for 450um detected
galaxies and <log(λpeak/um)≥2.12±0.04 for 850um only detected
galaxies.
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Global notes:
Note (G1): The 'raw' flux densities are those measured directly from our map.
Note (G2): The 'deboosted' flux densities are those given after correction for
confusion and Eddington boosting as a function of detection S/N, as
described in Section 3.1.
Note (G3): estimated probability of contamination from the results of our
Monte Carlo tests as functions of detection S/N.
Note (G4): Corresponding 850um (450um) counterparts if they exist.
If a 450um (850um) source is not detected at 850um (450um) at >3σ then
the flux density is measured at the 450um (850um) position.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 22-Oct-2014