J/A+A/602/A2 VLA-COSMOS 3 GHz Large Project. II. (Smolcic+, 2017)
The VLA-COSMOS 3 GHz Large Project. Multiwavelength counterparts and the
composition of the faint radio population.
Smolcic V., Delvecchio I., Zamorani G., Baran N., Novak M., Delhaize J.,
Schinnerer E., Berta S., Bondi M., Ciliegi P., Capak P., Civano F.,
Karim A., Le Fevre O., Ilbert O., Laigle C., Marchesi S., McCracken H.J.,
Tasca L., Salvato M., Vardoulaki E.
<Astron. Astrophys. 602, A2 (2017)>
=2017A&A...602A...2S 2017A&A...602A...2S (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxies, radio ; Active gal. nuclei ; Infrared sources
Keywords: radio continuum: galaxies - catalogs
Abstract:
We study the composition of the faint radio population selected from
the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed
at 10 cm wavelength. The survey covers a 2.6 square degree area with a
mean rms of ∼2.3uJy/beam, cataloging 10,830 sources above 5sigma, and
enclosing the full 2 square degree COSMOS field. By combining these
radio data with optical, near-infrared (UltraVISTA), and mid-infrared
(Spitzer/IRAC) data, as well as X-ray data (Chandra), we find
counterparts to radio sources for ∼93% of the total radio sample (in
the unmasked areas of the COSMOS field, i.e., those not affected by
saturated or bright sources in the optical to NIR bands), reaching out
to z∼6. We further classify the sources as star forming galaxies or
AGN based on various criteria, such as X-ray luminosity, observed MIR
color, UV-FIR spectral-energy distribution, rest-frame NUV-optical
color corrected for dust extinction, and radio-excess relative to that
expected from the hosts' star-formation rate. We separate the AGN
into sub-samples dominated by low-to-moderate and moderate-to-high
radiative luminosity AGN, candidates for high- redshift analogues to
local low- and high-excitation emission line AGN, respectively. We
study the fractional contributions of these sub-populations down to
radio flux levels of ∼11uJy at 3GHz (or ∼20uJy at 1.4GHz assuming a
spectral index of -0.7). We find that the dominant fraction at 1.4GHz
flux densities above ∼200uJy is constituted of low-to-moderate
radiative luminosity AGN. Below densities of ∼100uJy the fraction of
star-forming galaxies increases to ∼60%, followed by the
moderate-to-high radiative luminosity AGN (∼20%), and low-to-moderate
radiative luminosity AGN (∼20%). Based on this observational evidence,
we extrapolate the fractions down to sensitivities of the Square
Kilometer Array (SKA). Our estimates suggest that at the faint flux
limits to be reached by the (Wide, Deep, and UltraDeep) SKA1 surveys,
a selection based only on radio flux limits can provide a simple tool
to efficiently identify samples highly (>75%) dominated by
star-forming galaxies.
Description:
The catalog contains the full list of 9161 optical-MIR counterparts
collected over the largest unmasked area accessible to each catalog,
being 1.77, 1.73, and 2.35 square degrees for COSMOS2015, i-band, and
IRAC catalogs, respectively. The catalog lists the counterpart IDs,
properties, as well as the individual criteria used in this work to
classify our radio sources. We note that complete, non-overlapping
samples within a well defined, effective area of 1.77 square degrees
(COSMOS2015 masked area flag_C15=0, can be formed by combining i)
HLAGN, MLAGN, and clean SFG samples, or, alternatively, ii) the
radio-excess and no-radio-excess samples. The full catalog is
described in Section 7 of the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 167 9161 VLA-COSMOS 3GHz source counterpart catalog
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See also:
II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
J/ApJ/644/100 : SDSS quasars in the COSMOS field (Prescott+, 2006)
J/ApJS/172/523 : COSMOS field Lyα emitters at z∼5.7 (Murayama+, 2007)
J/ApJS/172/368 : XMM-Newton survey in COSMOS field. IV. (Mainieri+, 2007)
J/ApJS/175/128 : Hα emitting galaxies in COSMOS-2 field (Shioya+, 2008)
J/MNRAS/385/2225 : AzTEC millimetre survey of COSMOS field (Scott+, 2008)
J/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)
J/A+A/497/635 : XMM wide-field survey in COSMOS field (Cappelluti+, 2009)
J/AJ/138/1261 : Spitzer/MIPS observations of the COSMOS field (Frayer+ 2009)
J/ApJ/709/572 : COSMOS 70um sources (Kartaltepe+, 2010)
J/ApJ/716/348 : The XMM-Newton survey of the COSMOS field (Brusa+, 2010)
J/ApJ/760/128 : COSMOS 4<z<6 sources Lyα emission (Mallery+, 2012)
J/MNRAS/436/1919 : SCUBA observations of COSMOS galaxies (Casey+, 2013)
J/A+A/567/A76 : COSMOS field radio-loud AGN population at z>1 (Baldi+, 2014)
J/ApJ/819/62 : The COSMOS-Legacy Survey (CLS) catalog (Civano+, 2016)
J/AJ/128/1974 : The VLA-COSMOS survey (Schinnerer+, 2004)
J/ApJS/172/46 : VLA-COSMOS survey. II. (Schinnerer+, 2007)
J/ApJS/188/384 : The VLA-COSMOS survey. IV. (Schinnerer+, 2010)
J/MNRAS/443/2590 : The VLA-COSMOS Survey. V. 324MHz (Smolcic+, 2014)
J/A+A/602/A1 : VLA-COSMOS 3 GHz Large Project. I. (Smolcic+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- VLA [1/10966] Numerical ID of the VLA 3GHz source
7- 16 F10.6 deg RAdeg VLA right ascension at 3GHz (J2000)
18- 25 F8.6 deg DEdeg VLA declination at 3GHz (J2000)
27 I1 --- Multi [0/1] Multi-component flag (1 for
multi-component radio source)
29- 38 A10 --- CatCtp Counterpart catalog (1)
40- 46 I7 --- Ctp ID of the optical/MIR counterpart
48- 57 F10.6 deg RAcdeg Counterpart right ascension (J2000)
59- 66 F8.6 deg DEcdeg Counterpart declination (J2000)
68- 73 F6.4 arcsec Sep Angular distance between the VLA source and
its counterpart (2)
75- 80 E6.3 --- Pfalse ?=-1 False-match probability (3)
82- 89 F8.4 --- zbest ?=-99 Best available redshift
91-102 F12.6 uJy F3GHz Total integrated flux density at 3GHz
104-113 F10.6 [W/Hz] logL10cm ?=-99 Radio luminosity at 10cm (3GHz)
115-124 F10.6 [W/Hz] logL21cm ?=-99 Radio luminosity at 21cm (1.4GHz) (4)
126-135 F10.6 [Lsun] logLTIRSF ?=-99 8-1000um luminosity of the host
galaxy (5)
137-147 E11.6 Msun/yr SFR ?=-99 Star-formation rate from LTIRSF (6)
149 A1 --- XrayAGN [T/F] Boolean Flag for X-ray AGN
151 A1 --- MIRAGN [T/F] Boolean Flag for mid-IR AGN
153 A1 --- SEDAGN [T/F] Boolean Flag for SED AGN
155 A1 --- QMLAGN [T/F] Boolean Flag for Quiescent MLAGN
157 A1 --- SFG [T/F] Boolean Flag for star-forming galaxies
159 A1 --- CleanSFG [T/F] Boolean Flag for no radio-excess SFGs
161 A1 --- HLAGN [T/F] Boolean Flag for HLAGN
163 A1 --- MLAGN [T/F] Boolean Flag for MLAGN
165 A1 --- RExcess [T/F] Boolean Flag for (3sigma) radio-excess
167 I1 --- flagC15 [0/8] Flag for the area of 1.77sq.degrees (7)
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Note (1): Counterpart catalogs: COSMOS2015, IRAC or iband.
Note (2): The angular distance (Sep) between each single (MULTI=0) VLA source
and its counterpart is smaller than 0.8 (1.7) arcsec for counterparts taken
from COSMOS2015 or i-band (IRAC) catalogs.
Note (3): The false match probability was imposed to -1. for multi-component
radio sources (MULTI=1) as their counterpart association was performed
based on visual image inspection.
Note (4): L21cm (1.4GHz) estimates were taken from the observed 1.4-3GHz
spectral index, if the source was detected at 1.4GHz; otherwise, a spectral
index of -0.7 was assumed to convert the 3 GHzfluxes into L21cm.
Note (5): If the source is classified as HLAGN, this value represents the
fraction of the total infrared luminosity arising from star formation,
while it corresponds to the total IR luminosity otherwise (see
Delvecchio et al. 2017, in prep.).
Infrared luminosities were imposed to -99. if the SED-fitting was not run,
i.e. in case the redshift or the optical photometry were not available.
Note (6): by assuming the Kennicutt (1998ApJ...498..541K 1998ApJ...498..541K) conversion factor,
and scaled to a Chabrier (2003ApJ...586L.133C 2003ApJ...586L.133C) IMF.
SFR were imposed to -99. if the SED-fitting was not run, i.e. in case the
redshift or the optical photometry were not available.
Note (7): Flag as follows:
1 = COSMOS2015 masked area flag, true
0 = COSMOS2015 masked area flag, otherwise
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Acknowledgements:
Vernesa Smolcic, vs(at)phy.hr
Ivan Delvecchio, ivand(at)phy.hr
References:
Smolcic et al., Paper I 2017A&A...602A...1S 2017A&A...602A...1S, Cat. J/A+A/602/A1
Delvecchio et al., Paper III 2017A&A...602A...3D 2017A&A...602A...3D
Delhaize et al., Paper IV 2017A&A...602A...4D 2017A&A...602A...4D
Novak et al., Paper V 2017A&A...602A...5N 2017A&A...602A...5N
Smolcic et al., Paper VI 2017A&A...602A...6S 2017A&A...602A...6S
(End) Patricia Vannier [CDS] 26-Apr-2017