J/ApJ/903/139 COSMOS-XS. II. Ultra-faint radio population (Algera+, 2020)
A Multiwavelength Analysis of the Faint Radio Sky (COSMOS-XS): the Nature of the
Ultra-faint Radio Population.
Algera H.S.B., van der Vlugt D., Hodge J.A., Smail I.R., Novak M.,
Radcliffe J.F., Riechers D.A., Rottgering H., Smolcic V., Walter F.
<Astrophys. J., 903, 139 (2020)>
=2020ApJ...903..139A 2020ApJ...903..139A
ADC_Keywords: Surveys; Active gal. nuclei; Radio sources
Keywords: High-redshift galaxies ; Active galactic nuclei ; Radio source
counts ; Galaxy evolution ; Radio continuum emission ; Catalogs
Abstract:
Ultra-deep radio surveys are an invaluable probe of dust-obscured star
formation, but require a clear understanding of the relative
contribution from radio active galactic nuclei (AGNs) to be used to
their fullest potential. We study the composition of the µJy radio
population detected in the Karl G. Jansky Very Large Array COSMOS-XS
survey based on a sample of 1540 sources detected at 3GHz over an area
of ∼350arcmin2. This ultra-deep survey consists of a single pointing
in the well-studied COSMOS field at both 3 and 10GHz and reaches rms
sensitivities of 0.53 and 0.41µJy/beam, respectively. We find
multiwavelength counterparts for 97% of radio sources, based on a
combination of near-UV/optical to sub-millimeter data, and through a
stacking analysis at optical/near-IR wavelengths we further show that
the sources lacking such counterparts are likely to be high-redshift
in nature (typical z∼4-5). Utilizing the multiwavelength data over
COSMOS, we identify AGNs through a variety of diagnostics and find
these to make up 23.2∼1.3% of our sample, with the remainder
constituting uncontaminated star-forming galaxies. However, more than
half of the AGNs exhibit radio emission consistent with originating
from star formation, with only 8.8∼0.8% of radio sources showing a
clear excess in radio luminosity. At flux densities of ∼30µJy at
3GHz, the fraction of star formation-powered sources reaches ∼90%, and
this fraction is consistent with unity at even lower flux densities.
Overall, our findings imply that ultra-deep radio surveys such as
COSMOS-XS constitute a highly effective means of obtaining clean
samples of star formation-powered radio sources.
Description:
The COSMOS-XS survey consists of a single ultra-deep Very Large Array
(VLA) pointing in the well-studied COSMOS field at both 3 and 10GHz of
∼100 and ∼90hr of observation time, respectively. We complement our
radio observations with NUV to FIR data that have been compiled into
various multiwavelength catalogs: (I) the Super-deblended MIR to FIR
catalog containing photometry ranging from IRAC 3.6µm to 20cm radio
observations, (II) the z++YJHKs-selected catalog compiled by Laigle+,
2016, J/ApJ/817/34 (hereafter COSMOS2015), and (III) the i-band
selected catalog by Capak+, 2007,II/284 .Strong X-ray emission is a
vital diagnostic for AGN activity. The most recent X-ray data over the
COSMOS field is the 4.6Ms Chandra COSMOS Legacy survey covering the
full 2.2deg2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tabled1.dat 287 1437 COSMOS-XS Multi-wavelength and AGN catalog
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See also:
II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
VIII/103 : Herschel Multi-tiered Extragalactic Survey (Oliver+, 2012)
VIII/95 : Herschel Multi-tiered Extragalactic Survey (Oliver+, 2012)
J/ApJ/554/803 : New VLA Sky Survey Cat of IRAS 2 Jy Galaxies (Yun+ 2001)
J/ApJ/586/794 : Multiwavelength luminosities of galaxies (Bell, 2003)
J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007)
J/ApJS/172/46 : VLA-COSMOS survey. II. (Schinnerer+, 2007)
J/ApJ/690/1236 : COSMOS photometric redshift catalog (Ilbert+, 2009)
J/ApJS/184/218 : The zCOSMOS 10k-bright spectroscopic sample (Lilly+, 2009)
J/ApJ/690/20 : Models of the AGN and black hole populations (Shankar+, 2009)
J/ApJ/699/L43 : FIRST-NVSS-SDSS AGN sample catalog (Smolcic+, 2009)
J/ApJS/188/384 : The VLA-COSMOS survey. IV. (Schinnerer+, 2010)
J/MNRAS/415/3831 : AzTEC/ASTE source catalogue (Aretxaga+, 2011)
J/A+A/534/A110 : Type-2 AGN from XMM-COSMOS bolometric output (Lusso+, 2011)
J/A+A/532/A90 : PACS Evolutionary Probe (PEP-DR1) catalogs (Lutz+, 2011)
J/ApJ/742/61 : Photometric redshift AGNs from XMM & C-COSMOS (Salvato+ 2011)
J/A+A/544/A156 : UltraVISTA Catalogue Release DR1 (McCracken+, 2012)
J/ApJ/761/97 : Star Formation in Radio Survey: 33GHz obs. (Murphy+, 2012)
J/A+A/551/A100 : Panchromatic SED of Herschel sources (Berta+, 2013)
J/MNRAS/436/3759 : ECDFS sources optical/IR counterparts (Bonzini+, 2013)
J/ApJS/206/8 : COSMOS/UltraVISTA Ks-selected catalogs v4.1 (Muzzin+, 2013)
J/ApJ/788/125 : ALMA survey of ECDFS submillimeter galaxies (Simpson+, 2014)
J/MNRAS/442/577 : Selected ALESS submm galaxies radio prop. (Thomson+, 2014)
J/ApJ/803/34 : z∼4-10 galaxies from HST legacy fields (Bouwens+, 2015)
J/ApJ/806/110 : ALESS survey: SMGs in the ECDF-S data (da Cunha+, 2015)
J/ApJ/819/62 : The COSMOS-Legacy Survey (CLS) catalog (Civano+, 2016)
J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)
J/ApJ/817/34 : C-COSMOS Legacy sources multiwavelength cat. (Marchesi+, 2016)
J/MNRAS/465/1789 : SCUBA-2 Cosmology Legacy Survey (Geach+, 2017)
J/A+A/607/A132 : VLBA observations of the COSMOS field (Herrera Ruiz+, 2017)
J/A+A/602/A2 : VLA-COSMOS 3 GHz Large Project. II. (Smolcic+, 2017)
J/A+A/602/A1 : VLA-COSMOS 3 GHz Large Project (Smolcic+, 2017)
J/ApJ/856/67 : VLA 3GHz radio source catalog in Lockman Hole (Cotton+, 2018)
J/ApJ/853/172 : "Super-deblended" dust emission in galaxies. I. (Liu+, 2018)
Byte-by-byte Description of file: tabled1.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- ID Source identifier (1)
26- 43 F18.14 deg RAdeg [149/151] Right Ascension (J2000) (2)
45- 60 F16.14 deg DEdeg [2.37/2.73] Declination (J2000) (2)
62- 66 F5.3 --- z [0.001/5.31] Optimal radio source redshift
68- 72 A5 --- f_z Boolean flag on z (3)
74- 80 F7.1 uJy F1.4 [27/82740]?=-99 1.4 GHz flux density
82- 86 F5.1 uJy e_F1.4 [8/61]?=-99 Uncertainty in F1.4
88- 94 F7.1 uJy F3 [2.6/27443.1] The 3 GHz flux density
96- 99 F4.1 uJy e_F3 [0.5/35]? Uncertainty in F3
101-105 F5.1 uJy F10 [2.1/110]?=-99 The 10 GHz flux density
107-111 F5.1 uJy e_F10 [0.4/3.4]?=-99 Uncertainty in F10
113-123 E11.4 --- SD ?=-99 Super-Deblended catalog identifier
125-132 F8.1 --- C15 [709682/939857]?=-99 COSMOS2015 catalog
identifier (5)
134-142 F9.1 --- i07 [1226540/1682121]?=-99 The i-band selected
catalog identifier (5)
144-148 A5 --- Spur Potentially spurious flag (4)
150-159 E10.4 W/Hz L1.4 [1.2e+17/1.9e+26] Rest-frame 1.4GHz luminosity
161-170 E10.4 W/Hz e_L1.4 [2.4e+16/6.8e+25] The 16th percentile
uncertainty in L1.4
172-181 E10.4 W/Hz E_L1.4 [2.3e+16/9.9e+25] The 84th percentile
uncertainty in L1.4
183-193 E11.4 --- qTIR [-3.58/4.93] Radio-FIR correlation parameter eq1
195-204 E10.4 --- e_qTIR [0.0001/0.97] 16th percentile uncertainty qTIR
206-215 E10.4 --- E_qTIR [0.0001/0.83] 84th percentile uncertainty qTIR
217-221 A5 --- Xray AGN from X-ray flag
223-227 A5 --- IRAC AGN from mid-IR colors flag (5)
229-233 A5 --- SED AGN from SED fitting flag
235-239 A5 --- Torus SED-AGN from MIR torus component flag
241-245 A5 --- Disk SED-AGN from UV/opt accretion disk component
247-251 A5 --- rfopt AGN from red rest-frame near-UV & opt colors
253-257 A5 --- qe AGN from radio emission excess (6)
259-263 A5 --- iqe AGN from radio emission excess (7)
265-269 A5 --- HLAGN HLAGN flag (8)
271-275 A5 --- MLAGN MLAGN flag (9)
277-281 A5 --- agn-ex Radio-excess AGN flag (10)
283-287 A5 --- agn-noex AGN without radio excess (11)
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Note (1): Equal to the ID assigned in Paper I
(Van der Vlugt 2021ApJ...907....5V 2021ApJ...907....5V ;
<COSMOS-XS JHHMMSS.ss+DDMMSS.ss> in Simbad).
Note (2): Radio coordinates of the source as determined by PyBDSF.
Note (3): True indicates spectroscopic. False is photometric.
Note (4): Based on the discussion in Section 2.1, in which case it is set to
True.
Note (5): By means of the Donley+, 2012ApJ...748.142D wedge.
Note (6): From what is expected from the radio-FIR correlation, with FIR
luminosities calculated using MAGPHYS.
Note (7): From what is expected from the radio- FIR correlation, in the
absence of Herschel FIR- photometry, through comparison with the
detection limit of Herschel.
Note (8): Is True when either of columns 22-26 are True.
Note (9): Is True when all of columns 22-26 are False and either of columns
27-29 are True.
Note (10): Is True when either of columns 28-29 is True.
Note (11): Is True when either of columns 22-27 are True and
both columns 28-29 are False.
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History:
From electronic version of the journal
References:
Van der Vlugt et al. Paper I : 2021ApJ...907....5V 2021ApJ...907....5V
(End) Prepared by [AAS], Coralie Fix [CDS], 10-Feb-2022