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VLACOSXOID - VLA-COSMOS 3-GHz Large Project Multiwavelength Counterparts Catalog

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Overview

In the reference paper, the authors study the composition of the faint radio population selected from the VLA-COSMOS 3-GHz 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 ~2.3 µJy/beam (µJy/beam), cataloguing 10,830 sources above 5 sigma, 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), the authors 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 near-IR (NIR) bands, reaching out to z ~ 6. They further classify the sources as star-forming galaxies or AGN based on various criteria, such as X-ray luminosity, observed mid-infrare (MIR) color, UV-far-infrared (FIR) spectral-energy distribution (SED), rest-frame near-ultraviolet (NUV)-optical color corrected for dust extinction, and radio-excess relative to that expected from the the hosts' star-formation rate. The authors separate the AGN into sub-samples dominated by low-to-moderate and moderate-to-high radiative luminosity AGN, i.e., candidates for high-redshift analogs to local low- and high-excitation emission line AGN, respectively. They study the fractional contributions of these sub-populations down to radio flux levels of ~11 uJy at 3 GHz (or ~20 uJy at 1.4 GHz assuming a spectral index of -0.7), and find that the dominant fraction at 1.4 GHz flux densities above ~200 uJy is constituted of low-to-moderate radiative luminosity AGN MLAGN). Below densities of ~100 uJy the fraction of star-forming galaxies (SFG) increases to ~60%, followed by the moderate-to-high radiative luminosity AGN (HLAGN) with ~20%, and MLAGN with ~20%. Based on this observational evidence, the authors extrapolate the fractions down to sensitivities of the Square Kilometer Array (SKA). Their 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.

This table contains the full list of 9,161 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 these radio sources. The authors 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.


Catalog Bibcode

2017A&A...602A...2S

References

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        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in July 2017 based on CDS Catalog J/A+A/602/A2 file table1.dat, the VLA-COSMOS 3-GHz Large Project multiwavelength counterpart catalog.

Parameters

Source_Number
A unique source number ID for the radio source. The maximum source number ID is 10,966 although there are 10,830 radio sources, as some IDs were removed by joining them into multi-component sources. There are 9,161 optical-MIR counterparts to these radio sources in this table.

RA
The Right Ascension of the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees in the original table.

Dec
The Declination of the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees in the original table.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Multi_Component_Flag
This flag parameter is set to 1 to indicate a multi-component radio source; otherwise, it is set to 0.

Ctrpart_Catalog
The catalog from which the multiwavelength counterpart to the radio source was taken: COSMOS2015, IRAC or iband (see Section 2.2 of the reference paper for more details).

Ctrpart_Source_Number
The source number identification of the optical/MIR counterpart to the radio source.

Ctrpart_RA
The Right Ascension of the multiwavelength counterpart to the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees in the original table. The RA has been corrected for small astrometry offsets as described in the Appendix of the reference paper.

Ctrpart_Dec
The Declination of the multiwavelength counterpart to the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees in the original table. The Dec has been corrected for small astrometry offsets as described in the Appendix of the reference paper.

Offset
The angular distance, in arcseconds, between the VLA source and its counterpart. The angular distance between each single (multi_component_flag =0 ) VLA source and its counterpart is smaller than 0.8 arcseconds for counterparts taken from the COSMOS2015 or i-band catalogs, and smaller than 1.7 arcseconds for counterparts taken from the IRAC catalog.

False_Match_Prob
The probability that the counterpart is a false match to the radio source. The false match probability was set to null (rather than -1 as in the original CDS table) for multi-component radio sources (multi_component_flag = 1) as their counterpart association was performed based on visual image inspection.

Redshift
The best available redshift for the source.

Flux_3_GHz
The total integrated flux density of the radio source at 3 GHz, in milliJansky (mJy). This was converted by the HEASARC from the µJy units used in the original table.

Log_Lum_3_GHz
The logarithm of the specific rest-frame luminosity of the radio source at 10 cm (3 GHz), in W Hz-1.

Log_Lum_1p4_GHz
The logarithm of the specific rest-frame luminosity of the adio source at 21 cm (1.4 GHz), in W Hz-1, which is obtained using the measured 1.4 - 3 GHz spectral index, if available, otherwise assuming a spectral index of -0.7.

Log_Lum_Tot_Irsf
The logarithm of the star formation-related infrared (8-1000 micron) rest-frame luminosity of the host galaxy, in solar luminosities, derived from SED fitting. If the source is classified as a moderate-to-high radiative luminosity AGN (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, A&A, 602, A3, for more details). Infrared luminosities were set to null (rather than to -99 as in the original table), if the SED-fitting was not run, i.e. in cases where the redshift or the optical photometry were not available.

SF_Rate
The star-formation rate, in solar masses per year, obtained from the total infrared luminosity (log_lum_tot_irsf), by assuming the Kennicutt (1998, ApJ, 498, 541) conversion factor, and scaled to a Chabrier (2003, ApJ, 586, L133) initial mass function (IMF). Star-formation rates were set to null (rather than to -99 as in the original table), if the SED-fitting was not run, i.e. in cases where the redshift or the optical photometry were not available.

Xray_AGN_Flag
This Boolean flag parameter is set to 'T' if the source is an X-ray-selected AGN, else is set to 'F'. (See Section 6.1.1 of the reference paper for more details.)

MIR_AGN_Flag
This Boolean flag parameter is set to 'T' if the source is an mid-IR-selected AGN, else is set to 'F'. (See Section 6.1.1 of the reference paper for more details.)

SED_AGN_Flag
This Boolean flag parameter is set to 'T' if the source is an SED-selected AGN, else is set to 'F'. (See Section 6.1.1 of the reference paper for more details.)

Quiescent_MLAGN_Flag
This Boolean flag parameter is set to 'T' if the source is a quiescent low-to-moderate radiative luminosity AGN (MLAGN), else is set to 'F'. (See Section 6.4 of the reference paper for more details.)

SF_Gal_Flag
This Boolean flag parameter is set to 'T' if the source is a star-forming galaxy (SFG), else is set to 'F'. (See Section 6.4 of the reference paper for more details.)

Clean_SF_Gal_Flag
This Boolean flag parameter is set to 'T' if the source is a star-forming galaxy (SFG) in the so-called "clean" SFG sample, i.e., it has a <= 3-sigma radio excess in log(L1.4GHz/SFRIR), else is set to 'F'. (See Section 6.4 of the reference paper for more details.)

HL_AGN_Flag
This Boolean flag parameter is set to 'T' if the source is a moderate-to-high radiative luminosity AGN (HLAGN), else is set to 'F'. (See Section 6.4 of the reference paper for more details.)

ML_AGN_Flag
This Boolean flag parameter is set to 'T' if the source is a low-to-moderate radiative luminosity AGN (MLAGN), else is set to 'F'. (See Section 6.4 of the reference paper for more details.)

Radio_Excess_Flag
This Boolean flag parameter is set to 'T' if the source is a radio-excess (i.e., it has a > 3-sigma radio excess in log(L1.4GHz/SFRIR)) low-to-moderate radiative luminosity AGN (MLAGN), else is set to 'F'. (See Section 6.4 of the reference paper for more details.)

COSMOS2015_Maskarea_Flag
This flag parameter is set to 1 if the source is in a COSMOS2015 masked area, else is set to 0 if it is in . the area of 1.77 degree2 of the COSMOS2015 catalog that lies outside the masked areas. A handful of sources in this table have values of this parameter > 1 (up to a maximum value of 8): the significance of these values is unknown to the HEASARC scientist who worked on this table.


Contact Person

Questions regarding the VLACOSXOID database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 7-Jul-2017