LOWZVLQVLA - VLA 6-GHz Observations of Low-Redshift SDSS QSOs

Overview

This table contains results from 6-GHz Jansky Very Large Array (JVLA) observations covering a volume-limited sample of 178 low-redshift (0.2 < z <0.3) optically selected quasi-stellar objects (QSOs). These 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of L₆ >~ 10^23.2 W/Hz that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have 10²¹ <~ L₆ <~ 10^23.2 W/Hz and radio sizes <~ 10 kpc, and the authors suggest that the bulk of their radio emission is powered by star formation in their host galaxies. "Radio-silent" QSOs (L_6_<~ 10²¹ W/Hz) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not "red and dead" ellipticals. Earlier radio observations did not have the luminosity sensitivity of L₆ <~ 10²¹ W/Hz that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning >> 10 kpc was found to be associated with 13 of the 18 RLQ cores with peak flux densities of S_p > 5 mJy/beam (log(L) >~ 24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple "unified" models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGN or their host galaxies must also determine whether or not a QSO appears radio-loud.

The authors have reprocessed the VLA observations of a sample of SDSS QSOs discussed in Kimball et al. (2011, ApJ, 739, L29). These were obtained using the VLA C configuration with a central frequency of 6 GHz and a bandwidth of 2 GHz in each of the two circular polarizations: with natural weighting the synthesized beam width was 3.5 arcseconds FWHM. The authors generated a catalog of radio sources associated with each QSO. They detected radio emission at 6 GHz from all but two of the 178 color-selected SDSS QSOs contained in this volume-limited sample of QSOs more luminous than M_i = -23 and with redshifts 0.2 < z < 0.3.

All calculations in the reference paper assume a flat LambdaCDM cosmology with H₀ = 70 km s^-1 Mpc^-1 and Omega_Lambda = 0.7. Spectral luminosities are specified by their source-frame frequencies, flux densities are specified in the observer's frame, and a mean spectral index of alpha = d(log S)/d(log nu) = -0.7 is used to make frequency conversions

Catalog Bibcode

2016ApJ...831..168K

References

Radio-loud and radio-quiet QSOs.
    Kellermann K.I., Condon J.J., Kimball A.E., Perley R.A., Ivezic Z.
   <Astrophys. J., 831, 168-168 (2016)>
   =2016ApJ...831..168K    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in April 2017 based upon the CDS Catalog J/ApJ/831/168 file table1.dat.

Parameters

Name
The J2000.0 position-based SDSS designation, viz., 'SDSS JHHMMSS.SS+DDMMSS.S', for the selected QSO.

RA
The Right Ascension of the JVLA-detected radio source in the vicinity of the SDSS QSO in the selected equinox (except for the QSO named SDSS J103421.71+605318.1: this was not detected in the radio and the cited position in this HEASARC table is the optical SDSS one). The was given in J2000.0 equatorial coordinates to a precision of 0.001 seconds of time in the original table.

Dec
The Declination of the JVLA-detected radio source in the vicinity of the SDSS QSO in the selected equinox (except for the QSO named SDSS J103421.71+605318.1: this was not detected in the radio and the cited position in this HEASARC table is the optical SDSS one). The was given in J2000.0 equatorial coordinates to a precision of 0.01 arcseconds in the original table.

LII
The Galactic Longitude of the JVLA-detected radio source in the vicinity of the SDSS QSO.

BII
The Galactic Latitude of the JVLA-detected radio source in the vicinity of the SDSS QSO.

Offset
The angular separation between the radio and optical positions of the QSO, in arcseconds. The QSO named SDSS J103421.71+605318.1 was not detected in the radio and the HEASARC has therefore set the offset value for this source to null.

Redshift
The redshift of the QSO, taken from the SDSS.

Int_Flux_6_GHz
The 6-GHz integrated flux density S_int of the JVLA-detected radio source near the position of the SDSS QSO including any extended structure, in mJy (converted by the HEASARC from the original units of µJy used in the original reference and table).

Int_Flux_6_GHz_Error
The RMS error in the 6-GHz integrated flux density of the JVLA-detected radio source near the position of the SDSS QSO, in mJy (converted by the HEASARC from the original units of µJy used in the original reference and table), calculated as the quadratic sum of the statistical error and a 3% uncertainty in the calibration.

Flux_6_GHz
The 6-GHz peak flux density S_p of the JVLA-detected radio source near the position of the SDSS QSO when observed at 3.5 arcseconds resolution, in mJy/beam (converted by the HEASARC from the original units of µJy/beam used in the original reference and table).

Flux_6_GHz_Error
The RMS error in the 6-GHz peak flux density of the JVLA-detected radio source near the position of the SDSS QSO, in mJy/beam (converted by the HEASARC from the original units of µJy/beam used in the original reference and table), calculated as the quadratic sum of the statistical error and a 3% uncertainty in the calibration.

Peak_Over_Int_Ratio
The ratio of the peak to integrated 6-GHz flux density S_p/S_int of the JVLA-detected radio source near the position of the SDSS QSO.

Log_Luminosity_6_GHz
The logarithm of the 6-GHz spectral luminosity in the source frame, in W Hz^-1, of the radio source.

Imag
The i-band apparent magnitude i of the QSO, taken from the SDSS Catalog.

Abs_Imag
The i-band absolute magnitude I of the QSO, based on its apparent i magnitude and redshift and using the cosmology described in the Overview section above.

Radio_Over_Iband_Ratio
The ratio R of the radio (6 GHz) to the optical (i band) flux densities for the QSO, calculated from R = S_int/S_i, where S_int is the integrated 6-GHz flux density in µJy, and the i-band flux density S_i is 10^(9.56 - i/2.5)^ µJy.

Contact Person

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Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:30:14 EDT