GBT31GHZ - Green Bank Telescope 100-m 31-GHZ Radio Source Catalog

Overview

The 100m Robert C. Byrd Green Bank Telescope (GBT) and the 40m Owens Valley Radio Observatory (OVRO) telescope have been used to conduct a 31-GHz survey of 3165 known extragalactic radio sources over 143 deg² of the sky. Target sources were selected from the NRAO VLA Sky Survey (NVSS) in fields observed by the Cosmic Background Imager (CBI); most are extragalactic active galactic nuclei (AGNs) with 1.4-GHz flux densities of 3-10 mJy. Using a maximum-likelihood analysis to obtain an unbiased estimate of the distribution of the 1.4 - 31 GHz spectral indices of these sources, the authors find a mean 31 - 1.4 GHz flux ratio of 0.110 +/- 0.003 corresponding to a spectral index alpha = -0.71+/-0.01 (S_nu ~ nu^alpha); 9.0% +/- 0.8% of the sources have alpha > -0.5 and 1.2% +/- 0.2% have alpha > 0. By combining this spectral-index distribution with 1.4GHz source counts, the authors predict 31-GHz source counts in the range 1 mJy <S₃₁ < 4 mJy, N(>S₃₁) = (16.7+/-1.7)deg^-2(S₃₁/1mJy)^{(-0.80+/-0.07)}.

In this study, the authors present a detailed characterization of the impact of the discrete source foreground on arcminute-scale 31-GHz anisotropy measurements based upon two observational campaigns. The first campaign (the results of which are given in the OVRO31GHZ table) was carried out with the OVRO 40m telescope at 31 GHz from 2000 September through 2002 December. The second campaign (the results of which are given in the present table) used the GBT from 2006 February to May. A companion paper (Sievers et al. 2009arXiv0901.4540S) presents the five-year CBI total intensity power spectrum incorporating the results of the point-source measurements discussed here.

Reported error bars include a 10% and 5% rms gain uncertainty for GBT and OVRO measurements, respectively. Sources detected at greater than 4 sigma at 31 GHz are flagged (detection_flag = 'Y'); for this calculation, the random gain uncertainty was excluded. In all 3165 sources were observed. The GBT catalog (this table) contains 1490 sources. Of the 2315 useful OVRO observations many of the non-detections (and a few detections) were superceded by more sensitive GBT observations; the OVRO catalog contained in the HEASARC's OVRO31GHZ table therefore contains data on 1675 sources. The detection rate of the OVRO measurements was 11%, and that of the GBT measurements 25%. In all, 18% of the sources were detected at 31 GHz.

Catalog Bibcode

2009ApJ...704.1433M

References

A 31 GHz survey of low-frequency selected radio sources.
    Mason B.S., Weintraub L., Sievers J., Bond J.R., Myers S.T., Pearson T.J.,
    Readhead A.C.S., Shepherd M.C.
   <Astrophys. J., 704, 1433-1447 (2009)>
   =2009ApJ...704.1433M

Provenance

This table was created by the HEASARC in June 2012 based on CDS Catalpog J/ApJ/704/1433 file table3.dat.

Parameters

Name
The truncated NVSS source designation as given in this study, viz., 'NVSS JHHMMSS-DDMM', where the J2000.0 coordinates are used in the name. The CDS Dictionary of nomenclature of celestial Objects recommends the longer form 'NVSS JHHMMSS-DDMMSS' for NVSS sources. Users can recover these full NVSS names from the source position if so desired.

RA
The Right Ascension of the NVSS radio source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the NVSS radio source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the NVSS radio source.

BII
The Galactic Latitude of the NVSS radio source.

Flux_31_GHz
The 31-GHz flux density at the position of the NVSS radio source, in mJy.

Flux_31_GHz_Error
The uncertainty in the 31-GHz flux density, in mJy.

Flux_1p4_GHz
The 1.4-GHz NVSS integrated flux density, in mJy.

Flux_1p4_GHz_Error
The uncertainty in the 1.4-GHz NVSS integrated flux density, in mJy.

Major_Axis_1p4_GHz
The 1.4-GHz NVSS major axis, in arcseconds. If the source is unresolved, this is set to a null value.

Minor_Axis_1p4_GHz
The 1.4-GHz NVSS minor axis, in arcseconds. If the source is unresolved, this is set to a null value.

Detection_Flag
This flag parameter is set to 'Y' to indicate that there was a detection of >= 4 sigma at 31 GHz.

Conf_Corr_Flag
This flag parameter is set to 'Y' to indicate that a confusion correction has been performed on the measured 31-GHz flux density, as described in detail in Appendix A of the reference paper. In fact, in this table there are no such values.

Contact Person

Questions regarding the GBT31GHZ database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:27:51 EDT