ATCDFSSS82 - Australia Telescope Chandra Deep Field-South and SDSS Stripe 82 20-GHz Sources

Overview

This table contains a source catalog, one of the first results from a deep, blind radio survey carried out at 20 GHz with the Australia Telescope Compact Array, with follow-up observations at 5.5, 9 and 18 GHz. The Australia Telescope 20GHz (AT20G) deep pilot survey covers a total area of 5 deg² in the Chandra Deep Field South and in Stripe 82 of the Sloan Digital Sky Survey. The authors estimate the survey to be 90% complete above 2.5 mJy. Of the 85 sources detected, 55% have steep spectra (spectral index alpha_1.4²⁰ < -0.5) and 45% have flat or inverted spectra (alpha_1.4²⁰ >= -0.5). The steep-spectrum sources tend to have single power-law spectra between 1.4 and 18 GHz, while the spectral indices of the flat- or inverted-spectrum sources tend to steepen with frequency. Among the 18 inverted-spectrum (alpha_1.4²⁰ >= 0.0) sources, 10 have clearly defined peaks in their spectra with alpha_1.4^5.5 > 0.15 and alpha₉¹⁸ < -0.15. On a 3-yr time-scale, at least 10 sources varied by more than 15 percent at 20 GHz, showing that variability is still common at the low flux densities probed by the AT20G-Deep Pilot (AT20GDP) survey.

The AT20G-Deep Pilot survey was carried out with he ATCA in 2009 July, shortly after the telescope was provided with a new wide-bandwidth correlator, the CABB. As a result of this upgrade to the telescope, the observing bandwidth was increased by a factor of 16, from 2x128 to 2x2048 MHz, in all bands (ranging from 1.1 to 105 GHz), greatly increasing the sensitivity of continuum observations. These observations were made in continuum mode using two 2048-MHz CABB bands centered at 19 and 21 GHz, with each 2048-MHz band divided into 2048 1-MHz channels. All four Stokes parameters were measured.

Catalog Bibcode

2014MNRAS.439.1212F

References

Deep 20-GHz survey of the Chandra Deep Field-South and SDSS Stripe 82:
source catalogue and spectral properties.
    Franzen T.M.O., Sadler E.M., Chhetri R., Ekers R.D., Mahony E.K.,
    Murphy T., Norris R.P., Waldram E.M., Whittam I.H.
   <Mon. Not. R. Astron. Soc., 439, 1212-1230 (2014)>
   =2014MNRAS.439.1212F

Provenance

This table was created by the HEASARC in August 2015 based on the union of CDS Catalog J/MNRAS/439/1212 files table2.dat (the 50 sources in the 3-hr field) and table3.dat (the 35 sources in the 21-hr field).

Parameters

Source_ID
The AT20GDP catalog source identifier (S01 - S50 for the 50 sources in the 3-hr field, and S51 - S85 for the 35 sources in the 21-hr field), in order of increasing J2000.0 Right Ascension.

Name
The catalog source designation, cf 'AT20GDP JHHMMSS+DDMMSS', using the AT20GDP prefix (for AT20G-Deep Pilot survey) and the J2000.0 equatorial coordinates.

RA
The Right Ascension of the radio source centroid in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table. This is the centroid position of all components included in the source. The peak position, interpolated between pixels, is taken to best represent the position of a component classified as point-like; the peak position from the Gaussian fitting is taken to best represent the position of a component classified as extended.

Dec
The Declination of the radio source centroid in the selected equinox. This was given in J2000.0 coordinates to a precision of 1 arcsecond in the original table. This is the centroid position of all components included in the source. The peak position, interpolated between pixels, is taken to best represent the position of a component classified as point-like; the peak position from the Gaussian fitting is taken to best represent the position of a component classified as extended.

LII
The Galactic Longitude of the radio source centroid.

BII
The Galactic Latitude of the radio source centroid.

Flux_20_GHz
The total flux density S₂₀ of the radio source at 20 GHz, in mJy. This is the total flux density of all components included in the source. The peak flux density is taken to best represent the flux density of a component classified as point-like; the integrated flux density from the Gaussian fitting is taken to best represent the flux density of a component classified as extended

Flux_20_GHz_Error
The uncertainty delta(S₂₀) in the total flux density of the radio source at 20 GHz, in mJy. This is the sum of the uncertainties on the flux densities of all components included in the source. For a component classified as point-like, the uncertainty is 5% of the peak flux density added in quadrature with the local noise. For a component classified as extended, the uncertainty is 5% of the integrated flux density added in quadrature with the error in the integrated flux density reported by the Gaussian-fitting task (which accounts for the local noise). The 5% calibration error is based on findings shown in Murphy et al. (2010, MNRAS, 402, 2403). To provide errors for the 20-GHz flux density measurements in the AT20G catalogue, Murphy et al. (2010) estimated the calibration error for each observational epoch from the scatter in the visibility amplitudes of the calibrators in each observing run. The calibration error was found to be typically 4-5% of the total flux density.

NVSS_Flux_1p4_GHz_Limit
This limit parameter is set to '<' if the corresponding flux density is an upper limit rather than a detection.

NVSS_Flux_1p4_GHz
The total flux density at 1.4 GHz of the radio source, in mJy, taken from the NVSS catalog (available as the HEASARC NVSS table or as the CDS Cat. VIII/65) or as estimated from the NVSS image. The latter was done for sources that did not appear in the NVSS catalog (see Section 4 of the reference paper for details).

NVSS_Flux_1p4_GHz_Flag
This flag parameter is set to 'I' to indicate that the corresponding flux density was derived from the NVSS image rather than from the NVSS Catalog.

Alt_Flux_1p4_GHz_Limit
This limit parameter is set to '<' if the corresponding flux density is an upper limit rather than a detection.

Alt_Flux_1p4_GHz
The total flux density at 1.4 GHz of the radio source, in mJy, taken from the ATLAS/FIRST catalog (Norris et al. 2006, AJ, 132, 2409, available as the HEASARC tables ATLASCSCPT and ATLASCSID, or as the CDS Cat. J/AJ/132/2409) or as estimated from the ATLAS/FIRST image. The latter was done for sources that did not appear in the ATLAS/FIRST catalog (see Section 4 of the reference paper for details).

Alt_Flux_1p4_GHz_Flag
This flag parameter is set to 'I' to indicate that the corresponding flux density was derived from the ATLAS/FIRST image rather than from the ATLAS/FIRST Catalog.

Flux_1p4_GHz_Limit
This limit parameter is set to '<' if the corresponding flux density is an upper limit rather than a detection.

Flux_1p4_GHz
The 'best' 1.4-GHz flux density S_1.4 of the radio source, in mJy. This is the NVSS flux density if the source is present in the NVSS catalog, otherwise it is the ATLAS/FIRST flux density in the 03-hr/21-hr field.

Flux_1p4_GHz_Flag
This flag parameter is set to 'I' to indicate that the corresponding flux density was derived from the ATLAS/FIRST or NVSS images rather than from the ATLAS/FIRST or NVSS Catalogs.

Spectral_Index_Limit
This limit parameter is set to '>' if the corresponding radio spectral index is a lower limit rather than a measured value.

Spectral_Index
The spectral index alpha_1.4²⁰ of the radio source between 1.4 and 20 GHz, obtained using the 1.4-GHz and 20-GHz flux densities.

Spectral_Class_Flag
This flag indicates the radio spectral class of the radio source: S = Steep, F = Flat, I = Inverted, where the authors use the following definitions:

      Steep (S): alpha_1.4²⁰ < -0.5
      Flat  (F): 0.5 < alpha_1.4²⁰ < 0
   Inverted (I): alpha_1.4²⁰ >= 0

Contact Person

Questions regarding the ATCDFSSS82 database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:24:37 EDT