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ATLAS2P3GH - AT Large Area Survey (ATLAS) ELAIS-S1 & CDF-S 2.3-GHz Source Catalog

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Overview

The Australia Telescope Large Area Survey (ATLAS) aims to image a 7 deg2 region centered on the European Large Area ISO Survey - South 1 (ELAIS-S1) field and the Chandra Deep Field South (CDF-S) at 1.4 GHz with high sensitivity (up to sigma ~ 10 uJy) to study the evolution of star-forming galaxies (SFGs) and Active Galactic Nuclei (AGN) over a wide range of cosmic time.

The main goal of the present work is to study the radio spectra of an unprecedentedly large sample of sources (~ 2000 observed, ~ 600 detected in both frequencies). This table contains the results from ancillary radio observations at a frequency of 2.3 GHz which were obtained with the Australia Telescope Compact Array (ATCA). It comprises the catalog of sources with measured 1.4 GHz to 2.3 GHz spectral indices (Table 2 in the reference paper), compiled in the framework of ATLAS. It comprises only such sources which have unambiguous detections at both 1.4 GHz and 2.3 GHz, so no upper or lower limits on the spectral index based on non-detections are included.

The 2.3-GHz detection limit is 300 uJy (equivalent to 4.5 sigma in the ELAIS-S1 field and 4.0 sigma in the CDF-S). The authors compute spectral indices between 1.4 GHz and 2.3 GHz using matched-resolution images and investigate various properties of their source sample in their dependence on their spectral indices. The authors find the entire source sample to have a median spectral index of -0.74, in good agreement with both the canonical value of -0.7 for optically thin synchrotron radiation and other spectral index studies conducted by various groups. Regarding the radio spectral index Alpha as indicator for source type, they find only marginal correlations so that flat or inverted spectrum sources are usually powered by AGN and hence conclude that, at least for the faint population, the spectral index is not a strong discriminator. They investigate the z-Alpha relation for their source sample and find no such correlation between spectral index and redshift at all. The authors do find a significant correlation between redshift and radio to near-infrared flux ratio, making this a much stronger tracer of high-z radio sources. They also find no evidence for a dependence of the radio-IR correlation on spectral index.


Catalog Bibcode

2012A&A...544A..38Z

References

The Australia Telescope Large Area Survey: 2.3GHz observations of ELAIS-S1 and
CDF-S. Spectral index properties of the faint radio sky.
    Zinn P.-C., Middelberg E., Norris R.P., Hales C.A., Mao M.Y., Randall K.E.
    <Astron. Astrophys. 544, A38 (2012)>
    =2012A&A...544A..38Z        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in August 2012 based on CDS Catalog J/A+A/544/A38 file spix_pub.dat.

Parameters

Field_ID
This flag parameter indicates which of the two fields the radio source was found in: 'C' for CDF-S or 'E' for the ELAIS-S1 field.

Name
The ATLAS 2.3 and 1.4 GHz radio source designation, e.g., '[ZMN2012] F NNNCN', where the prefix stands for Zinn, Middelberg, Norris 2012, the middle character ('F', the field_id) is 'C' for sources in the CDF-S and 'E' for sources in the ELAIS-S1 field, and the final string ('NNNCN') is a unique identifier for the source within the specified field.

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 (3.6 mas). The actual accuracy of these precisions is presumably poorer, given the beam sizes of the ATCA at 1.4 and 2.3 GHz are much larger than this.

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 (3.6 mas). The actual accuracy of these precisions is presumably poorer, given the beam sizes of the ATCA at 1.4 and 2.3 GHz are much larger than this.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Flux_1p4_GHz
The integrated flux density of the radio source at 1.4 GHz in the original high-resolution map, as given by Hales et al. (in preparation), in mJy.

Flux_1p4_GHz_Error
The error in the integrated flux density of the radio source at 1.4 GHz in the original high-resolution map, as given by Hales et al. (in preparation), in mJy.

Flux_1p4_GHz_Low
The integrated flux density of the radio source at 1.4 GHz in the low-resolution map (where the original 1.4-GHz image has been convolved with a Gaussian kernel to match the resolution of the 2.3-GHz image), in mJy.

Flux_1p4_GHz_Low_Error
The error in the integrated flux density of the radio source at 1.4 GHz in the low-resolution map, as calculated using equation (1) in the reference paper, in mJy.

RMS_1p4_GHz_Low
The local rms noise at 1.4 GHz as measured in the low-resolution map, in mJy.

Flux_2p3_GHz
The integrated flux density of the radio source at 2.3 GHz, in mJy.

Flux_2p3_GHz_Error
The error in the integrated flux density of the radio source at 2.3 GHz, in mJy.

RMS_2p3_GHz
The local rms noise at 2.3 GHz, in mJy.

Spectral_Index
The spectral index obtained from the 1.4-GHz flux density (in the low-resolution map) and the 2.3-GHz flux density of the radio source.

Spectral_Index_Error
The error in the spectral index obtained from the 1.4-GHz flux density (in the low-resolution map) and the 2.3-GHz flux density of the radio source, as calculated using equation (4) in the reference paper.

Redshift
The spectroscopic redshift of the radio source, taken from Mao et al. (2012, MNRAS accepted), if available.

Spectral_Class
The spectroscopic classification of the radio source, taken from Mao et al. (2012, MNRAS accepted), if available, as follows:

          SF = optical spectrum dominated by star formation activity
         AGN = optical spectrum typical for AGN
               (e.g. AGNe for and AGN with characteristic emission lines)
           E = spectrum is that of an early-type galaxy and hence the radio
               emission must originate from an AGN hosted by it
  

Contact Person

Questions regarding the ATLAS2P3GH database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 20-Aug-2012