Query : 2012A&A...544A..38Z

2012A&A...544A..38Z - Astronomy and Astrophysics, volume 544A, 38-38 (2012/8-1)

The Australia Telescope Large Area Survey: 2.3 GHz observations of ELAIS-S1 and CDF-S. Spectral index properties of the faint radio sky.


Abstract (from CDS):

The Australia Telescope Large Area Survey (ATLAS) aims to image a 7deg2 region centred on the European Large Area ISO Survey - South 1 (ELAIS-S1) field and the Chandra Deep Field South (CDF-S) at 1.4GHz with high sensitivity (up to σ∼10µJy) to study the evolution of star-forming galaxies (SFGs) and Active Galactic Nuclei (AGN) over a wide range of cosmic time. We present here ancillary radio observations at a frequency of 2.3GHz obtained with the Australia Telescope Compact Array (ATCA). The main goal of this is to study the radio spectra of an unprecedented large sample of sources (∼2000 observed, ∼600 detected in both frequencies). With this paper, we provide 2.3GHz source catalogues for both ATLAS fields, with a detection limit of 300µJy (equivalent to 4.5σ in the ELAIS-S1 field and 4.0σ in the CDF-S). We compute spectral indices between 1.4GHz and 2.3GHz using matched-resolution images and investigate various properties of our source sample in dependence of their spectral indices. We find the entire source sample to have a median spectral index αmed=-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 as indicator for source type, we 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. We investigate the z-α relation for our source sample and find no such correlation between spectral index and redshift at all. We 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. We also find no evidence for a dependence of the radio-IR correlation on spectral index.

Abstract Copyright:

Journal keyword(s): galaxies: active - catalogs - galaxies: evolution - radio continuum: galaxies - surveys

VizieR on-line data: <Available at CDS (J/A+A/544/A38): spix_pub.dat>

Nomenclature: [ZMN2012] ELAIS-S1 NNN N=265, [ZMN2012] ELAIS-S1 NNNCN N=16. [ZMN2012] CDF-S NNN N=247, [ZMN2012] CDF-S NNNCN N=103.

Status at CDS : Acronym for new objects described in the dictionary of nomenclature and being created in SIMBAD.

Simbad objects: 5

goto Full paper

goto View the references in ADS

Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 ICRF J002442.9-420203 G 00 24 42.98993 -42 02 03.9507   22       ~ 62 0
2 ELAIS S1 reg 00 34 44 -43 28.2           ~ 177 0
3 QSO B0237-2322 QSO 02 40 08.1743783856 -23 09 15.729012036   16.78 16.63     ~ 493 0
4 NAME Chandra Deep Field-South reg 03 32 28.0 -27 48 30           ~ 1973 1
5 ICRF J193925.0-634245 Sy2 19 39 25.0245304992 -63 42 45.640373400   18.87 18.37 17.64   ~ 1116 1

To bookmark this query, right click on this link: simbad:objects in 2012A&A...544A..38Z and select 'bookmark this link' or equivalent in the popup menu


© Université de Strasbourg/CNRS

    • Contact