Smolčić, Vernesa and Ciliegi, Paolo and Jelić, Vibor and Bondi, Marco and Schinnerer, Eva and Carilli, Chris L. and Riechers, Dominik A. and Salvato, Mara and Brković, Alen and Capak, Peter and Ilbert, Olivier and Karim, Alexander and McCracken, Henry and Scoville, Nick Z. (2014) The VLA-COSMOS Survey - V. 324 MHz continuum observations. Monthly Notices of the Royal Astronomical Society, 443 (3). pp. 2590-2598. ISSN 0035-8711. http://resolver.caltech.edu/CaltechAUTHORS:20150717-093344696
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We present 90 cm Very Large Array imaging of the COSMOS field, comprising a circular area of 3.14 square degrees at 8.0arcsec × 6.0arcsec angular resolution with an average rms of 0.5 mJy beam^(−1). The extracted catalogue contains 182 sources (down to 5.5σ), 30 of which are multicomponent sources. Using Monte Carlo artificial source simulations, we derive the completeness of the catalogue, and we show that our 90 cm source counts agree very well with those from previous studies. Using X-ray, NUV–NIR and radio COSMOS data to investigate the population mix of our 90 cm radio sample, we find that our sample is dominated by active galactic nuclei. The average 90–20 cm spectral index (S_ν ∝ ν^α, where S_ν is the flux density at frequency ν and α the spectral index) of our 90 cm selected sources is −0.70, with an interquartile range from −0.90 to −0.53. Only a few ultra-steep-spectrum sources are present in our sample, consistent with results in the literature for similar fields. Our data do not show clear steepening of the spectral index with redshift. Nevertheless, our sample suggests that sources with spectral indices steeper than −1 all lie at z ≳ 1, in agreement with the idea that ultra-steep-spectrum radio sources may trace intermediate-redshift galaxies (z ≳ 1).
|Additional Information:||© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 July 1. Received 2014 June 23; in original form 2014 April 1. First published online August 4, 2014. VS acknowledges the European Unions Seventh Frame-work programme grant agreement 333654 (CIG, ‘AGN feedback’) and the Australian Group of Eight European Fellowship 2013. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. AK acknowledges support by the Collaborative Research Council 956, sub-project A1, funded by the Deutsche Forschungsgemeinschaft (DFG).|
|Subject Keywords:||radiation mechanisms: general – surveys – radio continuum: galaxies|
|Official Citation:||Vernesa Smolčić, Paolo Ciliegi, Vibor Jelić, Marco Bondi, Eva Schinnerer, Chris L. Carilli, Dominik A. Riechers, Mara Salvato, Alen Brković, Peter Capak, Olivier Ilbert, Alexander Karim, Henry McCracken, and Nick Z. Scoville The VLA-COSMOS Survey – V. 324 MHz continuum observations MNRAS (September 21, 2014) Vol. 443 2590-2598 doi:10.1093/mnras/stu1331 First published online August 4, 2014|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||22 Jul 2015 15:14|
|Last Modified:||22 Jul 2015 15:14|
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