Spectral index properties of milliJansky radio sources

Authors

  • K. E. Randall,

    Corresponding author
    1. Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
    2. CSIRO Astronomy and Space Science (CASS), PO Box 76, Epping, NSW 1710, Australia
      E-mail: krandall@physics.usyd.edu.au
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  • A. M. Hopkins,

    1. Australian Astronomical Observatory, PO Box 296, Epping, NSW 1710, Australia
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  • R. P. Norris,

    1. CSIRO Astronomy and Space Science (CASS), PO Box 76, Epping, NSW 1710, Australia
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  • P.-C. Zinn,

    1. Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany
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  • E. Middelberg,

    1. Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany
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  • M. Y. Mao,

    1. CSIRO Astronomy and Space Science (CASS), PO Box 76, Epping, NSW 1710, Australia
    2. Australian Astronomical Observatory, PO Box 296, Epping, NSW 1710, Australia
    3. School of Mathematics and Physics, University of Tasmania, Private Bag 27, Hobart, Tasmania 7001, Australia
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  • R. G. Sharp

    1. Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611, Australia
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E-mail: krandall@physics.usyd.edu.au

ABSTRACT

At the faintest radio flux densities (S1.4 < 10 mJy), conflicting results have arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610 MHz) and, for example, 1.4 GHz. We present a new catalogue of 843-MHz radio sources in the European Large Area ISO Survey-South 1 field, which contains the sources, their Australia Telescope Large Area Survey (ATLAS) counterparts and the spectral index distribution of the sources as a function of flux density. We do not find any statistically significant evidence for a trend towards flatter spectral indices with decreasing flux density. We then investigate the spectral index distribution with redshift for those sources with reliable redshifts and explore the infrared properties. An initial sample of faint compact steep-spectrum sources in ATLAS are also presented, with a brief overview of their properties.

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