University of Hertfordshire

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  • 1602.08869v1

    Accepted author manuscript, 306 KB, PDF document

  • aa27817-15

    Final published version, 280 KB, PDF document

  • M. Giroletti
  • F. Massaro
  • R. D'Abrusco
  • R. Lico
  • D. Burlon
  • N. Hurley-Walker
  • M. Johnston-Hollitt
  • J. Morgan
  • V. Pavlidou
  • M. Bell
  • G. Bernardi
  • R. Bhat
  • J. D. Bowman
  • F. Briggs
  • R. J. Cappallo
  • B. E. Corey
  • A. A. Deshpande
  • A. Ewall-Rice
  • D. Emrich
  • B. M. Gaensler
  • And 37 others
  • R. Goeke
  • L. J. Greenhill
  • B. J. Hazelton
  • L. Hindson
  • D. L. Kaplan
  • J. C. Kasper
  • E. Kratzenberg
  • L. Feng
  • D. Jacobs
  • N. Kurdryavtseva
  • E. Lenc
  • C. J. Lonsdale
  • M. J. Lynch
  • B. McKinley
  • S. R. McWhirter
  • D. A. Mitchell
  • M. F. Morales
  • E. Morgan
  • D. Oberoi
  • A. R. Offringa
  • S. M. Ord
  • B. Pindor
  • T. Prabu
  • P. Procopio
  • J. Riding
  • A. E. E. Rogers
  • A. Roshi
  • N. Udaya Shankar
  • K. S. Srivani
  • R. Subrahmanyan
  • S. J. Tingay
  • M. Waterson
  • R. B. Wayth
  • R. L. Webster
  • A. R. Whitney
  • A. Williams
  • C. L. Williams
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Original languageEnglish
Article numberA141
Number of pages9
JournalAstronomy & Astrophysics
Journal publication date1 Apr 2016
Volume588
Early online date1 Apr 2016
DOIs
Publication statusE-pub ahead of print - 1 Apr 2016

Abstract

Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. We characterize the spectral properties of the blazar population at low radio frequency compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. We cross-correlated the 6,100 deg^2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by \fermilat. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120--180 MHz) blazar spectral index is $\langle \alpha_\mathrm{low} \rangle=0.57\pm0.02$: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at $\sim$GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources. Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population.

Notes

This is the accepted version of the following article: Giroletti, M. et al., A&A, 588 (2016) A141, which has been published in final form at DOI: http://dx.doi.org/10.1051/0004-6361/201527817. This article may be used for non-commercial purposes in accordance with the EDP Sciences self-archiving policies.

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