High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars
Creators: name: Giroletti, M.
name: Massaro, F.
name: D'Abrusco, R.
name: Lico, R.
name: Burlon, D.
name: Hurley-Walker, N.
name: Johnston-Hollitt, M.
name: Morgan, J.
name: Pavlidou, V.
name: Bell, M.
name: Bernardi, G.
name: Bhat, R.
name: Bowman, J. D.
name: Briggs, F.
name: Cappallo, R. J.
name: Corey, B. E.
name: Deshpande, A. A.
name: Ewall-Rice, A.
name: Emrich, D.
name: Gaensler, B. M.
name: Goeke, R.
name: Greenhill, L. J.
name: Hazelton, B. J.
name: Hindson, L.
name: Kaplan, D. L.
name: Kasper, J. C.
name: Kratzenberg, E.
name: Feng, L.
name: Jacobs, D.
name: Kurdryavtseva, N.
name: Lenc, E.
name: Lonsdale, C. J.
name: Lynch, M. J.
name: McKinley, B.
name: McWhirter, S. R.
name: Mitchell, D. A.
name: Morales, M. F.
name: Morgan, E.
name: Oberoi, D.
name: Offringa, A. R.
name: Ord, S. M.
name: Pindor, B.
name: Prabu, T.
name: Procopio, P.
name: Riding, J.
name: Rogers, A. E. E.
name: Roshi, A.
name: Shankar, N. Udaya
name: Srivani, K. S.
name: Subrahmanyan, R.
name: Tingay, S. J.
name: Waterson, M.
name: Wayth, R. B.
name: Webster, R. L.
name: Whitney, A. R.
name: Williams, A.
name: Williams, C. L.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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 $\langle α_\mathrm{low} \rangle=0.57\pm0.02$: 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.
description: accepted for publication in A&amp;A