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        High-energy sources at low radio frequency : the Murchison Widefield Array view of Fermi blazars

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        aa27817_15.pdf (PDF, 280Kb)
        1602.08869v1.pdf (PDF, 306Kb)
        Author
        Giroletti, M.
        Massaro, F.
        D'Abrusco, R.
        Lico, R.
        Burlon, D.
        Hurley-Walker, N.
        Johnston-Hollitt, M.
        Morgan, J.
        Pavlidou, V.
        Bell, M.
        Bernardi, G.
        Bhat, R.
        Bowman, J. D.
        Briggs, F.
        Cappallo, R. J.
        Corey, B. E.
        Deshpande, A. A.
        Ewall-Rice, A.
        Emrich, D.
        Gaensler, B. M.
        Goeke, R.
        Greenhill, L. J.
        Hazelton, B. J.
        Hindson, L.
        Kaplan, D. L.
        Kasper, J. C.
        Kratzenberg, E.
        Feng, L.
        Jacobs, D.
        Kurdryavtseva, N.
        Lenc, E.
        Lonsdale, C. J.
        Lynch, M. J.
        McKinley, B.
        McWhirter, S. R.
        Mitchell, D. A.
        Morales, M. F.
        Morgan, E.
        Oberoi, D.
        Offringa, A. R.
        Ord, S. M.
        Pindor, B.
        Prabu, T.
        Procopio, P.
        Riding, J.
        Rogers, A. E. E.
        Roshi, A.
        Shankar, N. Udaya
        Srivani, K. S.
        Subrahmanyan, R.
        Tingay, S. J.
        Waterson, M.
        Wayth, R. B.
        Webster, R. L.
        Whitney, A. R.
        Williams, A.
        Williams, C. L.
        Attention
        2299/20344
        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.
        Publication date
        2016-04-01
        Published in
        Astronomy & Astrophysics
        Published version
        https://doi.org/10.1051/0004-6361/201527817
        Other links
        http://hdl.handle.net/2299/20344
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