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

GIROLETTI, MARCELLOMARCELLOGIROLETTIMASSARO, FrancescoFrancescoMASSAROD'Abrusco, R.R.D'AbruscoLico, R.R.LicoBurlon, D.D.BurlonHurley-Walker, N.N.Hurley-WalkerJohnston-Hollitt, M.M.Johnston-HollittMorgan, J.J.MorganPavlidou, V.V.PavlidouBell, M.M.BellBERNARDI, GIANNIGIANNIBERNARDIBhat, R.R.BhatBowman, J. D.J. D.BowmanBriggs, F.F.BriggsCappallo, R. J.R. J.CappalloCorey, B. E.B. E.CoreyDeshpande, A. A.A. A.DeshpandeEwall-Rice, A.A.Ewall-RiceEmrich, D.D.EmrichGaensler, B. M.B. M.GaenslerGoeke, R.R.GoekeGreenhill, L. J.L. J.GreenhillHazelton, B. J.B. J.HazeltonHindson, L.L.HindsonKaplan, D. L.D. L.KaplanKasper, J. C.J. C.KasperKratzenberg, E.E.KratzenbergFeng, L.L.FengJacobs, D.D.JacobsKudryavtseva, N.N.KudryavtsevaLenc, E.E.LencLonsdale, C. J.C. J.LonsdaleLynch, M. J.M. J.LynchMcKinley, B.B.McKinleyMcWhirter, S. R.S. R.McWhirterMitchell, D. A.D. A.MitchellMorales, M. F.M. F.MoralesMorgan, E.E.MorganOberoi, D.D.OberoiOffringa, A. R.A. R.OffringaOrd, S. M.S. M.OrdPindor, B.B.PindorPrabu, T.T.PrabuProcopio, P.P.ProcopioRiding, J.J.RidingRogers, A. E. E.A. E. E.RogersRoshi, A.A.RoshiUdaya Shankar, N.N.Udaya ShankarSrivani, K. S.K. S.SrivaniSubrahmanyan, R.R.SubrahmanyanTingay, S. J.S. J.TingayWaterson, M.M.WatersonWayth, R. B.R. B.WaythWebster, R. L.R. L.WebsterWhitney, A. R.A. R.WhitneyWilliams, A.A.WilliamsWilliams, C. L.C. L.Williams2020-06-162020-06-1620160004-6361http://hdl.handle.net/20.500.12386/26075Context. 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. Aims: 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. Methods: We cross-correlated the 6100 deg2 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 Fermi-LAT. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. Results: 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 ⟨αlow⟩ = 0.57 ± 0.02: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at ~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. Conclusions: 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. Tables 5-7 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A141">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A141STAMPAenHigh-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazarsArticle10.1051/0004-6361/2015278172-s2.0-84964336826000373207800153http://arxiv.org/abs/1602.08869v1https://www.aanda.org/articles/aa/abs/2016/04/aa27817-15/aa27817-15.html2016A&A...588A.141GFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering