@article{459d2f85158243fdbc0c00aac0e984d4,
title = "High-energy sources at low radio frequency: The Murchison Widefield Array view of Fermi blazars",
abstract = "Context. 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.",
keywords = "BL Lacertae objects: general, Catalogs, Gamma rays: galaxies, Quasars: general, Radiation mechanisms: non-thermal, Radio continuum: galaxies",
author = "M. Giroletti and F. Massaro and R. D'Abrusco and R. Lico and D. Burlon and N. Hurley-Walker and M. Johnston-Hollitt and J. Morgan and V. Pavlidou and M. Bell and G. Bernardi and R. Bhat and Judd Bowman and F. Briggs and Cappallo, {R. J.} and Corey, {B. E.} and Deshpande, {A. A.} and A. Ewall-Rice and D. Emrich and Gaensler, {B. M.} and R. Goeke and Greenhill, {L. J.} and Hazelton, {B. J.} and L. Hindson and Kaplan, {D. L.} and Kasper, {J. C.} and E. Kratzenberg and L. Feng and Daniel Jacobs and N. Kudryavtseva and E. Lenc and Lonsdale, {C. J.} and Lynch, {M. J.} and B. McKinley and McWhirter, {S. R.} and Mitchell, {D. A.} and Morales, {M. F.} and E. Morgan and D. Oberoi and Offringa, {A. R.} and Ord, {S. M.} and B. Pindor and T. Prabu and P. Procopio and J. Riding and Rogers, {A. E E} and A. Roshi and {Udaya Shankar}, N. and Srivani, {K. S.} and R. Subrahmanyan and Tingay, {S. J.} and M. Waterson and Wayth, {R. B.} and Webster, {R. L.} and Whitney, {A. R.} and A. Williams and Williams, {C. L.}",
note = "Funding Information: M.G. acknowledges financial support and kind hospitality during his visits at Curtin University and Sydney Institute for Astrophysics. We acknowledge financial contribution from grant PRIN-INAF-2011. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France, and of NASA's Astrophysics Data System. This scientific work makes use of the Murchison Radio-astronomy Observatory, operated by CSIRO. We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Support for the operation of the MWA is provided by the Australian Government Department of Industry and Science and Department of Education (National Collaborative Research Infrastructure Strategy: NCRIS), under a contract to Curtin University administered by Astronomy Australia Limited. We acknowledge the iVEC Petabyte Data Store and the Initiative in Innovative Computing and the CUDA Center for Excellence sponsored by NVIDIA at Harvard University. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat ? l'?nergie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucl?aire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A.Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden.",
year = "2016",
month = apr,
day = "1",
doi = "10.1051/0004-6361/201527817",
language = "English (US)",
volume = "588",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}