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

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; 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

doi:10.1051/0004-6361/201527817

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

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. GaenslerR. 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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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.

Original language	English
Article number	A141
Number of pages	9
Journal	Astronomy & Astrophysics
Volume	588
Early online date	1 Apr 2016
DOIs	https://doi.org/10.1051/0004-6361/201527817
Publication status	E-pub ahead of print - 1 Apr 2016

Keywords

astro-ph.HE

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10.1051/0004-6361/201527817

1602.08869v1Accepted author manuscript, 306 KB
aa27817-15Final published version, 281 KB

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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., ... Williams, C. L. (2016). High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars. Astronomy & Astrophysics, 588, Article A141. Advance online publication. https://doi.org/10.1051/0004-6361/201527817

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

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.",

keywords = "astro-ph.HE",

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 Bowman, {J. D.} 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 D. Jacobs and N. Kurdryavtseva 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 Shankar, {N. Udaya} 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 = "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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doi = "10.1051/0004-6361/201527817",

language = "English",

volume = "588",

journal = "Astronomy & Astrophysics",

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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, JD, Briggs, F, Cappallo, RJ, Corey, BE, Deshpande, AA, Ewall-Rice, A, Emrich, D, Gaensler, BM, Goeke, R, Greenhill, LJ, Hazelton, BJ, Hindson, L, Kaplan, DL, Kasper, JC, Kratzenberg, E, Feng, L, Jacobs, D, Kurdryavtseva, N, Lenc, E, Lonsdale, CJ, Lynch, MJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Oberoi, D, Offringa, AR, Ord, SM, Pindor, B, Prabu, T, Procopio, P, Riding, J, Rogers, AEE, Roshi, A, Shankar, NU, Srivani, KS, Subrahmanyan, R, Tingay, SJ, Waterson, M, Wayth, RB, Webster, RL, Whitney, AR, Williams, A & Williams, CL 2016, 'High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars', Astronomy & Astrophysics, vol. 588, A141. https://doi.org/10.1051/0004-6361/201527817

TY - JOUR

T1 - High-energy sources at low radio frequency

T2 - the Murchison Widefield Array view of Fermi blazars

AU - Giroletti, M.

AU - Massaro, F.

AU - D'Abrusco, R.

AU - Lico, R.

AU - Burlon, D.

AU - Hurley-Walker, N.

AU - Johnston-Hollitt, M.

AU - Morgan, J.

AU - Pavlidou, V.

AU - Bell, M.

AU - Bernardi, G.

AU - Bhat, R.

AU - Bowman, J. D.

AU - Briggs, F.

AU - Cappallo, R. J.

AU - Corey, B. E.

AU - Deshpande, A. A.

AU - Ewall-Rice, A.

AU - Emrich, D.

AU - Gaensler, B. M.

AU - Goeke, R.

AU - Greenhill, L. J.

AU - Hazelton, B. J.

AU - Hindson, L.

AU - Kaplan, D. L.

AU - Kasper, J. C.

AU - Kratzenberg, E.

AU - Feng, L.

AU - Jacobs, D.

AU - Kurdryavtseva, N.

AU - Lenc, E.

AU - Lonsdale, C. J.

AU - Lynch, M. J.

AU - McKinley, B.

AU - McWhirter, S. R.

AU - Mitchell, D. A.

AU - Morales, M. F.

AU - Morgan, E.

AU - Oberoi, D.

AU - Offringa, A. R.

AU - Ord, S. M.

AU - Pindor, B.

AU - Prabu, T.

AU - Procopio, P.

AU - Riding, J.

AU - Rogers, A. E. E.

AU - Roshi, A.

AU - Shankar, N. Udaya

AU - Srivani, K. S.

AU - Subrahmanyan, R.

AU - Tingay, S. J.

AU - Waterson, M.

AU - Wayth, R. B.

AU - Webster, R. L.

AU - Whitney, A. R.

AU - Williams, A.

AU - Williams, C. L.

N1 - 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.

PY - 2016/4/1

Y1 - 2016/4/1

N2 - 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.

AB - 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.

KW - astro-ph.HE

U2 - 10.1051/0004-6361/201527817

DO - 10.1051/0004-6361/201527817

M3 - Article

SN - 0004-6361

VL - 588

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - A141

ER -

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

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