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LOFAR reveals the giant: A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31

LOFAR reveals the giant: A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31
LOFAR reveals the giant: A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31

We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. Our new LOFAR 145-MHz map shows that 3C 31 has a largest physical size of 1.1Mpc in projection, which means 3C 31 now falls in the class of giant radio galaxies. We model the radio continuum intensitieswith advective cosmic ray transport, evolving the cosmic ray electron population and magnetic field strength in the tails as functions of distance to the nucleus. We find that if there is no in situ particle acceleration in the tails, then decelerating flows are required that depend on radius r as v α rβ (β ≈ -1). This then compensates for the strong adiabatic losses due to the lateral expansion of the tails. We are able to find selfconsistent solutions in agreement with the entrainment model of Croston & Hardcastle, where the magnetic field provides ≈1/3 of the pressure needed for equilibrium with the surrounding intracluster medium. We obtain an advective time-scale of ≈190 Myr, which, if equated to the source age, would require an average expansion Mach number M≈ 5 over the source lifetime. Dynamical arguments suggest that instead either the outer tail material does not represent the oldest jet plasma or else the particle ages are underestimated due to the effects of particle acceleration on large scales.

Cosmic rays, Galaxies: active, Galaxies: individual: 3C 31, Radiation mechanisms: non-thermal, Radio continuum: galaxies
0035-8711
5049-5067
Heesen, V.
b8b21826-1b25-493c-9f2a-9b0428dd1713
Croston, J.H.
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Morganti, R.
c7a8d138-2007-465a-bf3c-d6768d027c09
Hardcastle, M.J.
43e73b1a-9ff1-479c-b9d2-5a730f1bdc8e
Stewart, A.J.
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Best, P.N.
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Broderick, J.W.
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Brüggen, M.
22978d12-1091-42aa-a172-6cda407ba55b
Brunetti, G.
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Chyzy, K.T.
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Harwood, J.J.
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Haverkorn, M.
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Hess, K.M.
156c4c14-7ff3-4ada-b6ef-f93d864d552e
Intema, H.T.
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Jamrozy, M.
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Kunert-Bajraszewska, M.
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McKean, J.P.
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Orrú, E.
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Röttgering, H.J.A.
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Shimwell, T.W.
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Shulevski, A.
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White, G.J.
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Wilcots, E.M.
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Williams, W.L.
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Heesen, V.
b8b21826-1b25-493c-9f2a-9b0428dd1713
Croston, J.H.
b10aa3fb-620e-4ec2-93e5-8594748d4822
Morganti, R.
c7a8d138-2007-465a-bf3c-d6768d027c09
Hardcastle, M.J.
43e73b1a-9ff1-479c-b9d2-5a730f1bdc8e
Stewart, A.J.
f892bf1d-c923-405d-a33b-cc2935b3fc20
Best, P.N.
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Broderick, J.W.
a7a30064-d115-4cca-9c6b-dbb6f7e24a25
Brüggen, M.
22978d12-1091-42aa-a172-6cda407ba55b
Brunetti, G.
b13bc133-80cd-4937-9fbd-9c2de6126b45
Chyzy, K.T.
862efb8f-e0b5-42d6-b803-cbcfe2ab22d1
Harwood, J.J.
60420142-8884-47c6-8993-b0f8796cadb4
Haverkorn, M.
b6197a6a-fda1-45aa-999a-1d124cc80367
Hess, K.M.
156c4c14-7ff3-4ada-b6ef-f93d864d552e
Intema, H.T.
55b658ae-56dd-4400-9439-5aef19088173
Jamrozy, M.
f07502d3-dac4-4c67-99be-cf70dbe66d75
Kunert-Bajraszewska, M.
c0e0adbe-8c8c-4440-a3f7-1bc94d4a7e3c
McKean, J.P.
a63ec76b-4ab5-41bb-9d6b-29392fce25c8
Orrú, E.
d8cf2da4-cf13-416b-8ecf-f497a27e549a
Röttgering, H.J.A.
071a6f5d-9a84-41f9-8ede-ba2764d76a19
Shimwell, T.W.
5525d776-1e36-4d25-85ec-45bad5a60e68
Shulevski, A.
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White, G.J.
bac7401a-04a6-4e48-b009-1f004c48ff17
Wilcots, E.M.
4f44491f-b70b-4899-8968-25ed20226aa2
Williams, W.L.
1476e168-cee4-4adb-a9e8-1902e6478c18

Heesen, V., Croston, J.H., Morganti, R., Hardcastle, M.J., Stewart, A.J., Best, P.N., Broderick, J.W., Brüggen, M., Brunetti, G., Chyzy, K.T., Harwood, J.J., Haverkorn, M., Hess, K.M., Intema, H.T., Jamrozy, M., Kunert-Bajraszewska, M., McKean, J.P., Orrú, E., Röttgering, H.J.A., Shimwell, T.W., Shulevski, A., White, G.J., Wilcots, E.M. and Williams, W.L. (2018) LOFAR reveals the giant: A low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31. Monthly Notices of the Royal Astronomical Society, 474 (4), 5049-5067. (doi:10.1093/mnras/stx2869).

Record type: Article

Abstract

We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. Our new LOFAR 145-MHz map shows that 3C 31 has a largest physical size of 1.1Mpc in projection, which means 3C 31 now falls in the class of giant radio galaxies. We model the radio continuum intensitieswith advective cosmic ray transport, evolving the cosmic ray electron population and magnetic field strength in the tails as functions of distance to the nucleus. We find that if there is no in situ particle acceleration in the tails, then decelerating flows are required that depend on radius r as v α rβ (β ≈ -1). This then compensates for the strong adiabatic losses due to the lateral expansion of the tails. We are able to find selfconsistent solutions in agreement with the entrainment model of Croston & Hardcastle, where the magnetic field provides ≈1/3 of the pressure needed for equilibrium with the surrounding intracluster medium. We obtain an advective time-scale of ≈190 Myr, which, if equated to the source age, would require an average expansion Mach number M≈ 5 over the source lifetime. Dynamical arguments suggest that instead either the outer tail material does not represent the oldest jet plasma or else the particle ages are underestimated due to the effects of particle acceleration on large scales.

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More information

Accepted/In Press date: 24 October 2017
e-pub ahead of print date: 10 November 2017
Published date: 1 March 2018
Keywords: Cosmic rays, Galaxies: active, Galaxies: individual: 3C 31, Radiation mechanisms: non-thermal, Radio continuum: galaxies

Identifiers

Local EPrints ID: 420532
URI: http://eprints.soton.ac.uk/id/eprint/420532
ISSN: 0035-8711
PURE UUID: de8ae250-1c39-4eab-9ee4-0881bd32b807

Catalogue record

Date deposited: 10 May 2018 16:30
Last modified: 11 Jul 2019 16:30

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Contributors

Author: V. Heesen
Author: J.H. Croston
Author: R. Morganti
Author: M.J. Hardcastle
Author: A.J. Stewart
Author: P.N. Best
Author: J.W. Broderick
Author: M. Brüggen
Author: G. Brunetti
Author: K.T. Chyzy
Author: J.J. Harwood
Author: M. Haverkorn
Author: K.M. Hess
Author: H.T. Intema
Author: M. Jamrozy
Author: M. Kunert-Bajraszewska
Author: J.P. McKean
Author: E. Orrú
Author: H.J.A. Röttgering
Author: T.W. Shimwell
Author: A. Shulevski
Author: G.J. White
Author: E.M. Wilcots
Author: W.L. Williams

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