2016MNRAS.463.3143M

Query : 2016MNRAS.463.3143M

2016MNRAS.463.3143M - Mon. Not. R. Astron. Soc., 463, 3143-3150 (2016/December-2)

LOFAR imaging of Cygnus A - direct detection of a turnover in the hotspot radio spectra.

McKEAN J.P., GODFREY L.E.H., VEGETTI S., WISE M.W., MORGANTI R., HARDCASTLE M.J., RAFFERTY D., ANDERSON J., AVRUCH I.M., BECK R., BELL M.E., VAN BEMMEL I., BENTUM M.J., BERNARDI G., BEST P., BLAAUW R., BONAFEDE A., BREITLING F., BRODERICK J.W., BRUGGEN M., CERRIGONE L., CIARDI B., DE GASPERIN F., DELLER A., DUSCHA S., ENGELS D., FALCKE H., FALLOWS R.A., FRIESWIJK W., GARRETT M.A., GRIESSMEIER J.M., VAN HAARLEM M.P., HEALD G., HOEFT M., VAN DER HORST A.J., IACOBELLI M., INTEMA H., JUETTE E., KARASTERGIOU A., KONDRATIEV V.I., KOOPMANS L.V.E., KUNIYOSHI M., KUPER G., VAN LEEUWEN J., MAAT P., MANN G., MARKOFF S., McFADDEN R., McKAY-BUKOWSKI D., MULCAHY D.D., MUNK H., NELLES A., ORRU E., PAAS H., PANDEY-POMMIER M., PIETKA M., PIZZO R., POLATIDIS A.G., REICH W., ROTTGERING H.J.A., ROWLINSON A., SCAIFE A.M.M., SERYLAK M., SHULEVSKI A., SLUMAN J., SMIRNOV O., STEINMETZ M., STEWART A., SWINBANK J., TAGGER M., THOUDAM S., TORIBIO M.C., VERMEULEN R., VOCKS C., VAN WEEREN R.J., WUCKNITZ O., YATAWATTA S. and ZARKA P.

Abstract (from CDS):

The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for the dissipation of jet kinetic energy, particle acceleration, and magnetic-field generation. Here, we report new observations of the powerful radio galaxy Cygnus A using the Low Frequency Array (LOFAR) between 109 and 183 MHz, at an angular resolution of ∼3.5 arcsec. The radio emission of the lobes is found to have a complex spectral index distribution, with a spectral steepening found towards the centre of the source. For the first time, a turnover in the radio spectrum of the two main hotspots of Cygnus A has been directly observed. By combining our LOFAR imaging with data from the Very Large Array at higher frequencies, we show that the very rapid turnover in the hotspot spectra cannot be explained by a low-energy cut-off in the electron energy distribution, as has been previously suggested. Thermal (free-free) absorption or synchrotron self-absorption models are able to describe the low-frequency spectral shape of the hotspots; however, as with previous studies, we find that the implied model parameters are unlikely, and interpreting the spectra of the hotspots remains problematic.

Abstract Copyright: © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): radio continuum: galaxies - radio continuum: galaxies

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 M 82 AGN 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 6156 6
2 [HR74] A Rad 19 59 22.85 +40 44 25.5           ~ 18 0
3 [HR74] B Rad 19 59 23.05 +40 44 20.5           ~ 14 0
4 MCG+07-41-003 Bla 19 59 28.35656837 +40 44 02.0972325   16.22 15.10     ~ 2537 2
5 [HR74] D Rad 19 59 33.01 +40 43 40.7           ~ 17 0

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