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Probing the pc- and kpc-scale Environment of the Powerful Radio Galaxy Hercules A

Published online by Cambridge University Press:  05 March 2013

Nectaria A. B. Gizani
Centro de Astronomia e Astrofísica da Universidade de Lisboa, Observatório Astronómico de Lisboa, Tapada da Ajuda, Lisboa, Portugal, 1349-018;
M. A. Garrett
Joint Institute for VLBI in Europe, Postbus 2, Dwingeloo, The Netherlands, 7990 AA;
J. P. Leahy
Jodrell Bank Observatory, University of Manchester, Nr Macclesfield, UK, Cheshire SK 11 9DL;
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We present the kpc-scale behaviour of the powerful extragalactic radio source Hercules A and the behaviour of the intracluster gas in which the radio source is situated. We have found that Hercules A exhibits a strong Laing-Garrington effect. The X-ray observations have revealed an extended X-ray emission elongated along the radio galaxy axis. The estimated temperature of the cluster is kT=2.45 keV and the central electron density is n≃7.8×10−3 cm−3 which reveals a hot, dense environment in which Hercules A is situated. From the combined study of the radio and X-ray data we have estimated a central value of 3 ≲ B(μG)≲9.

We also present the most recent results from the analysis of the radio data on the pc-scale structure of the radio galaxy, observed at 18 cm by the EVN–MERLIN array. A faint but compact radio source, coincident with the optical centre of Hercules A, was detected by the EVN at 18 mas resolution. The total flux density of the EVN core is 14.6 mJy. Its angular size is 18×7 mas with a position angle of ≃139°. There is also evidence for extended emission in the NW–SE direction, most probably from the eastern pc-scale jet. If this is true then there is a misalignment between the direction of the pc-eastern and the aligned kpc-scale jets of ≃35°.

Research Article
Copyright © Astronomical Society of Australia 2002


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