Open AccessChandra and XMM–Newton observations of NGC 6251
Author(s) -
Evans D. A.,
Hardcastle M. J.,
Croston J. H.,
Worrall D. M.,
Birkinshaw M.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.08900.x
Subject(s) - physics , astrophysics , relativistic beaming , astronomy , radio galaxy , astrophysical jet , acis , jet (fluid) , nebula , synchrotron , fermi gamma ray space telescope , galaxy , rosat , active galactic nucleus , stars , nuclear physics , thermodynamics
We present new X‐ray observations of the nucleus, jet and extended emission of the nearby radio galaxy NGC 6251 using the Chandra /ACIS‐S camera, together with a reanalysis of archival Chandra /ACIS‐I and XMM–Newton /EPIC data. We find that the nuclear X‐ray spectrum is well fitted with an absorbed power law, and that there is tentative, but not highly significant, evidence for Fe Kα emission. We argue that the observed nuclear X‐ray emission is likely to originate in a relativistic jet, based on the double‐peaked nature, and our synchrotron self‐Compton modelling, of the radio to X‐ray spectral energy distribution. However, we cannot rule out a contribution from an accretion flow. We resolve X‐ray jet emission in three distinct regions, and argue in favour of a synchrotron origin for all three; inverse Compton emission models are possible but require extreme parameters. We detect thermal emission on both galaxy and group scales, and demonstrate that hot gas can confine the jet, particularly if relativistic beaming is important. We show evidence that the radio lobe has evacuated a cavity in the X‐ray‐emitting gas, and suggest that the lobe is close to the plane of the sky, with the jet entering the lobe close to the surface nearest to the observer.