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Article overview
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A Chandra Study of the Lobe/ISM Interactions Around the Inner Radio
Lobes of Centaurus A: Constraints on the Temperature Structure and Transport
Processes | | R. P. Kraft
; P. E. J. Nulsen
; M. Birkinshaw
; D. M. Worrall
; R. F. Penna
; W. R. Forman
; M. J. Hardcastle
; C. Jones
; S. S. Murray
; | | Date: |
27 Jun 2007 | | Abstract: | We present results from deeper {em Chandra} observations of the southwest
radio lobe of Centaurus A, first described by Kraft et al. (2003). We find that
the sharp X-ray surface brightness discontinuity extends around $sim$75% of
the periphery of the radio lobe, and detect significant temperature jumps in
the brightest regions of this discontinuity nearest to the nucleus. This
demonstrates that this discontinuity is indeed a strong shock which is the
result of an overpressure which has built up in the entire lobe over time.
Additionally, we demonstrate that if the mean free path for ions to transfer
energy and momentum to the electrons behind the shock is as large as the
Spitzer value, the electron and proton temperatures will not have equilibrated
along the SW boundary of the radio lobe where the shock is strongest. Thus the
proton temperature of the shocked gas could be considerably larger than the
observed electron temperature, and the total energy of the outburst
correspondingly larger as well. We investigate this using a simple
one-dimensional shock model for a two-fluid (proton/electron) plasma. We find
that for the thermodynamic parameters of the Cen A shock the electron
temperature rises rapidly from $sim$0.29 keV (the temperature of the ambient
ISM) to $sim$3.5 keV at which point heating from the protons is balanced by
adiabatic losses. The proton and electron temperatures do not equilibrate in a
timescale less than the age of the lobe. We note that the measured electron
temperature of similar features in other nearby powerful radio galaxies in poor
environments may considerably underestimate the strength and velocity of the
shock. | | Source: | arXiv, arxiv.0706.4013 | | Services: | Forum | Review | PDF | Favorites | |
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