1. Cen A & its interaction with the X-ray-emitting ISM
Worrall, Kraft, Hardcastle, Birkinshaw, Forman, Jones, Murray
The first definitive evidence for heating by a supersonically-expanding lobe is found in the inner SW lobe of Cen A.
12 kpc
500 kpc
3 keV
0.3 keV
radio contours on XMM
radio ~30’’ resolution
Chandra
See Kraft et al. 2003, ApJ, 592, 129
There is much current interest in the possibility of radio sources heating the ISM-ICM. The first definitive evidence for heating by a supersonically-expanding lobe is found in the inner SW lobe of Cen A.
Cen A is a 500 kpc-scale radio source within which sits a sub-galaxy-sized double-lobed inner radio structure.
With Chandra and XMM-Newton we measure a bright shell of X-ray-emitting gas capping the SW radio lobe. The resolution of these contours are poorer than the X-ray data, and the shell lies outside the radio emission.
The shell is hotter than the surrounding medium.
Since we have both density and temperature measurements in both these regions we can test a model of supersonic expansion and derive the expansion speed. The shell’s temperature and density are wrong for gas directly in contact with the bow shock but are correct for gas which has adiabatically cooled from about 6.8 keV to the 3 keV shell that we see.
The cooling increases the density and emissivity so that we can see it in contrast to the ambient medium as compared with the 6.8 keV gas which has poor contrast.
Santa Fe, Feb 2004