Irina I. Stefan, Chris L. Carilli, David A. Green, Zaki Ali, James E. Aguirre, Richard F. Bradley, Dave DeBoer, Matthew Dexter, Nicole E. Gugliucci, D. E. Harris, Daniel C. Jacobs, Dave MacMahon, Jason Manley, David F. Moore, Aaron R. Parsons, Jonathan C. Pober, William P. Walbrugh
We present observations taken with the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) of the Centaurus A field in the frequency range 120 to 180 MHz. The resulting image has a dynamic range of 3000 and an r.m.s. of 0.5 Jy/beam. A spectral index map of Cen A is produced across the full band. The spectral index distribution is qualitatively consistent with electron reacceleration in regions of excess turbulence in the radio lobes, as previously identified morphologically. Hence, there appears to be an association of `severe weather' in radio lobes with energy input into the relativistic electron population. We perform a detailed comparison of the large scale radio and X-ray emission from the ROSAT All Sky Survey. While the ROSAT field has significant gradients and structures on 10 deg scales possibly unrelated to Cen A, two interesting correlations are seen between the radio and X-ray emission. First is an apparent `cavity' generated by the northern radio lobe on a scale of 5 deg, possibly indicating excavation of thermal gas by the expanding radio source. Second is a correlation between radio and X-ray `hot spots' at the end of the southern lobe, some 200 kpc from the nucleus. This likely arises from Inverse Compton scattering of the CMB by the relativistic electrons also responsible for the radio synchrotron emission. The magnetic fields derived from the (possible) IC and radio emission are of similar magnitude as the minimum pressure fields, ~ 1 microG.
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http://arxiv.org/abs/1212.1624
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