An XMM-Newton study of the sub-structure in M87's halo
  The high signal to noise and good point spread function of XMM have allowed the first detailed study of the interaction between the thermal and radio emitting plasma in the central regions of M87. We show that the X-ray emitting structure, previously seen by ROSAT, is thermal in nature and that the east and southwest extensions in M87's X-ray halo have a significantly lower temperature (kT= 1.5 keV) than the surrounding ambient medium (kT= 2.3 keV). There is little or no evidence for non-thermal emission with an upper limit on the contribution of a power law component of spectral index flatter than 3 being less than 1% of the flux in the region of the radio lobes. 
E. Belsole, J.L. Sauvageot, H. Bohringer, D.M. Worrall, K. Matsushita,   R.F. Mushotzky, I. Sakelliou, S. Molendi, M. Ehle, ...