The Large Scale X-ray Emission from M87
  We describe asymmetrical features in a long exposure X-ray map of M87 made with the ROSAT High Resolution Imager (HRI). A bright triangular region is marked by a linear `spur' along one edge. The structure of this spur suggests an interpretation of a tangential view of a shock front 18 kpc long. None of the brighter features are spatially coincident with radio or optical structures so we concur with earlier investigators that most of the emission arises from thermal processes. 
D. E. Harris (Smithsonian Astrophysical Observatory) J. A. Biretta   (Space Telescope Science Institute) W. Junor (Universit...