Residuals of the X-ray surface brightness map after subtraction of the best fitting elliptical beta model (the colors correspond to the deviations in sigma to the surface brightness profile for each pixel). The black contours show the extended radio emission (Bacchi et al. 2003). The arrow indicates the position of the North surface brightness jump. The two red lines show the 70–120 deg sector used to produce the profile plotted in Fig. 11. Crosses show the positions of the peaks in the distribution of the optical spectroscopic members as in Figs. 8, and 9.