X-ray sources in the direction of M 22. Chandra sources, with the numbers given in Table 1 are shown with their 1σ error circles (red). The larger (blue) error circles show the XMM-Newton sources detected in the field of view, as extracted from the catalogue 2XMM (Watson et al. 2009). The crosses show the positions of the possible optical counterparts. The two largest circles centred on the image are the core radius (1.33′) and the half mass radius (3.36′) (Harris 1996, December 2010 revision).