Another set of surprises come from the presence of "unsuspected" large scale shocks, not seen/foreseen from the optical data. How many are we missing because we are not looking at the right wavelength?
This galaxy, brightest in a small poor group, became interesting because of its high Lx / Lb ratio as seen in the ROSAT All Sky Survey. X-ray emission was later measured to be very extended (>400 kpc), suggesting a large contribution from the group's potential [Trinchieri & Pietsch, 2000]. However, more interesting, the HRI saw an "arc" on arcmin scales, that was interpreted as the signature of a shock.
New Chandra data have now shown a quite dramatic view of the system (Fig. 8): a sharp discontinuity east of the central galaxy, with steep drops and a relatively narrow feature along a possible shock front, plus an arc to the NNW, are all indicative of a turmoil in the high energy component, possibly a trace of shocked material caused either by peculiar motions in the system or by a recent merger process. Although a better sampling of the velocity field is needed, neither the optical classification of the galaxy as a cD nor the small velocity dispersion for the group (300 km s-1, [Wegner et al. 1999]) could have suggested anomalous motions of this nature. A proper assessment of the X-ray properties in this and similar systems might be crucial for a more complete understanding of the dynamical and evolutionary properties of small galaxy systems.
Figure 8. The full Chandra field of IC1262 (LEFT). The oval indicates the optical position of the galxy. A turmoil at the center of the more diffuse emission and a sharp discontinuity in surface brightness are evident even in the raw data, in cuts across the narrow features visible.