Left panel: PlanckY_SZ map of PLCKG266.6−27.3 obtained with the modified internal linear combination algorithm (MILCA; Hurier et al. 2010) with a spatial resolution of 10′. Middle panel: XMM-Newton exposure-corrected count rate image of the region indicated by the black box in the left panel. It is obtained using data from the EMOS12 and EPN camera in the [0.3−2.0] keV energy band. The contours of the XMM-Newton image after wavelet filtering are overlaid in white. Right panel: corresponding XMM-Newton surface brightness profile. The green line indicates the best-fitting β-model with a cusp (see text); the red line is this model convolved with the point spread function (PSF) of XMM-Newton, and the dashed line is the on-axis PSF of XMM-Newton, normalised to the central intensity. The source is clearly significantly extended.