Optical and near-IR images of the field of 2XMMp J092120.2+371735. Panela: SDSS DR6 image. Panelb: W1-band (3.4 μm) image from the AllWISE survey. Panelc: LBC image (mean of the r- and z-SLOAN filters). North is up, east is left, and all images cover the same region. Blue dashed lines (middle and right images) indicate contours from the X-ray flux. Red squares overplotted on the LBC image refer to the z ~ 1.2 group, and green circles to spectroscopic sources outside our membership criteria. Blue cycles show galaxies from the foreground population (z ~ 1).