Adaptively smoothed and exposure-corrected (a) Chandra ACIS-I (ObsID 3712) and (b) XMM–Newton EPIC (ObsID 0300210201) images of the central 1.5 × 1.5 h⁻¹₇₁ Mpc² (21.93 × 21.93 arcmin²) region of Abell 3158. Both images are extracted in 0.3–2.0 keV and plotted in logarithmic scale. One small box and three crosses are used to mark the peak of the X-ray halo and the centres of luminous member galaxies PGC 13641, PGC 13652 and PGC 13679, respectively. (c) Optical DSS B-band image for the same sky field as (a) and (b), on which the Chandra X-ray intensity contours (square-root scale) are plotted.