X-ray and optical images of the galaxy group S4436. The left-hand panel shows the XMM-Newton/EPIC count map in the [0.7−1.2] keV band, smoothed with a Gaussian kernel of 10 arcsec width. The location of the central galaxy NGC 3298 is indicated with the white square, whereas the green circle shows the approximate location of R₅₀₀. The right-hand panel shows an SDSS RGB map of the system, with R = i, G = r, and B = g. The green contours show X-ray isophotes extracted from the smoothed XMM-Newton image.