rms coverage of the LOFAR XMM-LSS images. Panel a: image of the rms coverage across the field in which the flux scale varies between σ_cen and 5σ_cen, where σ_cen is the central rms of the image that was found to be 0.28 mJy beam⁻¹. Panel b: plot of the area of the field that has an rms less than the given value. On the left-hand y-axis this is as a function of area in deg² and on the right-hand y-axis it is given as a percentage of the total area. The noise can be relatively high around bright sources in the field.