X-ray surface brightness profile of MW-mass galaxies (left) in CEN_AGN sample, after subtracting background and masking X-ray sources (green points), the maximal X-ray emission from the unresolved point sources (blue points), in the shape of PSF (green dashed line). Observed maximal X-ray luminosity (right) of unresolved point source (blue), the model predicted XRB luminosity (purple), and the residual X-ray luminosity of unresolved AGN (orange).