UV magnitude M_UV at 1600 Å as a function of halo mass M_h. For each galaxy the “intrinsic” UV magnitude calculated with STARBURST99 (blue dots) and the reddened magnitudes calculated using the median and 68% scatter of the luminosity-weighted extinction along isotropically distributed sightlines from the star (red dots with error bars) are shown. The red line shows the best fit of the analytical relation in Eq. (16), with the red shaded region showing the prediction interval within which 68% measurements would fall. Only the most massive galaxies are seen to have UV escape fraction significantly below unity, with the red points falling below the blue.