Escape fraction f_esc of Lyα as a function of halo mass M_h, defined as the ratio of the number of Lyα photons that make it out through the galaxy to the total number emitted (i.e. if there were no dust and galaxies were isotropic, f_esc would be unity in all directions). The red points and the error bars denote the median and the 68% scatter of the six directions along the Cartesian axes, while the blue points show the global average. The extent of the error bars is chiefly dictated by the anisotropy of the ISM, but the scatter in the median values is partly due to only using six directions for the statistics. Only for galaxies above M_h ∼ 10¹⁰ h⁻¹ M_⊙ does dust play a significant role for the escape fraction. After escaping the galaxy, photons may still be scattered out of the LOS, so the observed f_esc would be (much) smaller than these values. To guide the eye, a dashed, grey line is shown at f_esc = 1.