Lyα profiles of LyC leaking (left) vs. non-leaking candidates (right) from the sample of Heckman et al. (2011). The data have been smoothed to the nominal COS resolution (i.e. R = 20 000 for a point source). The systemic redshifts and their errors (grey shaded area in each plot) were derived from SDSS emission lines. The blue horizontal line denotes the continuum level. The signal-to-noise differences across the sample reflect both the redshifts and the intrinsic properties of the galaxies as Lyα sources.