Spatial mapping results of Lyα emission. The contours are the same in all panels, with the green showing the position of the radio source (see the Fig. 1 caption for details; Parijskij et al. 2013, 2014) and black tracing the Lyα surface brightness resulting from spatial fitting (the levels are given arbitrarily). All these maps are constructed based on the fitting results, i.e., not directly from the data. (a) Intrinsic surface brightness map of Lyα emission. (b) W₈₀ map of Lyα emission (nonparametric measurement of the line width; see text). (c) v₅₀ map of the fitted Lyα emission profile (nonparametric measurement of the line-of-sight velocity; see text).