Moment maps of the extended Lyα around J0910−0414. The leftmost image was created by applying the 2D smoothing kernel from Section 3.3 to our nonquasar-subtracted cube and collapsing over our Lyα wavelength range. The black contour outlines the 2D spatial mask, and is identical to the contour in Figure 1. The second panel is the observed Lyα surface brightness in units of 10⁻¹⁷ erg s⁻¹ cm⁻² arcsec⁻². The third panel displays the velocity offset in km s⁻¹ relative to the centroid wavelength of the halo spectrum as described in Section 3.1. The rightmost panel is the velocity dispersion in km s⁻¹. North is up, and east is to the left.