Lyα narrowband surface brightness (SB) image of 4C04.11 derived from the data cube using 6704 − 6710 Å in the observed frame. The blue contour indicates the He II emission region. The contour is calculated from the pseudo-narrowband image of He II using 9028 − 9044 Å in the observed frame with the level of 3σ_He II and 2 × 3σ_He II, where σ_He II is the standard deviation derived from a source-less region of the He II pseudo-narrowband image. The white contour traces the position of the radio jet observed by MERLIN (Multi-Element-Radio-Link-Interferometer-Network; Parijskij et al. 2013, 2014) with the level of 0.45 × (−1, 1, 2, 4, 16, 32, 48) mJy beam⁻¹ following Parijskij et al. (2014). The overlaid red circle with a 1 arcsec radius marks the aperture over which the master spectrum is extracted. The green dashed box shows the FOV of individual panels in Figs. 7 and 8, which is the region we focus on in the spatial mapping in Sect. 5.