First row: PVDs along the major axis. Second row: PVDs along the SW slice. (a,d) HCN/CO(1–0) ratio in PVDs. The dashed black profiles in panel d outline the outflow in the SW streamer region. (b,e) H¹³CN/¹³CO(1–0) ratio in PVDs. In panel e, the black ellipse named region A outlines the gas with D ∼ 0 arcsec and V ∼ 300 km s ⁻¹ and the black ellipse named region B outlines the gas with D ∼ [ − 5, 0] arcsec and V ∼ 200 km s⁻¹; these are kept the same in subsequent figures. (c,f) N₂H⁺/¹³CO(1–0) ratio in PVDs.