Imagery of HL Tau. (a) Moment 0 of the HCO⁺ 3−2 line (Yen et al. 2019). (a_zoom): zoom onto the central region of a. (b) Moment 1 of the HCO⁺ 3−2 line. (c) Moment 0 of the CS 5−4 line. (d) Moment 1 of the CS 5−4 line. (e) Integrated spectra of HCO⁺, SO₂ 14_0,14 − 13_1,13, and SO 15₁₅−14₁₄ from the region labelled I in (d). (f) Integrated spectra of HCO⁺, SO₂ 14_0,14 − 13_1,13 and 5_2,4 −4_1,3 from the region labeled II in (b). In each map, red and white (or black) contours indicate the continuum and SO₂ 14_0,14 − 13_1,13 line emissionas in Fig. 1, except contours from (a_zoom) that indicatethe SO 15₁₅−14₁₄ line emission. The arrow points to the inner part of the HCO⁺ streamer visible as a SO protrusion. North is up, east is left.