HCO⁺(4−3) (ν_rest = 357 GHz, left panels) and HCN(4−3) (ν_rest = 355 GHz, right panels) moment maps. Top row: the total integrated line emission (moment 0) maps are shown; in the middle row, the velocity (moment 1) maps are displayed; the bottom row shows the velocity dispersion (moment 2). The green/grey contours in all panels are for the 345 GHz continuum as in Fig. 1. For HCN(4−3), only the velocity range from −300 to +15 km s⁻¹ is covered by the observations, so that the south-western, redshifted part of the emission is missing (see Sect. 2).