Central HCO⁺ (top) and HNC (bottom) 1–0 velocity fields. The grayscale range is from  − 64 to 9 km s^-1 (top) and from  − 43 to 24 km s^-1 (bottom). The contour levels are 5 km s^-1  ×  (–4, –3, –2, –1, 0, 1, 2, 3, 4). (1′′ = 870 pc and zero velocity was set to redshift z = 0.042170 for all lines). Cross refers to the center of the 85 GHz continuum. The emission is integrated over  ± 200 km s^-1 and excludes the line wings. Ellipse indicates beam size and orientation.