HCN 1–0 velocity field (including only velocities  ± 200 km s^-1) showing the rotation of the molecular disk. The HCN 1–0 emission rotates in the same east-west fashion as the ¹²CO emission (Bryant & Scoville 1996; Downes & Solomon 1998). The grayscale ranges from  − 100 to 100 km s^-1 and the contours are 20 km s^-1 ×  (−4,  −3,  −2,  −1, 0, 1, 2, 3, 4). Zero velocity was set to redshift z = 0.042170 and 1′′ = 870 pc. Cross marks the VLBI radio continuum position (see footnote to Table 1). Hatched ellipse indicates beam size and orientation.