Left panel: overlay of the integrated ¹²CO(1–0) emission, same as Fig. 4 (left panel), with CO mean-velocity field in contours spanning the range –180 to 180 km s^-1 in steps of 10 km s^-1. The white star indicates the dynamical center of the galaxy. The velocities are referred to V_sys,hel = 744 km s^-1, solid (red) lines are used for positive velocities, and dashed (blue) lines for negative velocities. The dashed line indicates the position angle of the major axis of the whole observed region (PA = 178°  ±  1°), while the dot-dashed line traces the position angle of the major axis of the bar-like structure (PA = 14°  ±  2°). The continuum line indicates the position angle of the primary stellar bar identified with the NIR H-band 2MASS image (PA =  −21°) (see later the left panel of Fig. 16 and Sect. 5.2). Right panel: same for ¹²CO(2–1). The dashed line indicates the position angle of the major axis of the whole ¹²CO(1–0) observed region (PA = 178° ± 1°, see left panel), while the dot-dashed line traces the position angle of the major axis of the ¹²CO(2–1) bar-like structure (PA = 15° ± 2°). The continuum line indicates the position angle of the primary stellar bar identified with the NIR H-band 2MASS image (PA =  −21°) (see later Fig. 16 and Sect. 5.2).