Central panel: integrated intensity of the blue and redshifted wing of the SiO (2–1) emission. In blue contours the blueshifted wing is shown, integrated from 6 km s^-1 to 19 km s^-1 (levels 0.2(0.2)2 Jy beam^-1 km s^-1). The red contours show the redshifted wing, integrated from 25 km s^-1 to 38 km s^-1 (levels 0.2(0.2)2 Jy beam^-1 km s^-1). In the background, the 3 mm continuum data in gray and dotted contours (levels 1.5(1.5)10 Jy beam^-1) are shown. Left and right sides: spectra at different points. For each point, the upper spectrum is from SiO and the lower one from H¹³CO⁺, each in the units of Jy beam^-1. The red dotted line shows the rest velocity of 22.4 km s^-1 and the blue number at the upper right of each spectrum the FWHM of the fitted Gaussian in km s^-1. In the SiO spectra, the fitted Gaussians are shown with red lines.