Top panel: distributions of the SiO (5−4)/(2−1) ratio for two different velocity regimes: systemic velocities (gray filled histogram) and high velocities (solid line histogram). The dotted line and numbers indicate the mean (±standard deviation) value. Bottom panel: LVG results produced by the RADEX code. We plot the density versus the SiO (5−4)/(2−1) ratio. The curves correspond to kinetic temperatures ranging from 100 K (upper curve) to 500 K (lower curve) in steps of 100 K. The two vertical lines correspond to the mean (5−4)/(2−1) ratios for systemic and high velocities.