Comparison between observed intensity ratios and RADEX models. Top: Observed intensity ratios between SO₂ 18_4.14–18_3.15 (E_up = 197 K) and the other five transitions, above a 3σ level. The synthesized beam is shown by the black filled ellipse in the bottom left corner of the first panel and the yellow star indicates the position of the source. Center: Intensity ratios from RADEX for the same transitions and employing a H₂ number density of 10⁹ cm⁻³. Bottom: Same analysis from RADEX, but employing a H₂ number density of 10⁸ cm⁻³. The black dashed contours indicate error values oiler and the limits of the possible ranges. All values are possible for the panels without black dashed contours.