Temperature structure of IRS 44. Left: rotational diagram at the source position, where only the optically thin SO₂ transitions (blue dots) and the ³⁴SO₂ lines (red dots) are used for the fit. The abundance ratio ³²S/³⁴S = 22 is from Wilson (1999). Optically thick SO₂ transitions (green dots) and those lines where the optical depth is not conclusive (open dots) show a significant offset with respect to the other lines, and they were not included in the calculation of the rotational temperature and SO₂ column densities. Center, rotational temperature map created from optically thin SO₂ and ³⁴SO₂ transitions. Contours show specific values of 140, 160, 180, and 200 K. Right: moment 1 map (right panel of Fig. 2) with the same specific values of the rotational temperature as those of the central panel, showing that the highest temperatures coincide with the redshifted protrusion. The synthesized beam is shown by the black ellipse in the upper left corner and the yellow star indicates the position of the source.