2022MNRAS.510.1106M

We present the results of NH₃ (1,1), (2,2), and (3,3) and H₂O maser simultaneous mapping observations toward the high-mass star-forming region W33 with the Nobeyama 45-m radio telescope. W33 has six dust clumps, one of which, W33 Main, is associated with a compact H II region. To investigate star-forming activity feedback on its surroundings, the spatial distribution of the physical parameters was established. The distribution of the rotational temperature shows a systematic change from west to east in our observed region. The high-temperature region obtained in the region near W33 Main is consistent with interaction between the compact H II region and the peripheral molecular gas. The size of the interaction area is estimated to be approximately 1.25 pc. NH₃ absorption features are detected toward the centre of the H II region. Interestingly, the absorption features were detected only in the NH₃ (1,1) and (2,2) transitions, with no absorption feature seen in the (3,3) transition. These complex profiles in NH₃ are difficult to explain by a simple model and may suggest that the gas distribution around the H II region is highly complicated.