KAgoshima Galactic Object survey with Nobeyama 45-metre telescope by Mapping in Ammonia lines (KAGONMA): Star formation feedback on dense molecular gas in the W33 complex

TL;DR

This study maps ammonia lines and water masers in the W33 star-forming region to analyze how star formation feedback influences dense molecular gas, revealing temperature gradients and complex gas dynamics near HII regions.

Contribution

First simultaneous NH3 and H2O maser mapping of W33, highlighting star formation feedback effects on dense gas and complex gas distributions around HII regions.

Findings

Temperature increases near W33 Main HII region

Interaction area between HII region and molecular gas is about 1.25 pc

NH3 absorption features indicate complex gas distribution

Abstract

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 and one of which, W33 Main, is associated with a compact HII region. To investigate star-forming feedback activity 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 HII region and the periphery 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 HII region. Interestingly, the absorption feature was 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 HII region is highly complicated.