Dense gas in IRAS 20343+4129: an ultracompact HII region caught in the act of creating a cavity

TL;DR

This study investigates how an ultracompact HII region influences its dense gas environment in IRAS 20343+4129, revealing cavity creation, filamentary gas distribution, and potential sites for high-mass star formation, highlighting feedback effects in clustered star formation.

Contribution

The paper provides detailed observations of dense gas and star-forming cores around an ultracompact HII region, demonstrating the impact of massive star feedback on surrounding dense gas and star formation processes.

Findings

Confirmed cavity created by an ultracompact HII region.

Identified five dense condensations as potential high-mass star birthplaces.

Observed differences in core properties compared to low-mass star-forming regions.

Abstract

The intermediate- to high-mass star-forming region IRAS 20343+4129 is an excellent laboratory to study the influence of high- and intermediate-mass young stellar objects on nearby starless dense cores, and investigate for possible implications in the clustered star formation process. We present 3 mm observations of continuum and rotational transitions of several molecular species (C2H, c-C3H2, N2H+, NH2D) obtained with the Combined Array for Research in Millimetre-wave Astronomy, as well as 1.3 cm continuum and NH3 observations carried out with the Very Large Array, to reveal the properties of the dense gas. We confirm undoubtedly previous claims of an expanding cavity created by an ultracompact HII region associated with a young B2 zero-age main sequence (ZAMS) star. The dense gas surrounding the cavity is distributed in a filament that seems squeezed in between the cavity and a collimated outflow associated with an intermediate-mass protostar. We have identified 5 millimeter continuum condensations in the filament. All of them show column densities consistent with potentially being the birthplace of intermediate- to high-mass objects. These cores appear different from those observed in low-mass clustered environments in sereval observational aspects (kinematics, temperature, chemical gradients), indicating a strong influence of the most massive and evolved members of the protocluster. We suggest a possible scenario in which the B2 ZAMS star driving the cavity has compressed the surrounding gas, perturbed its properties and induced the star formation in its immediate surroundings.