The shocked molecular layer in RCW 120

TL;DR

This study investigates the shocked molecular layer in RCW 120, revealing its structure, kinematics, and relation to star formation through detailed observations and simulations of CO emissions.

Contribution

It provides the first detailed spatial and velocity-resolved analysis of the shocked molecular layer in RCW 120, linking observations with simulations to understand its properties.

Findings

Identification of a bright CO-emitting shocked layer

Detection of dense environments around protostars and outflows

Agreement between simulated and observed emission line data

Abstract

Expansion of wind-blown bubbles or HII regions lead to formation of shocks in the interstellar medium, which compress surrounding gas into dense layers. We made spatially and velocity-resolved observations of the RCW~120 PDR and nearby molecular gas with CO(6-5) and 13CO(6-5) lines and distinguished a bright CO-emitting layer, which we related with the dense shocked molecular gas moving away from the ionizing star due to expansion of HII region. Simulating gas density and temperature, as well as brightness of several CO and C+ emission lines from the PDR, we found reasonable agreement with the observed values. Analysing gas kinematics, we revealed the large-scale shocked PDR and also several dense environments of embedded protostars and outflows. We observe the shocked layer as the most regular structure in the CO(6-5) map and in the velocity space, when the gas around YSOs is dispersed by the outflows.