Chemical Differentiation and Gas Kinematics around Massive Young Stellar Objects in RCW 120

Abstract

We present the results of a spectral survey towards a dense molecular condensation and young stellar objects (YSOs) projected on the border of the H II region RCW 120 and discuss the emission of the 20 molecules that produce the brightest lines. The survey is performed with the APEX telescope in the 200–260 GHz frequency range. We provide evidences for two outflows in the dense gas. The first one is powered by the RCW 120 S2 YSO and oriented along the line of sight. The second outflow around RCW 120 S1 is aligned almost perpendicular to the line of sight. We show that the areas with bright emission of CH\({}_{3}\)OH, CH\({}_{3}\)CCH and CH\({}_{3}\)CN are organised into an onion-like structure, where CH\({}_{3}\)CN traces warmer regions around the YSOs than the other molecules. Methanol seems to be released into the gas phase by shock waves in the vicinity of the outflows while thermal evaporation still does not work towards the YSOs. We find only a single manifestation of the UV radiation in the molecules, namely, enhanced abundances of small hydrocarbons CCH and c-C\({}_{3}\)H\({}_{2}\) in the photo-dissociation region.