The warm-up phase in massive star-forming cores around RCW 120

ABSTRACT We study molecular emission in a massive condensation at the border of H ii region RCW 120, paying particular attention to Core 1 and 2 objects, most fragments found previously by ALMA. The latter fragment was suggested host high-mass analogue Class 0 young stellar object. present spectra mm range made with APEX telescope. detect CH3OH C34S lines Cores 2. CH3CN series SO2 are only estimate gas physical parameters using methanol obtain temperature less than 100 K both regions. Molecular hydrogen number density is 105−107 cm−3 more uncertain 1. However, detection corresponding highly excited transitions (Eu > 400 K) indicates that contains hot gas, while abundances CH3OH, CS, SO2, quite low for core stage. propose warm-up phase prior establishing chemistry. suggest beginning There no detected 1; therefore, it might be on an even evolved evolutionary