2023MNRAS.518.1472Y

The study of the physical and chemical properties of gas infall motion in the molecular clumps helps us understand the initial stages of star formation. We used the FTS wide-sideband mode of the IRAM 30-m telescope to observe nine infall sources with significant double-peaked blue line profile. The observation frequency ranges are 83.7-91.5 GHz and 99.4-107.2 GHz. We have obtained numbers of molecular line data. Using XCLASS, a total of 7-27 different molecules and isotopic transition lines have been identified in these nine sources, including carbon chain molecules, such as CCH, c-C₃H₂ and HC₃N. According to the radiation transfer model, we estimated the rotation temperatures and column densities of these sources. Chemical simulations adopting a physical model of HMSFRs are used to fit the observed molecular abundances. The comparison shows that most sources are in the early HMPO stage, with the inner temperature around several 10 K.