Radiative transfer modeling of the observed line profiles in G31.41+0.31

TL;DR

This study models the line profiles of various molecules in G31.41+0.31 using radiative transfer techniques to understand the physical conditions and infall/outflow dynamics of the gas envelope surrounding a hot core.

Contribution

It introduces detailed radiative transfer modeling of multiple molecular lines in G31.41+0.31, revealing infall and outflow processes and deriving physical parameters of the gas envelope.

Findings

Infalling gas explains most observed line profiles.

SiO line profile requires an outflow component.

Physical conditions of the gas envelope were characterized.

Abstract

An inverse P-Cygni profile of H13CO+ (1-0) in G31.41+0.31 was recently observed, which indicates the presence of an infalling gas envelope. Also, an outflow tracer, SiO, was observed. Here, exclusive radiative transfer modelings have been implemented to generate synthetic spectra of some key species (H13 CO+, HCN, SiO, NH3, CH3 CN, CH3OH, CH3SH, and CH3NCO) and extract the physical features to infer the excitation conditions of the surroundings where they observed. The gas envelope is assumed to be accreting in a spherically symmetric system towards the central hot core region. Our principal intention was to reproduce the observed line profiles toward G31.41+0.31 and extract various physical parameters. The LTE calculation with CASSIS and non-LTE analysis with the RATRAN radiative transfer codes are considered for the modeling purpose. The best-fitted line parameters are derived, which represents the prevailing physical condition of the gas envelope. Our results suggest that an infalling gas could explain the observed line profiles of all the species mentioned above except SiO. An additional outflow component is required to confer the SiO line profile. Additionally, an astrochemical model is implemented to explain the observed abundancests various species in this source.