A New Reference Chemical Composition for TMC-1

TL;DR

This paper presents a new chemical composition reference for TMC-1, derived from advanced radiative transfer modeling and Bayesian analysis, providing updated molecular abundances and uncertainties for complex organic molecules in this dark cloud.

Contribution

It introduces a novel combination of LTE radiative transfer modeling with Bayesian statistics to analyze spectral survey data, improving abundance estimates for TMC-1 molecules.

Findings

Computed abundances for 57 molecules and isotopologues in TMC-1.

Results largely agree with previous studies, with some new upper/lower limits.

Enhanced understanding of molecular complexity in dark clouds.

Abstract

Recent detections of complex organic molecules in dark clouds have rekindled interest in the astrochemical modeling of these environments. Because of its relative closeness and rich molecular complexity, TMC-1 has been extensively observed to study the chemical processes taking place in dark clouds. We use local thermodynamical equilibrium radiative transfer modeling coupled with a Bayesian statistical method which takes into account outliers to analyze the data from the Nobeyama spectral survey of TMC-1 between 8 and 50 GHz. We compute the abundance relative to molecular hydrogen of 57 molecules, including 19 isotopologues in TMC-1 along with their associated uncertainty. The new results are in general agreement with previous abundance determination from Ohishi & Kaifu and the values reported in the review from Agundez & Wakelam. However, in some cases, large opacity and low signal to noise effects allow only upper or lower limits to be derived, respectively.