B335: a Laboratory for Astrochemistry in a Collapsing Cloud

Abstract

We present observations of 25 transitions of 17 isotopologues of 9 molecules toward B335. With a goal of constraining chemical models of collapsing clouds, we compare our observations, along with data from the literature, to models of chemical abundances. The observed lines are simulated with a Monte Carlo code, which uses various physical models of density and velocity as a function of radius. The dust temperature as a function of radius is calculated self-consistently by a radiative transfer code. The gas temperature is then calculated at each radius, including gas-dust collisions, cosmic rays, photoelectric heating, and molecular cooling. The results provide the input to the Monte Carlo code. We consider both ad hoc step function models for chemical abundances and abundances taken from a self-consistent modeling of the evolution of a star-forming core. The step function models can match the observed lines reasonably well, but they require very unlikely combinations of radial variations in chemical abundances. Among the self-consistent chemical models, the observed lines are matched best by models with somewhat enhanced cosmic-ray ionization rates and sulfur abundances. We discuss briefly the steps needed to close the loop on the modeling of dust and gas, including off-center spectra of molecular lines. Subject headings: ISM: abundances — ISM: molecules — ISM: individual (B335) — astrochemistry

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Cite this paper

@inproceedings{Evans2008B335AL, title={B335: a Laboratory for Astrochemistry in a Collapsing Cloud}, author={Neal J . Evans and Jeong-Eun Lee and Jonathan M. C. Rawlings and Minho Choi}, year={2008} }