Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-03-21
Astrophys.J. 626 (2005) 919-932
Astronomy and Astrophysics
Astrophysics
25 pages, 12 figures, in press in Ap.J
Scientific paper
10.1086/430295
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 {\it 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.
Choi Minho
Evans II Neal. J.
Lee Jeong-Eun
Rawlings Jonathan M. C.
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