EDP Sciences
Free access
Volume 376, Number 3, September IV 2001
Page(s) 1054 - 1063
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20011022

A&A 376, 1054-1063 (2001)
DOI: 10.1051/0004-6361:20011022

Deuterium fractionation along the TMC-1 ridge

A. J. Markwick1, S. B. Charnley2 and T. J. Millar1

1  Department of Physics, UMIST, PO Box 88, Manchester M60 1QD, UK
    e-mail: ajm@ajmarkwick.com; Tom.Millar@umist.ac.uk
2  Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA
    e-mail: charnley@dusty.arc.nasa.gov

(Received 6 February 2001 / Accepted 12 July 2001 )

In this paper, we present a model to predict and explain the observed gradients in deuterium fractionation and molecular abundance along the TMC-1 ridge. In TMC-1, gradients in the level of deuterium fractionation are observed for all the molecular species for which the measurement has been made; ${\rm HCO^+}$, ${\rm HC_3N}$, ${\rm C_3H_2}$ and HNC. The model is based on the assumption that the chemical evolution of the TMC-1 ridge has been affected by Alfvén waves. The structure of the model and its comparison with observations are discussed. We find that the model qualitatively and somewhat quantitatively reproduces the observations of the aforementioned molecular species. We present predictions of the fractionation gradients along the TMC-1 ridge for other molecules of observational interest.

Key words: MHD: waves -- ISM: abundances -- ISM: molecules -- ISM: individual: Taurus Molecular Cloud -- molecular processes

Offprint request: A. J. Markwick, ajm@jarus1.phy.unist.ac.uk

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