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Astron. Astrophys. 336, 309-314 (1998)

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The distribution of molecules in star-forming regions

S.D. Taylor 1, O. Morata 2 and D.A. Williams 1

1 Department of Physics and Astronomy, UCL, Gower St., London WC1E 6BT, UK
2 Departamento d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, E-08028 Barcelona, Spain

Received 26 June 1997 / Accepted 4 February 1998

Abstract

A number of maps of low-mass star-forming regions have shown the molecule CS to be more widespread than NH3, despite having a higher critical density in the transitions in question. In a previous paper a model was presented of unresolved clumps around the star-forming core. The clumps are transient and exhibit emission only from molecules that form quickly. In this paper it is shown how families of molecules can be found that ought to follow either the CS or NH3 behaviour if mapped adequately in similar sources. The first family of early-time molecules, includes such species as CH4, CH3, H2CO, H2CS, HC3N, CN and HCN. The second family of late-time molecules includes the species HCO+, NO, OH, SO, N2H+, O2, N2 and OCN. The chemistry of these molecules is discussed.

Key words: ISM: clouds – ISM: molecules – ISM: structure – molecular processes

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998
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