Free access article

A&A 407, 237-248 (2003)
DOI: 10.1051/0004-6361:20030798

A molecular line survey of the candidate massive Class 0 protostar IRAS 23385+6053

M. A. Thompson and G. H. Macdonald

Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NR, UK
    e-mail: m.a.thompson@kent.ac.uk; g.h.macdonald@kent.ac.uk
(Received 8 April 2003 / Accepted 21 May 2003 )

Abstract
We have carried out a molecular line survey of the candidate massive protostar IRAS 23385+6053 , covering a 27.2 GHz frequency range in the 330-360 GHz atmospheric window. We detected 27 lines originating from a total of 11 species. Over a third of the identified molecular lines are from the asymmetric top molecule methanol (CH ₃OH). We did not detect any emission from high-excitation lines or typical hot core tracers (e.g. CH ₃CN, HCOOCH ₃). We derive a rotation temperature and column density from the methanol emission and estimate lower limits to the beam-averaged column density of the remaining lines. Upper limits to the beam-averaged column density of selected species were determined from the non-detection of their rotation lines. We rule out the presence of a hot molecular core associated with IRAS 23385+6053 by a combination of the non-detection of CH ₃CN emission and a simple bolometric luminosity approach. The molecular inventory and chemistry of IRAS 23385+6053 are contrasted to that of more evolved massive star-forming regions and the abundances predicted by recent time-dependent chemical models. The physical and chemical nature of IRAS 23385+6053 is shown to be consistent with that immediately prior to the hot molecular core stage.

Key words: ISM: abundances -- ISM: individual object: IRAS 23385+6053 -- ISM: molecules -- stars: formation

Offprint request: M. A. Thompson, m.a.thompson@kent.ac.uk

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© ESO 2003

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