Volume 422, Number 2, August I 2004
|Page(s)||573 - 585|
|Section||Interstellar and circumstellar matter|
|Published online||09 July 2004|
Methanol as a diagnostic tool of interstellar clouds
I. Model calculations and application to molecular clouds
Max-Planck-Institut für Radioastronomie, Auf Dem Hügel 69, 53121, Bonn, Germany e-mail: [sleurini;schilke;kmenten]@mpifr-bonn.mpg.de
2 Physics Department, University of Durham, DH1 3LE, UK e-mail: [david.flower;j.t.pottage]@durham.ac.uk
3 Physical Sciences Department, University of New Brunswick, Saint John, NB, E2L 4L5, Canada e-mail: email@example.com
Accepted: 26 March 2004
We present a detailed analysis of the diagnostic properties of methanol, (CH3OH), in dense molecular clouds, made possible by the availability of new (CH3OH-He) collisional rate coefficients. Using a spherical Large Velocity Gradient (LVG) model, the dependence on kinetic temperature and spatial density of various millimeter and submillimeter line bands is investigated over a range of physical parameters typical of high- and low-mass star-forming regions. We find CH3OH to be a good tracer of high-density environments and sensitive to the kinetic temperature. Using our LVG model, we have also developed an innovative technique to handle the problem of deriving physical parameters from observed multi-line spectra of a molecule, based on the simultaneous fit of all the lines with a synthetic spectrum, finding the best physical parameters using numerical methods.
Key words: ISM: molecules / ISM: clouds / molecular processes
© ESO, 2004
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