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Astron. Astrophys. 332, 703-713 (1998)

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Monte Carlo simulations at very high optical depth:
non-LTE transfer in H2 O in the protostellar object B 335

Daniel Hartstein and René Liseau

Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden (daniel@astro.su.se; rene@astro.su.se)

Received 12 March 1997 / Accepted 4 December 1997


We present a formulation of the Monte Carlo method which should be capable of treating radiative transfer problems even at very high optical depths ([FORMULA]) and apply this tool to predict rotational H2 O line spectra for the protostellar object B 335 for future observational tests with space borne facilities. The physical model of the source is based on published observations in lines of CS, for which we obtain model results which are in agreement with previous computations. We apply our model also to line profiles of CO isotopomers observed at high spatial resolution and derive the total CO cooling rate for B 335. From the comparison with the derived H2 O cooling rates, we are led to conclude, quite generally, that H2 O is probably not the major coolant of low-mass protostellar collapse.

Key words: ISM: clouds – ISM: individual objects: B 335 – ISM: molecules – ISM: kinematics and dynamics – stars: formation – methods: numerical

Send offprint requests to: R. Liseau

© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998