EDP Sciences
Free access
Volume 445, Number 2, January II 2006
Page(s) 591 - 600
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20041881

A&A 445, 591-600 (2006)
DOI: 10.1051/0004-6361:20041881

The formation of interstellar molecular lines in a turbulent velocity field with finite correlation length

IV. Physical parameters of Bok Gobules
M. Hegmann1, C. Hengel2, M. Röllig3 and W. H. Kegel1

1  Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenberg 36, 10623 Berlin, Germany
    e-mail: hegmann@astro.physik.tu-berlin.de
2  Institut für Theoretische Physik, Universität Frankfurt, Robert-Mayer-Strasse 8-10, 60054 Frankfurt, Germany
3  I. Physikalisches Institut der Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany

(Received 23 August 2004 / Accepted 26 August 2005)

We present observational line data for five Bok Globules. Observations were made in the $J=2 \to 1$ and $J=3 \to 2$ rotational transitions of CO, 13CO and C18O at the Heinrich-Hertz-Telescope in Arizona. Using the stochastic radiative transfer model (SRTM) based on the generalized radiative transfer equation as described in the previous papers of this series, we were able to fit the observed CO lines for four of the five Bok globules. The derived parameters such as the hydrogen density, the cloud mass and temperature in part differ significantly from values obtained from a standard LVG analysis or a microturbulent approach. The best fits are obtained for models characterized by a ratio of the mean free path of photons to the correlation length of the turbulent velocity field of the order of unity. This is what characterizes the mesoturbulent regime that cannot be adressed by standard evaluation methods like LVG or microturbulent approximations.

Key words: radiative transfer -- turbulence -- ISM: clouds -- ISM: lines and bands

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