EDP Sciences
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Volume 434, Number 1, April IV 2005
Page(s) 167 - 180
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20041978

A&A 434, 167-180 (2005)
DOI: 10.1051/0004-6361:20041978

3D continuum radiative transfer in complex dust configurations

II. 3D structure of the dense molecular cloud core $\mathsf{\rho}$ Oph D
J. Steinacker1, A. Bacmann2, 3, Th. Henning1, R. Klessen4 and M. Stickel1

1  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: [stein;henning;stickel]@mpia.de
2  European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
3  Observatoire de Bordeaux, 2 rue de l'Observatoire, BP 89, 33270 Floirac, France
    e-mail: bacmann@obs.u-bordeaux1.fr
4  Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
    e-mail: rklessen@aip.de

(Received 9 September 2004 / Accepted 22 October 2004 )

Constraints on the density and thermal 3D structure of the dense molecular cloud core $\rho$ Oph D are derived from a detailed 3D radiative transfer modeling. Two ISOCAM images at 7 and 15 $\mu$m are fitted simultaneously by representing the dust distribution in the core with a series of 3D Gaussian density profiles. Size, total density and position of the Gaussians are optimized by simulated annealing to obtain a 2D column density map. The projected core density has a complex elongated pattern with two peaks. We propose a new method to calculate an approximate temperature in an externally illuminated complex 3D structure from a mean optical depth. This " $T_{\overline\tau}$"-method is applied to a 1.3 mm map obtained with the IRAM 30m telescope to find the approximate 3D density and temperature distribution of the core $\rho$ Oph D. The spatial 3D distribution deviates strongly from spherical symmetry. The elongated structure is in general agreement with recent gravo-turbulent collapse calculations for molecular clouds. We discuss possible ambiguities of the background determination procedure, errors of the maps, the accuracy of the $T_{\overline\tau}$-method and the influence of the assumed dust particle sizes and properties.

Key words: radiative transfer -- stars: formation -- infrared: stars -- stars: circumstellar mater -- methods: numerical -- ISM: dust, extinction

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