Schedule Aug 17, 2007
The Photon Dominated Region in the IC 348 Molecular Cloud
Kefeng Sun (Univ. Koeln)

K. Sun1, C. Kramer1, B. Mookerjea2, M. R? llig1, V. Ossenkopf1,3, M. Cubick1 & J. Stutzki1
1. I. Physikalisches Institut, Universit?t zu K?ln, Z?lpicher Stra?e 77 50937 K?ln, Germany
2. Department of Astronomy, University of Maryland, College Park, MD 20742, USA
3. SRON National Institut for Space Research, P.O. Box 800, 9700, AV Groningen, the Netherlands

The goal of this study is to discuss the physical conditions in the IC 348 molecular cloud, to derive the physical parameters such as the column densities of hydrogen, neutral carbon and CO, and to understand to what degree the millimeter and submillimeter line emission from the IC 348 molecular cloud can be modelled as a photon dominated region (PDR).

We study new fully sampled maps of [CI] at 492 GHz and 12CO 4-3 observed with KOSMA at about 1 arcmin resolution combined with FCRAO data of 12CO 1-0, 13CO 1-0 and far-infrared continuum data observed by the HIRES/IRAS. The line ratios of [CI] 3P1-3P0 vs. 12 CO 4-3, [CI] 3P1-3P0 vs. 13CO 1-0 and 12CO 4-3 vs. 12CO 1-0 have been analyzed. The KOSMA - ? spherical PDR model has been applied to obtain the physical parameters of the region.

We analyze the observed line intensities in an increasingly more sophisticated set of models, starting from an LTE analysis for the CO and C column densities to a single spherical clump PDR and to PDR clump ensembles. By examining seven positions in the cloud in detail, we obtain local densities between abut 4.4 x 104 cm-3 and 4.3 x 105 cm-3, and C/CO column density ratios varying with position between 0.02 and 2.0. The best fit UV field intensities are consistent with the FUV field derived from the FIR continuum data, spatially varying between 2 to 100 Draine units. The clumpy PDR model, implying a few hundred clumps with a total mass of a few M? and beam filling close to unity, reproduced the observed line intensities very well.

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