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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