Dust Structure and Composition Within Molecular Clouds and Cores

Details Dust Structure and Composition Within Molecular Clouds and Cores Dust Structure and Composition Within Molecular Clouds and Cores

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21115307c&link_type=abstract

American Astronomical Society, AAS Meeting #211, #153.07; Bulletin of the American Astronomical Society, Vol. 39, p.1005

Astronomy and Astrophysics

Astronomy

Scientific paper

We observed three molecular clouds and four isolated cores in both the JHK and Spitzer wavelengths. Our goal was to use these deep infrared data to map changes in the extinction law and the dust properties throughout our observed regions. The clouds we observed were Ophiuchus, Perseus, and Serpens and the cores were L204C-2, L1152, L1155C-2, and L1228.
From 3.6-8 microns, we found that regions with column densities Ak < 0.5 in our clouds have an extinction law similar to the one observed in the diffuse ISM. At higher extinctions, there is evidence for grain growth because the extinction law flattens compared to that of the diffuse ISM and becomes more consistent with the extinction law predicted by the Weingartner & Draine (2001) Rv = 5.5 dust model. This model utilizes dust grains up to 10 times larger than those in the diffuse ISM. We observed this same extinction law in the cores, even for column densities Ak 1-2 in some of our clouds and cores, we see evidence at 5.8 microns for water ice forming on the dust grains. Two of our cores have molecular outflows which appear to be destroying large dust grains resulting in an extinction law similar to that found in the diffuse ISM.
In both our clouds and cores, the extinction law at 24 microns is almost always 2-3 times higher than the value predicted by current dust models, consistent with the results found by Flaherty et al. (2007). Overall, there are relatively few stars with high S/N detections at 24 microns. More observations are needed to understand the nature of the extinction law at this wavelength.
Support for this work was provided by NASA through JPL contracts 1224608, 1230782, 1230779, 1264793, and 1264492.

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