Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-01-24
Mon.Not.Roy.Astron.Soc.375:278-300,2007
Astronomy and Astrophysics
Astrophysics
The second version includes some discussion of why previous models of dust-gas thermal coupling were simplistic. Paper III in
Scientific paper
10.1111/j.1365-2966.2006.11293.x
Determining temperatures in molecular clouds from ratios of CO rotational lines or from ratios of continuum emission in different wavelength bands suffers from reduced temperature sensitivity in the high-temperature limit. In theory, the ratio of far-IR, submillimeter, or millimeter continuum to that of a 13CO (or C18O) rotational line can place reliable upper limits on the temperature of the dust and molecular gas. Consequently, far-infrared continuum data from the {\it COBE}/{\it DIRBE} instrument and Nagoya 4-m $\cOone$ spectral line data were used to plot 240$\um$/13CO J=1-0 intensity ratios against 140$\um$/240$\um$ dust color temperatures, allowing us to constrain the multiparsec-scale physical conditions in the Orion$ $A and B molecular clouds. The best-fitting models to the Orion clouds consist of two components: a component near the surface of the clouds that is heated primarily by a very large-scale (i.e. $\sim 1 $kpc) interstellar radiation field and a component deeper within the clouds. The former has a fixed temperature and the latter has a range of temperatures that varies from one sightline to another. The models require a dust-gas temperature difference of 0$\pm 2 $K and suggest that 40-50% of the Orion clouds are in the form of dust and gas with temperatures between 3 and 10$ $K. These results have a number implications that are discussed in detail in later papers. These include stronger dust-gas thermal coupling and higher Galactic-scale molecular gas temperatures than are usually accepted, an improved explanation for the N(H$_2$)/I(CO) conversion factor, and ruling out one dust grain alignment mechanism.
No associations
LandOfFree
Comparison of 13CO Line and Far-Infrared Continuum Emission as a Diagnostic of Dust and Molecular Gas Physical Conditions: I. Motivation and Modeling does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Comparison of 13CO Line and Far-Infrared Continuum Emission as a Diagnostic of Dust and Molecular Gas Physical Conditions: I. Motivation and Modeling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Comparison of 13CO Line and Far-Infrared Continuum Emission as a Diagnostic of Dust and Molecular Gas Physical Conditions: I. Motivation and Modeling will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-550596