AAS 205th Meeting, 9-13 January 2005
Session 140 Cold Gas and Molecular Clouds
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[140.04] Inverting the Large Velocity Gradient

N.R. Hinkel, C.L. Martin (Oberlin College)

Large velocity gradient (LVG) models use an assumption that simplifies radiative transfer, allowing us to ignore the velocity of an entire molecular cloud, and concentrate solely on a small region. In the past, observational sub-millimeter astronomers did not have large amounts of data and thus the LVG inversion was done by hand. However, because of recent technological improvements and the advent of large sub-millimeter data sets, the need for an automated inversion has become more pressing. Many of the LVG models that we examined were developed to output tables listing abundance ratios between isotopes given a particular kinetic temperature, Tkin, and density, nH2. We approach the problem from the other direction by looking at the measured J-transition tables of CO, 13CO, C18O, and CI, and determining the Tkin and nH2 for thousands of points in the molecular cloud that we are examining.

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© 2004. The American Astronomical Society.