Line of Sight Radiative Transfer Analysis of B68 and TMC1-C


First Author:
Christopher De Vries
Email: devries AT science.csustan.edu
CSU Stanislaus
Department of Physics, Physical Science, and Geology
One University Circle
Turlock, CA 95382 USA

Abstract

We present the results of an analysis of CS J=2-1 and N2H+ J=1-0 spectral line observations of B68 and TMC1-C using best fit analytic radiative transfer models to simulate the emission along each line of sight. The radiative transfer model is designed to simulate self-absorbed asymmetric line profiles by assuming that there is an excitation temperature gradient along each line of sight and that there is a uniform infall or outflow velocity which results in a blue or red asymmetric line profile. Observation of optically thin isotopologues of CS and N2H+ indicate that the molecular line profiles in B68 and TMC1-C are self-absorbed, making these analytic line of sight models appropriate tools to analyze observations of these regions. Analysis of each line of sight using the analytic radiative transfer model yield maps of the five parameters that make up the model: line of sight velocity, infall speed, optical depth, peak excitation temperature, and line width. By mapping these parameters of the fit to the line profiles, we are able to find regions which have distinct spectral features, which may indicate a kinematically distinct regions of the larger cloud. Analysis of B68 and TMC1-C indicates that these clouds are complex regions which may both contain regions of infall, outflow, high optical depth, low optical depth, high peak excitation, and low peak excitation temperatures within the same core. In both clouds the region with the highest optical depth does not match the region with the highest excitation temperature, indicating that these regions should not be thought of as spherical dense central peaks, but rather complex dynamical structures. We identify spectrally unique signatures in each cloud and attempt to build a coherent picture of the physical state and dynamical processes in these star-forming regions.