8-12 juin, 2014


The Effect of Molecular Contamination on the Spectral Index of Emissivity in Orion A

Simon Coudé (Université de Montréal)

Pierre Bastien (Université de Montréal)
Emily Drabek (Imperial College London)
Doug Johnstone (Joint Astronony Center)
Jennifer Hatchell (University of Exeter)
Helen Kirk (National Research Council Canada)

Thermal emission from cold dust grains in giant molecular clouds can be used to probe the physical properties, such as density, temperature and emissivity in star-forming regions. We present the SCUBA-2 shared-risks observations at 450 µm and 850 µm of the Orion A molecular cloud complex taken at the James-Clerk-Maxwell telescope (JCMT). Previous studies showed that molecular emission lines can contribute significantly to the measured fluxes in those continuum bands. In order to evaluate the molecular line contamination and its effect in the SCUBA-2 maps, we use the HARP 12CO 3-2 integrated intensity map for Orion A in order to evaluate the molecular line contamination and its effect on the SCUBA-2 maps. With the corrected fluxes, we have obtained a new Rayleigh-Jeans spectral index map for the well-known integral-shaped filament. Furthermore, we compare a sample of 34 clumps, selected all over the molecular cloud complex for their high 12CO 3-2 line contamination, to previously identified reference clumps in OMC-4. This allows us to quantify the effect of line contamination on the ratio of 850 µm to 450 µm flux densities, and how it modifies the deduced spectral index for the dust grains. We also confirm that at least one pre-stellar core linked to a Spitzer-identified protostar shows a 12CO contamination level of 17 %. This work is part of the James-Clerk-Maxwell Telescope Gould Belt Legacy Survey.

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