A Near-Infrared Imaging Survey of Coalsack Globule 2

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Abstract
We describe a near-infrared imaging survey of Globule 2 in the Coalsack. This Bok globule is the highest density region of this southern hemisphere molecular cloud and is the most likely location for young stars in this complex. The survey is complete for K < 14.0, H < 14.5, and J < 15.5, several magnitudes more sensitive than previous observations of this globule. From the large number of background stars, we derive an accurate near-infrared extinction law for the cloud. Our result, E_{J-H}/E_{H-K} = 2.08 pm 0.03, is significantly steeper than results for other southern clouds. We use the J-H/H-K color-color diagram to identify two potential young stars with K < 14.0 in the region. We apply H-band star counts to derive the density profile of the Coalsack Globule 2 and use a polytropic model to describe the internal structure of this small cloud. For a gas temperature T sim 15 K, this globule is moderately unstable.Comment: 19 pages, manuscript format; 6 figures -- Accepted by A
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