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Dichotomy in the dynamical status of massive cores in Orion

Velusamy, T. and Peng, R. and Li, D. and Goldsmith, P. F. and Langer, William D. (2008) Dichotomy in the dynamical status of massive cores in Orion. Astrophysical Journal, 688 (2). L87-L90. ISSN 0004-637X. doi:10.1086/595585.

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To study the evolution of high-mass cores, we have searched for evidence of collapse motions in a large sample of starless cores in the Orion molecular cloud. We used the Caltech Submillimeter Observatory telescope to obtain spectra of the optically thin (H^(13)CO^+) and optically thick (HCO^+) high-density tracer molecules in 27 cores with masses >1 M⊙. The red-and blue-asymmetries seen in the line profiles of the optically thick line, with respect to the optically thin line indicate that 2/3 of these cores are not static. We detect evidence for infall (inward motions) in 9 cores and outward motions for 10 cores, suggesting a dichotomy in the kinematic state of the nonstatic cores in this sample. Our results provide an important observational constraint on the fraction of collapsing (inward motions) versus noncollapsing (reexpanding) cores for comparison with model simulations.

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Goldsmith, P. F.0000-0002-6622-8396
Additional Information:© 2008 The American Astronomical Society. Received 2008 September 2; accepted 2008 October 8; published 2008 October 21. We thank Konstantinos Tassis for comments on the dynamics of magnetically supported cores. We thank Jorge Pineda for running cloud models incorporating specific large-scale velocity fields to confirm the expected behavior of the red- and blue asymmetries in the Orion cores. The research described in this Letter was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration and supported by a grant from NASA Astronomy and Physics Research and Analysis Program. Research at the Caltech Submillimeter Observatory is supported by NSF grant AST-0229008.
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Subject Keywords:ISM: clouds; ISM: individual (Orion); ISM: kinematics and dynamics; ISM: molecules; stars: formation
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Record Number:CaltechAUTHORS:VELapjl08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13489
Deposited By: Tony Diaz
Deposited On:13 Jul 2009 16:13
Last Modified:08 Nov 2021 22:38

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