Massive Quiescent Cores in Orion: Dichotomy in the Dynamical Status of Cores

Details Massive Quiescent Cores in Orion: Dichotomy in the Dynamical Status of Cores Massive Quiescent Cores in Orion: Dichotomy in the Dynamical Status of Cores

Jan 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21343909v&link_type=abstract

American Astronomical Society, AAS Meeting #213, #439.09; Bulletin of the American Astronomical Society, Vol. 41, p.315

Astronomy and Astrophysics

Astronomy

Scientific paper

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 (H13CO+) and optically thick (HCO+) high density tracer molecules in 27 cores with masses > 1 MO. 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 and we interpret these as evidence for inward or outward motions in 19 cores. We present RATRAN radiative transfer models of these cores that support the interpretation of inward and outward motion consistent with the observed spectral asymmetries. Thus we detect infall (inward motions) in 9 cores and outward motions for 10 cores, suggesting a dichotomy in the kinematic state in this sample. This population of massive molecular cloud cores is in general likely to be dynamic, out-of-equilibrium structures, rather than quasi-hydro/magneto-static structures. Our results provide an important observational constraint on the fraction of collapsing (inward motions) versus non-collapsing (re-expanding) cores for comparison with model simulations.
This work was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Research at the Caltech Submillimeter Observatory is supported by NSF grant AST-0229008.

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