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| EPoS Contribution |
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Internal Motions in Starless Dense Cores
Chang Won Lee Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea | |
| Internal motions in the central regions of starless dense n_H2 > 10^4 cm^{-2} cores are a key issue in studying initial conditions of isolated star formation because these may indicate contraction, a sign of progress toward star formation. A single pointing survey of optically thin and thick tracers such as CS 2-1 and N2H+ 1-0 toward starless cores indicated a predominance of inward motions. However, mapping studies with the same tracers showed different or more complex distribution of the spectral asymmetry from what is seen toward the central regions of the cores. Our study introduces a detailed investigation of mapped molecular line profile data to know which kind of asymmetric profiles are the most typical and thus which kind of motions are the most likely. We investigated all existing data of optically thin and thick molecular lines for starless cores to assess the distribution of starless dense cores with primarily inward, outward, and mixed motions and analyzed the asymmetric patterns of these whole profiles. In total 34 starless cores are examined with the normalized velocity difference delta V_CS by which the optically thick spectrum is blue- or red-shifted with respect to the optically thin tracer. It was found that over 50% of the sample is dominated with blueskewed profiles, implying predominance of inward motions in starless cores, about 11% of the starless cores has the distribution of a mixture of blue and red profiles which are sometimes interpreted as oscillatory motions, and only one source is dominated with red-skewed profiles indicating outward gaseous motions, while the rest (about 35%) of the sample shows domiance of symmetric profiles. This study indicates that majority of the cores are likely to have motions which are infall-dominated. The pattern of inward motions are found to be dependent of several physical parameters. A core with higher column density tends to have better pronounced and more frequent inward motions, and a position with higher column density in a core tends to be in more chance of inward motions. Similarly, the blue profiles are generally more populated than the red profiles in the core and this tendency is stronger at smaller radius < 0.1 pc. Whether the core is isolated or in complexes do not seem to affect on how internal motions are occurring. | |
| Collaborators: P.C. Myers, CfA, USA |
Key publication
Suggested Session: Cores and Collaps |