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Dust dynamics in dense molecular cores |
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| Authors: | A P Whitworth M R Bate |
| Institution: | Department of Physics &Astronomy, Cardiff University, Cardiff CF24 3YB,; School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL and; Institute of Astronomy, Madingley Road, Cambridge CB3 0HA |
| Abstract: | We show that in a quiescent, dense pre-stellar core, exposed to the average interstellar radiation field, radiation pressure can cause the dust to migrate inwards, relative to the gas, on a time-scale of a few megayears – and faster if the radiation field is stronger than average. This has two potentially important effects. First, there is an increase in the abundance of dust relative to gas in the inner parts of the core, and hence also in the efficiency of gas-cooling by dust. The increased cooling efficiency predisposes these regions to dynamical collapse and star formation. Additionally, it predisposes them to fragmentation, particularly if – as seems likely – the dust enhancements are stochastic and inhomogeneous, due to anisotropy of the incident radiation field and/or to directing of the migration by the local magnetic field. It also increases the metallicities of the resulting stars, and hence presumably the likelihood of planet formation in their accretion discs. Secondly, there is a steepening of the optical-depth profile, especially at those impact parameters b where the visual optical depth through the core τ |
| Keywords: | dust extinction ISM: globules ISM: kinematics and dynamics ISM: magnetic fields |