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Paper: Dust Properties of the Dark Cloud IC 5146
Volume: 287, Galactic Star Formation Across the Stellar Mass Spectrum
Page: 25
Authors: Kramer, C.; Mookerjea, B.; Richer, J. S.; Lada, C. J.; Alves, J. F.
Abstract: We present the results of a submillimeter dust continuum study of a molecular ridge in IC 5146 carried out at 850 μm and 450 μm with SCUBA on the James Clerk Maxell Telescope (JCMT). The mapped region is ∼14'×2.' 5 in size (∼2 pc×0.3 pc) and consists of at least four dense cores which are likely to be prestellar in nature. To study the physical properties of the ridge and its embedded cores, we combined the dust emission data with dust extinction data obtained by Lada et al. (1999) from the NIR colors of background giant stars. The ridge shows dust extinctions above ∼10 mag, rising to up to 40 mag in the cores. A map of dust temperatures, constructed from the continuum flux ratios, shows strong temperature gradients: we find temperatures of up to ∼25 K in the outskirts and between the cores, down to less than 10 K in the cores themselves. Several cores appear isothermal, while two have inwardly decreasing temperatures profiles, which is expected if the cores are externally heated. Taking into account the derived map of dust temperature, the resulting map of H2 column densities shows a strong contrast between the dilute interclump medium and the dense cores. We used the extinction data to derive in addition a map of the dust emissivity parametrized by κ'=κ850V. Its average value corresponds well with the canonical value of Mathis (1990). The individual cores show significant differences, i.e. κ' varies between 1×10-5 and ∼7×10-5. We find an inverse correlation between κ' and Tdust which we interpret as signature of grain coagulation and the formation of ice mantles, in accordance with models of dust evolution in dense prestellar cores (Ossenkopf & Henning 1994, OH94) and the previous detection of gas-phase depletion of CO (Kramer et al. 1999).
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