Dust properties of the dark cloud IC5146 - Submillimeter and NIR imaging

TL;DR

This study combines submillimeter dust emission and NIR extinction data to analyze dust properties, temperature gradients, and emissivity variations in the dark cloud IC5146, revealing significant dust evolution in prestellar cores.

Contribution

It provides the first combined submillimeter and NIR analysis of IC5146, showing dust emissivity increases as temperature decreases, indicating dust evolution in prestellar cores.

Findings

Dust temperature ranges from 10K to 20K across the region.

Dust emissivity increases by a factor of 4 as temperature drops.

Cores are nearly isothermal with significant temperature gradients in the ridge.

Abstract

We present the results of a submillimeter dust continuum study of a molecular ridge in IC5146 carried out at 850micron and 450micron with SCUBA on the James Clerk Maxwell Telescope (JCMT). The mapped region is 14'x2.5' in size (2pc x 0.3pc) and consists of at least four dense cores which are likely to be prestellar in nature. To study the dust 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 ~10mag, rising up to 35mag in the cores. A map of dust temperatures, constructed from the continuum flux ratios, shows significant temperature gradients: we find temperatures of up to ~20K in the outskirts and between the cores, and down to ~10K in the cores themselves. The cores themselves are almost isothermal. We used the extinction data to derive in addition a map of the dust emissivity. Its average value agrees well with the canonical value of Mathis (1990). We find that the dust emissivity parametrized by kappa_850/kappa_V increases by a factor of about 4 when the dust temperature decreases from ~20K to ~12K. A Monte Carlo simulation shows that this change is significant with regard to the estimated calibration uncertainties. This is consistent with models of dust evolution in prestellar cores by Ossenkopf & Henning (1994) and with the previous detection of gas-phase depletion of CO in one of the IC5146 cores by Kramer et al. 1999.