Dust emissivity in the Submm/Mm: SCUBA and SIMBA observations of Barnard 68

TL;DR

This study measures dust emissivity in Barnard 68 using submillimetre and millimetre observations, revealing temperature gradients and comparing results with dust models.

Contribution

First to derive cloud-averaged dust emissivities at 850 um and 1.2 mm in Barnard 68 considering temperature gradients.

Findings

Dust emissivities at 850 um and 1.2 mm are quantified.

Dust temperatures are lower in the core, affecting emissivity measurements.

Results are compared with models of diffuse and dense cloud dust.

Abstract

We have observed the dark cloud Barnard 68 with SCUBA at 850 um and with SIMBA at 1.2 mm. The submillimetre and millimetre dust emission correlate well with the extinction map of Alves, Lada and Lada (2001).The A_V/850um correlation is clearly not linear and suggests lower temperatures for the dust in the inner core of the cloud. Assuming a model for the temperature gradient, we derive the cloud-averaged dust emissivities (normalised to the V-Band extinction efficiency) at 850 um and 1.2 mm. We find k_850um/k_V = 4.0 +/- 1.0 x 10^-5 and k_1.2mm/k_V = 9.0 +/- 3.0 x 10^-6. These values are compared with other determinations in this wavelength regime and with expectations for models of diffuse dust and grain growth in dense clouds.