Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds

TL;DR

This study compares Herschel and near-infrared data to evaluate dust opacity models in three isolated molecular cloud cores, revealing that existing models are inconsistent across sources and may require refinement.

Contribution

It provides an empirical assessment of four dust opacity models against observational data in three molecular cores, highlighting their limitations and the need for more complex modeling.

Findings

Dust models vary in consistency across sources.

Some models fit core envelopes better than others.

No single model fits all three cores perfectly.

Abstract

Density profiles of isolated cores derived from thermal dust continuum emission rely on models of dust properties, such as mass opacity, which are poorly constrained. With complementary measures from near-infrared extinction maps, we can assess the reliability of commonly-used dust models. In this work, we compare Herschel-derived maps of the optical depth with equivalent maps derived from CFHT WIRCAM near-infrared observations for three isolated cores: CB68, L429, and L1552. We assess the dust opacities provided from four models: OH1a, OH5a, Orm1, and Orm4. Although the consistency of the models differs between the three sources, the results suggest that the optical properties of dust in the envelopes of the cores are best described by either silicate and bare graphite grains (e.g., Orm1) or carbonaceous grains with some coagulation and either thin or no ice mantles (e.g., OH5a). None of the models, however, individually produced the most consistent optical depth maps for every source. The results suggest that either the dust in the cores is not well described by any one dust property model, the application of the dust models cannot be extended beyond the very center of the cores, or more complex SED fitting functions are necessary.