Implications of Grain Size Distribution and Composition for the Correlation between Dust Extinction and Emissivity
Abstract
We study the effect of variations in dust size distribution and composition on the correlation between the spectral shape of extinction (parameterized by RV) and far-infrared dust emissivity (parameterized by the power-law index β). Starting from the size distribution models proposed by Weingartner & Draine, using the dust absorption and emission properties derived by Laor & Draine for carbonaceous and silicate grains, and by Li & Draine for polycyclic aromatic hydrocarbon grains, we calculate the extinction and compare it with the reddening vector derived by Schlafly et al. An optimizer and an Markov chain Monte Carlo method are used to explore the space of available parameters for the size distributions. We find that larger grains are correlated with high RV. However, this trend is not enough to explain the emission-extinction correlation observed by Schlafly et al. For the RV - β correlation to arise, we need to impose explicit priors for the carbonaceous and silicate volume priors as functions of RV. The results show that a composition with higher ratio of carbonaceous to silicate grains leads to higher RV and lower β. A relation between E(B - V)/τ353 and RV is apparent, with possible consequences for the recalibration of emission-based dust maps as a function of RV.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2020
- DOI:
- 10.3847/1538-4357/abbb8d
- arXiv:
- arXiv:2009.11869
- Bibcode:
- 2020ApJ...904...38Z
- Keywords:
-
- Interstellar dust extinction;
- Interstellar medium;
- Interstellar dust processes;
- Carbonaceous grains;
- Silicate grains;
- Polycyclic aromatic hydrocarbons;
- Interstellar scattering;
- Interstellar absorption;
- 837;
- 847;
- 838;
- 201;
- 1456;
- 1280;
- 854;
- 831;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Published in The Astrophysical Journal. 28 pages, 27 figures, 3 Tables