Dust MODELS

Known Dust Models

The physical interstellar dust models that can be invoked via DustEMWrap are:

• MC10 : Compiègne et al., 2011, A&A, 525, 103

• DBP90 : Desert, Boulanger & Puget, 1990, A&A, 237, 215

• DL01 : Li & Draine, 2001, ApJ, 554, 778

• DL07 : Draine & Li, 2007, ApJ, 657, 810

• G17_MODELA : Guillet et al., 2018, A&A, 610, 16

• G17_MODELB : Guillet et al., 2018, A&A, 610, 16

• G17_MODELC : Guillet et al., 2018, A&A, 610, 16

• G17_MODELD : Guillet et al., 2018, A&A, 610, 16

• J13 : Jones et al., 2013, A&A, 558 , 62

• WD01_RV5P5B : Weingartner & Draine, 2001, ApJ, 548, 296. Case B model with Rv = 5.5

Users should refer to the original papers for a complete description of the dust models. Note that Guillet et al. (2017) models specifically address the polarisation of the thermal dust emission. DustEMWrap therefore requires Stokes Q and Stokes U information to perform SED-fitting with these models.

The DustEMWrap team is currently working to incorporate the 'astrodust+PAH' model presented in Hensley & Draine (2022). To keep informed of the next release that includes the 'astrodust+PAH' model, please subscribe to our mailing list.

Dust Model Parameters

DustEMWrap allows the user to fit an observational SED by optimising a user-defined combination of dust model and plug-in parameters. The DustEM Users’ Guide provides a detailed explanation of all the dust model parameters.

For each grain type in an available interstellar dust model, there are:

• MDUST_O_MH : the abundance of the grain type relative to H

• RHO : the grain material specific mass density in g/cm−3

• AMIN : the minimum grain size in cm

• AMAX : the maximum grain size in cm

• ALPHA_O_A0 : the centroid (A0) of a log-normal, or the index of a power law (ALPHA) that describes the grain size distribution.

• AT : shape parameter 1 of an exponential decay to a power-law grain size distribution

• AC : shape parameter 2 of an exponential decay to a power-law grain size distribution

• GAMMA : shape parameter 3 of an exponential decay to a power-law grain size distribution

• AU : shape parameter 1 of curvature term of a power-law grain size distribution

• ZETA : shape parameter 2 of curvature term of a power-law grain size distribution

• ETA : shape parameter 3 of curvature term of a power-law grain size distribution

This is a non-exhaustive list of the dust model parameters that can be adjusted during a fit using DustEMWrap. Other parameters include grain absorption and scattering efficiencies, heat capacities and charge, quantum effects that modify the opacity of amorphous grains at lower temperatures, grain alignment efficiencies and size thresholds (for polarized dust models). A temperature- or size-dependence of certain dust grain properties can also be modelled. Users should consult the DustEM Users’ Guide for a complete explanation of these "advanced" parameters and their implementation.