THEMIS 2.0: A self-consistent model for dust extinction, emission, and polarisation

Understand

Recent observations in emission, extinction, and polarisation have at least partially invalidated most of the astronomical standard grain models for the diffuse ISM.

• Moreover, lab measurements on interstellar silicate analogues have shown differences with the optical properties used in these standard models.
• To address these issues, our objective is twofold: (i) to update the optical properties of silicates and (ii) to develop the THEMIS dust model to allow the calculation of polarised extinction and emission.
• Based on optical constants measured in the lab for amorphous silicates and on observational constraints in mid-IR extinction and X-ray scattering, we defined new optical constants for the THEMIS silicates.