Including dust in Magritte #293
Description
Context
As dust might impact the radiation field in AGB stars (and other astrophysical environments), we can try to implement it.
However, given the variety of different prescriptions available for the dust opacity, we will only be including a few simple ones as example. In order to be flexible, we will require the computed total dust opacity and total dust emissivity as input.
Implementation
We will require these emissivities and opacities at every line frequency, as we will be assuming that the dust features vary slowly (compared to the line width). Evidently, I will implement a few python helper functions to help with calculating these values (and include a few example prescriptions). During radiative transfer calculations, we will add the dust opacity and emissivity contribution corresponding to the considered line transition. This does not require many changes in the C++ source code, however, I will still need to see whether the calculated ALI elements needs to be changed (might need to be corrected by a factor corresponding to the total source function divided by the line source function).
Limitations
This implementation will only be valid for non-relativistic velocities, as otherwise the doppler shift might prove too large for the assumption about the dust opacity/emissivity being unaffected by the doppler shift to hold. Either way, we do not yet properly treat relativistic velocities in Magritte.