In a phantom simulation run without dust, mcfost will use the gas-to-dust ratio from the .para file to set the total dust mass.
In a phantom simulation run with dust, mcfost instead takes the dust mass from the .para file and uses this to rescale the overall dust mass from phantom
For comparison of dusty with non-dusty simulations it would be better if the same behaviour occurred in both cases. i.e. for the simulations WITH dust it should also use the gas-to-dust ratio from the .para instead of the dust mass
In a phantom simulation run without dust, mcfost will use the gas-to-dust ratio from the .para file to set the total dust mass.
In a phantom simulation run with dust, mcfost instead takes the dust mass from the .para file and uses this to rescale the overall dust mass from phantom
For comparison of dusty with non-dusty simulations it would be better if the same behaviour occurred in both cases. i.e. for the simulations WITH dust it should also use the gas-to-dust ratio from the .para instead of the dust mass