Dear TNG team,
I have a quick question about the parent simulations with dark matter only and
their specific setup. Do they start from the same initial conditions as the full
hydro runs and the baryon particles are simply removed? Or are gas/star
particles left in the simulation, but treated as secondary species of dark matter?
Thank you for your time.
The baryonic and "dark-matter only" simulations start with the same initial conditions (same "phases").
In practice, the ICs (which you can download) give the displacements and velocities of "total matter particles". For baryonic runs, these are then split into DM and gas. For gravity-only runs, these remain as is. So in gravity-only simulations, there is only PartType1 (collisionless total matter i.e. dark matter particles).