On the other hand I find in Nelson et al. 2018: "the first simulation, TNG100 â€¦ the gravitational softening length of the dark matter and stars is 0.7 kpc at z=0, and the gas component has an adaptive softening with a minimum of 185 comoving parsecsâ€¦."

Sorry if I am missing an obvious point here but could you please help me understanding how these numbers relate to each other? What is the minimum comoving softening length and how can I get the softening length in physical units as a function of redshift?
And is the softening length for stellar particles the same as for gas particles?

Hi,

I have a question about the softening lengths. Using the api to access the data I find for example for TNG100-1

softening_dm_comoving = 1.0

softening_stars_comoving = 1.0.

On the other hand I find in Nelson et al. 2018:

"the first simulation, TNG100 â€¦ the gravitational softening length of the dark matter and stars is 0.7 kpc at z=0, and the gas component has an adaptive softening with a minimum of 185 comoving parsecsâ€¦."Sorry if I am missing an obvious point here but could you please help me understanding how these numbers relate to each other? What is the minimum comoving softening length and how can I get the softening length in physical units as a function of redshift?

And is the softening length for stellar particles the same as for gas particles?

Thanks a lot in advance,

Peter

Hi Peter,

The values

are in "code length units" of

`ckpc/h`

. So dividing by`h`

gives 0.7 ckpc, or 0.7 pkpc at z=0.Stars and DM have similar softenings, while for gas it is quite different (adaptive). This should be well described in Pillepich+ (2018).