Hello,
I want to estimate the effect of dust particles (derived from gas distribution) on the light emitted from star particles that are behind them(in z position) - only the absorbed light for the moment. I am doing a particle-based manipulation of the simulation outputs, i.e. I am using snapshot datasets, in particluar PartType0 for gas/dust and PartType4 for stars.
In order to estimate the column density of the gas, I would need to know the volume of every gas cell. My question: is it right to estimate the gas cell volume (the Voronoi cell volume I think) using Masses(PType0) / Density(PType0) ?
Thanks for your help.

Yes Volume = Mass / Density exactly, for PartType0. We have this "Volume" field saved in the original Illustris snapshots, but since it can be computed from these two other fields, in TNG we deleted it to save space.

Sorry, is it possible that for some snapshots - e.g. in TNG100-3 snapshots 32 and 34 - the field PartType0/NeutralHydrogenAbundance is not available? And also PartType0/GFM_Metals, while e.g. PartType0/GFM_Metallicity and other fields are available.

Hello,

I want to estimate the effect of dust particles (derived from gas distribution) on the light emitted from star particles that are behind them(in z position) - only the absorbed light for the moment. I am doing a particle-based manipulation of the simulation outputs, i.e. I am using snapshot datasets, in particluar PartType0 for gas/dust and PartType4 for stars.

In order to estimate the column density of the gas, I would need to know the volume of every gas cell. My question: is it right to estimate the gas cell volume (the Voronoi cell volume I think) using Masses(PType0) / Density(PType0) ?

Thanks for your help.

Yes

`Volume = Mass / Density`

exactly, for PartType0. We have this "Volume" field saved in the original Illustris snapshots, but since it can be computed from these two other fields, in TNG we deleted it to save space.Great. Thanks for your help.

and what if I want to know the column density of neutral hydrogen enclosed in a single gas volume? Or at least its (volumetric) density. Thank you

Please see

`PartType0/NeutralHydrogenAbundance`

.thanks, I was looking in the old Illustris documentation, I'm sorry.

Sorry, is it possible that for some snapshots - e.g. in

`TNG100-3`

snapshots 32 and 34 - the field`PartType0/NeutralHydrogenAbundance`

is not available? And also`PartType0/GFM_Metals`

, while e.g.`PartType0/GFM_Metallicity`

and other fields are available.That's correct, it is the difference in TNG between "full" and "mini" snapshots.