Calculating HI mass of particles in Halos/Subhalos

Avinash Chaturvedi
  • 1
  • 22 Mar '22

Dear TNG team,

Could you please help me how could I calculate the HI mass of halos/subhalos in the TNG50? I was using the HI and H2 catalogue, but I am unable to find the HI mass for individual particles.

From the halos/subhalos catalogue, I could use the gas metal fraction and can multiply it with the gas fraction, I believe this gives me the total H mass. Will I have to load the particle level information to calculate the HI mass, but I think there too I get only Neutral Hydrogen mass and not specifically HI mass.

Is there a way I could extract this information using the API?
Thank you so much for the response.


Dylan Nelson
  • 24 Mar '22

Dear Avinash,

In the simulation data itself, you are right that you can use the fields in the snapshot to compute the total neutral hydrogen mass. However, there is no split of this, into the atomic (HI) and molecular (H2) components. Such a split is exactly what the "HI and H2 post-processing data catalog" provides (under the assumptions of the particular models described therein).

There isn't HI or H2 mass per gas cell publicly available, but we do have such files floating around. If you'd like to use them, please email me directly.

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