How to get halo_id

HE ZHENTAO
  • 1 Jul

Hi, I appreciate that I can use this galaxy simulation and the API about halo.

I have some questions that I would like to have answered.
How to get halo_id in Browsable REST API?
I want to try to get the ids of all halo's (not subhalo's).
From there, I can determine if this halo is in a specific quality range.
They exist in a single specific page (similar to https://www.tng-project.org/api/Illustris-2/snapshots/135/halos/10/)
But there is no page like https://www.tng-project.org/api/Illustris-2/snapshots/135/halos/ (which shows that the page does not exist) that shows all halo_id's.
Is there any good way to count them?

Looking forward to hearing back from you.

HE ZHENTAO

Translated with www.DeepL.com/Translator (free version)

Dylan Nelson
  • 1 Jul

Hi Zhentao,

If you want to search by halo properties, e.g. m200 or rvir, then you should use the group catalog. You can either download it for a given snapshot (not too large, few GB), or else use the Lab service.

HE ZHENTAO
  • 5 Jul

Hi Dylan

Thank you very much for your assistance, I have successfully categorized the halo through catalog.

But I have a question, why groupcat is saving the data of halo by segmentation? And what is the basis for dividing a groupcat into multiple hdf5 to save?

hope you can answer my question.
thank you!

Dylan Nelson
  • 5 Jul

This is just to have smaller, more manageable files for e.g. downloading.

One could combine the entire catalog into a single file if you wanted, the information would be the same.

HE ZHENTAO
  • 6 Jul

Hi Dylan

Thank you very much!

HE ZHENTAO
  • 7 Jul

Hi Dylan

This is a question about halo and subhalo.

For example, in the simulation of illustris3, why is the halo with infoID = 0 in the same spatial position (with the same pos) as the subhalo with id = 0 does it mean they are the same?
But again their quality is totally different, why is that?

Dylan Nelson
  • 7 Jul

I would suggest perhaps to read the Subfind paper (Section 4), for another description of halos and subhalos, in addition to the documentation for IllustrisTNG in particular.

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