Tracers TNG50

Josue Lopez
  • 22 Jan


I am currently working with galaxy data in the TNG-50 simulation and would like to trace the origin of the gas. Specifically, I am interested in determining whether it comes from the intergalactic medium or from another galaxy, and if so, which one. While I have explored the tracers, I am having difficulty loading the necessary data. It appears that the files are empty, but I am not sure if I am doing it correctly. Any help would be greatly appreciated.

Dylan Nelson
  • 23 Jan

Are you loading them yourself from the snapshot files? Perhaps you can paste a code snippet.

Josue Lopez
  • 24 Jan

Thank you for your response. Firstly, I printed the number of particles for a subhalo in TNG50. The output showed that there was no data for Particle Type 3, which I understand corresponds to the tracers.
This is my code:

basePath = '../sims.TNG/TNG50-1/output'
snap = 99
subhaloID = 596660

sub = ill.groupcat.loadSingle(basePath,snap,subhaloID=subhaloID)


[456927 991693      0      0 281914      1]

I also tried using the dataset mentioned in index a) of the Data Specification. From the information provided, I understand that to trace the gas to a galaxy, we need to use the file 'tr_all_groups_99_subhalo_id'. I went to the path 'TNG/TNG50-1/postprocessing/tracer_tracks' to find the hdf5 file, but I only found two files: 'tr_all_groups_99_meta.hdf5' and 'tr_all_groups_99_parent_indextype.hdf5'. I do not understand how to trace the origin of the gas using these two files. Thanks in advance for your help.

Here is the other part of my code:

basePath = '../sims.TNG/TNG50-1/postprocessing/tracer_tracks'

file = basePath+"/tr_all_groups_99_meta.hdf5"

data = h5py.File(file,"r")

for f in data.keys():

Dylan Nelson
  • 24 Jan

Hi Josue,

I would suggest to read the data release papers, which describe the tracers a bit more. They are not so easy to work with. They are not ordered by (sub)halo, so (sub)halos do not "contain" any tracers. To load and use them, you have to load all PartType3 from the snapshot using ill.snapshot.loadSubset(), for example.

The supplementary data catalog "(a) Tracer Tracks" is a good alternative, it makes them easier to use. The documentation gives some pseudo-code advice on how to use this dataset.

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