Catalogue of clusters

Esteban Garcia
  • 1
  • 11 Nov '21

I´m trying to find a catalogue of clusters of the Illustris simulation with informacion of each galaxy: principally distance to the center of the cluster, velocities, mass, with z<1. Could you give me some advice?

Thank you

Dylan Nelson
  • 11 Nov '21

Hello Esteban,

There isn't any such catalog already available, but it would be easy to construct, at least an initial version.

If you select all halos above e.g. 10^14 Msun in TNG300-1, for example, there are a few hundred. You can loop over each, and obtain the properties of all its satellite (member) galaxies.

As you only need the "group catalog" to get started, I would either (i) download the TNG300-1 group catalog (for the redshift of interest) to your own computer, or (ii) use the Lab service. Then, go through the Example Scripts Getting Started guide to get familiar about loading data from these catalogs.

Esteban Garcia
  • 2
  • 26 Jan

I already downloaded the group catalog (TNG300-1, snapshop 99) and followed the starting guide for Python Illustris 3(, with the same files (groups_135) and it went perfectly... but when I tried with TNG300-1, snapshot 99 I changed this part...

subhalos = il.groupcat.loadSubhalos(basePath,99,fields=fields)

And marks an error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.8/dist-packages/illustris_python/", line 100, in loadSubhalos
    return loadObjects(basePath, snapNum, "Subhalo", "subgroups", fields)
  File "/usr/local/lib/python3.8/dist-packages/illustris_python/", line 38, in loadObjects
    with h5py.File(gcPath(basePath, snapNum), 'r') as f:
  File "/usr/local/lib/python3.8/dist-packages/h5py/_hl/", line 507, in __init__
    fid = make_fid(name, mode, userblock_size, fapl, fcpl, swmr=swmr)
  File "/usr/local/lib/python3.8/dist-packages/h5py/_hl/", line 220, in make_fid
    fid =, flags, fapl=fapl)
  File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
  File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
  File "h5py/h5f.pyx", line 106, in
FileNotFoundError: [Errno 2] Unable to open file (unable to open file: name = '/home/esteban/Escritorio/TNG300-1/output//groups_099/fof_subhalo_tab_099.0.hdf5', errno = 2, error message = 'No such file or directory', flags = 0, o_flags = 0)
Esteban Garcia
  • 26 Jan

Forget it, I fixed it. I changed the name of the folder to Groups_099 and manually put the folder illustris_python in the python folder.

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