Particle mass in TNG300-3-dark and substructure

Giorgos Korkidis
  • 3
  • 16 Feb '19

I have two questions, one about the mass of particles in TNG-300-3-dark and the other about the substructure in the group catalog. In particular, regarding the mass, here the mass of the particles is given to be 4.4 10^10 Msun (I have made a division by h) whereas in the paper of the public data release (table 1) the mass is given the value 6.6 10^10 Msun. Which is the correct value?

Regarding the substructure I was wondering if it is guaranteed that all the groups/halos in the group catalog are indeed groups/halos or if there is a chance to fell upon a subgroup there. That is, am I guaranteed that when I load a halo of mass, say, 10^14 Msun and then one of 10^12 Msun that the latter won't be a substructure of the former? I understand that this has to do with the boundary problem of DM halos, but since there is no flag-parameter I thought I should ask.

Thank you in advance.

Dylan Nelson
  • 1
  • 17 Feb '19

Hi Giorgos,

The DM particle mass in TNG300-3-Dark is 4.47 x 10^9 solar masses (note: not 10^10). You can verify this absolutely by looking at the MassTable in the Header entry of a snapshot. Yes I see Table 1 is a little iffy here... I will make sure this gets fixed.

For the group catalogs, there are two types of objects: "halos" (same as "groups"), and "subhalos".

While all halos/groups are "centrals", a subhalo can be either a central or a satellite.

So if you are loading Group* entries, these cannot be substructures, but if you are loading Subhalo* entries and specifically want to exclude substructures (i.e. satellites), then you must do this. The typical way is to use GroupFirstSub to make a list of indices of central subhalos.

Giorgos Korkidis
  • 18 Feb '19

Hi Dylan,
Thanks a lot for your quick reply. (indeed 10^10 was a typo)


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