I am trying to understand if the FoF structure finder applied in TNG indirectly identifies gravitationally bound groups of galaxies.
I was wondering if it is possible to guarantee that all subhalos in a FoF halo will not escape the halo potential. Is there any implicit requirement in your structure finder algorithm that ensures the subhalos are always gravitationally bound to their parent FoF halos?
Thank you in advance!
Dylan Nelson
16 Nov '22
FoF is a 3D spatial algorithm, it doesn't consider if any internal substructures are gravitationally bound.
For example, a very fast fly-by encounter would clearly enter, then be part of, a FoF group, but it could be unbound in the future.
If you are looking not at z=0, but at z>0, you could go forward in time and check that a subhalo of interest remains part of the halo. Or you could make a more theoretical/energetic argument, to assess this at fixed time. But you would have to do this yourself.
Hi,
I am trying to understand if the FoF structure finder applied in TNG indirectly identifies gravitationally bound groups of galaxies.
I was wondering if it is possible to guarantee that all subhalos in a FoF halo will not escape the halo potential. Is there any implicit requirement in your structure finder algorithm that ensures the subhalos are always gravitationally bound to their parent FoF halos?
Thank you in advance!
FoF is a 3D spatial algorithm, it doesn't consider if any internal substructures are gravitationally bound.
For example, a very fast fly-by encounter would clearly enter, then be part of, a FoF group, but it could be unbound in the future.
If you are looking not at z=0, but at z>0, you could go forward in time and check that a subhalo of interest remains part of the halo. Or you could make a more theoretical/energetic argument, to assess this at fixed time. But you would have to do this yourself.
Thank you Dylan!