I was wondering if there are resolved field halos in any TNG simulation? I saw the FAQ which states that halos with less than 32 particles may not have subhalos attached to them, but I was wondering if there are any that are better resolved. Either way, would the ones that are resolved (over 20 particles) be useful for the science? And which resolution TNG would have the most?
You should look at TNG50-1, which is the highest resolution simulation. It certainly can be used to study galaxies down to stellar masses of M* ~ 10^7.0 Msun or so.
In theory this could be pushed further, all the way to the mass of a single star particle (~10^5 Msun), but we wouldn't generally trust such small halos.
There are many low-mass field halos; the majority of halos at any mass are in the field.
Thanks for your response. In finding whether or not I have an isolated halo (like an isolated ~10¹⁰ M_sun in dark matter), am I right to assume that if it is the only galaxy in that halo, it would also have a central flag of 1 in the halo catalog, but also be the only galaxy in the group? I know we can also use other criteria that would ensure it is in fact an isolated halo, like how fast it is from a central, but in the case of one that's truly isolated and has no other members in its group. Will it still have info in the halo catalog, and would it be identified as the central with a value of 1, or does that change?
Yes, being the central is a requirement for being isolated. And you can always apply this rule. But, as you say, you should additionally require some distance to the nearest (high mass) halo, for instance.
Okay, that makes sense. Thank you very much, Dylan!