Hello, I am writing in with a question regarding the nucleus of dark matter halos. My purpose is to plot a 2D-histogram with stars, gas and nucleus of dark matter halos for a certain subhalo. The objective is to localize a satellite galaxy close to my main subhalo. The question is: how can I identify the particles that conform the nucleus of dark matter halos for the central and satellite galaxies? I am using the API in my code to download the data.
Thank you in advance.
It depends how you would like to define the nucleus. If you want just a spatial definition, e.g. R < 5 kpc, then you can calculate the distance to every particle and find those near the center.
Or you could use a non-spatial definition, e.g. related to the gravitational potential. You could select the N most bound particles, using the "Potential" field in the snapshots.
Yes I understand but my problem is that I'd have two DM nucleus (in the hypothesis that I have a small satellite galaxy close to my main subhalo). In this case, I'd have two centers, one for the main subhalo and another for the satellite which I want to plot together. In this sense, I suppose I have to manage to localize these small satellites since, as far as I know, they are not identified in the simulation. Or can I get direct outputs for a satellite galaxy?
Yes you should use the subhalo catalogs - these include all substructures identified, down to a minimum of 20 particles.
Each entry in the subhalo catalog has a SubhaloPos entry, which gives you the localized position.
Each entry is also one of two types: a "central", or a "satellite", so you can separate these two categories.
Thank you very much, this is what I needed