I would like to study the formation of dwarf galaxies. However, these systems are less in mass and most of them are not included in the merger tree. Do you know if there would be a possibility to check when these systems have been formed? Maybe by following their gas particle IDs back in time, but the whole particle catalogs are huge. Is there maybe a simple method to do this?
Thank you and best wishes,
There is an intrinsic lower mass limit to "galaxies" which can be studied - this is the smallest number of particles for our group finding algorithm (Subfind) to detect an object at all. In Illustris this is set at 20 particles. So if an object has e.g. 19 dark matter particles and just 1 gas cell or star particle, then the absolute minimum object (baryonic) mass is 10^6 msun. Below this, Illustris is not suitable for studying smaller mass galaxies. Furthermore, at such low masses, we would generally not trust the results, and would prefer to only consider objects with e.g. 10 or 100 baryonic elements, so total (baryonic) masses greater than 10^7 or 10^8. All of these objects will be in the group catalogs and so the trees.