Exotic galaxies as tests for hydrodynamical simulations

Hydrodynamical simulations considering baryonic physics have become a common tool for studying the evolution and properties of galaxies in a cosmological context. The sub-grid physics are tuned to reproduce the overall distribution of various types of galaxies similar to observations, but the details on how sub-grid physics are implemented vary from simulation to simulation. Rare and exotic galaxies provide an excellent way to test the limits of galaxy samples produced by hydrodynamical simulations, since the parameters of these simulations are not specifically fine-tuned to reproduced such uncommon galaxies. In our work, we take advantage of the growing number of large-scale hydrodynamical simulations that provide us with sufficiently rich galaxy samples and use data from Illustris, EAGLE, HorizonAGN, as well as IllustrisTNG. Within these simulations, we search for massive galaxies with low dark matter fractions and a subgroup of present-day survivors of red nuggets. In the case of galaxies with low dark matter fractions, the simulations show that those galaxies can be found in high density environment near BCGs, something that is supported by strong lensing studies. Additionally, the simulations predict outstanding internal kinematics and unusual stellar populations for these galaxies, both which have to be confirmed by observations yet. Furthermore, we also use these simulations to study the merger history and evolution of compact galaxies with high stellar masses in the present-day universe and compare this data with observations. When compared to observational data, uncommon galaxies with peculiar properties are interesting test objects for probing the limits of current hydrodynamical simulations.