A census of cool core galaxy clusters in IllustrisTNG

摘要

The thermodynamic structure of hot gas in galaxy clusters is sensitive toastrophysical processes and typically difficult to model with galaxy formationsimulations. We explore the fraction of cool-core (CC) clusters in a largesample of $370$ clusters from IllustrisTNG, examining six common CCdefinitions. IllustrisTNG produces continuous CC criteria distributions, theextremes of which are classified as CC and non-cool-core (NCC), and thecriteria are increasingly correlated for more massive clusters. At $z=0$ the CCfraction is systematically lower than observed for the complete sample,selecting massive systems increases the CC fraction for $3$ criteria andreduces it for others. This result is partly driven by systematic differencesbetween the simulated and observed gas fraction profiles. The simulated CCfraction increases more rapidly with redshift than observed, independent ofmass or redshift range, and the CC fraction is overpredicted at $z\geq1$. Theconversion of CCs to NCCs begins later and acts more rapidly in thesimulations. Examining the fraction of CCs and NCCs defined as relaxed we findno evidence that CCs are more relaxed, suggesting that mergers are not solelyresponsible for disrupting CCs. A comparison of the median thermodynamicprofiles defined by different CC criteria shows that the extent to which theyevolve in the cluster core is dependent on the CC criteria. We conclude thatthe thermodynamic structure of galaxy clusters in IllustrisTNG shares manysimilarities with observations, but achieving better agreement most likelyrequires modifications of the underlying galaxy formation model.