Cosmological Simulations of the Preheating Scenario for Galaxy Cluster Formation: Comparison to Analytic Models and Observations

摘要

We perform a set of non--radiative cosmological simulations of a preheatedintracluster medium in which the entropy of the gas was uniformly boosted athigh redshift. The results of these simulations are used first to test thecurrent analytic techniques of preheating via entropy input in the smoothaccretion limit. When the unmodified profile is taken directly fromsimulations, we find that this model is in excellent agreement with the resultsof our simulations. This suggests that preheated efficiently smoothes theaccreted gas, and therefore a shift in the unmodified profile is a goodapproximation even with a realistic accretion history. When we examine thesimulation results in detail, we do not find strong evidence for entropyamplification, at least for the high-redshift preheating model adopted here. Inthe second section of the paper, we compare the results of the preheatingsimulations to recent observations. We show -- in agreement with previous work-- that for a reasonable amount of preheating, a satisfactory match can befound to the mass-temperature and luminosity-temperature relations. However --as noted by previous authors -- we find that the entropy profiles of thesimulated groups are much too flat compared to observations. In particular,while rich clusters converge on the adiabatic self--similar scaling at largeradius, no single value of the entropy input during preheating cansimultaneously reproduce both the core and outer entropy levels. As a result,we confirm that the simple preheating scenario for galaxy cluster formation, inwhich entropy is injected universally at high redshift, is inconsistent withobservations.