Simulations Of Galaxy Clusters With And Without Winds: I. The Structure Of Clusters

Abstract

We use gas dynamic simulations to explore the effects of galactic winds on galaxy clusters. Two ensembles of 18 realizations, spanning a decade in temperature, are evolved with and without winds in an underlying biased CDM cosmology. Galaxies are identified as peaks in the initial density field, and are assumed to lose half their initial mass over a Hubble time in winds with an effective temperature of 8 keV. The energy input through winds boosts the entropy of the ICM above that generated by infall, resulting in a more extended density profile. The magnitude of this effect increases with decreasing mass or temperature, consistent with observations. The extended nature of the ICM with winds can lead to underestimates of the global baryon fraction, with low-temperature clusters particularly deficient. We calibrate the amplitude of this effect at density contrasts of 170 and 500. On the other hand, the final temperature of the gas is relatively unaffected; a similar mass-temperature relation exists with or without winds. The input wind energy is effectively consumed as work to lift the gas in the dark matter dominated potential. While the dark matter profile exhibits a self-similar form seen in other studies, the galaxy distribution is more centrally concentrated than either the dark matter or gas, and evidences a mild velocity bias. The gradient of galaxies with respect to primordial gas produces strong, negative radial gradients in metallicity within the ICM.