Abstract
We present the Rhapsody-G suite of cosmological hydrodynamic AMR zoom simulations of ten massive galaxy clusters at the $M_{\rm vir}\sim10^{15}\,{\rm M}_\odot$ scale. These simulations include cooling and sub-resolution models for star formation and stellar and supermassive black hole feedback. The sample is selected to capture the whole gamut of assembly histories that produce clusters of similar final mass. We present an overview of the successes and shortcomings of such simulations in reproducing both the stellar properties of galaxies as well as properties of the hot plasma in clusters. In our simulations, a long-lived cool-core/non-cool core dichotomy arises naturally, and the emergence of non-cool cores is related to low angular momentum major mergers. Nevertheless, the cool-core clusters exhibit a low central entropy compared to observations, which cannot be alleviated by thermal AGN feedback. For cluster scaling relations we find that the simulations match well the $M_{500}-Y_{500}$ scaling of Planck SZ clusters but deviate somewhat from the observed X-ray luminosity and temperature scaling relations in the sense of being slightly too bright and too cool at fixed mass, respectively. Stars are produced at an efficiency consistent with abundance matching constraints and central galaxies have star formation rates consistent with recent observations. While our simulations thus match various key properties remarkably well, we conclude that the shortcomings strongly suggest an important role for non-thermal processes (through feedback or otherwise) or thermal conduction in shaping the intra-cluster medium.
Highlights
While simulations of galaxy formation in Milky Way-sized haloes (e.g. Guedes et al 2011; Christensen et al 2014) or small cosmic volumes (e.g. Dubois et al 2014; Vogelsberger et al 2014; Schaye et al 2015) are making substantial progress, realizing the population of galaxies that reside in the most massive cosmic haloes, those hosting rich clusters of galaxies, remains a formidable challenge (Kravtsov & Borgani 2012)
In the simulations discussed in this paper, we include a purely thermal AGN feedback, based on the subgrid models of Springel, Di Matteo & Hernquist (2005) with the additional energy injection thresholding of Booth & Schaye (2009), which is commonly employed in smoothed-particle hydrodynamics (SPH) simulations (e.g. Le Brun et al 2014; Schaye et al 2015, for recent examples)
While we compare our scalings to observations, we caution that this type of exercise is non-ideal in that (i) we employ true, three-dimensional spherical masses in simulations while observational estimates may be biased with respect to these values; (ii) the intrinsic properties of the simulations are measured directly in the simulations rather than derived from models applied to mock observations; (iii) the statistics of the simulated sample are not necessarily representative of a broader mass-complete sample; and (iv) the correlated cluster evolution itself might lead to a departure from the scaling relations compared to studies that are performed at fixed redshift using larger samples
Summary
While simulations of galaxy formation in Milky Way-sized haloes (e.g. Guedes et al 2011; Christensen et al 2014) or small cosmic volumes (e.g. Dubois et al 2014; Vogelsberger et al 2014; Schaye et al 2015) are making substantial progress, realizing the population of galaxies that reside in the most massive cosmic haloes, those hosting rich clusters of galaxies, remains a formidable challenge (Kravtsov & Borgani 2012). Gas dynamic simulations using this approach to AGN feedback show improvements to central cluster galaxy morphology (Martizzi, Teyssier & Moore 2012a) as well as improved scaling of hot intracluster medium (ICM) properties with halo mass (e.g. Le Brun et al 2014; Planelles et al 2014, and references therein). RHAPSODY-G – I: massive galaxy clusters 167 to multiphysics adaptive mesh simulations They include cooling, star formation and SMBHs as well as their respective feedback. These subgrid models have been shown before to reproduce realistic brightest cluster galaxy (BCG) masses (Martizzi et al 2012a).
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