2007/03/08 by Stefan Gottloeber, Stefan Gottlober, Gustavo Yepes · 5 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/517907
published as Astrophys.J.664:117-122,2007 · 7 pages, 6 figures. Accepted for publication in The Astrophysical Journal
arxiv created 2007/03/08 · openalex publication_date 2007/07/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
The MareNostrum Universe is one of the largest cosmological smoothed particle hydrodynamics simulations done so far. It consists of 1024 3 dark and 1024 3 gas particles in a box of 500 h -1 Mpc on a side. Here we study the shapes and spins of the dark matter and gas components of the 10,000 most massive objects extracted from the simulation as well as the gas fraction in those objects. We find that the shapes of objects tend to be prolate both in the dark matter and gas. There is a clear dependence of shape on halo mass, the more massive ones being less spherical than the less massive objects. The gas distribution is nevertheless much more spherical than the dark matter, although the triaxiality parameters of gas and dark matter differ only by a few percent, and it increases with cluster mass. The spin parameters of gas and dark matter can be well fitted by a lognormal distribution function. On average, the spin of gas is 1.4 times larger than the spin of dark matter. We find a similar behavior for the spins at higher redshifts, with a slight decrease of the spin ratios to 1.16 at z = 1. The cosmic normalized baryon fraction in the entire cluster sample ranges from Y b = 0.94 at z = 1 to Y b = 0.92 at z = 0. At both redshifts we find a slight, but statistically significant, decrease of Y b with cluster mass.