The effect of baryons on the inner density profiles of rich clusters

McCarthy, I. G.; Schaye, J.; Dalla Vecchia, C.; Furlong, M.; Crain, R. A.; Theuns, T.; Trayford, J.; Frenk, C. S.; Bower, R. G.; Schaller, M.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 452, Issue 1, p.343-355

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9
2015
Number of authors
10
IAC number of authors
1
Citations
92
Refereed citations
87
Description
We use the `Evolution and assembly of galaxies and their environments' (EAGLE) cosmological simulation to investigate the effect of baryons on the density profiles of rich galaxy clusters. We focus on EAGLE clusters with M200 > 1014 M⊙ of which we have six examples. The central brightest cluster galaxies (BCGs) in the simulation have steep stellar density profiles, ρ*(r) ∝ r-3. Stars dominate the mass density for r < 10 kpc, and, as a result, the total mass density profiles are steeper than the Navarro-Frenk-White (NFW) profile, in remarkable agreement with observations. The dark matter halo itself closely follows the NFW form at all resolved radii (r ≳ 3.0 kpc). The EAGLE BCGs have similar surface brightness and line-of-sight velocity dispersion profiles as the BCGs in the sample of Newman et al., which have the most detailed measurements currently available. After subtracting the contribution of the stars to the central density, Newman et al. infer significantly shallower slopes than the NFW value, in contradiction with the EAGLE results. We discuss possible reasons for this discrepancy, and conclude that an inconsistency between the kinematical model adopted by Newman et al. for their BCGs, which assumes isotropic stellar orbits, and the kinematical structure of the EAGLE BCGs, in which the orbital stellar anisotropy varies with radius and tends to be radially biased, could explain at least part of the discrepancy.
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Numerical Astrophysics: Galaxy Formation and Evolution
How galaxies formed and evolved through cosmic time is one of the key questions of modern astronomy and astrophysics. Cosmological time- and length-scales are so large that the evolution of individual galaxies cannot be directly observed. Only through numerical simulations can one follow the emergence of cosmic structures within the current
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Dalla Vecchia