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David Cole, Walter Dehnen, Mark Wilkinson University of Leicester Dark Matter in clusters, groups and galaxies Nottingham-Birmingham extragalactic workshop Nottingham 14/15 September 2011

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The cusp/core problem log radius log density Navarro, Frenk & White 1997Navarro et al 2010

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Observations Oh et al 2008 IC 2574

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Analytical model Parabolic orbit Final halo mass model 1 Final halo mass model 2

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Fiducial runs t

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Effects on the dark matter halo r

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Halo shape rr

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Anisotropy r

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Satellite orbits Time evolution of the orbits of satellites representing baryonic clumps for four parabolic satellite orbits decaying in a dark matter halo with isotropic velocity distribution.

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Effect on Dark Matter Halo Radial profiles of the halos pseudo phase- space density ρ/σ 3 (top), density ρ (middle), and the change in cumulative halo mass ΔM (bottom) at the end of the simulations shown in the previous slide (colour coding the same).

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Effect of the Removal of the satellite Radial profiles of the halos pseudo phase- space density ρ/σ 3 (top), density ρ (middle), and the change in cumulative halo mass ΔM (bottom) for one of the satellites shown in the previous slide but also including the removal of the satellite.

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Effect of satellite Mass The variation with satellite mass of time to fall in,t infall, ΔM max, r max, r50%, and the maximum of ρ/σ 3 after the decay of a circular satellite orbit (red) or after the decay of a parabolic satellite orbit (blue). The lines are power- laws with exponent as indicated.

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Effect of satellite Size As previous slide, except that satellite size r s is varied and m s = 0.01 kept constant.

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Sinking clumps – minor mergers Hubble Interacting Galaxy NGC 695 Hubble Interacting Galaxy IRAS F10565

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Conclusions Sinking clumps can modify the cusp Parabolic orbits have a stronger effect Smaller clumps are more effective Halo shape and velocity structure changed Expulsion of the clump material produces an even greater effect

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