Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-01-19
Mon.Not.Roy.Astron.Soc.368:1073-1077,2006
Astronomy and Astrophysics
Astrophysics
6 pages, 5 figures, accepted for publication in MNRAS, high resolution simulations included
Scientific paper
10.1111/j.1365-2966.2006.10182.x
The dark matter dominated Fornax dwarf spheroidal has five globular clusters orbiting at ~1 kpc from its centre. In a cuspy CDM halo the globulars would sink to the centre from their current positions within a few Gyrs, presenting a puzzle as to why they survive undigested at the present epoch. We show that a solution to this timing problem is to adopt a cored dark matter halo. We use numerical simulations and analytic calculations to show that, under these conditions, the sinking time becomes many Hubble times; the globulars effectively stall at the dark matter core radius. We conclude that the Fornax dwarf spheroidal has a shallow inner density profile with a core radius constrained by the observed positions of its globular clusters. If the phase space density of the core is primordial then it implies a warm dark matter particle and gives an upper limit to its mass of ~0.5 keV, consistent with that required to significantly alleviate the substructure problem.
Goerdt Tobias
Moore Ben
Read Justin I.
Stadel Joachim
Zemp Marcel
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