Size matters: the non-universal density profile of subhaloes in SPH simulations and implications for the Milky Way's dSphs

Details Size matters: the non-universal density profile of subhaloes in SPH simulations and implications for the Milky Way's dSphs Size matters: the non-universal density profile of subhaloes in SPH simulations and implications for the Milky Way's dSphs

2012-04-02

arxiv.org/abs/1204.0515v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

8 pages, 4 figs, submitted to MNRAS

Scientific paper

We use dark matter only and full hydrodynamical Constrained Local UniversE Simulations (CLUES) of the formation of the Local Group to study the density profile of subhaloes of the simulated Milky Way and Andromeda galaxies. We show that the Einasto model provides the best description of the subhaloes' density profile, as opposed to the more commonly used NFW profile or any generalisation of it. We further find that the Einasto shape parameter \nEin\ is strongly correlated with the total subhalo mass, pointing towards the notion of a non-universality of the subhaloes' density profile. Assuming now that the dSphs of our Galaxy thus follow the Einasto profile and using the maximum and minimum values of \nEin\ from our SPH simulations as a gauge, we can improve the observational constraints on the \Rmax-\Vmax\ pairs obtained for the brightest satellite galaxies of the Milky Way. When considering only the subhaloes with $-13.2\lesssim M_V\lesssim-8.8$, i.e. the range of luminosity of the classical dwarfs, we find that all our simulated objects are consistent with the observed dSphs if their haloes follow the Einasto model with $1.6\lesssim n_{\rm E} \lesssim5.3$. The numerically motivated Einasto profile for the observed dSphs as well as the observationally motivated magnitude cut for the simulated subhaloes will eliminate the "massive failures" problem and results in a perfect agreement with observations.

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