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The dark outside: the density profile of dark matter haloes beyond the virial radius | | Hugo Tavio
; Antonio J. Cuesta
; Francisco Prada
; Anatoly A. Klypin
; Miguel A. Sanchez-Conde
; | | Date: |
18 Jul 2008 | | Abstract: | We present an approximation for the average density profile of dark matter
haloes in the LambdaCDM cosmological model, which is accurate to within 10--15%
even for large radial distances from 0.05R_{vir} up to 10R_{vir} for halo
masses ranging from 10^{11.5} to 10^{15.0} h^{-1}M_{Sun}. We propose a modified
form of the Navarro, Frenk & White (NFW) approximation:
ho(r)=
ho_{NFW}(r)+
A (r/R_{vir})^{-1}+B (1+r/R_{vir})^{-1}. This generalized expression, which is
applicable to the external regions of dark matter haloes, only very slightly
affects the density in the inner regions of haloes. The strong correlation
among the different parameters in the model allows us to describe the profile
in terms of just one parameter: the virial mass. We integrate our density
profile to derive the enclosed mass in a sphere of a given radius and compare
it with the NFW results. We find that the NFW underestimates the enclosed mass
by more than 50% at 10R_{vir}, whereas our model reproduces the results from
numerical simulations to within 2% accuracy even at this distance. We also use
this new approximation to study the weak gravitational lensing and to obtain an
analytic expression for the tangential shear. This allows us to quantify the
contribution to the shear from the outer regions of the density profile. For
the first time we calculate the difference between the tangential shear
calculated via the NFW profile and the corresponding result when the external
regions of haloes in cosmological simulations are taken into account. We find a
4% difference for all the mass ranges under study. | | Source: | arXiv, 0807.3027 | | Services: | Forum | Review | PDF | Favorites | |
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