http://arxiv.org/abs/1401.6195
We present a new method for studying tracers in gravitational systems where higher moments of the line-of-sight velocity distribution are introduced via Virial equations rather than the Jeans equations. Unlike the fourth order Jeans equations, the fourth order Virial equations can simply be added to the standard 2nd order Jeans equation without introducing a new anisotropy parameter beta’. We introduce two new global shape parameters zeta_A and zeta_B which replace the kurtosis as a more statistically robust measure of the shape of the line of sight velocity distribution. We show that in the case of stars in dwarf spheroidal galaxies these new parameters seem to discriminate powerfully between different density profiles that are otherwise consistent with the observed stellar kinematics (a problem sometimes known as the beta degeneracy). We present the new parameters in detail and recover the surprising result that the dark matter in Sculptor may be cuspy after all, in contrast to the conclusions of other approaches.
Mon, 27 Jan 14
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