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Spherical mass/orbit modeling in galaxies and clusters: constraints on the radial distribution of dark matter
  OKC colloquia

Tuesday 06 October 2015
from 13:15 to 15:00
at FB54
Speaker : Gary Mamon (IAP Paris)
Abstract : While there is a general consensus, assuming standard gravity, that dark matter accounts for roughly 85% of the mass of the Universe, it is not yet clear how this matter is distributed in galaxies and clusters of galaxies. On one hand, cosmological N-body simulations provide us a reference for the dark matter density profile, although this depends on the power spectrum of primordial density fluctuations, with standard Lambda Cold Dark Matter having cuspy inner density profiles. However, there are many physical processes that can affect the dark matter density profile: 1) the dissipative nature of gas from which stars form leads to a concentrated baryonic component that can entrain the dark matter with it; 2) supermassive black holes can swallow stars and dark matter in the inner regions of galaxies; 3) jets from these black holes as well as exploding stars (supernovae) can push the gas outwards and again entrain the dark matter with it. While the distribution of total mass can be constrained from observations using general relativity (gravitational lensing) or hydrodynamics (X-ray observations), I will concentrate on the more traditional method of using internal motions to constrain the dark matter distribution, as the other two methods cannot be applied to small dwarf spheroidal galaxies. Modeling these internal motions also leads to constraints on the orbital shapes of the stars in galaxies and galaxies in clusters, which in turn are important clues to their formation. Despite recent progress in modeling techniques, there is still much debate on the normalization, concentration and inner slope of the dark matter, and avenues for future progress will be discussed. (host: Doug Spolyar)

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