Bonn 2010 – scientific programme

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GR: Fachverband Gravitation und Relativitätstheorie

GR 12: Astrophysik

GR 12.2: Talk

Wednesday, March 17, 2010, 15:40–16:00, JUR K

Dark matter in galactic disks — •Peter M.W. Kalberla — Argelander-Institut für Astronomie

Dark matter (DM) is needed to explain the rotation of galaxies but details about the shape of the DM distribution are controversial, in particular for the Milky Way.

There is growing evidence that a significant fraction of the DM around galaxies is associated with the baryonic disks. We discuss observations and simulations that give evidence for such a distribution and constrain the properties of DM disks.

The gas distribution in the Milky Way disk and its halo is well known from high precision observations. The gas extends far beyond the stellar population and is therefore a perfect tracer of the gravitational potential. For the Milky Way we solve the combined Poisson-Boltzmann equations in a self-consistent way. Our results suggest a DM disk, in good agreement with mass models derived from the observed excess of diffuse gamma rays from EGRET. Dwarf galaxies recycled from the collisional debris of massive galaxies give additional evidence.

We compare observational constraints for the mass distribution in the Milky Way with results from recent n-body simulations of merger events. Alternative explanations from modified Newtonian dynamics are discussed. We comment on speculations about the origin of the DM disk.