The Distribution of Dark Matter in the Milky Way Galaxy

TL;DR

This paper reviews observational evidence indicating that dark matter in the Milky Way is distributed in a halo with no detectable presence in the disk, has a universal stellar mass function, and is concentrated in satellite dwarf galaxies.

Contribution

It synthesizes recent observational data to clarify the distribution and properties of dark matter in the Milky Way, emphasizing its halo nature and scale.

Findings

Dark matter is not associated with the Galactic disk.

The stellar mass function is universal and convergent.

Dark matter in dwarf spheroidal galaxies has a characteristic scale of about 1 kpc.

Abstract

A wealth of recent observational studies shows the dark matter in the Milky Way to have the following fundamental properties: 1) there is no detectable dark matter associated with the Galactic disk -- the dark matter is distributed in a purely halo distribution with local volume density near the Earth 0.3GeV/cc = 0.01Msun/pc3 2) The stellar mass function is both universal and convergent at low masses -- there is no significant very low luminosity baryonic dark matter associated with stellar light. Fundamentally, dark mass does not follow light. 3) The smallest scale length on which dark matter is clustered is in the Milky Way's satellite dwarf Spheroidal galaxies, where dark matter has a characteristic length scale about 1kpc = 10^{20}m, and mass density 0.05Msun/pc3 = 1.5GeV/cc.