Dark Matter in the Milky Way

TL;DR

This review discusses the dynamical constraints on the Milky Way's dark matter halo, highlighting uncertainties in key parameters and emphasizing the importance of the local dark matter density for detection efforts.

Contribution

It provides a comprehensive overview of observational constraints and uncertainties regarding the Milky Way's dark matter distribution, and discusses implications for dark matter detection.

Findings

Best-fit local dark matter density around 0.5 GeV/cm³

Significant uncertainties in virial mass and halo shape

Evidence for halo triaxiality remains inconclusive

Abstract

We review most dynamical constraints on the gravitational field of spiral galaxies in general, and of the Milky Way in particular. Such constraints are of prime importance for determining the characteristics of the putative dark matter haloes of galaxies. For the Milky Way, we review observational constraints in the inner parts (cored or cusped dark matter distribution, maximum disk or not), in the solar neighbourhood (local dark matter density) and in the outer parts (virial mass and triaxial shape of the dark matter halo). We also point out various caveats, systematic effects, and large current uncertainties. Many fundamental parameters such as the local circular velocity are poorly known, evidence for triaxiality of the dark halo is shaky, and different estimates of the virial mass as well as of the local dark matter density vary by at least a factor of two. We however argue that the current best-fit value for the local dark matter density, which should be used as a benchmark for direct dark matter detection searches, is of the order of 0.5 GeV/cm3. We also explain why alternatives to particle dark matter on galactic scales should still be very seriously considered.