Precision Astrometry, Galactic Mergers, Halo Substructure and Local Dark Matter

TL;DR

This paper discusses how future microarcsecond astrometry, like that from the SIM Planetquest mission, can test dark matter models by examining galactic mergers, halo substructure, and local dark matter in the Milky Way.

Contribution

It highlights the potential of microarcsecond astrometry to perform new tests of dark matter properties and distribution in our galaxy, advancing understanding beyond current capabilities.

Findings

Future astrometry can detect halo substructure

Microarcsecond precision enables local dark matter measurements

Tests can distinguish dark matter models based on galactic dynamics

Abstract

The concordance Cold Dark Matter model for the formation of structure in the Universe, while remarkably successful at describing observations on large scales, has a number of problems on galaxy scales. The Milky Way and its satellite system provide a key laboratory for exploring dark matter (DM) in this regime, but some of the most definitive tests of local DM await microarcsecond astrometry, such as will be delivered by the Space Interferometry Mission (SIM Planetquest). I discuss several tests of Galactic DM enabled by future microarcsecond astrometry.