Bound and unbound substructures in Galaxy-scale Dark Matter haloes

TL;DR

This paper analyzes the phase-space structure of galaxy-scale dark matter haloes, revealing the distribution and properties of bound and unbound substructures like tidal streams and subhaloes.

Contribution

It provides a detailed characterization of substructure mass functions and spatial distributions within galaxy-scale dark matter haloes using advanced 6D substructure detection.

Findings

35% of mass in substructures within r_50, mainly tidal streams

60% of mass in substructures near r_50, including 30% in subhaloes

Densest tidal streams near the solar position have about 1% of local mean density

Abstract

We analyse the coarse-grained phase-space structure of the six Galaxy-scale dark matter haloes of the Aquarius Project using a state-of-the-art 6D substructure finder. Within r_50, we find that about 35% of the mass is in identifiable substructures, predominantly tidal streams, but including about 14% in self-bound subhaloes. The slope of the differential substructure mass function is close to -2, which should be compared to around -1.9 for the population of self-bound subhaloes. Near r_50 about 60% of the mass is in substructures, with about 30% in self-bound subhaloes. The inner 35 kpc of the highest resolution simulation has only 0.5% of its mass in self-bound subhaloes, but 3.3% in detected substructure, again primarily tidal streams. The densest tidal streams near the solar position have a 3-D mass density about 1% of the local mean, and populate the high velocity tail of the velocity distribution.