Bound and unbound substructures in Galaxy-scale dark matter haloes

We analyse the coarse-grained phase-space structure of the six Galaxy-scale darkmatter haloes of the Aquarius Project using a state-of-the-art 6D substructure finder. Within r(50), we find that about 35 per cent of the mass is in identifiable substructures, predominantly tidal streams, but including about 14 per cent in self-bound subhaloes. The slope of the differential substructure mass function is close to -2, which should be compared to similar to -1.9 for the population of self-bound subhaloes. Near r(50), about 60 per cent of the mass is in substructures, with about 30 per cent in self-bound subhaloes. The inner 35 kpc of the highest resolution simulation has only 0.5 per cent of its mass in self-bound subhaloes, but 3.3 per cent in detected substructure, again primarily tidal streams. The densest tidal streams near the solar position have a 3D mass density about 1 per cent of the local mean, and populate the high-velocity tail of the velocity distribution.