The Aquarius Project: the subhaloes of galactic haloes

Abstract

We have performed the largest ever particle simulation of a Milky Way sized dark matter halo, and present the most comprehensive convergence study for an individual dark matter halo carried out thus far. We have also simulated a sample of six ultrahighly resolved Milky Way sized haloes, allowing us to estimate the halo-to-halo scatter in substructure statistics. In our largest simulation, we resolve nearly 300 000 gravitationally bound subhaloes within the virialized region of the halo. Simulations of the same object differing in mass resolution by factors of up to 1800 accurately reproduce the largest subhaloes with the same mass, maximum circular velocity and position, and yield good convergence for the abundance and internal properties of dark matter substructures. We detect up to four generations of subhaloes within subhaloes, but contrary to recent claims, we find less substructure in subhaloes than in the main halo when regions of equal mean overdensity are compared. The overall substructure mass fraction is much lower in subhaloes than in the main halo. Extrapolating the main halo's subhalo mass spectrum down to an Earth mass, we predict the mass fraction in substructure to be well below 3 per cent within 100 kpc, and to be below 0.1 per cent within the solar circle. The inner density profiles of subhaloes show no sign of converging to a fixed asymptotic slope and are well fitted by gently curving profiles of Einasto form. The mean concentrations of isolated haloes are accurately described by the fitting formula of Neto et al. down to maximum circular velocities of 1.5 km s −1 , an extrapolation over some five orders of magnitude in mass. However, at equal maximum circular velocity, subhaloes are more concentrated than field haloes, with a characteristic density that is typically ∼2.6 times larger and increases with decreasing distance from halo centre.

Anisotropy of the extragalactic radio background from dark matter annihilation

“…For a Milky Way sized halo, r sub = 4 r vir would result an integrated boost factor of 74.7. This boost factor is consistent with the results of the Aquarius simulation [47,50,51], but is disfavored by Sánchez-Conde and Prada [52].…”

“…39 halo for larger and smaller halos [46]. We note that the contribution from dark matter substructure can extend well beyond the virial radius of the host halo [47][48][49]. In order to account for the contribution from substructure outside of the virial radius, we extrapolate the density distribution function of Kamionkowski et al [44] out to a radius r sub = 1 − 10 r vir .…”

Redshift evolution of stellar mass versus gas fraction relation in 0 <z< 2 regime: observational constraint for galaxy formation models

“…• Lagos et al (2015, SIM) Lagos et al implemented H2 formation models as a post-process in EAGLE (Evolution and Assembly of GaLaxies and their Environments; Schaye et al 2015), which is a cosmological numerical simulation that uses an N -body/SPH code, GADGET-3 (Springel et al 2008). Here, H2 formation is modelled according to two prescriptions depending on the local dust-to-gas ratio and the interstellar radiation field (Gnedin & Kravtsov 2011;Krumholz 2013).…”

Dark matter indirect detection signals and the nature of neutrinos in the supersymmetricU(1)B−Lextension of the standard model

“…If the DM density profile near the galactic center (GC) of the Milky Way galaxy is well-described by an Einasto cusp [20], then it is a leading cosmic source of annihilation radiation, and will be the focus of discussion in this work. The Einasto density profile is…”