Quantifying the heart of darkness with GHALO – a multibillion particle simulation of a galactic halo

Abstract

We perform a series of simulations of a Galactic mass dark matter halo at different resolutions: our largest uses over 3 billion particles and has a mass resolution of 1000 M⊙. We quantify the structural properties of the inner dark matter distribution and study how they depend on numerical resolution. We can measure the density profile to a distance of 120 pc (0.05 per cent of Rvir), where the logarithmic slope is −0.8 and −1.4 at (0.5 per cent of Rvir). We propose a new two‐parameter fitting function that has a linearly varying logarithmic density gradient over the resolved radii which fits the GHALO and VL2 density profiles extremely well. Convergence in the halo shape is achieved at roughly three times the convergence radius for the density profile at which point the halo becomes more spherical due to numerical resolution. The six‐dimensional phase‐space profile is dominated by the presence of the substructures and does not follow a power law, except in the central few kpc which is devoid of substructure even at this resolution. The quantity, ρ/σ3, which is often used as a proxy for the six‐dimensional phase‐space density should be used with caution.

NIHAO – IV: core creation and destruction in dark matter density profiles across cosmic time

“…The starting redshift is zstart = 99, and each halo is initially simulated at high resolution with DM-only using PKDGRAV (Stadel 2001). More details on the sample selection can be found in Wang et al (2015).…”

“…In order to have an estimate of the size of such a core, we have decided to follow the approach of Macciò et al (2012) and fit the profiles with the following parametric description, originally presented in Stadel et al (2009):…”

The galaxy population in cold and warm dark matter cosmologies

“…The CDM cosmogony gives rise to many more substructures in halos of mass comparable to that of the Milky Way and M31 than there are known satellites of those two galaxies (Klypin et al 1999;Moore et al 1999;Stadel et al 2009). This discrepancy is known as the missing satellite problem.…”

Milky Way mass constraints from the Galactic satellite gap

“…(e.g. Diemand et al 2008;Springel et al 2008;Stadel et al 2009). However, the limited sample size, six in the Aquarius programme, the largest to date, limits the extent to which they can be used to study how common the MW satellite systems are.…”