Subhaloes in self-interacting galactic dark matter haloes

Abstract

We present N‐body simulations of a new class of self‐interacting dark matter models, which do not violate any astrophysical constraints due to a non‐power‐law velocity dependence of the transfer cross‐section which is motivated by a Yukawa‐like new gauge boson interaction. Specifically, we focus on the formation of a Milky‐Way‐like dark matter halo taken from the Aquarius project and resimulate it for a couple of representative cases in the allowed parameter space of this new model. We find that for these cases, the main halo only develops a small core (∼1 kpc) followed by a density profile identical to that of the standard cold dark matter scenario outside of that radius. Neither the subhalo mass function nor the radial number density of subhaloes is altered in these models but there is a significant change in the inner density structure of subhaloes resulting in the formation of a large density core. As a consequence, the inner circular velocity profiles of the most massive subhaloes differ significantly from the cold dark matter predictions and we demonstrate that they are compatible with the observational data of the brightest Milky Way dwarf spheroidals (dSphs) in such a velocity‐dependent self‐interacting dark matter scenario. Specifically, and contrary to the cold dark matter case, there are no subhaloes that are more concentrated than what is inferred from the kinematics of the Milky Way dSphs. We conclude that these models offer an interesting alternative to the cold dark matter model that can reduce the recently reported tension between the brightest Milky Way satellites and the dense subhaloes found in cold dark matter simulations.

Milky Way mass constraints from the Galactic satellite gap

“…Our results also confirm and extend the conclusion of Wang12 that the TBTF problem highlighted by Boylan-Kolchin et al (2011b is not a problem for the CDM model provided the MW halo mass is close to 1 × 10 12 M rather than to the ∼2 × 10 12 M of the Aquarius haloes used in the studies by Boylan-Kolchin et al Alternative solutions to the problem such as warm dark matter (Lovell et al 2012), self-interacting dark matter (Vogelsberger, Zavala & Loeb 2012) or baryonic effects (Brooks et al 2013) are therefore not required unless the mass of the MW halo can be shown to be larger than ∼2 × 10 12 M .…”

The variation of rotation curve shapes as a signature of the effects of baryons on dark matter density profiles

“…3. However, core size may also have a mass dependance in SIDM models (Vogelsberger et al 2012), which is not accounted for in our simple parameterization.…”

The galaxy population in cold and warm dark matter cosmologies

“…Nevertheless, recent progress on understanding the density profile of WDM haloes indicates that a realistic warm dark model cannot account for the sizes of cores in the density profiles of dwarf galaxies inferred from observations (Shao et al 2013;. The observed sizes of cores of dwarf galaxies (Gilmore et al 2007;Walker & Peñarrubia 2011) should be produced by some baryonic physics, such as outflows (Navarro et al 1996), supernovae feedback and baryon clumps (Del Popolo & Pace 2016), or reflect a different dark matter candidate such as self-interacting dark matter (Vogelsberger et al 2012;Zavala et al 2013).…”