The effect of a disc on the population of cuspy and cored dark matter substructures in Milky Way-like galaxies

TL;DR

This study uses high-resolution simulations to examine how a galactic disc influences the survival of dark matter substructures with different density profiles in Milky Way-like galaxies, revealing that cuspy profiles are more resilient than cored ones, especially near the galactic center.

Contribution

It provides new insights into the differential survival of cuspy versus cored dark matter substructures in the presence of a galactic disc, using detailed N-body simulations with realistic orbital parameters.

Findings

Cuspy satellites have twice as many survivors as cored ones at z=0.

Adding a disc reduces satellite survival by up to a factor of 2 for penetrating orbits.

Survival rates converge at large pericentric distances regardless of profile type.

Abstract

We use high-resolution $N$-body simulations to study the effect of a galactic disc on the dynamical evolution of dark matter substructures with orbits and structural parameters extracted from the Aquarius A-2 merger tree (Springel et al. 2008). Satellites are modelled as equilibrium $N$-body realizations of generalized Hernquist profiles with $2\times10^6$ particles and injected in the analytical evolving host potential at $z_\mathrm{infall}$, defined by the peak of their mass evolution. We select all substructures with $M_{200}(z_\mathrm{infall})\geq 10^8\,\mathrm{M_\odot}$ and first pericentric distances $r_p<r_{200}$. Motivated by observations of Milky Way dwarf spheroidal galaxies, we also explore satellite models with cored dark matter profiles with a fixed core size $r_c=0.8\,a_s$ where $a_s$ is the Hernquist scale radius. We find that models with cuspy satellites have twice as many surviving substructures at $z=0$ than their cored counterparts, and four times as many if we only consider those on orbits with $r_p\lesssim0.1\,r_{200}$. For a given profile, adding an evolving disc potential reduces the number of surviving substructures further by a factor of $\lesssim2$ for satellites on orbits that penetrate the disc ($r_p\lesssim 20\,\mathrm{kpc}$). For large $r_p$, where tidal forces and the effect of the disc become negligible, the number of satellites per pericentre bin converges to similar values for all four models.