Constraining the distribution of dark matter in dwarf spheroidal galaxies with stellar tidal streams

TL;DR

This study uses high-resolution simulations to explore how the shape of dark matter halos in dwarf spheroidal galaxies affects their tidal streams, revealing potential for constraining dark matter distribution.

Contribution

It demonstrates that the dark matter profile (core vs cusp) significantly influences the evolution and dynamics of tidal streams in dwarf spheroidal galaxies.

Findings

Cored halos lead to larger sizes and higher velocity dispersions in dSphs.

Stellar streams in cored models have higher velocity dispersions than in cuspy models.

Dark matter profile impacts the internal dynamics and observable properties of tidal streams.

Abstract

We use high-resolution N-body simulations to follow the formation and evolution of tidal streams associated to dwarf spheroidal galaxies (dSphs). The dSph models are embedded in dark matter (DM) haloes with either a centrally-divergent 'cusp', or an homogeneous-density 'core'. In agreement with previous studies, we find that as tides strip the galaxy the evolution of the half-light radius and the averaged velocity dispersion follows well-defined tracks that are mainly controlled by the amount of mass lost. Crucially, the evolutionary tracks behave differently depending on the shape of the DM profile: at a fixed remnant mass, dSphs embedded in cored haloes have larger sizes and higher velocity dispersions than their cuspy counterparts. The divergent evolution is particularly pronounced in galaxies whose stellar component is strongly segregated within their DM halo and becomes more disparate as the remnant mass decreases. Our analysis indicates that the DM profile plays an important role in defining the internal dynamics of tidal streams. We find that stellar streams associated to cored DM models have velocity dispersions that lie systematically above their cuspy counterparts. Our results suggest that the dynamics of streams with known dSph progenitors may provide strong constraints on the distribution of DM on the smallest galactic scales.