Dark Matter Subhalos in the Ursa Minor Dwarf Galaxy

TL;DR

This study uses numerical simulations to examine how dark matter substructures affect the survival of stellar clumps in the Ursa Minor dwarf galaxy, providing insights into dark matter distribution and testing cosmological models.

Contribution

It demonstrates that dark matter subhalos significantly shorten the survival time of stellar clumps, offering a new method to test dark matter theories at dwarf galaxy scales.

Findings

Stellar clumps survive over a Hubble time in smooth halos with large cores.

Presence of dark subhalos reduces clump survival to about 1.5 Gyr.

Results challenge the DM model predictions at dwarf galaxy scales.

Abstract

Through numerical simulations, we study the dissolution timescale of the Ursa Minor cold stellar clump, due to the combination of phase-mixing and gravitational encounters with compact dark substructures in the halo of Ursa Minor. We compare two scenarios; one where the dark halo is made up by a smooth mass distribution of light particles and one where the halo contains 10% of its mass in the form of substructures (subhalos). In a smooth halo, the stellar clump survives for a Hubble time provided that the dark matter halo has a big core. In contrast, when the point-mass dark substructures are added, the clump survives barely for \sim 1.5 Gyr. These results suggest a strong test to the \Lambda-cold dark matter scenario at dwarf galaxy scale.