Stellar Cores Live Long and Prosper in Cuspy Dark Matter Halos

TL;DR

This paper demonstrates through simulations that cored stellar systems can remain stable within cuspy dark matter halos, challenging previous claims and complicating the use of stellar configurations to infer dark matter density profiles.

Contribution

It provides the first explicit simulation evidence that stellar cores can survive in cuspy dark matter halos over cosmic timescales, countering prior dynamical arguments.

Findings

Cored stellar systems are stable in cuspy dark matter halos over several Hubble times.

Observations of ultrafaint dwarf galaxies cannot reliably determine the inner density slope.

Dynamical inference of the gravitational potential from stellar configurations is limited.

Abstract

The existence of cuspy or cored centers of dark matter halos is a crucial discriminant between different dark matter models. It has recently been claimed based on dynamical arguments that perfectly cored stellar systems cannot survive inside cuspy dark matter halos, which would make the observation of stellar cores in ultrafaint dwarf galaxies, where dark matter cores cannot form through baryonic processes, a direct falsification of the cold dark matter paradigm. Here, we use idealized simulations to show explicitly that cored stellar systems like those observed in dwarf galaxies can be stable within cuspy dark matter halos over at least several Hubble times. We also demonstrate that observations of ultrafaint dwarf galaxies cannot distinguish mildly positive, flat, or negative inner density slopes, further precluding the dynamical inference of the gravitational potential from the stellar configuration.