The GD-1 stellar stream perturber as a core-collapsed self-interacting dark matter halo

TL;DR

This paper demonstrates through simulations that a core-collapsed self-interacting dark matter halo can explain the dense perturber observed in the GD-1 stellar stream, offering a new way to probe dark matter properties.

Contribution

The study shows that SIDM halos undergoing gravothermal collapse can match the density of the GD-1 perturber, providing evidence for self-interacting dark matter.

Findings

SIDM halos can reach higher central densities than CDM halos.

Simulations match the GD-1 perturber's properties with SIDM models.

Stellar streams can serve as probes for dark matter self-interactions.

Abstract

The GD-1 stellar stream exhibits spur and gap structures that may result from a close encounter with a dense substructure. When interpreted as a dark matter subhalo, the perturber is denser than predicted in the standard cold dark matter (CDM) model. In self-interacting dark matter (SIDM), however, a halo could evolve into a phase of gravothermal collapse, resulting in a higher central density than its CDM counterpart. We conduct high-resolution controlled N-body simulations to show that a collapsed SIDM halo could account for the GD-1 perturber's high density. We model a progenitor halo with a mass of $3\times10^8~M_\odot$, motivated by a cosmological simulation of a Milky Way analog, and evolve it in the Milky Way's tidal field. For a cross section per mass of $\sigma/m\approx30-100~{\rm cm^2~g^{-1}}$ at $V_{\rm max }\sim10~{\rm km~s^{-1}}$, the enclosed mass of the SIDM halo within the inner $10~{\rm pc}$ can be increased by more than an order of magnitude compared to its CDM counterpart, leading to a good agreement with the properties of the GD-1 perturber. Our findings indicate that stellar streams provide a novel probe into the self-interacting nature of dark matter.