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

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 $3\times 10^8{M}_{\odot }$, 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 $\ddot{I}ƒ/m\approx 30-100\mathrm{c}{\mathrm{m}}^2{\mathrm{g}}^{-1}$ at $V_{\max }\sim 10\mathrm{km}{\mathrm{s}}^{-1}$, the enclosed mass of the SIDM halo within the inner $10\mathrm{pc}$ 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.

11 pages, 4 figures; Revised for publication in The Astrophysical Journal Letters; A minor error in obtaining density profiles of CDM progenitor halos fixed; additional simulations with live stellar particles presented; comparison with globular clusters added; main conclusions unchanged