Axion Minicluster Halo Limits from Wide Binary Disruption

TL;DR

This paper uses observations of wide binary stars in the Milky Way to place new constraints on the presence and properties of axion minicluster halos, which are potential dark matter structures formed in the early universe.

Contribution

It introduces a novel method to constrain axion minicluster halos using gravitational perturbations on wide binaries, based on recent Gaia data.

Findings

Constraints on MCH fraction in dark matter halo for specific axion masses.

Limits applicable to dense MCHs and isolated minicluster models.

Axion mass ranges constrained are approximately 10^{-15}-10^{-12} eV and 10^{-19}-10^{-16} eV.

Abstract

Axionic dark matter can form miniclusters and minicluster halos from inhomogenuities in the early Universe. If MCHs are sufficiently massive, their existence can be revealed by small-scale gravitational tidal perturbation to halo-like binary star system in the Galaxy. The observed population of the Milky Way's wide-separation binaries with $a\gtrsim\mathcal{O}(0.1)\,$ parsec offer a sensitive test to dynamic evaporation from MCHs. Considering data from recent GAIA observations, we derive significant constraints on the MCH fraction of the galactic dark matter halo. For several scenarios including dense MCHs and isolated minicluster models, these limits will apply to axion-like particles in the mass range $m_{a}\sim 10^{-15}-10^{-12}\,\rm eV$ and $m_{a}\sim 10^{-19}-10^{-16}\,\rm eV$, respectively.