Direct detection signatures of a primordial Solar dark matter halo

TL;DR

This paper proposes that a primordial Solar dark matter halo could survive to the present day, producing unique detection signatures such as nonstandard annual modulation and low velocity dispersion, making it a promising target for direct detection experiments.

Contribution

It introduces the concept of a Solar dark matter halo formed from primordial gravitationally bound dark matter, highlighting its potential observability and distinct signatures.

Findings

Approximately 25% of the Solar halo could survive today.

The Solar halo would have a nonstandard annual modulation signature.

It would exhibit extremely low velocity dispersion compared to the Galactic halo.

Abstract

A small admixture of dark matter gravitationally bound to the proto-Solar gas cloud could be adiabatically contracted into Earth-crossing orbits with a local density comparable to (or even exceeding) the Galactic halo density. We show that a significant fraction (~25%) of the resulting 'Solar halo' would remain today, surviving perturbations from Jupiter and close encounters with Earth, and would be potentially observable in direct detection experiments. The population would have distinct signatures, including a nonstandard annual modulation and extremely low velocity dispersion compared with the Galactic halo, making it an especially interesting target for coherent or resonant detection of ultralight particles such as axions or dark photons.