Dark Matter Particle Flux in a Dynamically Self-consistent Milky Way Model

TL;DR

This paper develops a self-consistent model of the Milky Way including a radially anisotropic dark matter component from the Gaia-Sausage-Enceladus debris, analyzing its impact on dark matter detection rates and signatures.

Contribution

It introduces the self-consistent Anisotropic Halo Model (scAHM) incorporating GSE debris, providing new velocity distribution functions and predictions for direct detection experiments.

Findings

GSE component's velocity distribution deviates from Gaussian.

Modest impact on detection rates due to anisotropic GSE component.

Direction-sensitive detectors could observe the GSE kinematic signature.

Abstract

We extend a recently developed dynamically self-consistent model of the Milky Way constrained by observations from the Gaia observatory to include a radially anisotropic component in the dark matter (DM) halo, which represents the debris from the accreted Gaia-Sausage-Enceladus (GSE) galaxy. In the new model, which we call a self-consistent Anisotropic Halo Model or scAHM, we derive distribution functions for DM velocity in heliocentric and geocentric reference frames. We compare them with the velocity distributions in the standard halo model (SHM) and another anisotropic model (SHM++). We compute predicted scattering rates in direct-detection experiments, for different target nuclei and DM particle masses. Seasonal dependencies of scattering rates are analyzed, revealing small but interesting variations in detection rates for different target nuclei and DM masses. Our findings show that the velocity distribution of the anisotropic GSE component significantly deviates from Gaussian, showing a modest impact on the detection rates. The peculiar kinematic signature of the radially anisotropic component would be most clearly observable by direction-sensitive detectors.