Galactoseismology and the Local Density of Dark Matter

TL;DR

This paper investigates how vertical breathing mode perturbations in the Milky Way's stellar disc affect estimates of local dark matter density, highlighting potential systematic errors and proposing methods for robust inference using multiple tracers.

Contribution

It models disc perturbations and assesses their impact on dark matter density estimates, suggesting tracer comparison as a robustness check.

Findings

Perturbations can cause over 10% errors in vertical force estimates.

Systematic errors can lead to over 25% inaccuracies in local dark matter density.

Using multiple tracers can help identify and mitigate these errors.

Abstract

We model vertical breathing mode perturbations in the Milky Way's stellar disc and study their effects on estimates of the local dark matter density, surface density, and vertical force. Evidence for these perturbations, which involve compression and expansion of the Galactic disc perpendicular to its midplane, come from the SEGUE, RAVE, and LAMOST surveys. We show that their existence may lead to systematic errors of $10\%$ or greater in the vertical force $K_z(z)$ at $|z|=1.1\,{\rm kpc}$. These errors translate to $\gtrsim 25\%$ errors in estimates of the local dark matter density. Using different mono-abundant subpopulations as tracers offers a way out: if the inferences from all tracers in the Gaia era agree, then the dark matter determination will be robust. Disagreement in the inferences from different tracers will signal the breakdown of the unperturbed model and perhaps provide the means for determining the nature of the perturbation.