The dark matter density at the Sun's location

TL;DR

This paper introduces a novel, model-independent method to estimate the local dark matter density at the Sun's position using local equilibrium equations, providing a reliable and adaptable measurement that accounts for observational uncertainties.

Contribution

The paper presents an analytic, model-independent approach to determine the local dark matter density without relying on global galaxy mass models or rotation curve data.

Findings

Estimated dark matter density: 0.43 GeV/cm³

Uncertainty sources: slope of circular velocity and disk scale length

Method is adaptable to future observational improvements

Abstract

We derive the value of the dark matter density at the Sun's location (rho_0) without globally mass-modeling the Galaxy. The proposed method relies on the local equation of centrifugal equilibrium and is independent of i) the shape of the dark matter density profile, ii) knowledge of the rotation curve from the galaxy center out to the virial radius, and iii) the uncertainties and the non-uniqueness of the bulge/disk/dark halo mass decomposition. The result can be obtained in analytic form. It explicitly includes the dependence on the relevant observational quantities and takes their uncertainties into account. By adopting the reference, state-of-the-art values for these, we find rho_0 = 0.43(11)(10)GeV/cm3, where the quoted uncertainties are respectively due to the uncertainty in the slope of the circular-velocity at the Sun location and the ratio between this radius and the length scale of the stellar exponential thin disk. We obtain a reliable estimate of rho_0, that, in addition, is ready to take into account any future change/improvement in the measures of the observational quantities it depends on.