Low-metallicity stellar halo populations as tracers of dark matter haloes

TL;DR

This study demonstrates that low-metallicity stellar halo populations in simulated Milky-Way-like galaxies can accurately trace dark matter halo profiles, enabling predictions of dark matter distribution from stellar observations.

Contribution

The paper establishes a correlation between the density profiles of low-metallicity stellar halos and dark matter halos, providing a method to predict dark matter profiles from stellar data.

Findings

Accreted stars follow an Einasto profile.

Strong correlation between stellar and dark matter profile parameters.

Predicted dark matter mass at 8 kpc matches observational estimates.

Abstract

We analyse the density profiles of the stellar halo populations in eight Milky-Way mass galaxies, simulated within the $\Lambda$-Cold Dark Matter scenario. We find that accreted stars can be well-fitted by an Einasto profile, as well as any subsample defined according to metallicity. We detect a clear correlation between the Einasto fitting parameters of the low-metallicity stellar populations and those of the dark matter haloes. The correlations for stars with [Fe/H]$<-3$ allow us to predict the shape of the dark matter profiles within residuals of $\sim 10 $ per cent, in case the contribution from in situ stars remains small. Using Einasto parameters estimated for the stellar halo of the Milky Way and assuming the later formed with significant contributions from accreted low-mass satellite, our simulations predict $\alpha \sim 0.15 $ and $r_2 \sim 15$ kpc for its dark matter profile. These values, combined with observed estimations of the local dark matter density, yield an enclosed dark matter mass at $\sim 8$ kpc in the range $3.9 - 6.7 \times 10^{10}$ M$_{\odot}$, in agreement with recent observational results. These findings suggest that low-metallicity stellar haloes could store relevant information on the DM haloes. Forthcoming observations would help us to further constrain our models and predictions.