Sizing from the Smallest Scales: The Mass of the Milky Way

TL;DR

This paper estimates the Milky Way's dark matter halo mass using Gaia satellite data and simulations, finding a mass around 1-1.2 trillion solar masses, with results robust to various assumptions.

Contribution

It provides a new constraint on the Milky Way's dark matter halo mass by combining Gaia data with cosmological simulations, improving accuracy over previous estimates.

Findings

Milky Way halo mass estimated at ~1-1.2×10^{12} solar masses.

Host halo mass inconsistent with more or less massive hosts at 3σ confidence.

Results are insensitive to LMC association, formation thresholds, and observational completeness.

Abstract

As the Milky Way and its satellite system become more entrenched in near field cosmology efforts, the need for an accurate mass estimate of the Milky Way's dark matter halo is increasingly critical. With the second and early third data releases of stellar proper motions from {\it Gaia}, several groups calculated full $6$D phase-space information for the population of Milky Way satellite galaxies. Utilizing these data in comparison to subhalo properties drawn from the Phat ELVIS simulations, we constrain the Milky Way dark matter halo mass to be $\sim 1-1.2\times10^{12}~\msun$. We find that the kinematics of subhalos drawn from more- or less-massive hosts (i.e. $>1.2\times10^{12}~\msun$ or $<10^{12}~\msun$) are inconsistent, at the $3\sigma$ confidence level, with the observed velocities of the Milky Way satellites. The preferred host halo mass for the Milky Way is largely insensitive to the exclusion of systems associated with the Large Magellanic Cloud, changes in galaxy formation thresholds, and variations in observational completeness. As more Milky Way satellites are discovered, their velocities (radial, tangential, and total) plus Galactocentric distances will provide further insight into the mass of the Milky Way dark matter halo.