Halo Densities and Pericenter Distances of the Bright Milky Way Satellites as a Test of Dark Matter Physics

TL;DR

This study uses phase-space distribution functions to analyze Milky Way dwarf spheroidal galaxies, revealing diverse inner halo densities and an anti-correlation with pericenter distance, challenging current dark matter simulations.

Contribution

It introduces a new application of the phase-space distribution function method to MW dwarf galaxies and compares results with previous analyses and simulations.

Findings

Diverse inner halo densities among dSphs

Anti-correlation between density and pericenter distance

Inconsistency with high-res N-body simulations including disk potential

Abstract

We provide new constraints on the dark matter halo density profile of Milky Way (MW) dwarf spheroidal galaxies (dSphs) using the phase-space distribution function (DF) method. After assessing the systematics of the approach against mock data from the Gaia Challenge project, we apply the DF analysis to the entire kinematic sample of well-measured MW dwarf satellites for the first time. Contrary to previous findings for some of these objects, we find that the DF analysis yields results consistent with the standard Jeans analysis. In particular, in the present study we rediscover: i) a large diversity in the inner halo densities of dSphs (bracketed by Draco and Fornax), and ii) an anti-correlation between inner halo density and pericenter distance of the bright MW satellites. Regardless of the strength of the anti-correlation, we find that the distribution of these satellites in density vs. pericenter space is inconsistent with the results of the high-res N-body simulations that include a disk potential. Our analysis motivates further studies on the role of internal feedback and dark matter microphysics in these dSphs.