Matching the dark matter profiles of dSph galaxies with those of simulated satellites: a two parameter comparison

TL;DR

This study compares observed dwarf galaxy dark matter profiles with simulated subhalos, revealing discrepancies in structural parameters and exploring baryonic feedback as a potential solution.

Contribution

It introduces a two-parameter comparison method revealing inconsistencies between observed and simulated dark matter profiles, and assesses supernova feedback effects.

Findings

Mass estimates are consistent between observations and simulations.

Including the density slope reveals little overlap, with simulated halos being steeper.

Supernova feedback can plausibly reshape halos at low efficiencies.

Abstract

We compare the dark matter halos' structural parameters derived for four Milky Way dwarf spheroidal galaxies to those of subhalos found in cosmological $N$-body simulations. We confirm that estimates of the mass at a single fixed radius are fully consistent with the observations. However, when a second structural parameter such as the logarithmic slope of the dark halo density profile measured close to the half-light radius is included in the comparison, we find little to no overlap between the satellites and the subhalos. Typically the right mass subhalos have steeper profiles at these radii than measurements of the dSph suggest. Using energy arguments we explore if it is possible to solve this discrepancy by invoking baryonic effects. Assuming that feedback from supernovae can lead to a reshaping of the halos, we compute the required efficiency and find entirely plausible values for a significant fraction of the subhalos and even as low as 0.1%. This implies that care must be taken not to exaggerate the effect of supernovae feedback as this could make the halos too shallow. These results could be used to calibrate and possibly constrain feedback recipes in hydrodynamical simulations.