New constraints on the dark matter density profiles of dwarf galaxies from proper motions of globular cluster streams

TL;DR

This study uses Gaia data and simulations to analyze globular cluster streams, providing new constraints on the dark matter density profiles of dwarf galaxy halos, favoring cored over cuspy profiles.

Contribution

It demonstrates that tangential velocity dispersion of streams can distinguish between cored and cuspy dark matter profiles in dwarf galaxies, refining previous methods.

Findings

Streams with larger $\sigma_{v_ ext{Tan}}$ suggest cuspy profiles.

Current data favors cored or low-mass cuspy subhalos.

Future Gaia data will improve constraints on dark matter profiles.

Abstract

The central density profiles in dwarf galaxy halos depend strongly on the nature of dark matter. Recently, in Malhan et al. (2021), we employed N-body simulations to show that the cuspy cold dark matter (CDM) subhalos predicted by cosmological simulations can be differentiated from cored subhalos using the properties of accreted globular cluster (GC) streams since these GCs experience tidal stripping within their parent halos prior to accretion onto the Milky Way. We previously found that clusters that are accreted within cuspy subhalos produce streams with larger physical widths and higher dispersions in line-of-sight velocity and angular momentum than streams that are accreted within cored subhalos. Here, we use the same suite of simulations to demonstrate that the dispersion in the tangential velocities of streams ($\sigma_{v_\mathrm{Tan}}$) is also sensitive to the central DM density profiles of their parent dwarfs and GCs that were accreted from: cuspy subhalos produce streams with larger $\sigma_{v_\mathrm{Tan}}$ than those accreted inside cored subhalos. Using Gaia EDR3 observations of multiple GC streams we compare their $\sigma_{v_\mathrm{Tan}}$ values with simulations. The measured $\sigma_{v_\mathrm{Tan}}$ values are consistent with both an ``in situ'' origin and with accretion inside cored subhalos of $M\sim 10^{8-9}M_{\odot}$ (or very low-mass cuspy subhalos of mass $\sim 10^8M_{\odot}$). Despite the large current uncertainties in $\sigma_{v_\mathrm{Tan}}$, we find a low probability that any of the progenitor GCs were accreted from cuspy subhalos of $M_{\rm subhalo}\buildrel > \over \sim$ $10^9 M_{\odot}$. The uncertainties on Gaia tangential velocity measurements are expected to decrease in future and will allow for stronger constraints on subhalo DM density profiles.