New constraints on the dark matter density profiles of dwarf galaxies from proper motions of globular cluster streams by Khyati Malhan et al. on Wednesday 30 November

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.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2201.03571v2