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

Abstract

The central density profiles in low-mass and 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 streams -those stellar streams produced from the tidal stripping of globular clusters that initially evolved within their parent dwarf galaxies and only later merged with the Milky Way. In particular, we previously found that clusters that are accreted within cuspy CDM subhalos produce streams with larger physical widths and higher line-of-sight velocity dispersions as compared to those streams that accrete inside cored subhalos. Here, we use the same suite of simulations to demonstrate that the dispersion in the tangential velocity of streams (σ vTan ) is another parameter that is also sensitive to the central DM density profile of their parent dwarfs. We find that globular clusters that were accreted from cuspy CDM subhalos produce streams with larger σ vTan than those that were accreted inside cored subhalos. Furthermore, we use Gaia EDR3 observations of multiple GC streams to compare their σ vTan values with simulations. This comparison indicates that the five observed streams we analyze are more likely to be associated with globular clusters of 'accreted' rather than 'in situ' origin. We also find evidence that their progenitor globular clusters were probably accreted inside cored DM subhalos (with M subhalo > ∼ 10 8−9 M ).

Snowmass2021 Cosmic Frontier White Paper: Prospects for obtaining Dark Matter Constraints with DESI

“…Cocoons, spurs and gaps have now been detected with Gaia photometry and proper-motions in several GC streams [121,122]. It has been shown recently that quantities that measure the "hottness" of accreted GC tidal streams (physical width, line-of-sight velocity dispersion, tangential velocity dispersion, and angular momentum spread) are sensitive to whether the parent satellite from which the GC was accreted had a cuspy or cored dark matter halo [119,123]. These simulations have found that stellar streams formed in cored DM halos are systematically narrower (in physical width) and have lower velocity dispersion (both lineof-sight and tangential) than those formed in cuspy halos [119,123].…”

“…It has been shown recently that quantities that measure the "hottness" of accreted GC tidal streams (physical width, line-of-sight velocity dispersion, tangential velocity dispersion, and angular momentum spread) are sensitive to whether the parent satellite from which the GC was accreted had a cuspy or cored dark matter halo [119,123]. These simulations have found that stellar streams formed in cored DM halos are systematically narrower (in physical width) and have lower velocity dispersion (both lineof-sight and tangential) than those formed in cuspy halos [119,123]. A comparison of simulations with existing Gaia proper motions in about 7 streams already imply that many observed GC streams are too cold to be consistent with formation in cuspy CDM halos of mass 10 9 M ⊙ .…”