The MUSE-Faint survey. III. No large dark-matter cores and no significant tidal stripping in ultra-faint dwarf galaxies
/ Authors
S. L. Zoutendijk, Mariana P. J'ulio, J. Brinchmann, J. Read, D. Vaz, L. Boogaard, N. Bouch'e, Davor Krajnovi'c, K. Kuijken, J. Schaye
and 27 more authors
Matthias Steinmetz Leiden Observatory, Leiden University, Leiden, The Netherlands., I. D. A. E. C. D. Espacco, U. Porto, Caup, Porto, Portugal, D. D. Astronomia, F. Ciencias, U. Surrey, P. Department, Guildford, UK., M. F. Astronomy, Heidelberg, H Germany, Univ. Lyon, Univ. Lyon1, É. Lyon, Cnrs, C. Lyon, Saint-Genis-Laval, France., Leibniz-Institut fur Astrophysik Potsdam, Potsdam
/ Abstract
Aims. The lowest-mass galaxies, ultra-faint dwarf galaxies, promise unparalleled constraints on how feedback regulates galaxy formation, and on the small-scale matter power spectrum. Their inner dark-matter densities can also be used to constrain dark-matter models and to determine the most promising targets for potential signals from dark-matter annihilation or decay. However, these goals are limited by the current large uncertainties on the properties of the dark-matter haloes that these galaxies inhabit. In this paper, we present 201 new stellar line-of-sight velocities from the MUSE-Faint survey for the faint and ultra-faint dwarf galaxies Antlia B, Leo T, Hydra II, and Grus 1. Combining these with literature data, we obtain the tightest constraints to date on their dark-matter halo masses and inner dark-matter densities. Methods. We use the Jeans equations implemented in CJAM to model the density profiles and constrain the presence of dark-matter cores and solitons (a prediction of fuzzy dark-matter models). Further modelling is done with GravSphere to test the influence of the choice of modelling tool. We calculate masses, concentrations, and circular velocities from the profiles, include results for Eridanus 2 from our previous work, and compare these properties to theoretical scaling relations, deriving constraints on tidal stripping in the process. Results. We find that dark-matter cores as large as those of more massive dwarf galaxies are ruled out for our galaxies (core radius rc < 66–95 pc at the 68% confidence level). We constrain the soliton radii to rsol < 13–112 pc (68% confidence level). We find that the galaxies are consistent with not having been significantly tidally stripped within their half-light radii. The virial masses and concentrations are sensitive to the choice of dynamical modelling tool: GravSphere produces results consistent with M200 ∼ 109 M , as expected from models in which ultra-faint dwarf galaxies are re-ionization fossils, while CJAM prefers haloes that are less massive.