期刊
ASTROPHYSICAL JOURNAL
卷 874, 期 1, 页码 -出版社
IOP Publishing Ltd
DOI: 10.3847/1538-4357/ab095b
关键词
dark matter; Galaxy: evolution; Galaxy: kinematics and dynamics; stars: kinematics and dynamics; surveys
资金
- DOE [DESC0007968, DESC0011632]
- Sherman Fairchild Fellowship
- Alfred P. Sloan Foundation
- Cottrell Scholar Program through the Research Corporation for Science Advancement
- European Research Council under the European Union's Seventh Framework Programme (FP/20072013)/ERC grant [308024]
- Science AMP
- Technology Facilities Council (STFC)
- European Research Council (ERC)
- National Science Foundation
- U.S. Department of Energy Office of Science
- University of Arizona
- Brazilian Participation Group
- Brookhaven National Laboratory
- Carnegie Mellon University
- French Participation Group
- German Participation Group
- Harvard University
- Instituto de Astrofisica de Canarias
- Michigan State/Notre Dame/JINA Participation Group
- Johns Hopkins University
- Lawrence Berkeley National Laboratory
- Max Planck Institute for Astrophysics
- Max Planck Institute for Extraterrestrial Physics
- Pennsylvania State University
- Princeton University
- Spanish Participation Group
- Yale University
- University of Florida
- New Mexico State University
- New York University
- University of Portsmouth
- University of Tokyo
- University of Utah
- Ohio State University
- Vanderbilt University
- University of Virginia
- University of Washington
We use the distribution of accreted stars in Sloan Digital Sky Survey-Gaia DR2 to demonstrate that a nontrivial fraction of the dark matter halo within galactocentric radii of 7.5-10 kpc and vertical bar z vertical bar > 2.5 kpc is in substructure and thus may not be in equilibrium. Using a mixture likelihood analysis, we separate the contributions of an old, isotropic stellar halo and a younger anisotropic population. The latter dominates and is uniform within the region studied. It can be explained as the tidal debris of a disrupted massive satellite on a highly radial orbit and is consistent with mounting evidence from recent studies. Simulations that track the tidal debris from such mergers find that the dark matter traces the kinematics of its stellar counterpart. If so, our results indicate that a component of the nearby dark matter halo that is sourced by luminous satellites is in kinematic substructure referred to as debris flow. These results challenge the Standard Halo Model, which is discrepant with the distribution recovered from the stellar data, and have important ramifications for the interpretation of direct detection experiments.
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