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Inferred Evidence for Dark Matter Kinematic Substructure with SDSS–Gaia

Necib, Lina and Lisanti, Mariangela and Belokurov, Vasily (2019) Inferred Evidence for Dark Matter Kinematic Substructure with SDSS–Gaia. Astrophysical Journal, 874 (1). Art. No. 3. ISSN 1538-4357.

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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 |z| > 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.

Item Type:Article
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URLURL TypeDescription
Necib, Lina0000-0003-2806-1414
Belokurov, Vasily0000-0002-0038-9584
Additional Information:© 2019 The American Astronomical Society. Received 2018 September 27; revised 2019 February 4; accepted 2019 February 20; published 2019 March 15. We would like to thank J. Bochanski, J. Bovy, G. Collin, A. Drlica-Wagner, D. Hogg, K. Hawkins, A. Kaboth, L. Lancaster, T. Li, S. McDermott, G. C. Myeong, D. Spergel, and N. Weiner for useful conversations. We also acknowledge use of the Astropy (Astropy Collaboration et al. 2013), emcee (Foreman-Mackey et al. 2013), gala (Price-Whelan et al. 2017), and IPython (Pérez & Granger 2007) software packages. This project was developed in part at the NYC Gaia DR2 Workshop in 2018 April, as well as the 2018 NYC Gaia Sprint, hosted by the Center for Computational Astrophysics of the Flatiron Institute in New York City. L.N. is supported by the DOE under award No. DESC0011632 and the Sherman Fairchild Fellowship. M.L. is supported by the DOE under award No. DESC0007968, the Alfred P. Sloan Foundation, and the Cottrell Scholar Program through the Research Corporation for Science Advancement. V.B. is supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC grant agreement No. 308024. This paper made used of the Whole Sky Database (WSDB) created by Sergey Koposov and maintained at the Institute of Astronomy, Cambridge by Sergey Koposov, Vasily Belokurov, and Wyn Evans with financial support from the Science & Technology Facilities Council (STFC) and the European Research Council (ERC). This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III website is SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration, including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the 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, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.
Group:Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0011632
Sherman Fairchild FoundationUNSPECIFIED
Department of Energy (DOE)DE-SC0007968
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
European Research Council (ERC)308024
Science and Technology Facilities Council (STFC)UNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Subject Keywords:dark matter – Galaxy: evolution – Galaxy: kinematics and dynamics – stars: kinematics and dynamics – surveys
Record Number:CaltechAUTHORS:20190315-082818515
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Official Citation:Lina Necib et al 2019 ApJ 874 3
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93856
Deposited By: Tony Diaz
Deposited On:15 Mar 2019 15:35
Last Modified:15 Mar 2019 15:35

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