Inferred Evidence For Dark Matter Kinematic Substructure with SDSS-Gaia

Abstract

We use the distribution of accreted stars in SDSS-Gaia DR2 to demonstrate that a non-trivial 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.

17 + 4 pages, 10 + 5 figures. Supplementary Data can be found here: https://linoush.github.io/DM_Velocity_Distribution/ v2: Title updated, small modifications of discussions, results unchanged. Version published in ApJ

References in corpus (31)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Dark Matter Search Results from a One Tonne$\times$Year Exposure of XENON1T
• galpy: A Python Library for Galactic Dynamics
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Co-formation of the Galactic disc and the stellar halo
• Two Stellar Components in the Halo of the Milky Way
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• The Radial Velocity Experiment (RAVE): Fifth Data Release
• The Local Dark Matter Density
• Low-Mass Dark Matter Search with the DarkSide-50 Experiment
• Non-relativistic effective theory of dark matter direct detection
• The stellar halo of the Galaxy
• Phase-space structure in the local dark matter distribution and its signature in direct detection experiments
• The Sausage Globular Clusters
• First model independent results from DAMA/LIBRA-phase2
• A universal density slope - velocity anisotropy relation for relaxed structures
• Revealing the Dark Matter Halo with Axion Direct Detection
• US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
• Apocenter Pile-Up: Origin of the Stellar Halo Density Break
• The Dark Matter at the End of the Galaxy
• The Milky Way Halo in Action Space
• Halo-to-Halo Similarity and Scatter in the Velocity Distribution of Dark Matter
• Weak Galactic halo--dwarf spheroidal connection from RR Lyrae stars
• The Graininess of Dark Matter Haloes
• The Progenitors of the Milky Way Stellar Halo: Big Bricks Favoured over Little Bricks
• Unmixing the Galactic Halo with RR Lyrae tagging
• Model Independent Direct Detection Analyses
• Modulation Sensitive Search for Non-Virialized Dark-Matter Axions
• Halo-independent comparison of direct dark matter detection data: a review
• Observationally inferred dark matter phase-space distribution and direct detection experiments

Cited by in corpus (78)

• The Biggest Splash
• The Large-Misalignment Mechanism for the Formation of Compact Axion Structures: Signatures from the QCD Axion to Fuzzy Dark Matter
• Dark matter local density determination: recent observations and future prospects
• Reconstructing the Last Major Merger of the Milky Way with the H3 Survey
• The shape of the Galactic halo with $Gaia$ DR2 RR Lyrae. Anatomy of an ancient major merger
• The origin of galactic metal-rich stellar halo components with highly eccentric orbits
• Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
• Cosmological Constraints on Dark Matter Interactions with Ordinary Matter
• The Halo's Ancient Metal-Rich Progenitor Revealed with BHB Stars
• Status, Challenges and Directions in Indirect Dark Matter Searches
• Galactic Archaeology with Gaia
• Dark Shards: velocity substructure from Gaia and direct searches for dark matter
• Searching for Dark Photon Dark Matter in LIGO O1 Data
• Directional recoil detection
• The Stellar Halo of the Galaxy is Tilted & Doubly Broken
• Merger-induced galaxy transformations in the ARTEMIS simulations
• Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way
• Constraints on the assembly history of the Milky Way's smooth, diffuse stellar halo from the metallicity-dependent, radially-dominated velocity anisotropy profiles probed with K giants and BHB stars using LAMOST, SDSS/SEGUE, and Gaia
• Limits on Sub-GeV Dark Matter from the PROSPECT Reactor Antineutrino Experiment
• The Kinematic Properties of Milky Way Stellar Halo Populations
• Via Machinae: Searching for Stellar Streams using Unsupervised Machine Learning
• The highest-speed local dark matter particles come from the Large Magellanic Cloud
• Constraints on dark matter-nucleon effective couplings in the presence of kinematically distinct halo substructures using the DEAP-3600 detector
• Energy wrinkles and phase-space folds of the last major merger
• Chasing Accreted Structures within Gaia DR2 using Deep Learning
• Measuring the local matter density using Gaia DR2
• New Experimental Constraints in a New Landscape for Composite Dark Matter
• The Detailed Science Case for the Maunakea Spectroscopic Explorer, 2019 edition
• Faint objects in motion: the new frontier of high precision astrometry
• Gravitational Focusing of Wave Dark Matter
• The Local Stellar Halo is Not Dominated by a Single Radial Merger Event
• Milky Way Accelerometry via Millisecond Pulsar Timing
• The impact of the Large Magellanic Cloud on dark matter direct detection signals
• Substructure at High Speed II: The Local Escape Velocity and Milky Way Mass with Gaia DR2
• Dark Matter Bars in Spinning Halos
• Uncertainties in Direct Dark Matter Detection in Light of Gaia's Escape Velocity Measurements
• Contribution of Gaia Sausage to the Galactic Stellar Halo Revealed by K Giants and Blue Horizontal Branch Stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and Gaia
• Parametrics of electromagnetic searches for axion dark matter
• The flavor vacuum in the expanding universe and dark matter
• Implications of the Gaia Sausage for Dark Matter Nuclear Interactions
• Probing the Galactic halo with RR Lyrae stars $-$ III. The chemical and kinematic properties of the stellar halo
• The Coupling of Galactic Dark Matter Halos with Stellar Bars
• On the correlation between the local dark matter and stellar velocities
• Effects on the local dark matter distribution due to the Large Magellanic Cloud
• Axion dark matter-induced echo of supernova remnants
• The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter
• Directional Detection of Dark Matter Using Solid-State Quantum Sensing
• The Escape Velocity Profile of the Milky Way from Gaia DR3
• Dark Matter Substructure under the Electron Scattering Lamppost
• On the Edge: the relation between stellar and dark matter haloes of Milky Way-mass galaxies
• Ironing the folds: The phase space chevrons of a GSE-like merger as a dark matter subhalo detector
• The Milky Way Revealed by Variable Stars I: Sample Selection of RR Lyrae stars, and Evidence for the Merger History
• Robust Clustering of the Local Milky Way Stellar Kinematic Substructures with Gaia eDR3
• Influence of the Gaia-Sausage-Enceladus on the density shape of the Galactic stellar halo revealed by halo K giants from the LAMOST survey
• Impact of uncertainties in the halo velocity profile on direct detection of sub-GeV dark matter
• Direct Detection Anomalies in light of $Gaia$ Data
• Halo-independent bounds on the non-relativistic effective theory of WIMP-nucleon scattering from direct detection and neutrino observations
• ALETHEIA: Hunting for Low-mass Dark Matter with Liquid Helium TPCs
• Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect DM searches
• Machine Learning the 6th Dimension: Stellar Radial Velocities from 5D Phase-Space Correlations
• Recommended conventions for reporting results from direct dark matter searches
• Dark Matter Directionality Detection performance of the Micromegas-based $\mu$TPC-MIMAC detector
• Dark Matter Raining on DUNE and Other Large Volume Detectors
• Measuring the Matter Density of the Galactic Disk Using Stellar Streams
• Substructure at High Speed I: Inferring the Escape Velocity in the Presence of Kinematic Substructure
• Cosmological Simulations of Stellar Halos with Gaia Sausage-Enceladus Analogues: Two Sausages, One Bun?
• Gravitational Potential from small-scale clustering in action space: Application to Gaia DR2
• Limits on Kaluza-Klein dark matter annihilation in the Sun from recent IceCube results
• Revealing the Milky Way's Most Recent Major Merger with a Gaia EDR3 Catalog of Machine-Learned Line-of-Sight Velocities
• Dark Matter Velocity Distributions for Direct Detection: Astrophysical Uncertainties are Smaller Than They Appear
• Halo-independent bounds on Inelastic Dark Matter
• Deciphering the Kinematic Substructure of Local Dark Matter with LAMOST K Giants
• The secular evolution of a uniform density star cluster immersed in a compressible galactic tidal field
• Astrophysical Tests of Dark Matter with Maunakea Spectroscopic Explorer
• Information divergences to parametrize astrophysical uncertainties in dark matter direct detection
• Stellar halo striations from assumptions of axisymmetry
• How to Build an Empirical Speed Distribution for Dark Matter in the Solar Neighborhood
• Information-theoretic astrophysical uncertainties in the effective theory of dark matter direct detection