The phase-space structure of cold dark-matter halos: Insights into the Galactic halo

Abstract

We study the formation of the Milky Way's halo in a $\Lambda$CDM cosmology by scaling down a high resolution simulation of the formation of a cluster of galaxies. We determine how much phase-space substructure is left over from the objects that merge to build up the present galaxy. We study the debris streams originating from such objects and find that their evolution can be explained simply in terms of the conservation of phase-space density. Analysing the mass growth history of our halo we find that its inner regions have been in place for more than 10 Gyr, but that the growth of the halo as a whole is more gradual, in agreement with other high resolution simulations of dark-matter halos. Recent accretion contributes to the inner 10 kpc of the halo only at the 10${}^{-4}$ level. Finally we determine the number of dark-matter streams as a function of distance from the centre of the halo. In the equivalent of the ``Solar vicinity'', we find that the dark-matter is smoothly distributed in space, and that the velocity ellipsoid is formed by hundreds of thousands of streams, most of which have velocity dispersions of the order of 1 km/s or less.

16 pages, 21 figures, MNRAS in press. Postscript version with high resolution figures available from http://www.mpa-garching.mpg.de/~ahelmi/research/lcdm_cl.html. Minor changes

Cited by in corpus (95)

• The Aquarius Project: the subhalos of galactic halos
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Tracing Galaxy Formation with Stellar Halos I: Methods
• Multi-Phase Galaxy Formation: High Velocity Clouds and the Missing Baryon Problem
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• Streams, substructures and the early history of the Milky Way
• The Dual Origin of Stellar Halos
• The stellar halo of the Galaxy
• Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history
• Phase-space structure in the local dark matter distribution and its signature in direct detection experiments
• Chemical Abundance Distributions of Galactic Halos and their Satellite Systems in a Lambda CDM Universe
• The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach
• Chemical Evolution in Hierarchical Models of Cosmic Structure II: The Formation of the Milky Way Stellar Halo and the Distribution of the Oldest Stars
• Pieces of the puzzle: Ancient substructure in the Galactic disk
• One large blob and many streams frosting the nearby stellar halo in Gaia DR2
• Assembly History and Structure of Galactic Cold Dark Matter Halos
• Tracing out the Northern Tidal Stream of the Sagittarius Dwarf Spheoridal Galaxy
• Neutralino annihilation into gamma-rays in the Milky Way and in external galaxies
• Characterization and history of the Helmi streams with Gaia DR2
• Cosmic axion thermalization
• Phase-Space Distributions of Chemical Abundances in Milky Way-type Galaxy Halos
• A box full of chocolates: The rich structure of the nearby stellar halo revealed by Gaia and RAVE
• Simulating Galaxy Clusters - III: Properties of the Intracluster Stars
• On the kinematic detection of accreted streams in the Gaia era: a cautionary tale
• Halo-to-Halo Similarity and Scatter in the Velocity Distribution of Dark Matter
• Not too big, not too small: the dark halos of the dwarf spheroidals in the Milky Way
• On the identification of merger debris in the {\it Gaia} Era
• Disassembling the Galaxy with angle-action coordinates
• Fashionably Late? Building up the Milky Way's Inner Halo
• On the identification of substructure in phase-space using orbital frequencies
• The Graininess of Dark Matter Haloes
• Numerical estimation of densities
• Blue horizontal branch stars in the Sloan Digital Sky Survey: II. Kinematics of the Galactic halo
• Kinematics and simulations of the stellar stream in the halo of the Umbrella Galaxy
• Spectroscopic Survey of the Galaxy with Gaia II. The expected science yield from the Radial Velocity Spectrometer
• Peaks above the Maxwellian Sea: A New Approach to Finding Substructure in N-Body Haloes
• The core of the Canis Major galaxy as traced by Red Clump stars
• The velocity distribution of nearby stars from Hipparcos data I. The significance of the moving groups
• The angular momentum of dark halos: merger and accretion effects
• Using gaps in N-body tidal streams to probe missing satellites
• Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way
• Streams in the Aquarius stellar haloes
• Caustics in growing Cold Dark Matter Haloes
• The effects of dynamical substructure on Milky Way mass estimates from the high velocity tail of the local stellar halo
• Stellar halo streams in the Solar neighbourhood
• Substructure Boosts to Dark Matter Annihilation from Sommerfeld Enhancement
• Expected coalescence rates of NS-NS binaries for laser beam interferometers
• The Evolution of Substructure in Galaxy, Group and Cluster Haloes III: Comparison with Simulations
• On the common mass scale of the Milky Way satellites
• On the genealogy of the Orphan Stream
• Detection of satellite remnants in the Galactic Halo with Gaia - I. The effect of the Galactic background, observational errors and sampling
• Gravitational cooling and density profile near caustics in collisionless dark matter haloes
• Simulating tidal streams in a high resolution dark matter halo
• Streams Going Notts: The tidal debris finder comparison project
• Theoretical dark matter halo density profile
• On Dark Matter Annihilation in the Local Group
• The kinematics of globular cluster populations in the E-MOSAICS simulations and their implications for the assembly history of the Milky Way
• The origin of abundance gradients in the Milky Way: the predictions of different models
• The energetics, evolution, and stellar depletion of Li6 in the early Galaxy
• Robustness of Discrete Flows and Caustics in Cold Dark Matter Cosmology
• A deep view of the Monoceros ring in the Anticenter direction: clues of its extra-Galactic origin
• Surveying the Inner Halo of the Galaxy with 2MASS-Selected Horizontal Branch Candidates
• Identifying Galactic Halo Substructure in 6D Phase-space Using $\sim$13,000 LAMOST K Giants
• An Upper Limit on the Granularity of the Local Stellar Halo
• Recent Progress in Search for Dark Sector Signatures
• Linking the brightest stellar streams with the accretion history of Milky Way-like galaxies
• On the relevance of chaos for halo stars in the Solar Neighbourhood
• The stellar content of the Hamburg/ESO survey. III. Field horizontal-branch stars in the Galaxy
• The sense of rotation of subhaloes in cosmological dark matter haloes
• Exploring the diversity and similarity of radially anisotropic Milky Way-like stellar haloes: implications for disrupted dwarf galaxy searches
• Simulating cosmological substructure in the solar neighbourhood
• Smoothing Algorithms and High-order Singularities in Gravitational Lensing
• Spiral arm kinematics for Milky Way stellar populations
• A Spatial Characterization of the Sagittarius Dwarf Galaxy Tidal Tails
• The Effect of Substructure on Mass Estimates of Galaxies
• On the relevance of chaos for halo stars in the solar neighbourhood II
• Typhon: a polar stream from the outer halo raining through the Solar neighborhood
• The contribution of dissolving star clusters to the population of ultra-faint objects in the outer halo of the Milky Way
• A new fitting-function to describe the time evolution of a galaxy's gravitational potential
• Hierarchical Phase Space Structure of Dark Matter Haloes: Tidal debris, Caustics, and Dark Matter annihilation
• Is there a disk of satellites around the Milky Way?
• Stellar Over-densities in the Outer Halo of the Milky Way
• $\gamma$-ray flux from Dark Matter Annihilation in Galactic Caustics
• MACHOs in dark matter haloes
• VI Photometry of Globular Clusters NGC6293 and NGC6541: The Formation of the Metal-Poor Inner Halo Globular Clusters
• Searching Extra-tidal Features around the Globular Cluster Whiting 1
• The Structure of Cold Dark Matter Halos: Recent Insights from High Resolution Simulations
• Revealing the Milky Way's Most Recent Major Merger with a Gaia EDR3 Catalog of Machine-Learned Line-of-Sight Velocities
• Semi-analytic modelling of the europium production by neutron star mergers in the halo of the Milky Way
• Constraints on Galaxy Structure and Evolution from the Light of Nearby Systems
• A new test for the Galactic formation and evolution -- prediction for the orbital eccentricity distribution of the halo stars
• Accreted stars and stellar haloes of simulated galaxies in TNG50
• Statistical Properties of Blue Horizontal Branch Stars in the Spheroid: Detection of a Moving Group approximately 50 kpc from the Sun
• Morphology of dark matter haloes beyond triaxiality
• White dwarfs in the building blocks of the Galactic spheroid