The origin of galactic metal-rich stellar halo components with highly eccentric orbits

Abstract

Using the astrometry from the ESA's Gaia mission, previous works have shown that the Milky Way stellar halo is dominated by metal-rich stars on highly eccentric orbits. To shed light on the nature of this prominent halo component, we have analysed 28 Galaxy analogues in the Auriga suite of cosmological hydrodynamics zoom-in simulations. Some three quarters of the Auriga galaxies contain significant components with high radial velocity anisotropy, beta > 0.6. However, only in one third of the hosts do the high-beta stars contribute significantly to the accreted stellar halo overall, similar to what is observed in the Milky Way. For this particular subset we reveal the origin of the dominant stellar halo component with high metallicity, [Fe/H]~-1, and high orbital anisotropy, beta>0.8, by tracing their stars back to the epoch of accretion. It appears that, typically, these stars come from a single dwarf galaxy with a stellar mass of order of 10^9-10^10 Msol that merged around 6-10 Gyr ago, causing a sharp increase in the halo mass. Our study therefore establishes a firm link between the excess of radially anisotropic stellar debris in the Milky Way halo and an ancient head-on collision between the young Milky Way and a massive dwarf galaxy

arXiv commentreplaced with the accepted version (very minor changes)

References in corpus (97)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Planck 2013 results. XVI. Cosmological parameters
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• The Aquarius Project: the subhalos of galactic halos
• GADGET: A code for collisionless and gasdynamical cosmological simulations
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
• Galactic star formation and accretion histories from matching galaxies to dark matter haloes
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• Tracing Galaxy Formation with Stellar Halos I: Methods
• Co-formation of the Galactic disc and the stellar halo
• The Field of Streams: Sagittarius and its Siblings
• The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies
• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• Two Stellar Components in the Halo of the Milky Way
• The Auriga Project: the properties and formation mechanisms of disc galaxies across cosmic time
• Galactic stellar haloes in the CDM model
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7
• The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars
• Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
• The formation and assembly history of the Milky Way revealed by its globular cluster population
• In disguise or out of reach: first clues about in-situ and accreted stars in the stellar halo of the Milky Way from Gaia DR2
• The Dual Origin of Stellar Halos
• ELVIS: Exploring the Local Volume in Simulations
• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• Galactic Rotation and Solar Motion from Stellar Kinematics
• The Formation and Survival of Discs in a Lambda-CDM Universe
• The origin of accreted stellar halo populations in the Milky Way using APOGEE, $\text{Gaia}$, and the EAGLE simulations
• Galactic Halo substructure in the Sloan Digital Sky Survey: the ancient tidal stream from the Sagittarius dwarf galaxy
• Substructure revealed by RR Lyraes in SDSS Stripe 82
• The Sagittarius impact as an architect of spirality and outer rings in the Milky Way
• Vertical density waves in the Milky Way disc induced by the Sagittarius Dwarf Galaxy
• The Influence of Sagittarius and the Large Magellanic Cloud on the Milky Way Galaxy
• The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach
• Quenching and ram pressure stripping of simulated Milky Way satellite galaxies
• The stellar mass-halo mass relation of isolated field dwarfs: a critical test of $\Lambda$CDM at the edge of galaxy formation
• Gaia reveals a metal-rich in-situ component of the local stellar halo
• Sagittarius Tidal Debris 90 kpc from the Galactic Center
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• Broken and unbroken: the Milky Way and M31 stellar haloes
• Contributions to the accreted stellar halo: an atlas of stellar deposition
• The Shape and Profile of the Milky Way Halo as Seen by the CFHT Legacy Survey
• Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
• The upper bound on the lowest mass halo
• The Sagittarius Streams in the Southern Galactic Hemisphere
• The chosen few: the low mass halos that host faint galaxies
• Galaxy groups in the 2dFGRS: the luminous content of the groups
• Assembly History and Structure of Galactic Cold Dark Matter Halos
• Extreme deconvolution: Inferring complete distribution functions from noisy, heterogeneous and incomplete observations
• Global structure and kinematics of stellar haloes in cosmological hydrodynamic simulations
• Disentangling the Galactic Halo with APOGEE: I. Chemical and Kinematical Investigation of Distinct Metal-Poor Populations
• Gaia Data Release 2: Processing the spectroscopic data
• GALAXY DYNAMICS IN CLUSTERS
• Formation of In Situ Stellar Haloes in Milky Way-Mass Galaxies
• Accretion relicts in the solar neighbourhood: debris from omegaCen's parent galaxy
• The shape of the Galactic halo with $Gaia$ DR2 RR Lyrae. Anatomy of an ancient major merger
• Using Cumulative Number Densities to Compare Galaxies across Cosmic Time
• Apocenter Pile-Up: Origin of the Stellar Halo Density Break
• Origin of chemically distinct discs in the Auriga cosmological simulations
• Stellar haloes of simulated Milky Way-like galaxies: Chemical and kinematic properties
• Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest
• A new way of setting the phases for cosmological multi-scale Gaussian initial conditions
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• The Milky Way Halo in Action Space
• Tidal stripping and the structure of dwarf galaxies in the Local Group
• The Eating Habits of Milky Way Mass Halos: Destroyed Dwarf Satellites and the Metallicity Distribution of Accreted Stars
• Inferred Evidence For Dark Matter Kinematic Substructure with SDSS-Gaia
• The stellar-to-halo mass relation for Local Group galaxies
• The Gravitational Force Field of the Galaxy Measured From the Kinematics of RR Lyrae in Gaia
• A re-interpretation of the Triangulum-Andromeda stellar clouds: a population of halo stars kicked out of the Galactic disk
• The Halo's Ancient Metal-Rich Progenitor Revealed with BHB Stars
• On the identification of substructure in phase-space using orbital frequencies
• Galactic Halo Stars in Phase Space :A Hint of Satellite Accretion?
• The slight spin of the old stellar halo
• Substructure in the stellar halos of the Aquarius simulations
• Two chemically similar stellar overdensities on opposite sides of the plane of the Galaxy
• Stray, swing and scatter: angular momentum evolution of orbits and streams in aspherical potentials
• Lessons from the Auriga discs: The hunt for the Milky Way's ex-situ disc is not yet over
• Modeling Tidal Streams in evolving dark matter halos
• Common origin for Hercules-Aquila and Virgo Clouds in Gaia DR2
• The Alpha-element knee of the Sagittarius Stream
• The Progenitors of the Milky Way Stellar Halo: Big Bricks Favoured over Little Bricks
• Anisotropy of the Milky Way's stellar halo using K giants from LAMOST and $Gaia$
• Structure of the Galactic Stellar Halo Prior to Disk Formation
• Unmixing the Galactic Halo with RR Lyrae tagging
• The fall of the Northern Unicorn: Tangential motions in the Galactic Anti-centre with SDSS and Gaia
• Through Thick and Thin: Kinematic and Chemical Components in the Solar Neighbourhood
• Disk-Like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE
• Quantifying the Smoothness of the Stellar Halo: A Link to Accretion History
• The evolution of streams in a time-dependent potential
• Cresting the wave: Proper motions of the Eastern Banded Structure
• The assembly history of the Galactic inner halo inferred from alpha-patterns

Cited by in corpus (103)

• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• Streams, substructures and the early history of the Milky Way
• The Biggest Splash
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• The Milky Way has no in-situ halo other than the heated thick disc. Composition of the stellar halo and age-dating the last significant merger with Gaia DR2 and APOGEE
• Reconstructing the Last Major Merger of the Milky Way with the H3 Survey
• Chemodynamics of barred galaxies in cosmological simulations: On the Milky Way's quiescent merger history and in-situ bulge
• Mapping the Stellar Halo with the H3 Spectroscopic Survey
• The total stellar halo mass of the Milky Way
• The Fall of a Giant. Chemical evolution of Enceladus, alias the Gaia Sausage
• The Hestia project: simulations of the Local Group
• Sausage & Mash: The dual origin of the Galactic thick disc and halo from the gas-rich Gaia-Enceladus-Sausage merger
• The local high velocity tail and the Galactic escape speed
• Weighing the stellar constituents of the Galactic halo with APOGEE red giant stars
• Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
• The Chemo-Dynamical Groups of Galactic Globular Clusters
• Reconstructing the Disrupted Dwarf Galaxy $Gaia$-Sausage/Enceladus Using its Stars and Globular Clusters
• The mass of the Milky Way out to 100 kpc using halo stars
• Galactic Archaeology with Gaia
• A tale of two populations: surviving and destroyed dwarf galaxies and the build up of the Milky Way's stellar halo
• GASTRO library I: the simulated chemodynamical properties of several GSE-like stellar halos
• Dark Shards: velocity substructure from Gaia and direct searches for dark matter
• Nitrogen enrichment and clustered star formation at the dawn of the Galaxy
• The Edge of the Galaxy
• Boötes IV: A New Milky Way Satellite Discovered in the Subaru Hyper Suprime-Cam Survey and Implications for the Missing Satellite Problem
• A Gaia-Enceladus Analog in the EAGLE Simulation: Insights into the Early Evolution of the Milky Way
• Merger-induced galaxy transformations in the ARTEMIS simulations
• Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way
• The effects of dynamical substructure on Milky Way mass estimates from the high velocity tail of the local stellar halo
• 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
• Constraints on axionlike dark matter with masses down to $10^{-23}$ eV/c${}^2$
• The Kinematic Properties of Milky Way Stellar Halo Populations
• The little things matter: relating the abundance of ultrafaint satellites to the hosts' assembly history
• Disentangling the formation history of galaxies via population-orbit superposition: method validation
• Energy wrinkles and phase-space folds of the last major merger
• The stellar velocity distribution function in the Milky Way galaxy
• The Saga of M81: Global View of a Massive Stellar Halo in Formation
• How Unusual is the Milky Way's Assembly History?
• Elemental Abundances in M31: First Alpha and Iron Abundance Measurements in M31's Giant Stellar Stream
• The impact of early massive mergers on the chemical evolution of Milky Way-like galaxies: insights from NIHAO-UHD simulations
• Formation of Galactic Disks I: Why Did the Milky Way's Disk Form Unusually Early?
• Local RR Lyrae Stars: native and alien
• Stars made in outflows may populate the stellar halo of the Milky Way
• The Fornax3D project: discovery of ancient massive merger events in the Fornax cluster galaxies NGC 1380 and NGC 1427
• The dark matter component of the Gaia radially anisotropic substructure
• Distant Echoes of the Milky Way's Last Major Merger
• Stellar halos from The Dragonfly Edge-on Galaxies Survey
• The chemodynamics of prograde and retrograde Milky Way stars
• VINTERGATAN-GM: The cosmological imprints of early mergers on Milky-Way-mass galaxies
• Cosmological insights into the assembly of the radial and compact stellar halo of the Milky Way
• A torsion-balance search for ultra low-mass bosonic dark matter
• Baryonic effects on the detectability of annihilation radiation from dark matter subhaloes around the Milky Way
• 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
• The stellar halo in Local Group Hestia simulations II. The accreted component
• Milky Way globular clusters on cosmological timescales. I. Evolution of the orbital parameters in time-varying potentials
• Formation imprints in the kinematics of the Milky Way globular cluster system
• Exploring the diversity and similarity of radially anisotropic Milky Way-like stellar haloes: implications for disrupted dwarf galaxy searches
• Probing the Galactic halo with RR Lyrae stars $-$ III. The chemical and kinematic properties of the stellar halo
• Milky Way-est: Cosmological Zoom-in Simulations with Large Magellanic Cloud and Gaia-Sausage-Enceladus Analogs
• The impact of two massive early accretion events in a Milky Way-like galaxy: repercussions for the buildup of the stellar disc and halo
• Dark Matter Candidates and Searches
• The GALAH Survey: Accreted stars also inhabit the Spite Plateau
• Taking the Milky Way for a spin: disc formation in the ARTEMIS simulations
• The globular cluster system of the Auriga simulations
• Elemental Abundances in M31: Properties of the Inner Stellar Halo
• Constraints on the Galactic Inner Halo Assembly History from the Age Gradient of Blue Horizontal-branch Stars
• Explaining the chemical trajectories of accreted and in-situ halo stars of the Milky Way
• Ironing the folds: The phase space chevrons of a GSE-like merger as a dark matter subhalo detector
• The GALAH Survey: No chemical evidence of an extragalactic origin for the Nyx stream
• The Mass and Age Distribution of Halo White Dwarfs in the Canada-France Imaging Survey
• Unravelling the mass spectrum of destroyed dwarf galaxies with the metallicity distribution function
• Influence of the Gaia-Sausage-Enceladus on the density shape of the Galactic stellar halo revealed by halo K giants from the LAMOST survey
• Auriga Streams I: disrupting satellites surrounding Milky Way-mass haloes at multiple resolutions
• Bar-driven dispersal of Galactic substructure
• How well can we unravel the accreted constituents of the Milky Way stellar halo? A test on cosmological hydrodynamical simulations
• Europium enrichment and hierarchical formation of the Galactic halo
• Peeking beneath the precision floor -- II. Probing the chemo-dynamical histories of the potential globular cluster siblings, NGC 288 and NGC 362
• The formation history of the Milky Way disc with high-resolution cosmological simulations
• An observational testbed for cosmological zoom-in simulations: constraining stellar migration in the solar cylinder using asteroseismology
• Accelerated phase-mixing in the stellar halo due to a rotating bar
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data II. Chrono-chemo-kinematics of the disc
• Deciphering the Milky Way disc formation time encrypted in the bar chrono-kinematics
• L-GALAXIES 2020: The formation and chemical evolution of stellar haloes in Milky Way Analogues and galaxy clusters
• Element abundance analysis of the metal-rich stellar halo and high-velocitythick disk in the galaxy
• Dynamical streams in the local stellar halo
• Cosmological Simulations of Stellar Halos with Gaia Sausage-Enceladus Analogues: Two Sausages, One Bun?
• AuriDESI: Mock Catalogues for the DESI Milky Way Survey
• Observing EAGLE galaxies with JWST: predictions for Milky Way progenitors and their building blocks
• Dark Matter Velocity Distributions for Direct Detection: Astrophysical Uncertainties are Smaller Than They Appear
• From order to chaos: the blurred out metallicity gradient of the Gaia-Enceladus/Sausage progenitor
• First resolved stellar halo kinematics of a MW-mass galaxy outside the Local Group: A flat counter-rotating halo in NGC 4945
• A correlation between accreted stellar kinematics and dark matter halo spin in the ARTEMIS simulations
• The Milky Way in context: The formation of galactic discs and chemical sequences from a cosmological perspective
• Deciphering the Kinematic Substructure of Local Dark Matter with LAMOST K Giants
• Auriga Streams II: orbital properties of tidally disrupting satellites of Milky Way-mass galaxies
• Numerical effects on the stripping of dark matter and stars in IllustrisTNG galaxy groups and clusters
• Build-up and survival of the disc: From numerical models of galaxy formation to the Milky Way
• Partitioning the Galactic Halo with Gaussian Mixture Models
• Stellar halo striations from assumptions of axisymmetry
• Stirring Things Up: Bar-induced substructures in the stellar halo of a cosmological Milky Way analogue
• A Tilt in the Dark Matter Halo of the Galaxy
• How to Build an Empirical Speed Distribution for Dark Matter in the Solar Neighborhood
• Globular clusters of the Gaia Enceladus/Sausage -- I. Orbital and dynamical evolution on cosmological timescales