Influence of the Gaia-Sausage-Enceladus on the density shape of the Galactic stellar halo revealed by halo K giants from the LAMOST survey

Abstract

We present a study of the influence of the Gaia-Sausage-Enceladus (GSE) on the density shape of the Galactic stellar halo using 11624 K giants from the LAMOST survey. Every star is assigned a probability of being a member of the GSE based on its spherical velocities and metallicity by a Gaussian Mixture Model. We divide the stellar halo into two parts by the obtained probabilities, of which one is composed of the GSE members and defined as the GSE-related halo, and the other one is referred to as the GSE-removed halo. Using a non-parametric method, the radial number density profiles of the two stellar halos can be well described by a single power law with a variable flattening $q$ ($r=\sqrt{R^2+[(Z/q(r)){]}^2},\nu ={\nu }_0{r}^{-\alpha }$). The index $\alpha$ is $4.92\pm 0.12$ for the GSE-related halo and $4.25\pm 0.14$ for the GSE-removed halo. Both the two stellar halos are vertically flattened at smaller radii but become more spherical at larger radii. We find that the GSE-related halo is less vertically flattened than the GSE-removed halo, and the difference of $q$ between the two stellar halos ranges from 0.07 to 0.15. However, after the consideration of the bias, it is thought to be within 0.08 at most of the radii. Finally, we compare our results with two Milky Way analogues which experience a significant major merger in the TNG50 simulation. The study of the two analogues also shows that the major merger-related stellar halo has a smaller ellipticity than the major merger-removed stellar halo.

arXiv comment19 Pages, 14 figures, Accepted by AJ

References in corpus (85)

• Array Programming with NumPy
• emcee: The MCMC Hammer
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Simulating Galaxy Formation with the IllustrisTNG Model
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Local stellar kinematics from Hipparcos data
• Co-formation of the Galactic disc and the stellar halo
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Triaxial Modeling of Halo Density Profiles with High-resolution N-body Simulations
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• The merger rate of galaxies in the Illustris Simulation: a comparison with observations and semi-empirical models
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars
• Vertical waves in the solar neighbourhood in Gaia DR2
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• The Growth and Structure of Dark Matter Haloes
• The formation and assembly history of the Milky Way revealed by its globular cluster population
• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• The origin of accreted stellar halo populations in the Milky Way using APOGEE, $\text{Gaia}$, and the EAGLE simulations
• Substructure revealed by RR Lyraes in SDSS Stripe 82
• Towards a more realistic population of bright spiral galaxies in cosmological simulations
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• Multiple retrograde substructures in the Galactic halo: A shattered view of Galactic history
• Light Curve Templates and Galactic Distribution of RR Lyrae Stars from Sloan Digital Sky Survey Stripe 82
• Automatic Determination of Stellar Atmospheric Parameters and Construction of Stellar Spectral Templates of the Guoshoujing Telescope (LAMOST)
• The Sausage Globular Clusters
• The Auriga Stellar Haloes: Connecting stellar population properties with accretion and merging history
• Broken and unbroken: the Milky Way and M31 stellar haloes
• Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
• The Shape and Profile of the Milky Way Halo as Seen by the CFHT Legacy Survey
• Reconstructing the Last Major Merger of the Milky Way with the H3 Survey
• The Shape of Dark Matter Haloes in the Aquarius Simulations: Evolution and Memory
• Ages and kinematics of chemically selected, accreted Milky Way halo stars
• The Shapes and Alignments of Dark Matter Halos
• Dynamical Relics of the Ancient Galactic Halo
• The total stellar halo mass of the Milky Way
• The Fall of a Giant. Chemical evolution of Enceladus, alias the Gaia Sausage
• Apocenter Pile-Up: Origin of the Stellar Halo Density Break
• 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
• The radial profile and flattening of the Milky Way's stellar halo to $80$kpc from the SEGUE K-giant Survey
• The SkyMapper-Gaia RVS view of the Gaia-Enceladus-Sausage -- an investigation of the metallicity and mass of the Milky Way's last major merger
• Timing the Early Assembly of the Milky Way with the H3 Survey
• Weighing the stellar constituents of the Galactic halo with APOGEE red giant stars
• Inferred Evidence For Dark Matter Kinematic Substructure with SDSS-Gaia
• Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
• Warps and waves in the stellar discs of the Auriga cosmological simulations
• Selecting accreted populations: metallicity, elemental abundances, and ages of the Gaia-Sausage-Enceladus and Sequoia populations
• The SEGUE K giant survey II: A Catalog of Distance Determinations for the SEGUE K giants in the Galactic Halo
• The Halo's Ancient Metal-Rich Progenitor Revealed with BHB Stars
• The GALAH Survey: Chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and $Gaia$ eDR3
• The K giant stars from the LAMOST survey data I: identification, metallicity, and distance
• Elevated r-process enrichment in Gaia Sausage and Sequoia
• The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae
• Identifying stellar streams in the 1st RAVE public data release
• A Gaia-Enceladus Analog in the EAGLE Simulation: Insights into the Early Evolution of the Milky Way
• The Profile of the Galactic Halo from Pan-STARRS1 3$\pi$ RR Lyrae
• The stellar halos of ETGs in the IllustrisTNG simulations: II. Accretion, merger history, and dark halo connection
• Stellar Halos in Illustris- Probing the Histories of Milky Way-Mass Galaxies
• A Catalog of Moving Group Candidates in The Solar Neighborhood
• 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
• Characterizing stellar halo populations II: The age gradient in blue horizontal-branch stars
• A skewer survey of the Galactic halo from deep CFHT and INT images
• Tracing Kinematic and Chemical Properties of Sagittarius Stream by K-Giants, M-Giants, and BHB stars
• The SEGUE K Giant Survey. III. Quantifying Galactic Halo Substructure
• Mapping the Milky Way with LAMOST II: the stellar halo
• Chasing Accreted Structures within Gaia DR2 using Deep Learning
• The twisted dark matter halo of the Milky Way
• Characteristics of the two sequences seen in the high-velocity Hertzsprung-Russell diagram in Gaia DR2
• DM halo morphological types of MW-like galaxies in the TNG50 simulation: Simple, Twisted, or Stretched
• Stellar Stream Candidates in the Solar Neighborhood Found in the LAMOST DR3 and TGAS
• RR Lyrae in XSTPS: The halo density profile in the North Galactic Cap
• Identifying Galactic Halo Substructure in 6D Phase-space Using $\sim$13,000 LAMOST K Giants
• 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 nature of the Milky Way's stellar halo revealed by the three integrals of motion
• A Blueprint for the Milky Way's Stellar Populations. III. Spatial Distributions and Population Fractions of Local Halo Stars
• Major mergers between dark matter haloes -- I. Predictions for size, shape, and spin
• Revealing a spiral-shaped molecular cloud in our galaxy - Cloud fragmentation under rotation and gravity
• Modelling the stellar halo with RR-Lyrae stars
• The Age-Metallicity-Specific Orbital Energy Relation for the Milky Way's Globular Cluster System Confirms the Importance of Accretion for Its Formation
• Three Moving Groups Detected in the LAMOST DR1 Archive
• Inferring the Morphology of Stellar Distribution in TNG50: Twisted and Twisted-Stretched shapes
• The Milky Way Revealed by Variable Stars I: Sample Selection of RR Lyrae stars, and Evidence for the Merger History
• The global structure of the Milky Way's stellar halo based on the orbits of local metal-poor stars

Cited by in corpus (5)

• The Stellar Halo of the Galaxy is Tilted & Doubly Broken
• Milky Way Mass with K Giants and BHB Stars Using LAMOST, SDSS/SEGUE, and Gaia: 3D Spherical Jeans Equation and Tracer Mass Estimator
• Mapping the anisotropic Galactic stellar halo with Blue Horizontal Branch stars
• Constructing the Milky Way Stellar Halo in the Galactic Center by Direct Orbit Integration
• Probing the spatial and velocity anisotropies in stellar halos from the Aquarius simulations