Metallicity distributions of halo stars: do they trace the Galactic accretion history?

Abstract

The standard cosmological scenario predicts a hierarchical formation for galaxies. Many substructures were found in the Galactic halo, identified as clumps in kinematic spaces, like the energy-angular momentum one (E-Lz), under the hypothesis of the conservation of these quantities. If these clumps also feature different chemical properties, e.g. metallicity distribution functions (MDF), they are often associated to independent merger debris. The aim of this study is to explore to what extent we can couple kinematics and metallicities of stars in the Galactic halo to reconstruct the accretion history of the Milky Way. In particular, we want to understand whether different clumps in the E-Lz space with different MDF should be associated to distinct merger debris. We analysed dissipationless, self-consistent high-resolution N-body simulations of a MW-type galaxy accreting a satellite with mass ratio 1:10, with different orbital parameters and metallicity gradients (assigned a posteriori). We confirm that accreted stars from a ~1:10 satellite redistribute in a wide range of E and Lz, due to the dynamical friction, thus not being associated to a single clump. Because satellite stars with different metallicities can be deposited in different regions of the E-Lz space (on average the more metal-rich ones end up more gravitationally bound to the MW), this implies that a single ~1:10 accretion can manifest with different MDFs, in different regions of the E-Lz space. Groups of stars with different E, Lz and metallicities may be interpreted as originating from different satellites, but our analysis shows that these interpretations are not physically motivated. In fact, the coupling of kinematics with MDFs to reconstruct the accretion history of the MW can bias the reconstructed merger tree towards increasing the number of past accretions and decreasing the masses of the progenitor galaxies.

References in corpus (33)

• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The GALAH Survey: Scientific Motivation
• The GALAH+ Survey: Third Data Release
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• Gaia Data Release 3 Properties and validation of the radial velocities
• The Dual Origin of Stellar Halos
• The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
• The Global Dynamical Atlas of the Milky Way mergers: Constraints from Gaia EDR3 based orbits of globular clusters, stellar streams and satellite galaxies
• ZFOURGE/CANDELS: On the Evolution of M* Galaxy Progenitors from z=3 to 0.5
• Disentangling the Galactic Halo with APOGEE: I. Chemical and Kinematical Investigation of Distinct Metal-Poor Populations
• The chemical characterisation of halo substructure in the Milky Way based on APOGEE
• 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
• Origin of the excess of high-energy retrograde stars in the Galactic halo
• Selecting accreted populations: metallicity, elemental abundances, and ages of the Gaia-Sausage-Enceladus and Sequoia populations
• Fashionably Late? Building up the Milky Way's Inner Halo
• An Iterative Method for Constructing Equilibrium Phase Models of Stellar Systems
• GASTRO library I: the simulated chemodynamical properties of several GSE-like stellar halos
• A massive mess: When a large dwarf and a Milky Way-like galaxy merge
• The dynamics of tidal tails from massive satellites
• Substructure in the stellar halo near the Sun. II. Characterisation of independent structures
• The distribution of globular clusters in kinematic spaces does not trace the accretion history of the host galaxy
• The stellar metallicity gradients of Local Group dwarf galaxies
• The Milky Way as a High Redshift Galaxy: The Importance of Thick Disk Formation in Galaxies
• High-precision chemical abundances of Galactic building blocks. The distinct chemical abundance sequence of Sequoia
• High-precision chemical abundances of Galactic building blocks. II. Revisiting the chemical distinctness of the Helmi streams
• What the Milky Way bulge reveals about the initial metallicity gradients in the disc
• Timing the Milky Way bar formation and the accompanying radial migration episode
• The stellar halo in Local Group Hestia simulations I. The in-situ component and the effect of mergers
• A Swing of the Pendulum: The Chemodynamics of the Local Stellar Halo Indicate Contributions from Several Radial Merger Events
• The stellar halo in Local Group Hestia simulations II. The accreted component
• The stellar halo in Local Group Hestia simulations III. Chemical abundance relations for accreted and in-situ stars

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• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
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• How well can we unravel the accreted constituents of the Milky Way stellar halo? A test on cosmological hydrodynamical simulations
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data I. Method validation
• The role of accreted and in situ populations in shaping the stellar halos of low-mass galaxies
• Chronology of our Galaxy from Gaia colour-magnitude diagram fitting (ChronoGal) -- III. Age and metallicity distribution of Gaia-Sausage-Enceladus stars near the Sun
• From order to chaos: the blurred out metallicity gradient of the Gaia-Enceladus/Sausage progenitor
• Nearby stellar substructures in the Galactic halo from DESI Milky Way Survey Year 1 Data Release
• Tidal mass loss in the Fornax dwarf spheroidal galaxy through N-body simulations with Gaia DR3-based orbits
• The Nephele ecosystem: stars, globular clusters, and stellar streams associated with the progenitor galaxy of $\omega$ Centauri
• The metal-poorest tail of the Galactic halo: hypothesis on its origin from precise spectral analysis
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data III. Panoramic view of the bulge
• Two faces of Gaia-Sausage-Enceladus: Mining the chemical abundance space with graph attention networks
• The DORCHA suite: nature, nurture, and the phase space distribution of the Milky Way's high redshift progenitors today
• Probing the Milky Way Halo with RR Lyrae Stars from Gaia Data Release 3
• The chemodynamical memory of a major merger in a NIHAO-UHD Milky Way analogue -- I. A golden thread through time and space