The heavy-elements heritage of the falling sky

Abstract

Recent dynamical analysis based on Gaia data have revealed major accretion events in Milky Way's history. Nevertheless, our understanding of the primordial Galaxy is hindered because the bona fide identification of the most metal-poor and correspondently oldest accreted stars remains challenging. Contrary to alpha-elements, neutron-capture elements present unexplained large abundance spreads for low metallicity stars, that could result from a mixture of formation sites. We have analysed the abundances of yttrium, europium, magnesium and iron in Milky Way satellite galaxies, field halo stars and globular clusters. The chemical information has been complemented with orbital parameters based on Gaia data. In particular, the orbit's average inclination has been considered. The [Y/Eu] abundance behaviour with respect to the [Mg/Fe] turnovers for satellite galaxies of different masses reveals that higher luminosity systems, for which the [Mg/Fe] abundance declines at higher metallicities, present enhanced [Y/Eu] abundances, particularly in the [Fe/H] regime between -2.25 and -1.25 dex. In addition, the analysis has uncovered a chemo-dynamical correlation for both globular clusters and field stars of the Galactic halo, accounting for about half of the [Y/Eu] abundance spread. [Y/Eu] under-abundances typical of protracted chemical evolutions, are preferentially observed in polar-like orbits, pointing to a possible anisotropy in the accretion processes. Our results strongly suggest that the observed [Y/Eu] abundance spread in the Milky Way halo could result from a mixture of systems with different masses. They also highlight that both nature and nurture are relevant to the Milky Way formation, since its primordial epochs, opening new pathways for chemical diagnostics of our Galaxy building up.

arXiv commentSubmitted to A&A Letters, comments welcome

References in corpus (31)

• Gaia Data Release 2. Summary of the contents and survey properties
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• 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
• The New Galaxy: Signatures of its Formation
• Co-formation of the Galactic disc and the stellar halo
• Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• Magnetorotationally driven Supernovae as the origin of early galaxy $r$-process elements?
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• The Stellar Abundances for Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor Stars
• Chemical evolution with rotating massive star yields: I. The solar neighbourhood and the s-process elements
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• The Biggest Splash
• Proper motions and dynamics of the Milky Way globular cluster system from Gaia DR2
• 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
• Distances and parallax bias in Gaia DR2
• On the kinematic detection of accreted streams in the Gaia era: a cautionary tale
• Stellar Abundances for Galactic Archaeology Database IV - Compilation of Stars in Dwarf Galaxies
• The Pristine survey X: a large population of low-metallicity stars permeates the Galactic disk
• A massive mess: When a large dwarf and a Milky Way-like galaxy merge
• Non-LTE effects on the lead and thorium abundance determinations for cool stars
• Heavy Element Dispersion in the Metal-Poor Globular Cluster M92
• The Pisces Plume and the Magellanic Wake
• The Origin and Chemical Evolution of the Exotic Globular Cluster NGC3201
• The chemical composition of the low-mass Galactic globular cluster NGC 6362
• Heavy elements abundances in turn-off stars and early subgiants in NGC 6752
• Chemical Complexity in the Eu-enhanced Monometallic Globular Cluster NGC 5986
• From globular clusters to the disc: the dual life of our Galaxy

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• The GALAH Survey: Chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and $Gaia$ eDR3
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• The Pristine survey -- XVI. The metallicity of 26 stellar streams around the Milky Way detected with the STREAMFINDER in Gaia EDR3
• The cerium content of the Milky Way as revealed by Gaia DR3 GSP-Spec abundances
• Exploring the dependence of chemical traits on metallicity: chemical trends for red giant stars with asteroseismic ages