Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances

Abstract

The Gaia-Sausage-Enceladus merger was a major event in the history of the Milky Way. Studies on Milky Way satellite dwarf galaxies show that key elemental abundance patterns, which probe different nucleosynthetic channels, reflect the host galaxy's star formation history. We gather Mg, Fe, Ba, and Eu abundance measurements for Gaia-Sausage-Enceladus stars from the SAGA database and use [Fe/Mg], [Ba/Mg], [Eu/Mg], and [Eu/Ba], as a function of [Fe/H] to constrain the star formation history of Gaia-Sausage-Enceladus. We use the known star formation histories and elemental abundance patterns of the Sculptor and Fornax dwarf spheroidal galaxies as comparison. The elemental abundance ratios of [Fe/Mg], [Ba/Mg], [Eu/Mg], and [Eu/Ba] all increase with [Fe/H] in Gaia-Sausage- Enceladus. The [Eu/Mg] begins to increase at [Fe/H]= -2.0 and continues steadily, contrasting with the Sculptor dSph galaxy. The [Eu/Ba] increases and remains high across the [Fe/H] range, contrasting with that of the Sculptor dSph galaxy and deviating from the Fornax dSph galaxy at high [Fe/H]. The [Ba/Mg] is higher than those of the Sculptor dSph galaxy at the lowest [Fe/H] and gradually increases, similar to the Fornax dSph galaxy. We constrain three main properties of the Gaia-Sausage-Enceladus star formation history: 1) star formation started gradually, 2) it extended for over 2 Gyr, and 3) it was quenched around [Fe/H] of -0.5, likely when it fell into the Milky Way.

Accepted in A&A

References in corpus (55)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• galpy: A Python Library for Galactic Dynamics
• GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence
• The mass distribution and gravitational potential of the Milky Way
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• astroquery: An Astronomical Web-Querying Package in Python
• Nucleosynthesis and Remnants in Massive Stars of Solar Metallicity
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Magnetorotationally driven Supernovae as the origin of early galaxy $r$-process elements?
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Identification of strontium in the merger of two neutron stars
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Sulphur and zinc abundances in Galactic halo stars revisited
• Silver and palladium help unveil the nature of a second r-process
• APOGEE Chemical Abundance Patterns of the Massive Milky Way Satellites
• The chemical characterisation of halo substructure in the Milky Way based on APOGEE
• High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey
• Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
• 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
• The $R$-Process Alliance: Fourth Data Release from the Search for $r$-Process-Enhanced Stars in the Galactic Halo
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• Selecting accreted populations: metallicity, elemental abundances, and ages of the Gaia-Sausage-Enceladus and Sequoia populations
• Elemental abundances and classification of CEMP stars
• A high-resolution spectral analysis of three carbon-enhanced metal-poor stars
• Elevated r-process enrichment in Gaia Sausage and Sequoia
• Lithium abundances in CEMP stars
• $R$-process enhancements of Gaia-Enceladus in GALAH DR3
• Evidence from Disrupted Halo Dwarfs that $r$-process Enrichment via Neutron Star Mergers is Delayed by $\gtrsim 500$ Myrs
• The mass-metallicity relations for gas and stars in star-forming galaxies: strong outflow vs variable IMF
• Carbon and oxygen in metal-poor halo stars
• Evidence for $\gtrsim 4$ Gyr timescales of neutron star mergers from Galactic archaeology
• Age-chemical abundance structure of the Galaxy I: Evidence for a late accretion event in the outer disc at z ~ 0.6
• Beryllium abundances in metal-poor stars
• The star formation history of the Sculptor dwarf spheroidal galaxy
• High-precision chemical abundances of Galactic building blocks. The distinct chemical abundance sequence of Sequoia
• Abundances of neutron-capture elements in thin- and thick-disc stars in the solar neighbourhood
• Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study
• Fluorine Abundances of Galactic Low-Metallicity Giants
• Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictions
• Metallicity distributions of halo stars: do they trace the Galactic accretion history?
• Diversity of Abundance Patterns of Light Neutron-capture Elements in Very-metal-poor Stars
• Star Formation Timescales of the Halo Populations from Asteroseismology and Chemical Abundances
• Metal-Poor Stars Observed with the Southern African Large Telescope
• Detection of Al II in the Ultraviolet Spectra of Metal-Poor Stars: An Empirical LTE Test of NLTE Aluminum Abundance Calculations
• Galactic Chemical Evolution Models Favor an Extended Type Ia Supernova Delay-Time Distribution
• Cosmic Type Ia SN rate and constraints on SN Ia progenitors
• Detection of Pb II in the Ultraviolet Spectra of Three Metal-Poor Stars
• Sr and Ba abundance determinations: comparing machine-learning with star-by-star analyses -- High-resolution re-analysis of suspected LAMOST barium stars
• Improved Atomic Transition Probabilities for UV and Optical Lines of Hf II and Determination of the Hf Abundance in Two Metal-Poor Stars
• Something borrowed, something blue: The nature of blue metal-poor stars inferred from their colours and chemical abundances
• Estimating the age-metallicity distribution of a stellar sample from the probability distributions of the individual stars

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• Evidence of Gaia Enceladus experiencing at least two passages around the Milky Way
• Europium, we have a problem. Modelling r-process enrichment across Local Group galaxies
• Cosmological Simulations of Stellar Halos with Gaia Sausage-Enceladus Analogues: Two Sausages, One Bun?
• Discovery of a pair of very metal-poor stars enriched in neutron-capture elements: The proto-disk r-II star BPS CS 29529-0089 and the Gaia-Sausage-Enceladus r-I star TYC 9219-2422-1
• 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
• A chemical close-up of the main body of the Sagittarius dwarf galaxy
• Discovery of Galactic center ejected star in DESI DR1
• Disentangling Milky Way halo populations at low metallicities using [Al/Fe]
• The GALAH Survey: Neutron-Capture Elemental Abundances for 350,000 Gaia-RVS spectra and the Chemodynamics of Accreted Structures
• Globular clusters of the Gaia Enceladus/Sausage -- I. Orbital and dynamical evolution on cosmological timescales
• Gaia-Sausage-Enceladus: Lithium evolution from early red-giant-branch and main-sequence stars