The neutron-capture and alpha-elements abundance ratios scatter in old stellar populations. Cosmological simulations of the stellar halo

Abstract

We investigate the origin of the abundance ratios and scatter of the neutron-capture elements Sr, Ba and Eu in the stellar halo of a Milky Way-mass galaxy formed in a hydrodynamical cosmological simulation, and compare them with those of $\alpha$-elements. For this, we implement a novel treatment for chemical enrichment of Type II supernovae which considers the effects of the rotation of massive stars on the chemical yields and differential enrichment according to the life-times of progenitor stars. We find that differential enrichment has a significant impact on the early enrichment of the interstellar medium which is translated into broader element ratio distributions, particularly in the case of the oldest, most metal-poor stars. We find that the [element/Fe] ratios of the $\alpha -$elements O, Mg and Si have systematically lower scatter compared to the neutron-capture elements ratios Sr, Ba and Eu at [Fe/H]$<-2$, which is $\sim 0.1-0.4$ dex for the former and between $\sim 0.5$ and $1$ dex for the latter. The different scatter levels found for the neutron-capture and $\alpha$-elements is consistent with observations of old stars in the Milky Way. Our model also predicts a high scatter for the [Sr/Ba] ratio, which results from the treatment of the fast-rotating stars and the dependence of the chemical yields on the metallicity, mass and rotational velocities. Such chemical patterns appear naturally if the different ejection times associated to stars of different mass are properly described, without the need to invoke for additional mixing mechanisms or a distinct treatment of the $\alpha -$ and neutron-capture elements.

arXiv commentMNRAS accepted

References in corpus (78)

• Gaia Data Release 2. Summary of the contents and survey properties
• Star Formation in Galaxies Along the Hubble Sequence
• Cosmological SPH simulations: A hybrid multi-phase model for star formation
• The Aquarius Project: the subhalos of galactic halos
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• First results from the IllustrisTNG simulations: A tale of two elements -- chemical evolution of magnesium and europium
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• Origin of the Heaviest Elements: the Rapid Neutron-Capture Process
• Galactic Evolution of Sr, Y, Zr: A Multiplicity of Nucleosynthetic Processes
• Stellar evolution with rotation VIII: Models at Z = 10^{-5} and CNO yields for early galactic evolution
• Presupernova evolution and explosive nucleosynthesis of rotating massive stars in the metallicity range -3 <=[Fe/H]<= 0
• 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
• The Aquila comparison Project: The Effects of Feedback and Numerical Methods on Simulations of Galaxy Formation
• Evolution, nucleosynthesis and yields of low mass AGB stars
• Streams, substructures and the early history of the Milky Way
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• Spectroscopic Studies of Extremly Metal-Poor Stars with Subaru/HDS:II.The r-process Elements, Including Thorium
• Neutron star mergers versus core-collapse supernovae as dominant r-process sites in the early Galaxy
• Chemical evolution with rotating massive star yields: I. The solar neighbourhood and the s-process elements
• The Most Metal-Poor Stars. II. Chemical Abundances of 190 Metal-Poor Stars Including 10 New Stars With [Fe/H] < -3.5
• First Stars VIII -- Enrichment of the neutron-capture elements in the early Galaxy
• The Formation and Survival of Discs in a Lambda-CDM Universe
• The evolution of the Milky Way from its earliest phases : constraints on stellar nucleosynthesis
• Effects of Supernova Feedback on the Formation of Galaxy Disks
• Very low metallicity massive star models: Pre-SN evolution and primary nitrogen production
• $s$-process production in rotating massive stars at solar and low metallicities
• Feedback and metal enrichment in cosmological SPH simulations - II. A multiphase model with supernova energy feedback
• Gaia Early Data Release 3: Summary of the contents and survey properties
• A strong case for fast stellar rotation at very low metallicities
• Non-standard s process in low metallicity massive rotating stars
• Feedback and metal enrichment in cosmological SPH simulations I. A model for chemical enrichment
• The s process in massive stars at low metallicity. Effect of primary N14 from fast rotating stars
• The r-Process in Neutrino-Driven Winds from Nascent, "Compact" Neutron Stars of Core-Collapse Supernovae
• Galactic evolution of rapid neutron capture process abundances: the inhomogeneous approach
• Age dissection of the Milky Way discs: red giants in the Kepler field
• From Nuclei to the Cosmos: Tracing Heavy-Element Production with the Oldest Stars
• Nucleosynthesis in the Early Galaxy
• Galactic r-process enrichment by neutron star mergers in cosmological simulations of a Milky Way-mass galaxy
• The History of R-Process Enrichment in the Milky Way
• Formation of Isolated Dwarf Galaxies with Feedback
• Stellar haloes of simulated Milky Way-like galaxies: Chemical and kinematic properties
• Characterization and history of the Helmi streams with Gaia DR2
• The role of neutron star mergers in the chemical evolution of the Galactic halo
• Chronologically dating the early assembly of the Milky Way
• The s-process in the Galactic halo: the fifth signature of spinstars in the early Universe?
• Stellar haloes in Milky-Way mass galaxies: From the inner to the outer haloes
• An observer's view of simulated galaxies: disc-to-total ratios, bars, and (pseudo-)bulges
• The chemical evolution of Barium and Europium in the Milky Way
• A new imprint of fast rotators: low 12C/13C ratios in extremely metal-poor halo stars
• An inhomogeneous model for the Galactic halo: a possible explanation for the spread observed in s- and r-process elements
• Explaining the Ba, Y, Sr, and Eu abundance scatter in metal-poor halo stars: constraints to the r-process
• Non standard s-process in massive rotating stars. Yields of $10-150$ $M_{\odot }$ models at $Z=10^{-3}$
• What is the (Dark) Matter with Dwarf Galaxies?
• Formation history, structure and dynamics of discs and spheroids in simulated Milky Way mass galaxies
• Elevated r-process enrichment in Gaia Sausage and Sequoia
• Kinematics of Highly R-Process-Enhanced Field Stars: Evidence for an Accretion Origin and Detection of Several Groups from Disrupted Satellites
• Neutron star mergers and rare core-collapse supernovae as sources of r-process enrichment in simulated galaxies
• High-resolution spectroscopy of extremely metal-poor stars in the least evolved galaxies: Bootes II
• The distribution of gas in the Local Group from constrained cosmological simulations: the case for Andromeda and the Milky Way galaxies
• Galactic Simulations of r-process Elemental Abundances
• Local Group Dwarf Galaxies: Nature And Nurture
• The Pisces Plume and the Magellanic Wake
• Abundance ratios of red giants in low mass ultra faint dwarf spheroidal galaxies
• Stellar Abundances in the Early Galaxy and Two r-Process Components
• The R-Process Alliance: Chemo-Dynamically Tagged Groups of Halo $r$-Process-Enhanced Stars Reveal a Shared Chemical-Evolution History
• Unmixing the Galactic Halo with RR Lyrae tagging
• Collapsar R-Process Yields Can Reproduce [Eu/Fe] Abundance Scatter in Metal-Poor Stars
• Using failed supernovae to constrain the Galactic r-process element production
• Icarus: a Flat and Fast Prograde Stellar Stream in the Milky Way disk
• The effects of stellar winds of fast-rotating massive stars in the earliest phases of the chemical enrichment of the Galaxy
• R-process-rich stellar streams in the Milky Way
• Abundance Patterns of $\alpha$ and Neutron-capture Elements in the Helmi Stream
• Correlations of r-Process Elements in Very Metal-Poor Stars as Clues to their Nucleosynthesis Sites
• Physical properties of galaxies: toward a consistent comparison between hydrodynamical simulations and SDSS
• Precision Pollution - The effects of enrichment yields and timing on galactic chemical evolution