Bimodal Distribution of Galactic Disk Stars on the [alpha/Fe]-[Fe/H] Plane as a Possible Evidence of Discontinuous Radial Migration History

Abstract

We investigate the role of radial migration history of stars in chemical evolution of a disk galaxy, in particular in understanding the origin of their bimodal distribution on the [alpha/Fe]-[Fe/H] plane. For this purpose, we examine the three different models with no, continuous, and discontinuous radial migration, respectively. We find that for the model with radial migration, the [alpha/Fe] ratios of stars in outer disk regions decrease more rapidly with time than the model without radial migration, because the associated net transfer of intermediate and old disk stars from inner to outer disk regions increases the rate of Type Ia relative to that of Type II supernovae in the latter regions. Moreover, in the model assuming rapid and discontinuous radial migration, its effect on the stellar abundances at larger radii is significant enough to provide the large difference in the evolution of stars on the [alpha/Fe]-[Fe/H] plane between inner and outer disk regions. As a result we obtain the bimodal distribution of disk stars on the [alpha/Fe]-[Fe/H] plane as observed in the Galactic stellar disk, thereby implying that the event of discontinuous radial migration may play a key role in reproducing the observed bimodality of stars on this abundance-ratio diagram. We discuss possible mechanisms causing such discontinuous radial migration in the early evolution of the Galactic disk, including the event of minor merging of a relatively massive satellite onto the stellar disk.

arXiv comment39 pages, 12 figures. Accepted for publication in ApJ

References in corpus (42)

• The Star Formation Law in Nearby Galaxies on Sub-Kpc Scales
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• Nucleosynthesis in Chandrasekhar Mass Models for Type Ia Supernovae and Constraints on Progenitor Systems and Burning-Front Propagation
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• Radial Mixing in Galactic Discs
• The Chemical Evolution of the Galaxy: the two-infall model
• Chemical evolution with radial mixing
• Abundance Gradients and the Formation of the Milky Way
• The Role of Pressure in GMC Formation II: The H_2 - Pressure Relation
• Chemical Cartography with APOGEE: Metallicity Distribution Functions and the Chemical Structure of the Milky Way Disk
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program.Galactic stellar populations and planets
• The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk
• Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7
• Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks
• Chemodynamical evolution of the Milky Way disk I: The solar vicinity
• The spatial structure of mono-abundance sub-populations of the Milky Way disk
• A Spectroscopic Study of the Ancient Milky Way: F- and G-Type Stars in the Third Data Release of the Sloan Digital Sky Survey
• Origin and structure of the Galactic disc(s)
• On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy
• Sinking Satellites and the Heating of Galaxy Discs
• The evolution of the Milky Way from its earliest phases : constraints on stellar nucleosynthesis
• The Genesis of the Milky Way's Thick Disk via Stellar Migration
• The Milky Way's Stellar Disk
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• The Distribution of the Elements in the Galactic Disk III. A Reconsideration of Cepheids from l = 30 to 250 Degrees
• The stellar population structure of the Galactic disk
• Formation and Evolution of the Disk System of the Milky Way: [alpha/Fe] Ratios and Kinematics of the SEGUE G-Dwarf Sample
• Chemodynamics of the Milky Way. I. The first year of APOGEE data
• Evolution of the Milky Way with radial motions of stars and gas I. The solar neighborhood and the thin and thick disk
• Chemistry and Kinematics in the Solar Neighborhood: Implications for Stellar Populations and for Galaxy Evolution
• Fuel Efficient Galaxies: Sustaining Star Formation with Stellar Mass Loss
• When the Milky Way turned off the lights: APOGEE provides evidence of star formation quenching in our Galaxy
• Metallicity Gradients in the Milky Way Disk as Observed by the SEGUE Survey
• The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release
• The Gaia-ESO Survey: Characterisation of the [alpha/Fe] sequences in the Milky Way discs
• Through Thick and Thin: Kinematic and Chemical Components in the Solar Neighbourhood
• The imprint of satellite accretion on the chemical and dynamical properties of disc galaxies
• A New Chemical Evolution Model for Dwarf Spheroidal Galaxies based on Observed Long Star Formation Histories
• The gas inflow and outflow rate in star-forming galaxies at $z\sim 1.4$
• On the Chemical and Structural Evolution of the Galactic Disk
• Gas Inflow and Outflow Histories in Disk Galaxies as Revealed from Observations of Distant Star-Forming Galaxies

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