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We examine the distribution of the [O/Fe] abundance ratio in stars across the Galactic disk using H-band spectra from the Apache Point Galactic Evolution Experiment (APOGEE). We minimize systematic errors by considering groups of stars with…

We find two chemically distinct populations separated relatively cleanly in the [Fe/H] - [Mg/Fe] plane, but also distinguished in other chemical planes, among metal-poor stars (primarily with metallicities [Fe/H] $< -0.9$) observed by the…

A scenario for the formation of the bi-modality in the chemical space [$\alpha$/Fe] vs [Fe/H] of the Milky Way was recently proposed in which $\alpha$-enhanced stars are produced early and quickly in clumps. Besides accelerating the…

Astrophysics of Galaxies · Physics 2020-02-12 Leandro Beraldo e Silva , Victor P. Debattista , Tigran Khachaturyants , David Nidever

We examine the \alpha-element abundance ratio, [\alpha/Fe], of 5620 stars, observed by the Sloan Extension for Galactic Understanding and Exploration survey in the region 6 kpc < R < 16 kpc, 0.15 kpc < |Z| < 1.5 kpc, as a function of…

We investigate how the stellar and gas-phase He abundances evolve as functions of time within simulated star-forming disc galaxies with different star formation histories. We make use of a cosmological chemodynamical simulation for galaxy…

Astrophysics of Galaxies · Physics 2019-10-09 Fiorenzo Vincenzo , Andrea Miglio , Chiaki Kobayashi , J. Ted Mackereth , Josefina Montalban

An ensemble of chemical abundances probing different nucleosynthetic channels can be leveraged to build a comprehensive understanding of the chemical and structural evolution of the Galaxy. Using GALAH DR3 data, we seek to trace the…

Astrophysics of Galaxies · Physics 2022-05-25 Danny Horta , Melissa K. Ness , Jan Rybizki , Ricardo P. Schiavon , Sven Buder

We develop a chemical evolution model in order to study the star formation history of the Milky Way. Our model assumes that the Milky Way is formed from a closed box-like system in the inner regions, while the outer parts of the disc…

Astrophysics of Galaxies · Physics 2015-06-10 O. Snaith , M. Haywood , P. Di Matteo , M. D. Lehnert , F. Combes , D. Katz , A. Gómez

The spatial structure of stellar populations with different chemical abundances in the Milky Way contains a wealth of information on Galactic evolution over cosmic time. We use data on 14,699 red-clump stars from the APOGEE survey, covering…

Based on the [Fe/H] versus [Mg/Fe] diagram and distances from APOGEE data release 14, we compare the spatial distributions, the l-Vlos diagram and the abundance gradients between high-[Mg/Fe] and low-[Mg/Fe] sequences. The two sequences are…

Astrophysics of Galaxies · Physics 2019-02-13 Y. Q. Chen , G. Zhao , X. X. Xue , J. K. Zhao , X. L. Liang , Y. P. Jia , C. Q. Yang

Previous studies based on the analysis of Gaia DR2 data have revealed that accreted stars, possibly originating from a single progenitor satellite, are a significant component of the halo of our Galaxy, potentially constituting most of the…

Astrophysics of Galaxies · Physics 2019-11-27 P. Di Matteo , M. Haywood , M. D. Lehnert , D. Katz , S. Khoperskov , O. N. Snaith , A. Gómez , N. Robichon

The proto-Milky Way epoch forms the earliest stars in our Galaxy and sets the initial conditions for subsequent disk formation. Recent observations from APOGEE and H3 surveys showed that the [$\alpha$/Fe] ratio slowly declined between…

Astrophysics of Galaxies · Physics 2024-11-11 Boquan Chen , Yuan-Sen Ting , Michael Hayden

The relative enrichment of s-process to $\alpha$-elements ([s/$\alpha$]) has been linked with age, providing a potentially useful avenue in exploring the Milky Way's chemical evolution. However, the age--[s/$\alpha$] relationship is…

Important insights into the formation and evolution of the Galactic disc(s) are contained in the chemical compositions of stars. We analysed high-resolution and high signal to noise HARPS spectra of 79 solar twin stars in order to obtain…

We use observations from the APOGEE survey to explore the relationship between stellar parameters and multiplicity. We combine high-resolution repeat spectroscopy for 41,363 dwarf and subgiant stars with abundance measurements from the…

Stellar ages are a crucial component to studying the evolution of the Milky Way. Using Gaia DR2 distance estimates, it is now possible to estimate stellar ages for a larger volume of evolved stars through isochrone matching. This work…

We analyse the kinematics and chemistry of the bulge stars of two simulated disc galaxies using our chemodynamical galaxy evolution code GCD+. First we compare stars that are born inside the galaxy with those that are born outside the…

Astrophysics of Galaxies · Physics 2015-05-14 A. Rahimi , D. Kawata , Chris B. Brook , Brad K. Gibson

In the Milky Way, the distribution of stars in the $[\alpha/\mathrm{Fe}]$ vs. $[\mathrm{Fe/H}]$ and $[\mathrm{Fe/H}]$ vs. age planes holds essential information about the history of star formation, accretion, and dynamical evolution of the…

Astrophysics of Galaxies · Physics 2023-06-16 Aarya A. Patil , Jo Bovy , Sebastian Jaimungal , Neige Frankel , Henry W. Leung

We explore the structure of the element abundance--age--orbit distribution of the stars in the Milky Way's low-$\alpha$ disk, by (re-)deriving precise [Fe/H], [X/Fe] and ages, along with orbits, for red clump stars from the APOGEE survey.…

Solar and Stellar Astrophysics · Physics 2019-10-09 Melissa K. Ness , Kathryn V. Johnston , Kirsten Blancato , Hans-Walter Rix , Angus Beane , Jonathan C. Bird , Keith Hawkins

We derive age-metallicity relations (AMRs) and orbital parameters for the 1658 solar neighbourhood stars to which accurate distances are measured by the HIPPARCOS satellite. The sample stars comprise 1382 thin disc stars, 229 thick disc…

Astrophysics · Physics 2009-11-07 A. Ibukiyama , N. Arimoto

We constrain the formation history of the Milky Way bulge using a two-infall Galactic Chemical Evolution (GCE) framework implemented in the OMEGA++ code. We recover a best-fit scenario in which the bulge forms through an early, rapid…

Astrophysics of Galaxies · Physics 2025-12-10 Niall Miller , Meridith Joyce , Christian I. Johnson , Jamie Tayar , Thomas Trueman , R Michael Rich
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