Exploring the Milky Way stellar disk - A detailed elemental abundance study of 714 F and G dwarf stars in the solar neighbourhood

By T. Bensby, S. Feltzing, M. Observatory, Sweden., D. O. Astronomy, U. Michigan. 2013

792 citations recorded by the source corpus.

Aims. The aim of this paper is to explore and map the age and abundance structure of the stars in the nearby Galactic disk. Methods. We have conducted a high-resolution spectroscopic study of 714 F and G dwarf and subgiant stars in the Solar neighbourhood. The star sample has been kinematically selected to trace the Galactic thin and thick disks to their extremes, the metal-rich stellar halo, sub-structures in velocity space such as the Hercules stream and the Arcturus moving group, as well as stars that cannot (kinematically) be associated with either the thin disk or the thick disk. The determination of stellar parameters and elemental abundances is based on a standard analysis using equivalent widths and one-dimensional, plane-parallel model atmospheres calculated under the assumption of local thermodynamical equilibrium (LTE). The spectra have high resolution (R = 40 000-110 000) and high signal-to-noise)S/V = 150-300) and were obtained with the FEROS spectrograph on the ESO 1.5 in and 2.2 in telescopes, the SOFIN and PIES spectrographs on the Nordic Optical Telescope, the LIVES spectrograph on the E50 Very Large Telescope, the HARPS spectrograph on the ESO 3.6 m telescope, and the MIKE spectrograph on the Magellan Clay telescope. The abundances from individual Fe I lines were were corrected for non-LTE effects in every step of the analysis. Results. We present stellar parameters, stellar ages, kinematical parameters, orbital parameters, and detailed elemental abundances for 0, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y. and Ba for 714 nearby 12 and G dwarf stars. Our data show that there is an old and a-enhanced disk population, and a younger and less a-enhanced disk population. While they overlap greatly in metallicity between 0.7 < [Fe/HI] less than or similar to +0.1, they show a bimodal distribution in [alpha/Fe]. This bimodality becomes even clearer if stars where stellar parameters and abundances show larger uncertainties (T-eff less than or similar to 5400 K) are discarded, showing that it is important to constrain the data set to a narrow range in the stellar parameters if small differences between stellar populations are to be revealed. In addition, we find that the a-enhanced population has orbital parameters placing the stellar birthplaces in the inner Galactic disk while the loss-alpha stars mainly come from the outer Galactic disk, fully consistent with the recent claims of a short scale-length for the alpha-enhanced Galactic thick disk. We have also investigated the properties of the Hercules stream and the Arcturus moving group and find that neither of them presents chemical or age signatures that could suggest that they are disrupted clusters or extragalactic accretion remnants from ancient merger events. Instead, they are most likely dynamical features originating within the Galaxy. We have also discovered that a standard 1D. LTE analysis, utilising ionisation and excitation balance of Fe I and Fen lines produces a flat lower main sequence. As the exact cause for this effect is unclear we chose to apply an empirical correction. Turn-off stars and more evolved stars appear to be unaffected. (Less)

Subfields: Astronomy and Astrophysics

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Citations in the corpus

APOGEE Data Releases 13 and 14: Data and Analysis (2018, methodology): “This is motivated by studies of the solar neighborhood (e.g., Bensby et al. 2014) that suggest that most stars in the solar neighborhood have solar abundance ratios at solar abundance.”
The age–metallicity structure of the Milky Way disc using APOGEE (2017, background): “Martig et al. (2016b) comment on the bias in the context that the ages returned for high [α/Fe] stars appear younger than previous estimates (from Haywood et al. 2013; Bensby et al. 2014; Bergemann et al. 2014).”
Impacts of a flaring star-forming disc and stellar radial mixing on the vertical metallicity gradient (2016, background): “…that kinematically selected geometrically thick (thin) disc stars do not always follow the high-α (low-α) sequence (e.g. Adibekyan et al. 2012), and the phase-space distribution of the high-α and c© 2016 The Authors low-α disc stars overlaps significantly with each other (e.g. Bensby et al. 2014).”
SPECTRAL PROPERTIES OF COOL STARS: EXTENDED ABUNDANCE ANALYSIS OF 1,617 PLANET-SEARCH STARS (2016, background): “Our [Mg/H] abundances are ∼ 0.06 dex higher than large samples in the literature (Bensby et al. 2014; Adibekyan et al. 2012) and have better precision and similar trends versus temperature as those studies.”
THE RADIAL VELOCITY EXPERIMENT (RAVE): FIFTH DATA RELEASE (2013, background): “…which concentrate on bright metalpoor stars, the study of Trevisan et al. (2011), which concentrates on old, metal-rich stars, and the studies of Ramı́rez et al. (2013); Reddy et al. (2003, 2006); Valenti & Fischer (2005); Bensby et al. (2014), which target FGK stars in the solar neighbourhood.”
Chemodynamics of the Milky Way - I. The first year of APOGEE data (2013, background): “The recent study by Bensby et al. (2013a), analyzing high-resolution spectra of more than 700 solar-neighbourhood dwarf stars, also points into this direction.”
Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA (2015, background): “This interpretation however has been recently challenged by the observational evidence that alphaenhanced thick disc stars may also extend to super-solar metallicities (e.g. Feltzing & Bensby 2008; Casagrande et al. 2011; Trevisan et al. 2011; Bensby et al. 2014).”
CHEMICAL CARTOGRAPHY WITH APOGEE: METALLICITY DISTRIBUTION FUNCTIONS AND THE CHEMICAL STRUCTURE OF THE MILKY WAY DISK (2015, background): “…2003, 2011; Allende Prieto et al. 2006; Bovy et al. 2012c; Cheng et al. 2012a; Anders et al. 2014), although there do exist thick-disk stars with solar-[α/Fe] abundances and supersolar metallicities (Bensby et al. 2003, 2005, 2014; Adibekyan et al. 2011; Nidever et al. 2014; Snaith et al. 2014).”
PLATO as it is: a legacy mission for Galactic archaeology (2017, neutral): “…et al. 2013, 2014; Snaith et al. 2015), where current data suggest that the thick disk formation started at z ∼ 3.5 (12 Gyear ago) while the thin disk began to form at z ∼ 1.5 (8 Gyear ago) (e.g., Bensby et al. 2014; Bergemann et al. 2014; Fuhrmann 2011; Haywood et al. 2013; Robin et al. 2014).”
The structure and dynamical evolution of the stellar disc of a simulated Milky Way-mass galaxy (2016, background): “These two populations are attributed to the thick and thin disks (e.g. Adibekyan et al. 2013; Bensby et al. 2014; Anders et al. 2014; Nidever et al. 2014; Mikolaitis et al. 2014; Kordopatis et al. 2015).”
The GALAH survey: observational overview and Gaia DR1 companion (2016, background): “A clear chemical separation in the [α/Fe]− [Fe/H] abundance plane can be made between these two populations (see, e.g., Adibekyan et al. 2012; Bensby et al. 2014; Hayden et al. 2015).”
The PASTEL catalogue: 2016 version (2016, background): “Since 2010, eleven papers have published more than 250 (Teff , log g, [Fe/H]) determinations, and four papers present more than 500 stars (Bensby et al. 2014; Luck 2014; Ramírez et al. 2013; Sousa et al. 2011).”
APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South (2020, background): “Instead, we build upon many results reported in the literature that suggest that the mean [X/Fe] in solar neighborhood stars is close to solar at solar abundance (Reddy et al. 2003; Adibekyan et al. 2012; Bensby et al. 2014, among others).”
AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS (2015, methodology): “These results would then, by exclusion, be compatible with a dynamical origin (Bensby et al. 2014).”
The Gaia-ESO Survey : radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk (2014, background): “Bensby et al. (2014) also found a knee at 9 Gyr, with a clear increase in [Mg/Fe] with age (their Fig.”