FORMATION AND EVOLUTION OF THE DISK SYSTEM OF THE MILKY WAY: [α/Fe] RATIOS AND KINEMATICS OF THE SEGUE G-DWARF SAMPLE

By Y. S. Lee, Timothy C. Beers, D. An, Željko Ivezic´, Andreas Just, C. Rockosi, H. Morrison, Jennifer A. Johnson, R. Schönrich, J. Bird and 3 more. 2011

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We employ measurements of the [α/Fe] ratio derived from low-resolution (R ∼ 2000) spectra of 17,277 G-type dwarfs from the SEGUE survey to separate them into likely thin- and thick-disk subsamples. Both subsamples exhibit strong gradients of orbital rotational velocity with metallicity, of opposite signs, −20 to −30 km s−1 dex−1 for the thin-disk and +40 to +50 km s−1 dex−1 for the thick-disk population. The rotational velocity is uncorrelated with Galactocentric distance for the thin-disk subsample and exhibits a small trend for the thick-disk subsample. The rotational velocity decreases with distance from the plane for both disk components, with similar slopes (−9.0 ± 1.0 km s−1 kpc−1). Thick-disk stars exhibit a strong trend of orbital eccentricity with metallicity (about −0.2 dex−1), while the eccentricity does not change with metallicity for the thin-disk subsample. The eccentricity is almost independent of Galactocentric radius for the thin-disk population, while a marginal gradient of the eccentricity with radius exists for the thick-disk population. Both subsamples possess similar positive gradients of eccentricity with distance from the Galactic plane. The shapes of the eccentricity distributions for the thin- and thick-disk populations are independent of distance from the plane, and include no significant numbers of stars with eccentricity above 0.6. Among several contemporary models of disk evolution that we consider, radial migration appears to have played an important role in the evolution of the thin-disk population, but possibly less so for the thick disk, relative to the gas-rich merger or disk heating scenarios. We emphasize that more physically realistic models and simulations need to be constructed in order to carry out the detailed quantitative comparisons that our new data enable.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/a34ee64916fd87d8c59d1da67722987d8637cbeb

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Citations in the corpus

CHEMICAL CARTOGRAPHY WITH APOGEE: LARGE-SCALE MEAN METALLICITY MAPS OF THE MILKY WAY DISK (2013, methodology): “The structure of the disk is also reflected in detailed abundances, with stars at greater distances from the plane typically having higher [α/Fe] ratios than stars closer to the plane (e.g., Lee et al. 2011; Bovy et al. 2012c; Schlesinger et al. 2012).”
Radial migration in disc galaxies — I. Transient spiral structure and dynamics (2011, methodology): “…has been important for the Milky Way, it most likely played a key role in determining the mix of stars in the solar neighborhood today (Sellwood & Binney 2002; Roškar et al. 2008b,a; Schönrich & Binney 2009a,b; Loebman et al. 2011; Minchev & Famaey 2010; Bird et al. 2012; Lee et al. 2011).”
THE SPATIAL STRUCTURE OF MONO-ABUNDANCE SUB-POPULATIONS OF THE MILKY WAY DISK (2011, methodology): “Note that our signal-to-noise-ratio cut of SN > 15 is more inclusive than recommended by Lee et al. (2011a) (who recommend SN > 20), but this does not increase the uncertainties in [α/Fe] by much.”
TRACING CHEMICAL EVOLUTION OVER THE EXTENT OF THE MILKY WAY'S DISK WITH APOGEE RED CLUMP STARS (2014, background): “G A ] 1 1 Se p 20 disk, because of the large velocity dispersion of its stars (Fuhrmann 1998; Prochaska et al. 2000; Bensby et al. 2005; Reddy et al. 2006; Ramı́rez et al. 2007; Lee et al. 2011).”
OXYGEN ABUNDANCES IN NEARBY FGK STARS AND THE GALACTIC CHEMICAL EVOLUTION OF THE LOCAL DISK AND HALO (2013, background): “…(e.g., Fuhrmann 1998; Bensby et al. 2005; Reddy et al. 2006; Ramı́rez et al. 2007), as well as the analysis of stars in low to medium spectral resolution surveys of much larger volumes such as the Radial Velocity Experiment (RAVE, e.g., Veltz et al. 2008) and SEGUE/SDSS (e.g., Lee et al. 2011).”
Chemodynamics of the Milky Way - I. The first year of APOGEE data (2013, methodology): “Here, we will briefly explore this approach, and divide the chemical plane in a similar way to Lee et al. (2011) and Adibekyan et al. (2011), as illustrated in Fig.”
THE MILKY WAY HAS NO DISTINCT THICK DISK (2011, methodology): “This approach has been re-advocated in recent studies (Navarro et al. 2011; Lee et al. 2011), drawing on the seemingly bi-modal distribution of stars in the [α/Fe] - [Fe/H] plane of elemental abundances; however, these studies did not account for selection effects and volume corrections.”
INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS (2013, background): “However, bimodal distributions in vertical star counts (e.g., Gilmore & Reid 1983), kinematics (e.g., Bensby et al. 2003), and chemistry (e.g., Lee et al. 2011) in the solar neighborhood suggest a distinct thick disk.”
THE EFFECT OF RADIAL MIGRATION ON GALACTIC DISKS (2014, background): “…thick disk by their α enhancement (see, e.g., Navarro et al. 2011) show a gradient in the Vφ versus [Fe/H] relation of opposite sign (see, e.g., Lee et al. 2011; Kordopatis et al. 2013; RecioBlanco et al. 2014), a result that is difficult to reconcile in our models assuming a…”
LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) — The survey's science plan (2012, background): “Observational evidence of radial migration has been reported by Yu et al. (2012), Lee et al. (2011), Loebman et al. (2011), Liu & Van de Ven (2012) etc.”
THE VERTICAL METALLICITY GRADIENT OF THE MILKY WAY DISK: TRANSITIONS IN [α/Fe] POPULATIONS (2014, methodology): “This value is larger than that obtained when using the Lee et al. (2011b) criteria.”
Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program - Galactic stellar populations and planets (2012, background): “…metal-poor and α-enhanced (Fuhrmann 1998; Prochaska et al. 2000; Feltzing et al. 2003; Mishenina et al. 2004; Reddy et al. 2006; Haywood 2008b, Lee et al. 2011) stars that move in Galactic orbits with a large-scale height and long-scale length (Robin et al. 1996; Buser et al. 2001; Jurić et…”
Extragalactic science, cosmology, and Galactic archaeology with the Subaru Prime Focus Spectrograph (2012, background): “Furthermore, the [α/Fe] ratios are excellent discriminators of the thick disk from the thin disk, with which one can set important limits on the formation scenario of the thick disk by investigating its rotational and orbital properties as a function of [Fe/H] (Lee et al. 2011).”
THE METALLICITY DISTRIBUTION FUNCTIONS OF SEGUE G AND K DWARFS: CONSTRAINTS FOR DISK CHEMICAL EVOLUTION AND FORMATION (2011, methodology): “For the overlap region for the G and K dwarfs, i.e., between 1.59 and 1.84 kpc, both spectral types peak at around [Fe/H] of −0.5, consistent with the peak metallicity for the α-enhanced sample identified by Lee et al. (2011b).”
Impacts of a flaring star-forming disc and stellar radial mixing on the vertical metallicity gradient (2016, background): “Therefore, these studies suggest that we should define thick and thin disc stars depending on their chemical properties (e.g. Lee et al. 2011; Navarro et al. 2011), although it requires high-quality high-resolution spectroscopic survey which is observationally quite expensive.”
Constraining the Galaxy's dark halo with RAVE stars (2014, background): “16 from several populations within the sample of G dwarfs studied by Lee et al. (2011) as part of SEGUE.”
The Gaia-ESO Survey : radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk (2014, methodology): “…distribution function and abundance gradients of the disk using data from recent large-scale spectroscopic surveys, such as SEGUE/SDSS (e.g. Lee et al. 2011; Bovy et al. 2012b,c; Schlesinger et al. 2012; Cheng et al. 2012), RAVE (e.g. Boeche et al. 2013), and APOGEE (e.g. Anders et al.…”
The age structure of stellar populations in the solar vicinity Clues of a two-phase formation history of the Milky Way disk (2013, result): “The existence of a double gradient in the V−[Fe/H] relation for thick disk stars may reconcile the apparent contradictory results, as those by Lee et al. (2011) and Loebman et al. (2011).”
The biggest splash (2019, background): “Starting from the highest values of vφ and going down, a bifurcated chevron-like >-sign feature is discernible, corresponding to the ‘thin’ (upper portion of >) and the ‘thick’ (lower portion of >) discs (see also Lee et al. 2011).”