Query : 2020A&A...643A..69K

2020A&A...643A..69K - Astronomy and Astrophysics, volume 643A, 69-69 (2020/11-1)

The chemodynamics of prograde and retrograde Milky Way stars.


Abstract (from CDS):

Context. The accretion history of the Milky Way is still unknown, despite the recent discovery of stellar systems that stand out in terms of their energy-angular momentum space, such as Gaia-Enceladus-Sausage. In particular, it is still unclear how these groups are linked and to what extent they are well-mixed.
Aims. We investigate the similarities and differences in the properties between the prograde and retrograde (counter-rotating) stars and set those results in context by using the properties of Gaia-Enceladus-Sausage, Thamnos/Sequoia, and other suggested accreted populations.
Methods. We used the stellar metallicities of the major large spectroscopic surveys (APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE, SEGUE) in combination with astrometric and photometric data from Gaia's second data-release. We investigated the presence of radial and vertical metallicity gradients as well as the possible correlations between the azimuthal velocity, vph, and metallicity, [M/H], as qualitative indicators of the presence of mixed populations.
Results. We find that a handful of super metal-rich stars exist on retrograde orbits at various distances from the Galactic center and the Galactic plane. We also find that the counter-rotating stars appear to be a well-mixed population, exhibiting radial and vertical metallicity gradients on the order of ~-0.04dex/kpc and -0.06dex/kpc, respectively, with little (if any) variation when different regions of the Galaxy are probed. The prograde stars show a vph-[M/H] relation that flattens - and, perhaps, even reverses as a function of distance from the plane. Retrograde samples selected to roughly probe Thamnos and Gaia-Enceladus-Sausage appear to be different populations yet they also appear to be quite linked, as they follow the same trend in terms of the eccentricity versus metallicity space.

Abstract Copyright: © G. Kordopatis et al. 2020

Journal keyword(s): Galaxy: abundances - Galaxy: formation - Galaxy: disk - Galaxy: kinematics and dynamics - Galaxy: stellar content - stars: abundances

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