文章基本信息

标题：The GALAH survey: An abundance, age, and kinematic inventory of the solar neighbourhood made with TGAS ⋆
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作者：S. Buder ; K. Lind ; M. K. Ness 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：624
DOI：10.1051/0004-6361/201833218
语种：English
出版社：EDP Sciences
摘要：The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey andGaiaprovides a high-dimensional chemodynamical space of unprecedented size. We present a first analysis of a subset of this overlap, of 7066 dwarf, turn-off, and sub-giant stars. These stars have spectra from the GALAH survey and high parallax precision from theGaiaDR1 Tycho-GaiaAstrometric Solution. We investigate correlations between chemical compositions, ages, and kinematics for this sample. Stellar parameters and elemental abundances are derived from the GALAH spectra with the spectral synthesis code SPECTROSCOPYMADEEASY. We determine kinematics and dynamics, including action angles, from theGaiaastrometry and GALAH radial velocities. Stellar masses and ages are determined with Bayesian isochrone matching, using our derived stellar parameters and absolute magnitudes. We report measurements of Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, as well as Ba and we note that we have employed non-LTE calculations for Li, O, Al, and Fe. We show that the use of astrometric and photometric data improves the accuracy of the derived spectroscopic parameters, especially logg. Focusing our investigation on the correlations between stellar age, iron abundance [Fe/H], and mean alpha-enhancement [α/Fe] of the magnitude-selected sample, we recover the result that stars of the high-αsequence are typically older than stars in the low-αsequence, the latter spanning iron abundances of −0.7 < [Fe/H] < +0.5. While these two sequences become indistinguishable in [α/Fe] vs. [Fe/H] at the metal-rich regime, we find that age can be used to separate stars from the extended high-αand the low-αsequence even in this regime. When dissecting the sample by stellar age, we find that the old stars (>8 Gyr) have lower angular momentaLzthan the Sun, which implies that they are on eccentric orbits and originate from the inner disc. Contrary to some previous smaller scale studies we find a continuous evolution in the high-α-sequence up to super-solar [Fe/H] rather than a gap, which has been interpreted as a separate “high-αmetal-rich” population. Stars in our sample that are younger than 10 Gyr, are mainly found on the lowα-sequence and show a gradient inLzfrom low [Fe/H] (Lz > Lz, ⊙) towards higher [Fe/H] (Lz < Lz, ⊙), which implies that the stars at the ends of this sequence are likely not originating from the close solar vicinity.
关键词：ensurveyssolar neighborhoodGalaxy: evolutionstars: fundamental parametersstars: abundancesstars: kinematics and dynamics