The overlap between the spectroscopic Galactic Archaeology with HERMES ( GALAH ) survey and Gaia provides 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 the Gaia DR1 Tycho- Gaia Astrometric 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 Spectroscopy Made Easy .
We determine kinematics and dynamics , including action angles , from the Gaia astrometry 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 employ 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 \log g .
Focusing our investigation on the correlations between stellar age , iron abundance [ Fe/H ] , and mean alpha-enhancement [ \upalpha /Fe ] of the magnitude-selected sample , we recover the result that stars of the high- \alpha sequence are typically older than stars in the low- \upalpha sequence , the latter spanning iron abundances of -0.7 < \mathrm { [ Fe / H ] } < +0.5 .
While these two sequences become indistinguishable in [ \upalpha /Fe ] vs. [ Fe/H ] at the metal-rich regime , we find that age can be used to separate stars from the extended high- \upalpha and the low- \upalpha sequence even in this regime .
When dissecting the sample by stellar age , we find that the old stars ( > 8 \mathrm { Gyr } ) have lower angular momenta L _ { z } than the Sun , which implies that they are on eccentric orbits and originate from the inner disk .
Contrary to some previous smaller scale studies we find a continuous evolution in the high- \upalpha -sequence up to super-solar [ Fe/H ] rather than a gap , which has been interpreted as a separate ” high- \upalpha metal-rich ” population .
Stars in our sample that are younger than 10 \mathrm { Gyr } , are mainly found on the low \upalpha -sequence and show a gradient in L _ { z } from low [ Fe/H ] ( L _ { z } > L _ { z, \odot } ) towards higher [ Fe/H ] ( L _ { z } < L _ { z, \odot } ) , which implies that the stars at the ends of this sequence are likely not originating from the close solar vicinity .