We know that high redshift disk galaxies are gas-rich and turbulent. But how did they transform into galaxies like the Milky Way ? Did the star formation start from the inner regions of a flat thin gas disk and work its way out, with the stellar disk gradually getting thicker as the disk heats up dynamically? Or is this the wrong narrative – recent studies suggest that it may be the other way around – the disk was born hot from a thick turbulent gas layer at high z and then became thinner with age as the gas disk settled for several billion years. How did the abundances of the chemical elements change as the Galaxy formed: why are the abundances now higher on average in the inner disk ? And where did the super-metal-rich stars near the sun come from: we believe they formed in the inner Galaxy and migrate outwards, but when did this all happen?
The Milky Way provides a unique opportunity to address these questions by studying in detail how a giant spiral galaxy is assembled and evolves. At this time, however, our understanding of Galactic formation and evolution is still severely hampered by the lack of precise and accurate determinations of stellar properties such as masses, radii, chemical compositions, and, most notably, ages. Accurate stellar ages are critical for all of these studies, so that we can observe directly what happened over a large region of the Galactic disc as the Galaxy assembled and evolved. Combining asteroseismic and spectroscopic constraints provides the way forward. Distances can now be measured and ages can be inferred for the solar-like pulsating red giants observed by the space-borne telescopes CoRoT, Kepler, and K2. These giants represent ideal tracers of the Galactic disc because they are bright enough to be observed at large distances and numerous enough to map and date the Galactic disc.
The proposed interdisciplinary team will develop, test, and apply methods to characterise the full crono-chemo- dynamical properties of giant stars in the Milky Way’s disc.This includes data analysis of spectra and of photometric light curves, the determination of relevant stellar properties using models of stellar evolution, and the comparison of observational constraints with chemo-dynamical models of the Milky Way. The interaction between researchers of complementary expertise (stellar evolution, asteroseismology, spectroscopy, Galaxy formation and evolution) will also foster synergies with the forthcoming Gaia data release, and devise a strategy for future endeavours in the field of galactic archaeology and asteroseismology.This will be key for defining the observing strategies of the NASATESS and the ESA PLATO missions and their massive spectroscopic follow-up with e.g. 4MOST, WEAVE, and APOGEE2.
The activities driven by the team will benefit and involve a larger community interested in asteroseismology of ensembles of stars: http://www.asterostep.eu