Galactic Archaeology in the Bulge : in the era of Gaia & Large Spectroscopic Surveys

The lack of large samples of high-resolution spectra of individual stars tracing large areas around the Galactic Bulge and inner-most regions of the Galaxy has been a long-standing missing information piece. This has prevented so far a clearer picture of how the Bulge/bar was formed, its connection to the thin disk inside-out grow as well as to a pristine thick disk and halo. In this review I present a summary of where we stand in our understanding of the properties of the Bulge stellar populations, with focus on chemistry and ages, and on the still open issues. I briefly summarise the different theoretical approaches that have been used to describe the Bulge assembly history underlying how the lack of better constraints have still hampers the construction of a self-consistent picture for the Bulge assembly and evolution. I then show how in the Gaia era, the combination of photometric and spectroscopic surveys will be a game change in this field, with a particular focus on APOGEE and Gaia DR2. In addition, I discuss how could we attempt to provide more robust comparisons of the bulge stellar populations with other galactic components such as the inner-thin and thick disks as well as the halo. Once sub-populations are more robustly traced, we enter in a new phase where the abundance patterns of different chemical elements, for different galactic components, will be able not only to provide more stringent constraints to chemodynamical models, but also to much more efficiently help constraining stellar yields of the several nucleosynthetic channels. I close the review with a look into the future and discuss an opportunity not to be missed by the Galactic Archaeology community in the era of massive spectroscopic follow-up of Gaia, namely: to obtain a large number of red giant stars with seismic information using PLATO. This will provide the only direct age measurements (to the 10-20% precision level) of large samples of stars in the Bulge area, complementing what is now done for a few Bulge micro-lensed stars