This IAU Symposium is very much inspired by IAU Symposium 254, which has been very influential in the field. While there are many symposia organized each year on several sub-topics, we instead aim for one that keeps the big picture in mind: our developing understanding of the Milky Way as a galaxy.
In the last decade we have stepped out of the volume surveyed by the Hipparcos mission, reaching far-out regions of the Milky Way with spectroscopic surveys such as RAVE, SEGUE, APOGEE, LAMOST, GALAH and Gaia-ESO. In particular, with the near-infrared APOGEE spectrograph, and the photometric ESO-VVV survey, we were able to penetrate the dust that obscures significant fractions of the disk and bulge of our Galaxy, seriously complementing our view of the Milky Way. The discovery potential increases further when combining the above information with large time-domain photometric surveys such as OGLE, CRTS, Pan-STARRs, SkyMapper and the future LSST. Two illustrative examples are the discovery of a large number of RR Lyrae by OGLE/CRTS and very metal-poor candidates, now also in the Bulge, with SkyMapper. Spectroscopic follow-up of these precious fossil records is already ongoing in several of the 8m-class telescopes, and in two years from now breakthroughs are to be expected.
A further step on measuring accurate ages for stars out of the Hipparcos volume has been made with the use of asteroseismology (from CoRoT and Kepler), combined with the above spectroscopic surveys. This combination also enables drastic improvements in the attainable precision in the masses, radii and ages of giant stars that are as far as ~5 kpc away from us. Further breakthroughs are expected with the K2 mission in the next couple of years (after Kepler’s loss of a second spacecraft reaction wheel in May 2013 the original Kepler mission was formally ended, and the K2 mission started with observed fields, now located along the ecliptic plane, hence beautifully complementing CoRoT). Several key K2 fields will be completed already one year before the proposed Symposium takes place, in particular with seismic data for stars near the Galactic Center – for the first time in the history of Galactic Archaeology.
Finally, yet another big step forward will be taken thanks to the first and second Gaia data releases which take place in the summers of 2016 and 2017 (see www.cosmos.esa.int/web/gaia/release for details on the Gaia data release scenario). The first release will consist of only positions and magnitudes, but will also provide a major improvement in the proper motion and parallax uncertainties over the Hipparcos and Tycho-2 volumes. The second data release will contain Gaia parallaxes and proper motions, complemented by broad-band colours and radial velocities for the brighter stars. The time between the first and third Gaia data releases consists also of a sweet spot for RAVE, which overlaps with Tycho-2 and Gaia for around 300.000 stars, providing key complementary information, in particular chemistry for several individual elements, which will not yet be available from Gaia at the proposed time of this symposium. This will hence be our first example (in a smaller volume) of what we will have in our hands at the end of the Gaia mission, and will already certainly lead to breakthroughs in our knowledge of the Milky Way. In this golden era for Galactic Archaeology we are thus about to rediscover our Galaxy.
In summary, the field of Galactic Archaeology is quickly transforming. Many of the advances described above are going to take shape in the next 1-2 years. In this sense, the IAU symposium proposed here is timely. Having this Symposium in 2017 is very important because at that time we will have learned lessons from Gaia, APOGEE-2, GALAH and LAMOST, while there will still be enough time to fine-tune the observational strategies of the major Gaia follow-up spectroscopic surveys WEAVE and 4MOST.
For a more detailed list of topics, click here.