Looking for the imprints of the first stars in the Universe

Our team has designed the largest and most efficient survey of the very metal-poor tail of the Milky Way stellar halo, Pristine. A total 6,000 deg2 has been imaged with MEGACAM in a new narrow band CaH&K filter at the Canada France Hawaii telescope (CFHT). As such, Pristine will produce the most unbiased pho- tometric metallicity distribution and substructure search of the metal-poor Galactic halo. At full completion, it will clearly change the observational landscape of near-field cosmology.

A companion survey, targeting the Milky Way dwarf satellites in the Northern Hemisphere, has been designed with a similar strategy. For the first time, one is able to reach the outskirts of these small systems, opening new venues such as the ability i) to derive accurate dynamical masses – this is essential to the quest of the nature of the dark matter –, and ii) to conduct robust comparisons with the Milky Way halo – a crucial step forward for our quest to understand galaxy formation.

Our goals will be successfully reached in full synergy of a large variety of expertises. This includes: low and high resolution spectroscopic follow-ups – with in particular the preparation of WEAVE –,precision photometry, derivation of chemical abundances, NLTE corrections, dynamical modeling. While the ESA Gaia mission’s data releases will each be an invaluable boon for Pristine, our team is also committed to provide calibrators to Gaia, in the extremely metal-poor regime.

Our team is composed of 12 internationally and highly recognized experts in the scientific components covered by Pristine: E. Caffau (Obs. Paris, FR), P. Côté (UVIC, CA), M. Fouesneau (MPIA, DE), J. I. Gonzallez Hernandez (IAC, ES), V. Hill (OCA, FR), R. Ibata (Obs. Strasbourg, FR), P. Jablonka (EPFL, CH), C. Lardo (EPFL, CH), N. Martin (Obs. Strasbourg, FR), L. Mashonkina (IoA, Moscow, RU), R. Sanchez- Janssen (ROE, UK), and E. Starkenburg (AIP, DE).