The signatures of the formation and evolution of a galaxy are imprinted in its stars. Their velocities, ages, and chemical compositions present major constraints on models of galaxy formation, and on various processes such as the gas inflows and outflows, the accretion of cold gas, radial migration, and the variability of star formation activity. Understanding the evolution of the Milky Way requires large observational datasets of stars via which these quantities can be determined accurately.
This is the science driver of the 4MOST MIlky way Disc And BuLgE High-Resolution (4MIDABLE-HR) survey: to obtain high-resolution spectra at R=20 000 and to provide detailed elemental abundances for large samples of stars in the Galactic disc and bulge.
These data will allow us to obtain precise spectroscopic diagnostics of more than three million stars: precise radial velocities; rotation; abundances of many elements, including those that are currently only accessible in the optical, such as Li, s-, and r-process; and multi-epoch spectra for a sub-sample of stars. Synergies with complementary missions like Gaia and TESS will provide masses, stellar ages and multiplicity, forming a multi-dimensional dataset that will allow us to explore and constrain the origin, chemical evolution, and structure of the Milky Way.
The goal of the 4MIDABLE-HR survey is to explore and constrain the evolution and chemical enrichment of the Milky Way galaxy via studies of:
Galactic discs: radial migration, mergers, response to perturbations, structure of the inner vs outer, primordial disc?
Bulge: formation, growth, classical or pseudo-bulge?
Galactic chemical evolution (all nucleosynthesis channels) and history of chemical elements
Our understanding of GCE progressively shifts with the availability of new of data: different types of sub-Ch SN Ia, WD-WD violent mergers, head-on collisions, PISN, massive binaries...
Stellar chemical composition provides a baseline against which stellar explosion models and their nuclear yields are compared to in order to test their role in Galactic chemical evolution.
Were mergers of neutron stars and Black holes seeds of all heavy chemical elements?
Fig. adapted from Lian et al. 2023
Survey science overview and motivation
Bergemann, Bensby et al. and the team
Survey strategy, catalogues, and selection
Gerber et al. and the team
...