TREASURES: Digging into dwarf galaxies

Introduction

The Milky Way is an environment rich with satellite galaxies, stellar streams, and accreted systems. Encoded in these structures is the formation and evolution of the Galaxy through cosmic time. Fortunately, these nearby relics can be studied in extraordinary detail – star by star – revealing the properties of the first stars, the build-up of chemical elements in the Universe, the nature of dark matter, and hierarchical galaxy formation.

Project Overview

To unlock these treasure troves of hidden information, I designed a large-scale survey: 4DWARFS (PI: Skúladóttir, 520,000 fibre hours) that after a very competitive 2-year selection has now been accepted as a 5-year 4MOST survey, starting in 2024. 4DWARFS will collect high-quality spectra of individual stars in close to 50 dwarf galaxies and dozens of stellar streams from systems currently undergoing disruption.

Goals of TREASURES

The goal of TREASURES is to execute and exploit this large 4DWARFS survey to its highest scientific potential. TREASURES will provide the community with:

1. Stellar ages
2. Radial velocities
3. Chemical abundances for over 130,000 stars

This will increase the number of stars with detailed abundance information in dwarf galaxies and streams by several orders of magnitude, ensuring the far-reaching impact of this project.

Methodology

Furthermore, TREASURES will use state-of-the-art models to contrast these new large data against theory and put them in context with the Milky Way. Through an ambitious combination of modelling and data of unprecedented magnitude and completeness, TREASURES will quantify and put fundamental constraints on:

• (I) The properties of the first stars (mass and energy distributions)
• (II) The origin of the chemical elements (physics of stars, supernovae, and neutron star mergers)
• (III) Hierarchical galaxy formation at the smallest mass scales, and structure of dark matter halos

Conclusion

TREASURES will thus paint a comprehensive picture of the formation and evolution of the Milky Way environment, from cosmic dawn until the present day.