The Local Group is a unique laboratory for near-field cosmology : the motions of its galaxies, satellites, and stellar streams record how galaxies form and evolve, and trace the underlying distribution of dark matter. The Gaia mission has revolutionized Local Group astrophysics by providing first-ever positions, parallaxes, and proper motions (PMs) for more than one billion stars. However, Gaia uncertainties become prohibitively large for faint stars (G ≳ 20 mag), restricting our view of the local universe at large distances and small angular scales. To overcome these limits, we must harness the strengths of multiple observatories simultaneously. In this talk, I will present work combining Hubble, James Webb, and ground-based imaging with Gaia data to measure PMs up to 50 times more precise than Gaia alone, and to extend high-quality PMs to stars hundreds of times fainter than Gaia’s limit. In a single deep, multi-epoch HST field of a nearby dwarf galaxy, our approach increases the number of stars with precise PMs from roughly 500 to 100,000. These PMs for faint stars let us resolve kinematic structure in distant systems and with high spatial resolution, connecting the motions of individual stars to the assembly histories and dark matter content of the systems they trace. I will highlight ongoing applications, including bulk motions of galaxies in and around the Local Group, internal kinematics of dwarf galaxies, and the detection and characterization of stellar streams. Finally, I will discuss how these combined-telescope techniques will complement Gaia DR4 and beyond, as well as next-generation surveys from Rubin, Euclid, and Roman.
Combining Telescopes to Push the Faint Frontier of Local Group Proper Motions
Lundi 9 novembre 2026
de
14:00 à
15:00
Room 108, Les Communs
