The Department of Astronomy 2025-2026 Colloquium Series Presents:

"Unraveling hierarchical galaxy formation: the potential of galaxy stellar halos beyond the Milky Way"

Stellar halos are amazingly rich records of their host galaxy’s history. During the hierarchical galaxy formation process smaller galaxies and star clusters are stripped apart in the outskirts of their larger hosts, leaving their stars as tracers of their origin. This tidal debris survives as stellar streams and substructures and is sensitive to the underlying gravitational potential, providing constraints on the nature of dark matter and the physics of low-mass galaxy formation. Upcoming large surveys such as those from the Vera C. Rubin Observatory, the Nancy Grace Roman Space Telescope, and Euclid will provide an unprecedented deep and wide view of this low-surface brightness discovery space, detecting stellar halo substructure for numerous galaxies in our nearby universe. Modeling of stellar halo structures has traditionally focused on our own Milky Way, with limited exploration of diverse galaxy formation histories. In this talk I will highlight how using a variety of modeling techniques can aid in understanding how physical processes in hierarchical galaxy formation link to observational signatures, facilitating interpretation of observations by the next generation of telescopes. Additionally, I will briefly discuss ongoing interdisciplinary work, among other things in AI models for strong lens modeling, at the Astro-AI Institute for the Sky—the SkAI Institute.