Colloquium by Emily Cunningham and Nicholas Luber, Columbia
Testing Galaxy Formation Models with Large-scale Surveys of the Milky Way Stellar Halo
Emily Cunningham
While the vast majority of the light from our galaxy comes from the Galactic disk, the vast majority of the mass of the Milky Way (MW) is in its dark matter halo. Because we cannot directly observe the MW's dark matter halo, we must use luminous tracer populations (i.e., stars) to study the mass distribution indirectly. Fortunately, there are stars strewn throughout the MW's dark matter halo. We believe the MW built up its halo of dark matter over cosmic time by consuming smaller dwarf galaxies; the remnants of these dwarf galaxies make up the MW's stellar halo. Halo stars can therefore be used both to constrain the dark matter distribution of the MW as well as inform us about the dwarf galaxies in which they formed. I will present my ongoing theoretical and observational work using halo stars to map the dark matter distribution and disequilibrium in the MW, as well as study the faint, low-mass galaxies that were consumed by the MW during its formation. I will discuss the crucial roles of current and upcoming large-scale surveys of the MW halo (such as the Rubin Observatory Legacy Survey of Space and Time) for addressing fundamental questions in galaxy formation.
Tuning in: Using Deep Radio Observations to Study the Evolution of Neutral Hydrogen
Nicholas Luber
The evolution of neutral atomic hydrogen (HI) plays a fundamental role in regulating star formation and shaping galaxy properties over time. In this talk, I will present new insights into HI evolution using the COSMOS HI Large Extragalactic Survey (CHILES), which provides an unprecedented view of HI in galaxies out to redshift 0.47. I will begin by discussing challenges related to imaging and artifact mitigation, how we addressed these issues using the CHILES data, and how our techniques produce science-ready data products. Additionally, I will introduce the CHILES Continuum & Polarization (CHILES Con Pol) survey, a deep L-band radio continuum survey designed to complement the HI dataset. I will outline our novel imaging strategies and present the most sensitive 1.4 GHz image ever taken at this resolution. With these datasets, I will present measurements of HI gas fractions and star formation rates across different galaxy populations, revealing distinct evolutionary trends as a function of stellar mass. To further explore the role of environment in HI evolution, we compare CHILES data with the IllustrisTNG simulation, investigating the relationship between HI content, star formation, and a galaxy’s proximity to cosmic web filaments. Interestingly, CHILES observations challenge theoretical predictions, showing environmental trends that diverge from simulation expectations, particularly in void regions. Finally, I will discuss future prospects for understanding the evolution of neutral hydrogen and the role of the cosmic web in shaping galaxy gas reservoirs at higher redshifts.
Cookies will be available, starting at 3:45.
Host: Mary Putman