Encoded in the atomic ISM is physics crucial to the baryonic cycle, including the formation of molecular clouds and the origin of interstellar turbulence from stellar feedback. Nearby galaxies provide an important top-down view on how these processes act over a wide range of ISM environments, however, existing extragalactic observations of the 21-cm HI line have limited resolution---both spatial and spectral---that provides a coarse view of the intricate atomic gas structure that has long been studied within the Milky Way. To bridge our Galactic and extragalactic views of the atomic ISM, I present the initial results from a new 21-cm HI VLA survey of M31 and M33 on 80 pc scales. These new observations combine high sensitivity with a fine spectral resolution to reveal ubiquitous HI spectral complexity, and our initial results demonstrate how modelling this complexity unveils new relations between the neutral ISM phases while challenging results from archival observations. In this talk, I will present two of our key findings: (i) HI spectra are comprised of multiple components along most lines-of-sight, and (ii) linking these HI components with molecular gas tracers reveals a strong correlation between the molecular and atomic ISM phases through the star formation process. These results from our continuing HI survey provide crucial insights into the role of the atomic gas in the baryonic cycle and serve as a galaxy-scale perspective for Milky Way ISM studies.
BIO
Eric Koch is a Submillimeter Array (SMA) Postdoctoral Fellow at the Harvard & Smithsonian Center for Astrophysics. His research focusses on linking the interstellar medium and star formation from the scales where individual stars form to whole galaxies. To do this, his work combines novel analysis techniques with observations from radio and sub-millimeter interferometers to trace the atomic and molecular gas in nearby galaxies. He also develops and maintains tools for the radio astronomy community (spectral-cube; FilFinder; TurbuStat).
Host: Zhuo Chen
