February 4
Tracing Molecular Hydrogen from the Solar Neighborhood to Cosmic Dawn
Speaker: Prof. Blakesley Burkhart, Rutgers University
Abstract: Far-ultraviolet (FUV) fluorescent emission from molecular hydrogen (H₂) is a powerful tracer of the dynamic boundary layers where the interstellar medium transitions from atomic to star-forming molecular gas. In this talk, I will highlight how this diagnostic of molecular clouds enables us to trace the lifecycle of molecular gas—from the closest interstellar clouds to the most distant galaxies observed by JWST. Close to home, we have uncovered Eos, the nearest and largest molecular cloud on the sky at just 94 parsecs, the first molecular complex identified directly in H₂ FUV fluorescence. Eos provides an unprecedented laboratory to study an ultra-close hot/cold interface region, multiphase molecular gas at the interface of extreme stellar feedback, and motivates future space missions in the FUV. At the opposite end of the distance ladder, I will present a theoretical framework for interpreting H₂ FUV fluorescence in the distant Universe, applied to stacked JWST/NIRSpec spectra of galaxies at z ≥ 7. These data show tantalizing evidence for H₂ emission in galaxies during cosmic dawn. Together, these results demonstrate how FUV fluorescent H₂ provides a powerful window on the life cycle of molecular gas—from the edge of our Local Bubble to cosmic dawn.
Host: Dr. Benedikt Diemer