Pahl, Anthony

NSF Awards · FY 2026 · 2026-08

Anthony Pahl is awarded an NSF Astronomy and Astrophysics Fellowship to carry out a program of research and education at Carnegie Science Observatories. The space between galaxies is not completely empty. Rather, it is filled with very low-density atoms, mostly Hydrogen and Helium. In the early phases of the Universe, this intergalactic medium (IGM) is thought to be opaque and neutral, until ionized by the UV light from the first stars. Pahl will develop computer models to study this phase. They will help to determine the precise timing of this phase of cosmic history. The project will also expand Carnegie’s undergraduate internship curriculum to include modules on software development and machine learning. Two key unknowns in current reionization models are the ionizing photon production efficiency and the escape fraction. While next-generation space telescopes have probed the former into the early Universe, systematic discrepancies between measurements of galaxies at fixed redshift and UV brightness still exist. Pahl will develop an updated model of ionizing radiation transmission through the high-redshift IGM through novel integration with hydrodynamical simulations. Pahl will build an end-to-end predictive framework, including analytical and machine-learning-based models. This will improving significantly the accuracy of constraints on the escape fraction at cosmic noon. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.