Collaborative Research: Resolving Physical Conditions of Diffuse Ionized Gas throughout the Milky Way-Magellanic System

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Clouds of gas, where stars are born, show us the spectacular impact of stars on their immediate surroundings. The stars’ ultraviolet light strips electrons from atoms, ionizing them. These free electrons eventually combine again with atoms and emit telltale colors. Over the last few decades, the Wisconsin H-Alpha Mapper (WHAM) discovered that the entire sky is glowing faintly in red light emitted by ionized hydrogen atoms that pervade the Milky Way. The WHAM group has been exploring this "diffuse ionized gas" throughout the Milky Way and its neighboring satellite galaxies, the Magellanic Clouds. WHAM can reveal emission nearly a 100-million times fainter than the Orion Nebula. WHAM remains one of the most sensitive instruments in the world for studying faint, diffuse light in our sky. The Team is developing a new exhibit and educational activities that will help show how scientists use spectroscopy to identify elements and explore the properties of distant objects. The exhibit will engage the public and student groups with the same Fabry-Perot technology used by WHAM. The investigators will continue to provide excellent opportunities for undergraduate and graduate students.During previous NSF-funded studies, WHAM investigators produced the first surveys that traced diffuse ionized gas in the Milky Way and the Magellanic Clouds. These efforts complement radio surveys of hydrogen that trace its cooler, neutral phase. Neutral and ionized hydrogen emission are now detected in every direction from our location inside the Galaxy. With this award, the investigators use WHAM to embark on a diverse observational program. Capturing emission from other elements, they are tracing the temperature and degree of ionization throughout the diffuse gas. This new study advances our understanding of interstellar matter, the processes that shape it, and how stars affect our Galaxy.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.