On Monday, June 16, 2025, at 12:00 c.t., the next date of our physics colloquium will take place.
Dr. Brandt Gaches heads the Emmy Noether Group Cosmic ray astrochemistry - from atomic to astrophysical scales at the University of Duisburg-Essen. In the colloquium he will give a lecture on "Cosmic Rays and the Molecular Universe".
In the local universe, star and planet formation occur ubiquitously in cold, dense molecular gas, with gas temperatures dropping to 10 - 30 Kelvin, and densities exceeding 100 particles/cc. Due to the cold temperatures, the gas-phase molecular chemistry is driven by ion-neutral reactions. In the dense gas, shielded from ultraviolet radiation, energetic, charged particles, dubbed cosmic rays, are the dominant source of ionization. Cosmic-ray ionizations drive a diverse gas-phase chemistry and their interactions with icy dust grans stimulate complex organic and prebiotic chemistry in their ice. The cosmic-ray ionization rate, a statistical quantization of the average number of ionizations per second, is thus a fundamental parameter in astrochemical models. Despite their importance, cosmic rays are often treated simply, with models assuming a constant rate, although energy losses via interactions produce strong gradients. New observations also show that particles are accelerated within clouds during star formation. I will present an overview of cosmic-ray-driven astrochemistry from the point of view of theory and modeling.
I will highlight key results on identifying potentialnparticle acceleration sources in star-forming regions, and their role in gas-phase chemistry. I will show three-dimensional chemical models of molecular clouds that include cosmic-ray attenuation, enabling unique studies in cosmic-ray astrochemistry. I will also introduce a new large, public database of electron-impact ionization cross-sections for molecules of astrochemical interest. Finally, I will showcase future plans for my Emmy Noether group to investigate the role of cosmic rays on the gas- and ice-phase chemistry of star-forming gas from the atomic to astrophysical scales.
Abstract of the presentation by Dr. Gaches
Prof. Dr. Julia Tjus will give an introduction to the lecture.
The faculty cordially invites all interested parties. The event will take place in lecture hall NB 3/99.
All dates of the Physics Colloquium can be found here.
Picture: © Gaches