| Number | R8-5/ IPMU/ILANCE/ICRR joint seminar |
| Date&time | Mon. September 7, 2026, 15:00 – |
| Place | ICRR 6F Large seminar room Zoom:https://u-tokyo-ac-jp.zoom.us/j/83892452225?pwd=gZJEGUinBMjfJ1GN2OQyMaLSWvSJHq.1 |
| Speaker | Bing Liu (Purple Mountain Observatory, Chinese Academy of Sciences) |
| Title | “MeV Nuclear De-excitation Lines from Low-Energy Cosmic Rays” |
| Abstract | Low-energy cosmic rays (LECRs) play a crucial role in the energy balance, ionization, and chemistry of the interstellar medium, thereby influencing star formation. Although direct measurements of LECRs remain challenging, next-generation MeV telescopes may enable indirect probes through nuclear de-excitation lines produced by LECR interactions with ambient gas. I will present the results on the production of MeV de‑excitation lines from various LECR sources, based on numerical nuclear reaction simulations performed with the code TALYS. Estimates are made of the expected line emission from both a point‑like CR source and passive molecular clouds, and the detectability of these lines from young supernova remnants such as Cas A is assessed. The high ionization rate in the Central Molecular Zone (CMZ) of the Galactic Center, often attributed to LECRs, is also examined. It is found that only an extremely soft CR component can account for this rate, and future MeV observations are shown to be capable of distinguishing its origin. Overall, these results demonstrate that MeV nuclear de‑excitation lines provide a powerful diagnostic for the injection, propagation, and feedback of LECRs, especially when improved instrumental capabilities become available. |
