Séminaire IPAG

---

Gas-phase chemistry to trace radiative feedback of massive stars on star and planet formation

jeudi 12 novembre 2026 - 11h00

Marion Zannese - IFF Madrid
--- 
Most forming planetary systems, including the early Solar System are located in environments irradiated by massive stars. Study photodissociation regions (PDRs) exposed to this intense UV field is therefore essential to characterize stellar and planetary formation under these conditions. To probe the impact of UV field from the warm surface of the cloud (or protoplanetary disk) to the denser shielded gas, multi-wavelength studies are crucial. In this context, the Orion Bar, a prototypical PDR, acts as an interesting interstellar laboratory. In this seminar, I will focus on how gas-phase tracers can be used as to derive strong constraints on physical and chemical conditions of irradiated regions. I will present an overview of the main results obtained with the spectro-imaging data, acquired with the James Webb Space Telescope (JWST) (PDRs4All program) as well as with ALMA, of the Orion Bar and the protoplanetary disks observed in the region. I will show how H2 is a unique tracer of gas temperature and how hydrides (e.g., CH+ , OH) excited by UV-induced processes, and HCN are robust diagnostics of gas density. Finally, I will show how the high spectral resolution of ALMA is critical to study the influence of UV radiation on the gas dynamics of interstellar clouds.

---

Salle Manuel Forestini, 414 rue de la piscine, 38400 Saint Martin d'Hères