Séminaire IPAG

---

Molecular Cloud Evolution in Nearby Galaxies as First Step for Galaxy Evolution and Star Formation

jeudi 25 juin 2026 - 14h00

Jin Koda - Stony Brook U.
--- 
The structure and evolution of the ISM strongly affect galactic gas dynamics, star formation (SF), and galaxy evolution. Recent studies emphasize the very rapid formation and destruction of molecular clouds by stellar feedback (Schinnerer & Leroy 2024). However, this conflicts with the observed deficiency of HI gas expected from such destruction. I revisit the alternative view that molecular structures survive for long periods and evolve mainly through galactic dynamics. Using ALMA observations of M83 and 12 nearby galaxies from our Fundamental CO(1–0) Transition Survey (FACTS), I will show that molecular cloud properties evolve alongside large-scale galactic structures. Correlations between galactic environment, CO 2–1/1–0 line ratios, and cloud boundedness support this picture. While stellar feedback enhances CO 2–1/1–0 ratios, it is only in the immediate vicinity of HII regions. We also find no evidence for increased velocity dispersions around star-forming regions or supernova remnants, implying limited feedback-driven turbulence. These results suggest that molecular clouds are not rapidly destroyed by feedback, but instead persist, coagulating and fragmenting through galactic dynamical processes. This framework shifts the focus of SF theory toward identifying the mechanisms that trigger star formation within long-lived molecular clouds, rather than attributing SF simply to the gravitational collapse of diffuse gas.

---

Hôtes : Romana Grossova

IRAM, 300 rue de la piscine, 38400 Saint Martin d'Hères