Promotionskolloquium
Zein Bazzi	SCHEDULED

AIfA, Bonn

Molecular clouds are the sites of star formation, which plays a fundamental role in the evolution of galaxies. Yet, despite their importance, their physical properties, formation timescales, and evolution remain incompletely understood. In particular, our understanding of low-mass molecular clouds in nearby galaxies remains limited by the sensitivity of traditional CO observations, which primarily trace the brighter and more massive cloud populations. Furthermore, how molecular clouds are affected by their galactic environments and how stellar feedback influences their evolution are still open questions. In this talk, I present a combined observational and theoretical investigation of molecular cloud populations, using high-resolution observations from JWST, ALMA, and VLT-MUSE, together with semi-analytical modeling and numerical simulations. First, I present the largest molecular cloud catalog constructed to date, identifying more than 100,000 clouds across 66 nearby galaxies using PHANGS-JWST observations, extending the observed molecular cloud population down to masses of ∼ 10³ M⊙. The analysis reveals substantial variations in cloud properties both within and between galaxies, highlighting the influence of galactic environment on cloud structure and mass distributions. Second, I investigate the formation and evolution of these clouds using a semi-analytical growth model. The results suggest that cloud formation timescales depend strongly on cloud mass and local galactic conditions, with more massive clouds requiring longer to assemble and cloud growth proceeding more rapidly in regions of enhanced gas density and star formation activity. Finally, I complement these observational findings with numerical simulations of a low-metallicity dwarf galaxy, tracing the evolution of molecular cloud populations over time. The simulations reveal a highly dynamic interstellar medium in which stellar feedback can both disperse molecular gas and compress surrounding material, promoting the formation of new dense structures. Together, these results support a picture in which molecular clouds are dynamic structures whose properties and evolution are governed by the interplay between self-gravity, stellar feedback, and their galactic environment. Understanding these interactions is essential for establishing a more complete physical picture of the molecular cloud lifecycle and the regulation of star formation across galaxies.