From short-lived to long-lived clouds: Impact of star formation models on giant molecular cloud evolution in simulations of an NGC 300-like galaxy

Multiwavelength observations of molecular and ionized gas indicate that giant molecular clouds (GMCs) are short-lived and generally disperse within one or two dynamical timescales. To investigate the physical origin of these short lifetimes and the role of star formation prescriptions, we conducted radiation-hydrodynamic simulations of an NGC 300-like disk galaxy with ̊amsesrt. We compared two distinct star formation models, one based on a local gravo-thermo-turbulent (GTT) condition and the other employing sink particles, to examine how star formation and feedback collectively regulate GMC evolution. The sink-particle-based model yields bursty yet self-regulated global star formation rates of 0.1--0.5, and produces GMC lifetimes of sim20--30, with star formation efficiencies (SFEs) per free-fall time (ε_ of a few percent, consistent with observations. In contrast, our GTT model based on unresolved turbulence generates a population of long-lived clouds with lifetimes gtrsim200, owing to the extremely low ε_ (łesssim3 ), which renders stellar feedback ineffective. With both models, cloud-cloud mergers extend the lifetimes of GMCs and increase their integrated SFEs by lengthening the star-forming duty cycle, while having only a minor impact on instantaneous efficiencies. On galactic scales, both models broadly reproduce the observed Kennicutt-Schmidt relation within its scatter, and yield gas depletion times of a few gigayears. In comparison, an extreme feedback model with the supernova energy boosted by a factor of five, combined with the GTT star formation model, excessively suppresses star formation and produces much longer depletion times (6--20, ff,cl -3 for this isolated system. These results demonstrate that GMC lifecycles are strongly governed by the adopted star formation model, which highlights the need for improved prescriptions that realistically capture clump-scale star formation.