The masses, structure, and lifetimes of cold clouds in a high-resolution simulation of a low-metallicity starburst

We present an analysis of the cold gas phase in a low-metallicity starburst generated in a high-resolution hydrodynamical simulation of a gas-rich dwarf galaxy merger as part of the griffin project. The simulations resolve (4 M-circle dot gas phase mass resolution, similar to 0.1 pc spatial resolution) the multiphase interstellar medium with a non-equilibrium chemical heating/cooling network at temperatures below 10(4) K. Massive stars are sampled individually and interact with the interstellar medium (ISM) through the formation of H ii regions and supernova explosions. In the extended starburst phase, the ISM is dominated by cold (T-gas < 300 K) filamentary clouds with self-similar internal structures. The clouds have masses of 10(2.6)-10(5.6) M-circle dot with a power-law mass function, dN/dM proportional to M-alpha with alpha = -1.78 (+/- 0.08). They also follow the Larson relations, in good agreement with observations. We trace the lifecycle of the cold clouds and find that they follow an exponential lifetime distribution and an e-folding time of similar to 3.5 Myr. Clouds with peak masses below 10(4)M(circle dot) follow a power-law relation with their average lifetime tau(life) proportional to M-max(0.3) which flattens out for higher cloud masses at < 10 Myr. A similar relation exists between cloud size at peak mass and lifetime. This simulation of the evolution of a realistic galactic cold cloud population supports the rapid formation and disruption of star-forming clouds by stellar radiation and supernovae on a time-scale less than 10 Myr.