STAR FORMATION IN DISK GALAXIES. I. FORMATION AND EVOLUTION OF GIANT MOLECULAR CLOUDS VIA GRAVITATIONAL INSTABILITY AND CLOUD COLLISIONS

摘要: We investigate the formation and evolution of giant molecular clouds (GMCs) in a Milky-Way-like disk galaxy with flat rotation curve. perform series three-dimensional adaptive mesh refinement numerical simulations that follow both global on scales ~20 kpc resolve down to 10 pc multiphase atomic interstellar medium. In this first study, we omit star feedback, focus processes gravitational instability cloud collisions interactions. define as regions n H ≥ 100 cm-3 track individual they orbit through from their birth eventual destruction via merger or destructive collision another cloud. After ~140 Myr large fraction gas has fragmented into masses ~106 M ☉ mass spectrum similar Galactic GMCs. The settles quasi-steady-state which scattering keeps near threshold instability. time is found be small fraction, ~1/5, orbital time, an efficient mechanism inject turbulence clouds. This helps keep only moderately gravitationally bound, virial parameters order unity. Many other observed GMC properties, such surface density, angular momentum, velocity dispersion, vertical distribution, can accounted for simple model no stellar feedback.