Large-scale gravitational instability in the formation of GMCS

Two models of molecular cloud in disk galaxies are proposed to investigate the formation of giant molecular clouds (GMCs) under the gravitational instability and random collision using PP (Particle-Particle) simulation. Having analysed simulation outputs of the two models and comparing them with observation, we are able to draw some general conclusions, the most significant ones of which are: 1) Similar to results obtained previously, the gravitational instability can make small clouds form large clouds faster than random collision. 2) The differential rotation in gravitational instability model plays a positive role in agglomeration of molecular clouds.