Bottom-Up Model For The Formation Of Gmc's

A bottom-up model for the formation of GMCs is described, where the observed GMCs are the aggregates of less massive clouds. The aggregates are getting more and more massive in the process of consecutive collision between clouds. Key Words : aggregation formation, molecular clouds I. INTRODUCTION Molecular clouds, especially, Giant Molecular Clouds (GMCs) with mass greater than 10 5 M fi , are the major sites, where the star birth takes place. GMCs will be fragmented to less massive clouds by expanding HII region, stellar wind and supernova explosion by the star birth, particularly, the massive stars within them. If there was no effective formation of GMCs from less massive clouds, the star birth would stop. The coalescence formation of GMCs was studied by Kwan and Valdes(1987). The observational evidence indicates that the massive cloud consists of emission cores, which could pose the question: if the collision between clouds leads to the coalescence. Clifford and Elmegreen(1983) ..