• CS 59
• CS 63
• NGC6357
• photoionization
• Pismis-24
• protoplanetary disks
• stellar feedback
• young star forming regions

Giant Molecular Clouds (GMCs) have been observed to be strongly correlated with ongoning star formation. The estimated lifetime of a GMC is of order 10-30 Myr, much shorter than the gas depletion timescale, estimated to be around 1-2 Gyr. This points to an alternative cause for the cloud's destruction, which is feedback from massive, early-type stars, in particular photoionization. This thesis focuses on the young star forming region of NGC6357, with the aims of creating an optical catalog for the region, refine the membership of the young stellar population and characterize the latter's stellar parameters in order to study the impact of stellar feedback on both the cloud's morphology and the dissipation of protoplanetary disks. In this study, the estimated disk fractions for the three subregions of NGC6357 (Pismis-24, CS 63 and CS 59) are significantly lower than those of low mass star forming regions with similar ages. This and the presence of several HII regions and ionized pillars in NGC6357 points to stellar feedback having a crucial impact on both the disks' premature dissipation and on the cloud's morphology. Additionally, for the first time, this work studies the 3D structure of NGC6357, revealing that the young stellar population formes two filamentary structures, one comprising of the cluster Pismis-24, the other being formed by the two subgroups CS 63 and CS 59.