Author(s): , , ,
Institution(s): 1. Astronomical Institute, Czech Academy of Sciences, 2. Instituto Nacional de Astrofísica Óptica y Electrónica
Young and massive star clusters above a critical mass form thermally unstable clumps reducing locally the temperature and pressure of the hot 10^7 K cluster wind. The matter reinserted by stars, and mass loaded in interactions with pristine gas and with evaporating circumstellar disks, accumulates on clumps that are ionized with photons produced by massive stars. We shall discuss if they may become self-shielded when they reach the central part of the cluster, or even before it during their free fall to the cluster center, we shall explore the importance of early mass loading of the stellar winds, and we shall analyse the role of additional cooling by dust produced in supernova events.