Radiative Feedback and the Formation of Massive Stars and Stellar Clusters
Radiative feedback is a key process in astrophysics that may play a crucial role in the formation of massive stars as well as stellar clusters in which they form. I will review the physical problems and large body of work that has addressed these basic questions before turning to our own contributions. The central question is whether or not feedback limits the mass of stars or clusters, and limits the efficiency of star formation in clusters in a significant way. For massive star formation, we have developed a new "hybrid" radiative transfer code that operates in a full 3D, adaptive mesh environment that can, for the first time, follow the heating and momentum transfer by both discrete stellar sources as well as by diffuse radiative background within molecular clouds. We simulate the gravitational collapse of massive dense gaseous "cores" of 30 to 200 solar masses and follow the formation and evolution of massive disks and the radiation driven bubbles. Our simulations show that massive disks do not readily fragment into multiple stars on 1000 AU scales. We follow the evolution of collapse, accretion,and radiatively driven outflow to show that feedback by itself, does not limit the mass of stars. I will also present our new work on radiative feedback simulations of the formation of young clusters in turbulent Giant Molecular Clouds and on how cloud structure affects this process. In particular, we find that the star formation efficiency in such clouds and the masses of star clusters are strongly influenced by how gravitationally bound the cloud are initially - an effect that is at least as important as that of radiative feedback. These results have important consequences for our understanding of feedback on galactic evolution.