Understanding the formation of stars and brown dwarfs

We review recent results from hydrodynamical calculations of the formation of young stellar clusters. The calculations present a highly dynamical picture of star formation where the mass function of stars originates from competitive accretion between protostars and dynamical ejections that halt accretion. Using calculations that resolve fragmentation beyond the opacity limit, we examine the origin of the stellar initial mass function and its dependence on the metallicity and mean thermal Jeans mass of molecular clouds. We find that the mean 'stellar' mass is relatively independent of the mean thermal Jeans mass and depends more on opacity limit for fragmentation. However, progenitor clouds with a lower mean thermal Jeans mass do produce a greater fraction of brown dwarfs.