case western reserve university



Second Stars

Steinn Sigurdsson (Penn State)

The first stars formed from primordial gas, formed in the Big Bang, composed primarily of hydrogen and helium. It is generally thought the formation process of the first stars is relatively well understood, and leads to the formation of predominantly very massive stars. At some later stage, star formation in the universe appears to be dominated by a near universal Initial Mass Function, biased towards low mass stars, with an approximate power law dependence between the number of stars formed and their mass, over a factor of a few hundred in mass. We explore the effect of metallicity on fragmentation in cold low metallicity gas, using a new implementation of radiative cooling combined with adaptive mesh refinement simulations of the gas dynamics under gravity. Given some simplifying assumptions, we find a transition to the normal mode of star formation, evidence for an intermediate third mode of star formation, and discuss some of the possible implications and physical issues.