Formation of primordial stars and blackholes, and where are they now ?

     
 

 

The nature of the first generation of stars in the Universe remains largely unknown. The first stars terminate the Dark Ages, set the scene for galaxy formation, and might also seed the formation of massive blackholes in the early universe. We have developed an ab initio computer simulation of the formation of the first stars that follows the relevant atomic and molecular processes on a first-principle basis. The results show that primeval density fluctuations left over from the Big Bang can drive the formation of a tiny protostar when the age of the universe is less than a few hundred million years. Our detailed calculations of proto-stellar evolution suggest that the protostar grows quickly, and, under some plausible conditions, becomes more massive than a few hundred solarmasses, to collapse to a blackhole. We use another set of cosmological simulations to answer to an important question, "where are the first stars now ?" I propose a model that explains the apparent absence of pair-instability signature in metal-poor halo stars. Finally, I will discuss prospects for future observations of the first stars and their signatures.

Naoki Yoshida