Scientific Seminars

Cosmic pollution: metals and dust from the first stars

Raffaella Schneider
Osservatorio Arcetri

2009-03-05    11.00    Merate - POE

The epoch of the Cosmic Dawn, when the first stars start to form has only recently moved into the focus of research in Cosmology. New observational probes of the high redshift universe have become available and the ability to carry out sophisticated numerical simulations have improved dramatically. Yet, the formation mechanisms and the properties of the first stars are still largely unknown. Physical conditions in primordial star forming regions appear to favour the formation of massive stars, with masses of 100 Msun. On the other hand, observations of local stellar populations show that stars form with characteristic masses of 1 Msun. The novel concept of a critical metallicity of the gas, above which the fragmentation properties of pre-stellar clouds change dramatically, appears to be the most likely explanation for this transition. The detailed physics of this process still requires extensive study and its consequences on the history of metal enrichment and reionization need to be fully investigated. We will discuss recent developments in the field aimed at (i) understanding the interplay of first stars and their environment (ii) investigating the role of first stars in cosmic reionization (iii) using low and high-redshift observations to constrain the properties of the first stars.