A view of the Galactic halo using beryllium as a time scale

Rodolfo Smiljanic, L. Pasquini, P. Bonifacio, D. Galli, B. Barbuy, R. Gratton, S. Randich

Published 2009-09-14Version 1

Beryllium stellar abundances were suggested to be a good tracer of time in the early Galaxy. In an investigation of its use as a cosmochronometer, using a large sample of local halo and thick-disk dwarfs, evidence was found that in a log(Be/H) vs. [alpha/Fe] diagram the halo stars separate into two components. One is consistent with predictions of evolutionary models while the other is chemically indistinguishable from the thick-disk stars. This is interpreted as a difference in the star formation history of the two components and suggests that the local halo is not a single uniform population where a clear age-metallicity relation can be defined.