Beryllium abundances and the formation of the halo and the thick disk

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Smiljanic, Rodolfo ; Pasquini, L. ; Bonifacio, P. ; Galli, D. ; Barbuy, B. ; Gratton, R. ; Randich, S. ; Charbonnel, C ; Tosi, M ; Primas, F ; Chiappini, C

• Tipo de documento: Artigo Científico
• Fonte: COSMIC MAGNETIC FIELDS: FROM PLANETS, TO STARS AND GALAXIES; v. N/A, n. 268, p. 2-pg., 2010-01-01.

Resumo

The single stable isotope of beryllium is it pure product of cosmic-ray spallation in the ISM Assuming that the cosmic-rays are globally transported across the Galaxy, the beryllium production should be a widespread process and its abundance should be roughly homogeneous in the early-Galaxy at a given time. Thus, it could be useful as a tracer of time. In an investigation of the use of Be as a cosmochronometer and of its evolution in the Galaxy, we found evidence that, in a log(Be/H) vs (a/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. We also found evidence that the star formation rate was lower in the outer regions of the thick disk, pointing towards an inside-out formation (AU)

• Processo FAPESP: 04/13667-4 - Bandas moleculares e índices espectrais na região ultravioleta 3200-4500a
• Beneficiário: Rodolfo Henrique Silva Smiljanic
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 08/55923-8 - Abundancias de oxigenio e a formacao do halo e do disco espesso
• Beneficiário: Rodolfo Henrique Silva Smiljanic
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado