An inhomogeneous model for the Galactic halo: a possible explanation for the spread observed in s- and r-process elements
Dipartimento di Astronomia, Universitá di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy e-mail: email@example.com
Accepted: 14 January 2008
Aims. We propose an explanation for the considerable scatter of the abundances of neutron capture elements observed in low-metallicity stars in the solar vicinity, compared to the small star-to-star scatter observed for the α-elements.
Methods. We have developed a stochastic chemical evolution model in which the main assumption is a random formation of new stars subject to the condition that the cumulative mass distribution follows a given initial mass function.
Results. With our model, we are able to reproduce the different spreads of neutron capture elements and α-elements in low-metallicity stars.
Conclusions. The reason for different observed spreads in neutron capture elements and α-elements resides in the random birth of stars, coupled with different stellar mass ranges, from which α-elements and neutron capture elements originate. In particular, the site of production of α-elements is the whole range of massive stars, from 10 to 80 whereas the mass range of production for neutron capture elements lies between 12 and 30 .
Key words: Galaxy: halo / Galaxy: evolution / stars: abundances / nuclear reactions, nucleosynthesis, abundances
© ESO, 2008