An inhomogeneous model for the Galactic halo: a possible explanation for the spread observed in s- and r-process elements

• Published in: Astronomy and astrophysics (Berlin) 2008-04, Vol.481 (3), p.691-699
• Main Author: Cescutti, G.
• Format: Article
• Language: English
• Subjects: abundances; Astronomy; Earth, ocean, space; Exact sciences and technology; Galaxy: evolution; Galaxy: halo; nuclear reactions; nucleosynthesis; stars: abundances
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20078571

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 $M_{\odot}$ whereas the mass range of production for neutron capture elements lies between 12 and 30 $M_{\odot}$.