The Galactic Evolution of Beryllium and Boron

Abstract

The galactic chemical evolution of Be and B provides unique information about the origin and history of cosmic rays. The available Pop II data demonstrate that Be and B have a Galactic source, probably in one or more kinds of spallation processes. However, the data are not unequivocal about the nature of Be and B origin, as encoded in the primary or secondary (linear or quadratic) scaling with metallicity. We summarize a careful analysis of the trends among Be, B, Fe, and O observations. We show that if O/Fe is constant, some other cosmic ray origin or component is needed. On the other hand, if O/Fe is not constant, as recent data suggest, then the data could indicate a standard cosmic ray origin, wherein the abundances of cosmic rays scale with those of the ISM. We suggest future observational tests which will distinguish several proposed scenarios of LiBeB and cosmic ray origin.