Spallogenic Light Elements and Cosmic-Ray Origin

Abstract

Using a Monte Carlo code which incorporates the delayed mixing into the ISM of supernovae nucleosynthetic yields and ejecta kinetic energies (including events with very large energies, e.g. collapsars/hypernovae), we tested three evolutionary models of spallogenic light element origin, specifically Be. The CRI, in which the cosmic rays are accelerated out of an ISM which is increasingly metal poor at early times, under-predicts the measured Be abundance at the lowest [Fe/H], the increase in [O/Fe] with decreasing [Fe/H] indicated by recent data notwithstanding. The CRS, in which cosmic rays with composition similar to that of the current epoch cosmic rays are accelerated out of fresh supernova ejecta and maintain a constant metallicity at all epochs, can account for the measured Be abundances with an acceleration efficiency that is in good agreement with the current epoch cosmic-ray data. The LECR, in which a postulated low energy component also accelerated out of fresh ejecta coexists with the CRI cosmic rays, can account for the observations as well, except that the required acceleration efficiency becomes prohibitively large for some of the parameters that have been previously assumed for this as-yet undetected cosmic-ray component.