The Galactic Evolution of Beryllium

Abstract

The abundance of beryllium has been determined in unevolved stars over a range metal abundances in order to enhance our understanding of the chemical evolution of our Galaxy, cosmic-ray theory, and cosmology. Observations of 27 stars have been made with Keck I with HIRES at high spectral resolution (45,000) and high signal-to-noise ratios (60 - 110 typically). We find a remarkably linear relationship between log N(Be/H) and [Fe/H] with a slope of 0.96 (±0.04). Similarly, the relationship between log N(Be/H) and [O/H] is linear with a slope of 1.45 (±0.04). Beryllium increases at the same rate as Fe, but much faster than O. This provides constraints for and insights into models of Galactic chemical evolution. There is some evidence for an intrinsic spread in Be at a given [O/H] or [Fe/H]. There is no evidence of a plateau in Be at the lowest metallicities down to log N(Be/H) = —13.5.