Extragalactic Abundances of Hydrogen, Deuterium and Helium

摘要: Estimates of the deuterium abundance in quasar absorbers are reviewed, including a brief account incorrect claims published by author and review problem hydrogen contamination. It is concluded that primordial may be universal with value (D/H)p ≈ 10−4, within about factor two, corresponding to ΩB h 0.7 2 ≈0.02 or η10 2.7 Standard Big Bang. This agrees current limits on helium, Yp ≤ 0.243, which shown surprisingly insensitive models stellar enrichment. also tabulated sum total density baryons observed components. Much lower (≈ × 10−5) possible but disagrees currently estimated helium abundances; larger baryon this case fits better Lyman-α forest requires bulk some uncounted form.