The deuterium abundance toward QSO 1009+2956

摘要

We present a measurements of the deuterium to hydrogen ratio (D/H) in a metal-poor absorption system at redshift z = 2.504 toward the QSO 1009+2956. We apply the new method of Burles & Tytler to robustly determine D/H in high-resolution Lyα forest spectra and include a constraint on the neutral hydrogen column density determined from the Lyman continuum optical depth in low-resolution spectra. We introduce six separate models to measure D/H and to assess the systematic dependence on the assumed underlying parameters. We find that the deuterium absorption feature contains a small amount of contamination from unrelated H I.