2009/08/31 by Matthew M. Pieri, Stephan Frank, F. Stephan +4
Chemistry · Physics and Astronomy · #Absorption (acoustics) #Absorption spectroscopy #Analytical Chemistry (journal) #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Chemistry #Galaxies: Formation, Evolution, Phenomena #Galaxy #Metallicity #Optics #Oxygen #Physics #Quasar #Sky #Spectral line #Stellar, planetary, and galactic studies #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/716/2/1084
12 pages, 9 figures. Accepted by ApJ (minor changes)
arxiv created 2010/04/26 · openalex publication_date 2010/05/27 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We use 2167 Sloan Digital Sky Survey quasar spectra to search for low-density oxygen in the intergalactic medium (IGM). Oxygen absorption is detected on a pixel-by-pixel basis by its correlation with Lyα forest absorption. We have developed a novel locally calibrated pixel (LCP) search method that uses adjacent regions of the spectrum to calibrate interlopers and spectral artifacts, which would otherwise limit the measurement of O vi absorption. Despite the challenges presented by searching for weak O vi within the Lyα forest in spectra of moderate resolution and signal-to-noise, we find a highly significant detection of absorption by oxygen at 2.7 < z < 3.2 (the null hypothesis has a χ 2 = 80 for nine data points). We interpret our results using synthetic spectra generated from a log-normal density field assuming a mixed quasar–galaxy photoionizing background and that it dominates the ionization fraction of detected O vi . The LCP search data can be fit by a constant metallicity model with [O/H] = −2.15 +0.07 −0.09 but also by models in which low-density regions are unenriched and higher density regions have a higher metallicity. The density-dependent enrichment model by Aguirre et al. is also an acceptable fit. All our successful models have similar mass-weighted oxygen abundance, corresponding to [〈O/H〉 MW ] = −2.45 ± 0.06. This result can be used to find the cosmic oxygen density in the Lyα forest, Ω Oxy,IGM = 1.4(±0.2) × 10 −6 ≈ 3 × 10 −4 Ω b . This is the tightest constraint on the mass-weighted mean oxygen abundance and the cosmic oxygen density in the Lyα forest to date and indicates that it contains ≈16% of the total expected metal production by star formation up to z = 3.