2006/10/31 by John M. O’Meara, John M O'Meara, Jason X. Prochaska +4 · 8 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Distribution (mathematics) #Electrical and Electromagnetic Research #Flattening #Galaxies: Formation, Evolution, Phenomena #Limit (mathematics) #Lyman limit #Observable #Range (aeronautics) #Redshift #Spectral line #astro-ph
paper · pdf · doi:10.1086/510711
published as Astrophys.J.656:666-679,2007 · 15 pages, 10 figures, accepted to the Astrophysical Journal. Revision includes updated references
arxiv created 2006/11/01 · openalex publication_date 2007/02/14 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present the results of a survey for super Lyman limit systems (SLLSs; defined to be absorbers with 19.0 cm -2 ≤ log N H I ≤ 20.3 cm -2 ) from a large sample of high-resolution spectra acquired using the Keck and Magellan telescopes. Specifically, we present 47 new SLLSs from 113 QSO sight lines. We focus on the neutral hydrogen frequency distribution f H I ( N , X ) of the SLLS and its moments and compare these results with the Lyα forest and the damped Lyα systems (DLAs; absorbers with log N H I ≥ 20.3 cm -2 ). We find that the f H I ( N , X ) of the SLLSs can be reasonably described with a power law of index α = -1.43 or -1.19 depending on whether we set the lower N H I bound for the analysis at 10 19.0 or 10 19.3 cm -2 , respectively. The results indicate a flattening in the slope of f H I ( N , X ) between the SLLSs and DLAs. We find little evidence for redshift evolution in the shape of f H I ( N , X ) for the SLLSs over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of f H I ( N , X ), the line density ℓ SLLS ( X ). We introduce the observable distribution function ( N , X ) and its moment, which elucidates comparisons of H I absorbers from the Lyα forest through to the DLA. We find that a simple three-parameter function can fit ( N , X ) over the range 17.0 cm -2 ≤ log N H I ≤ 22.0 cm -2 . We use these results to predict that f H I ( N , X ) must show two additional inflections below the SLLS regime to match the observed f H I ( N , X ) distribution of the Lyα forest. Finally, we demonstrate that SLLSs contribute a minor fraction (≈15%) of the universe's hydrogen atoms and, therefore, an even smaller fraction of the mass in predominantly neutral gas.