Astrophys. J., 656, 666-679 (2007/February-3)
The Keck+Magellan survey for Lyman limit absorption. I. The frequency distribution of super Lyman limit systems.
O'MEARA J.M., PROCHASKA J.X., BURLES S., PROCHTER G., BERNSTEIN R.A. and BURGESS K.M.
Abstract (from CDS):
We present the results of a survey for super Lyman limit systems (SLLSs; defined to be absorbers with 19.0/cm2≤logN_HI_≤20.3/cm2) 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_HI_(N,X) of the SLLS and its moments and compare these results with the Lyα forest and the damped Lyα systems (DLAs; absorbers with logN_HI_≥20.3/cm2). We find that the f_HI_(N,X) of the SLLSs can be reasonably described with a power law of index α=-1.43+0.15–0.16 or -1.19+0.20–0.21depending on whether we set the lower N_HI_ bound for the analysis at 1019.0 or 1019.3/cm2, respectively. The results indicate a flattening in the slope of f_HI_(N,X) between the SLLSs and DLAs. We find little evidence for redshift evolution in the shape of f_HI_(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_HI_(N,X), the line density ℓSLLS(X). We introduce the observable distribution function O(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 O(N,X) over the range 17.0/cm2≤logN_HI_≤22.0/cm2. We use these results to predict that f_HI_(N,X) must show two additional inflections below the SLLS regime to match the observed f_HI_(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.
Galaxies: Intergalactic Medium - Galaxies: Quasars: Absorption Lines
Tables 2, 3, 4: [OPB2007] QSO JHHMM+DDMM abs N.NNN N=51.
In table 3, SDSS J0949+0355, J1034+0358, J1307+0422, J1621-0042: too short format for SDSS objects (SDSS JHHMMSS.ss+DDMMSS.s), These objects are QSO J0949+0355, QSO J1034+0358, QSO J1307+0422, QSO J1621-0042 in SIMBAD. Tables 2, 3, 4: only the objects with unknown z(abs) are designated as [OPB2007].
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