Statistical properties of damped Lyman-alpha systems from Sloan Digital Sky Survey DR12

We present new estimates for the statistical properties of damped Lyman- alpha absorbers (DLAs). We compute the column density distribution function at z > 2, the line density, dN/dX, and the neutral hydrogen density, Omega sub( DLA). Our estimates are derived from the DLA catalogue of Garnett et...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2017-04, Vol.466 (2), p.2111-2111
Main Authors: Bird, Simeon, Garnett, Roman, Ho, Shirley
Format: Article
Language:English
Subjects:
Astronomy
Density
Density distribution
Estimates
Hydrogen
Mathematical analysis
Mathematical models
Quasars
Signal to noise ratio
Sky surveys (astronomy)
Statistics
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Summary:We present new estimates for the statistical properties of damped Lyman- alpha absorbers (DLAs). We compute the column density distribution function at z > 2, the line density, dN/dX, and the neutral hydrogen density, Omega sub( DLA). Our estimates are derived from the DLA catalogue of Garnett et al. (2016), which uses the Sloan Digital Sky Survey III Data Release 12 (SDSS-III DR12) quasar spectroscopic survey. This catalogue provides a probability that a given spectrum contains a DLA. It allows us to use even the noisiest data without biasing our results and thus substantially increases our sample size. We measure a non-zero column density distribution function at 95 per cent confidence for all column densities N sub( HI) < 5 x 10 super( 22) Cm super( -2). We make the first measurements from SDSS of dN/dX and Omega sub( DLA) at z > 4. We show that our results are insensitive to the signal-to-noise ratio of the spectra, but that there is a residual dependence on quasar redshift for z < 2.5, which may be due to remaining systematics in our analysis.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stw3246