Abstract
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, $Ømega_DLA$. Our estimates are derived from the DLA
catalogue of Garnett:2016, which uses the SDSS--III DR12 quasar
spectroscopic survey. This catalogue provides a probability that a given
spectrum contains a DLA, allowing us to use even the noisiest data without
biasing our results and thus substantially increase our sample size. We measure
a non-zero column density distribution function at $95\%$ confidence for all
column densities $N_HI < 510^22$ cm$^-2$. We make the first
measurements from SDSS of $dN/dX$ and $Ømega_DLA$
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.
Users
Please
log in to take part in the discussion (add own reviews or comments).