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, $\mathrm{ d}N/\mathrm{ d}X$, and the neutral hydrogen density, $\Omega_\mathrm{ DLA}$. 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 $N_\mathrm{ HI} < 5\times 10^{ 22}$ cm$^{ -2}$. We make the first measurements from SDSS of $\mathrm{ d}N/\mathrm{ d}X$ and $\Omega_\mathrm{ DLA}$ 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.
Categories: astro-ph.GA astro-ph.CO