High Redshift Lyman Limit and Damped Lyman-Alpha Absorbers
| dc.creator | Storrie-Lombardi, L. J. | |
| dc.creator | McMahon, R. G. | |
| dc.creator | Irwin, M. J. | |
| dc.creator | Hazard, C. | |
| dc.date | 1995-03-24 | |
| dc.date.accessioned | 2026-07-07T02:19:41Z | |
| dc.date.available | 2026-07-07T02:19:41Z | |
| dc.description | We have obtained high signal:to:noise optical spectroscopy at 5Å resolution of 27 quasars from the APM z$>$4 quasar survey. The spectra have been analyzed to create new samples of high redshift Lyman-limit and damped Lyman-$α$ absorbers. These data have been combined with published data sets in a study of the redshift evolution and the column density distribution function for absorbers with $\log$N(HI)$\ge17.5$, over the redshift range 0.01 $<$ z $<$ 5. The main results are: \begin{itemize} \item Lyman limit systems: The data are well fit by a power law $N(z) = N_0(1 + z)^γ$ for the number density per unit redshift. For the first time intrinsic evolution is detected in the product of the absorption cross-section and comoving spatial number density for an $Ω= 1$ Universe. We find $γ= 1.55$ ($γ= 0.5$ for no evolution) and $N_0 = 0.27$ with $>$99.7\% confidence limits for $γ$ of 0.82 \& 2.37. \item Damped \lya systems: The APM QSOs provide a substantial increase in the redshift path available for damped surveys for $z>3$. Eleven candidate and three confirmed damped Ly$α$ absorption systems, have been identified in the APM QSO spectra covering the redshift range $2.8\le z \le 4.4$ (11 with $z>3.5$). Combining the APM survey confirmed and candidate damped \lya absorbers with previous surveys, we find evidence for a turnover at z$\sim$3 or a flattening at z$\sim$2 in the cosmological mass density of neutral gas, $Ω_g$. \end{itemize} The Lyman limit survey results are published in Storrie-Lombardi, et~al., 1994, ApJ, 427, L13. Here we describe the results for the DLA population of absorbers. | |
| dc.description | latex, 5 pages + 4 postscript figures | |
| dc.identifier | https://arxiv.org/abs/astro-ph/9503089 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/9503089 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/9964 | |
| dc.subject | Astrophysics | |
| dc.title | High Redshift Lyman Limit and Damped Lyman-Alpha Absorbers | |
| dc.type | text |