Storrie-Lombardi, L. J. and McMahon, R. G. and Irwin, M. J. and Hazard, C. (1995) High Redshift Lyman Limit and Damped Lyman-Alpha Absorbers. . (Submitted) https://resolver.caltech.edu/CaltechAUTHORS:20170323-081823891
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Abstract
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-ɑ 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 logN(HI)≥ 17.5, over the redshift range 0.01 < z < 5. The main results are: Lyman limit systems: The data are well fit by a power law N(z) = N_0(1 + z)^y 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 y = 1.55 (y = 0.5 for no evolution) and N_0 = 0.27 with >99.7% confidence limits for y of 0.82 & 2.37. Damped Lyɑ 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 Lyɑ absorption systems, have been identified in the APM QSO spectra covering the redshift range 2.8 ≤ z ≤ 4.4 (11 with z > 3.5). Combining the APM survey confirmed and candidate damped Lyɑ absorbers with previous surveys, we find evidence for a turnover at z∼3 or a flattening at z∼2 in the cosmological mass density of neutral gas, Ωg. 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.
Item Type: | Report or Paper (Discussion Paper) | ||||||
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Additional Information: | (Submitted on 24 Mar 1995) | ||||||
DOI: | 10.48550/arXiv.9503089 | ||||||
Record Number: | CaltechAUTHORS:20170323-081823891 | ||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20170323-081823891 | ||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||
ID Code: | 75346 | ||||||
Collection: | CaltechAUTHORS | ||||||
Deposited By: | Ruth Sustaita | ||||||
Deposited On: | 23 Mar 2017 19:17 | ||||||
Last Modified: | 02 Jun 2023 01:30 |
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