A Caltech Library Service

Damped and sub-damped Lyman-α absorbers in z > 4 QSOs

Guimarães, R. and Petitjean, P. and de Carvalho, R. R. and Djorgovski, S. G. and Noterdaeme, P. and Castro, S. and da R. Poppe, P. C. and Aghaee, A. (2009) Damped and sub-damped Lyman-α absorbers in z > 4 QSOs. Astronomy and Astrophysics, 508 (1). pp. 133-140. ISSN 0004-6361.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present the results of a survey of damped (DLA, log N(H I) > 20.3) and sub-damped Lyman-α systems (19.5 < log N(H I) < 20.3) at z > 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 < z_(em) < 6.3. Intermediate resolution (R ~ 4300) spectra were obtained with the Echellette Spectrograph and Imager (ESI) mounted on the Keck telescope. A total of 100 systems with log N(H I) > 19.5 were detected of which 40 systems are damped Lyman-α systems for an absorption length of ΔX = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs. We study the evolution with redshift of the cosmological density of the neutral gas and find, consistent with previous studies at similar resolution, that Ω_(DLA,HI) decreases at z > 3.5. The overall cosmological evolution of Ω_(HI) shows a peak around this redshift. The H I column density distribution for log N(H I) ≥ 20.3 is fitted, consistent with previous surveys, with a single power-law of index α ~ −1.8 ± 0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a flattening of the function at lower H I column densities with an index of α ~ −1.4 for the column density range log N(H I) = 19.5−21. The fraction of H I mass in sub-DLAs is of the order of 30%. The H I column density distribution does not evolve strongly from z ~ 2.5 to z ~ 4.5.

Item Type:Article
Related URLs:
URLURL TypeDescription
de Carvalho, R. R.0000-0002-1283-3363
Djorgovski, S. G.0000-0002-0603-3087
Additional Information:© ESO 2009. Received 17 December 2008. Accepted 7 September 2009. Published online 15 October 2009. G.D. is supported by the NSF grant AST-0407448, and the Ajax Foundation. Cataloguing of DPOSS and discovery of PSS QSOs was supported by the Norris Foundation and other private donors. We thank E. Thiébaut, and D. Munro for freely distributing his yorick programming language (available at, which we used to implement our analysis. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaian community. We are most fortunate to have the opportunity to conduct observations from this mountain. We acknowledge the Keck support staff for their efforts in performing these observations.
Funding AgencyGrant Number
Ajax FoundationUNSPECIFIED
Kenneth T. and Eileen L. Norris FoundationUNSPECIFIED
Subject Keywords:Galaxy: evolution; Galaxy: formation; quasars: absorption lines; intergalactic medium; cosmology: observations
Issue or Number:1
Record Number:CaltechAUTHORS:20100106-080049821
Persistent URL:
Official Citation:Damped and sub-damped Lyman-α absorbers in z > 4 QSOs R. Guimarães, P. Petitjean, R. R. de Carvalho, S. G. Djorgovski, P. Noterdaeme, S. Castro, P. C. da R. Poppe and A. Aghaee A&A 508 (1) 133-140 (2009) DOI: 10.1051/0004-6361/200811541
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17069
Deposited By: Tony Diaz
Deposited On:06 Jan 2010 17:26
Last Modified:03 Oct 2019 01:22

Repository Staff Only: item control page