Annu. Rev. Astron. Astrophys. 2005. 43: 861-918
Copyright © 2005 by . All rights reserved

This article is in LEVEL5 at the specific request of the author and is derived from the on-line and publicly available version posted at astro-ph/0509481

For a PDF version of the article, click here.

DAMPED Lyalpha SYSTEMS

Arthur M. Wolfe

Department of Physics, and Center for Astrophysics and Space Sciences, University of California, San Diego, Gilman Dr., La Jolla; CA 92093-0424, awolfe@ucsd.edu

Eric Gawiser

NSF Astronomy & Astrophysics Postdoctoral Fellow, Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8108, gawiser@astro.yale.edu

Jason X. Prochaska

University of California Observatories / Lick Observatory, University of California, 333 Interdisciplinary Science Building, Santa Cruz CA 95064, xavier@ucolick.org


Abstract. Observations of damped Lyalpha systems offer a unique window on the neutral-gas reservoirs that gave rise to galaxies at high redshifts. This review focuses on critical properties such as the H I and metal content of the gas and on independent evidence for star formation. Together, these provide an emerging picture of gravitationally bound objects in which accretion of gas from the IGM replenishes gas consumed by star formation. Other properties such as dust content, molecular content, ionized-gas content, gas kinematics, and galaxy identifications are also reviewed. These properties point to a multi-phase ISM in which radiative and hydrodynamic feedback processes are present. Numerical simulations and other types of models used to describe damped Lyalpha systems within the context of galaxy formation are also discussed.


Table of Contents

WHAT ARE THE DAMPED Lyalpha SYSTEMS and HOW ARE THEY FOUND?
History of damped Lyalpha Surveys
Modern Surveys and Identification of damped Lyalpha systems
The Significance of the N(H I) geq 2 × 1020 cm-2 Survey Threshold

THE NEUTRAL GAS CONTENT OF THE UNIVERSE
Formalism
f (N, X)
dN / dX
Omegag(z)
Model Comparisons

CHEMICAL ABUNDANCES
Methodology
Metallicity
Relative Abundances

IONIZED GAS

MOLECULAR GAS

KINEMATICS

GALAXY IDENTIFICATIONS
Galaxies with z geq 1.6
Galaxies with z < 1.6

STAR FORMATION IN DAMPED Lyalpha SYSTEMS
Direct Emission Measurements of Star Formation Rates in Damped Lyalpha Systems with z > 1.6
Star Formation Rates from the C II* Technique
Implications

CHEMICAL EVOLUTION MODELS for DAMPED Lyalpha SYSTEMS

ARE DAMPED Lyalpha SAMPLES BIASED BY DUST?
Observational estimates of reddening
Surveys of radio-selected QSOs
Empirical Estimates of Damped Lyalpha System Obscuration

ARE DAMPED Lyalpha SAMPLES BIASED BY GRAVITATIONAL LENSING ?

CONCLUSIONS

REFERENCES

Next