The Role of Sub-damped Lyman-alpha Absorbers in the Cosmic Evolution of Metals

Abstract

Observations of low mean metallicity of damped Lyman-alpha (DLA) quasar absorbers at all redshifts studied appear to contradict the predictions for the global mean interstellar metallicity in galaxies from cosmic chemical evolution models. On the other hand, a number of metal-rich sub-DLA systems have been identified recently, and the fraction of metal-rich sub-DLAs appears to be considerably larger than that of metal-rich DLAs, especially at z < 1.5. In view of this, here we investigate the evolution of metallicity in sub-DLAs. We find that the mean Zn metallicity of the observed sub-DLAs may be higher than that of the observed DLAs, especially at low redshifts, reaching a near-solar level at z <~ 1. This trend does not appear to be an artifact of sample selection, the use of Zn, the use of N_{HI}-weighting, or observational sensitivity. While a bias against very low metallicity could be present in the sub-DLA sample in some situations, this cannot explain the difference between the DLA and sub-DLA metallicities at low z. The primary reason for the difference between the DLAs and sub-DLAs appears to be the dearth of metal-rich DLAs. We estimate the sub-DLA contribution to the total metal budget using measures of their metallicity and comoving gas density. These calculations suggest that at z <~ 1, the contribution of sub-DLAs to the total metal budget may be several times that of DLAs. At higher redshifts also, there are indications that the sub-DLAs may contribute significantly to the cosmic metal budget.

arXiv comment9 pages, 2 figures, Accepted for Publication in the Astrophysical Journal

References in corpus (65)

• The Origin of the Mass--Metallicity Relation: Insights from 53,000 Star-Forming Galaxies in the SDSS
• The Star Formation History of Field Galaxies
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• The Mass-Metallicity Relation at z~2
• The Nature of High-Redshift Galaxies
• The Cosmic Energy Inventory
• The Gemini Deep Deep Survey. VII. The Redshift Evolution of the Mass-Metallicity Relation
• Damped Lyman Alpha Systems at z<1.65: The Expanded SDSS HST Sample
• The SDSS Damped Lya Survey: Data Release 3
• Abundances at High Redshifts: the Chemical Enrichment History of Damped Lyman-alpha Galaxies
• The Age-Metallicity Relation of the Universe in Neutral Gas: The First 100 Damped Lya Systems
• Cosmic Histories of Stars, Gas, Heavy Elements, and Dust
• Velocity-Metallicity Correlation for high-z DLA Galaxies: Evidence for a Mass-Metallicity Relation?
• Surveys for z > 3 Damped Lyman-alpha Absorption Systems
• Metal Abundances at z < 1.5: Fresh Clues to the Chemical Enrichment History of Damped Lyman alpha Systems
• Average Extinction Curves and Relative Abundances for QSO Absorption Line Systems at 1 <= z_abs < 2
• Chemical Abundances of the Damped Lya Systems at z>1.5
• Reconciling the local galaxy population with damped Ly-alpha cross sections and metal abundances
• Dust in High Redshift Galaxies
• Protogalactic Disk Models of Damped Lya Kinematics
• New perspectives on strong z=0.5 MgII absorbers: are halo-mass and equivalent width anti-correlated?
• Abundance Profiles and Kinematics of Damped Lyman-alpha Absorbing Galaxies at z < 0.65
• A Homogeneous Sample of Sub-DLAs III: Total Gas Mass Omega_(HI+HeII) at z>2
• Si and Mn Abundances in Damped Lya Systems with Low Dust Content
• Hubble Space Telescope Observations of Element Abundances in Low-redshift Damped Lyman-alpha Galaxies and Implications for the Global Metallicity-Redshift Relation
• The ESI/KeckII Damped Lya Abundance Database
• Ionization Properties and Elemental Abundances in Damped Ly alpha Systems
• A Homogeneous Sample of Sub-DLAs I: Construction of the Sample and Chemical Abundance Measurements
• A Homogeneous Sample of Sub-DLAs II: Statistical, Kinematic and Chemical Properties
• Zn and Cr abundances in damped Lyman alpha systems from the CORALS survey
• CII* Absorption in Damped Lyman Alpha Systems: (II) A New Window on the Star Formation History of the Universe
• The Homogeneity of Interstellar Elemental Abundances in the Galactic Disk
• Early stages of Nitrogen enrichment in galaxies: Clues from measurements in damped Lyman alpha systems
• Star formation rate and metallicity of damped Lyman-alpha absorbers in cosmological SPH simulations
• UVES observations of QSO 0000-2620: oxygen and zinc abundances in the Damped Ly-alpha galaxy at z_abs=3.3901
• First Comparison of Ionization and Metallicity in Two Lines of Sight Toward HE 1104-1805 AB at z=1.66
• The Metal-Strong Damped Lyman-alpha Systems
• The dust obscuration bias in Damped Lyman alpha systems
• Damped Lyman alpha absorber and the faint end of the galaxy luminosity function at high redshift
• Metals and Dust in Intermediate-redshift Damped Ly-alpha Galaxies
• Metal abundances and ionization conditions in a possibly dust-free damped Ly-alpha system at z=2.3
• Metallicity Evolution of Damped Lyman-Alpha Galaxies
• Super-Solar Super Lyman Limit Systems
• Where are the missing cosmic metals ?
• The Most Metal-Rich Intervening Quasar Absorber Known
• The UCSD HIRES/KeckI Damped Lya Abundance Database III. An Empirical Study of Photoionization in the Damped Lya System Toward GB1759+7539
• A Fabry-Perot Imaging Search for Lyman-alpha Emission in Quasar Absorbers at z ~ 2.4
• Metal-rich Damped/sub-Damped Lyman-alpha Quasar Absorbers at z<1
• Extinction and metal column density of HI regions up to redshift z~2
• Metallicity Evolution of Damped Lyman Alpha Systems In Lambda CDM Cosmology
• Galactic Chemical Abundances at z>3 I: First Results from the Echellette Spectrograph and Imager
• Elemental Abundance Measurements in Low-redshift Damped Lyman Alpha Absorbers
• The nature of damped Lyman alpha and sub-damped Lyman alpha absorbers
• Distinct Abundance Patterns in Multiple Damped Ly-alpha Galaxies: Evidence for Truncated Star Formation?
• The [Zn/Fe] -- [Fe/H] trend for disk and halo stars
• A near-solar metallicity damped Lyman-alpha system toward the BAL quasar Tol 1037-2703
• The missing metals problem: II. How many metals are in z ~ 2.2 galaxies?
• Hot Baryons and the Distribution of Metals in the Intergalactic Medium
• Elemental Abundances in Two High Column Density Damped Lyman Alpha Systems at z < 1.5
• The missing metals problem: I. How many metals are in submm galaxies?
• Emission Line Abundances of Absorption Selected Galaxies at z<0.5
• Unusual Metal Abundances in a Pair of Damped Lyman Alpha Systems at z~2
• New Damped Lya Metallicities from ESI Spectroscopy of Five Palomar Sky Survey Quasars
• A new measurement of zinc metallicity in a DLA at z=3.35
• Building Blocks in Hierarchical Clustering Scenarios and their Connection with Damped Ly$\alpha$ Systems

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• A Hubble Space Telescope Study of Lyman Limit Systems: Census and Evolution
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• Galaxies with Background QSOs, I: A Search for Strong Galactic H-alpha Lines
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• Keck and VLT Observations of Super-damped Lyman-alpha Absorbers at z=2=2.5: Constraints on Chemical Compositions and Physical Conditions
• Interstellar Ti II in the Milky Way and Magellanic Clouds
• Sub-damped Lyman alpha systems in the XQ-100 survey I -- Identification and contribution to the cosmological HI budget
• On the selection of damped Lyman alpha systems using MgII absorption at 2<z<4
• Interstellar Silicate Dust in the z=0.89 Absorber Towards PKS 1830-211: Crystalline Silicates at High Redshift?
• Adaptive Optics Imaging of a Massive Galaxy Associated with a Metal-rich Absorber
• Sub-damped Lyman alpha systems in the XQ-100 survey II -- Chemical evolution at 2.4<z<4.3
• Element Abundances in a Gas-rich Galaxy at z = 5: Clues to the Early Chemical Enrichment of Galaxies
• Metal-enriched Galaxies in the First ~1 Billion Years: Evidence of a Smooth Metallicity Evolution at z ~ 5
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• Damped Lyman-$\alpha$ absorbers and atomic hydrogen in galaxies: the view of the GAEA model
• A Sub-Damped Ly$\alpha$ Absorber with Unusual Abundances: Evidence of Gas Recycling in a Low-Redshift Galaxy Group
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• GALEX Discovery of a Damped Ly-alpha System at Redshift z = 1
• DLA and sub-DLA metallicity evolution: A case study of absorbers towards Q0338-0005
• HI-selected Galaxies as a probe of Quasar Absorption Systems
• Metals and a Search for Molecules in the Distant Universe: Magellan MIKE Observations of sub-DLAs at 2<z<3
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