The Metallicity of Intergalactic Gas in Cosmic Voids

Abstract

We have used the Hubble/STIS and FUSE archives of ultraviolet spectra of bright AGN to identify intergalactic Lya absorbers in nearby (z < 0.1) voids. From a parent sample of 651 Lya absorbers, we identified 61 void absorbers located more than 1.4/h_70 Mpc from the nearest L* or brighter galaxy. Searching for metal absorption in high-quality (S/N > 10) spectra at the location of three diagnostic metal lines (O VI 1032, C IV 1548, Si III 1206), we detected no metal lines in any individual absorber, or in any group of absorbers using pixel co-addition techniques. The best limits on metal-line absorption in voids were set using four strong Lya absorbers with N(H I) > 10^{14} cm^-2, with 3-sigma equivalent-width limits ranging from 8 mA (O VI), 7-15 mA (C IV), and 4-10 mA (Si III). Photoionization modeling yields metallicity limits Z < 10^{-1.8+/-0.4} Z_sun, from non-detections of C IV and O VI, some 6 times lower than those seen in Lya and OVI absorbers at z < 0.1. Although the void Lya absorbers could be pristine material, considerably deeper spectra are required to rule out a universal metallicity floor produced by bursts of early star formation, with no subsequent star formation in the voids. The most consistent conclusion derived from these low-z results, and similar searches at z = 3-5, is that galaxy filaments have increased their mean IGM metallicity by factors of 30-100 since z = 3.

arXiv commentAccepted for ApJ, 8 pages including Fig 1a,b

References in corpus (36)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Overview of the Far Ultraviolet Spectroscopic Explorer Mission
• The Rest-Frame Extreme Ultraviolet Spectral Properties of QSOs
• A stellar relic from the early Milky Way
• The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies
• Metallicity of the intergalactic medium using pixel statistics. II. The distribution of metals as traced by C IV
• Early Metal Enrichment of the Intergalactic Medium by Pregalactic Outflows
• Model-independent insights into the nature of the Lyman-alpha forest and the distribution of matter in the universe
• The Minimum Universal Metal Density Between Redshifts of 1.5 and 5.5
• The Distribution of Metallicity in the IGM at z~2.5: OVI and CIV Absorption in the Spectra of 7 QSOs
• The Enrichment History of the Intergalactic Medium: Measuring the CIV/HI Ratio in the Lyman Alpha Forest
• The Fate of the First Galaxies. II. Effects of Radiative Feedback
• The structure of voids
• Photometric Properties of Void Galaxies in the Sloan Digital Sky Survey
• The Local Ly-alpha Forest IV: STIS G140M Spectra and Results on the Distribution and Baryon Content of HI Absorbers
• The Luminosity Function of Void Galaxies in the Sloan Digital Sky Survey
• Spectroscopic Properties of Void Galaxies in the Sloan Digital Sky Survey
• An OVI Baryon Census of the Low-z Warm-Hot Intergalactic Medium
• The High-Redshift He II Gunn-Peterson Effect: Implications and Future Prospects
• The HST Quasar Absorption Line Key Project. XIV. The Evolution of Ly-alpha Absorption Lines in the Redshift Interval 0 to 1.5
• Mixing Metals in the Early Universe
• The Metagalactic Ionizing Radiation Field at Low Redshift
• The Galaxy Environment of O VI Absorption Systems
• Nucleosynthesis, Reionization, and the Mass Function of the First Stars
• The C IV Mass Density of the Universe at Redshift 5
• The Local Lya Forest. III. Relationship between Lya Absorbers and Galaxies, Voids and Superclusters
• The Local Lyman-alpha Forest. II: Distribution of HI Absorbers, Doppler Widths, and Baryon Content
• Metallicity of the intergalactic medium using pixel statistics: III. Silicon
• The Influence of the Photoionizing Radiation Spectrum on Metal-Line Ratios in Ly alpha Forest Clouds
• The Low-z Intergalactic Medium. II. LyB, OVI, and CIII Forest
• The Hot Intergalactic Medium - Galaxy Connection: Two Strong Absorbers in the Sightline Toward PG 1211+143
• The Local Lyman-alpha Forest. I: Observations with the GHRS/G160M on the Hubble Space Telescope
• Probing the IGM/Galaxy Connection Toward PKS0405-123 III: The Galaxy Survey and Correlations with OVI Absorbers
• The Local Lyman-Alpha Forest: Absorbers in Galaxy Voids

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• Broad HI Absorbers as Metallicity-Independent Tracers of the Warm-Hot Intergalactic Medium
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• HST/COS Spectra of Three QSOs That Probe The Circumgalactic Medium of a Single Spiral Galaxy: Evidence for Gas Recycling and Outflow
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• The MOSDEF Survey: Environmental dependence of the gas-phase metallicity of galaxies at $1.4\le z\le 2.6$
• The Dearth of Chemically Enriched Warm-Hot Circumgalactic Gas
• Large Scale Structure in Absorption: Gas within and around Galaxy Voids
• The Surprisingly Constant Strength of O VI Absorbers over Cosmic Time
• The Spread of Metals into the Low-Redshift Intergalactic Medium
• The Low-Redshift Lyman Alpha Forest toward 3C 273
• Correlations between O VI Absorbers and Galaxies at Low Redshift
• A Detection of Gas Associated with the M 31 Stellar Stream
• The End of the Rainbow: What Can We Say About the Extragalactic Sub-Megahertz Radio Sky?
• Stochastic Order Redshift Technique (SORT): a simple, efficient and robust method to improve cosmological redshift measurements
• Updated Models for the Creation of a Low-z QSO Absorber by a Dwarf Galaxy Wind