A STIS Survey for OVI Absorption Systems at 0.12 < z < 0.5 I.: The Statistical Properties of Ionized Gas

Abstract

We have conducted a systematic survey for intervening OVI absorbers in available echelle spectra of 16 QSOs at z_QSO = 0.17-0.57. These spectra were obtained using HST/STIS with the E140M grating. Our search uncovered a total of 27 foreground OVI absorbers with rest-frame absorption equivalent width W_r(1031) > 25mA. Ten of these QSOs exhibit strong OVI absorbers in their vicinity. Our OVI survey does not require the known presence of Lya, and the echelle resolution allows us to identify the OVI absorption doublet based on their common line centroid and known flux ratio. We estimate the total redshift survey path, Δz, using a series of Monte-Carlo simulations, and find that Δz=1.66, 2.18, and 2.42 for absorbers of strength W_r = 30, 50 and 80mA, respectively, leading to a number density of dN(W > 50mA)/dz = 6.7 +/- 1.7 and dN(W > 30mA)/dz = 10.4 +/- 2.2. In contrast, we also measure dN/dz = 27 +/- 9 for OVI absorbers of W_r > 50mA at |Δv|< 5000 kms from the background QSOs. Using the random sample of OVI absorbers with well characterized survey completeness, we estimate a mean cosmological mass density of the OVI gas Ω(OVI)h = 1.7 +/- 0.3 x 10^-7. In addition, we show that <5% of OVI absorbers originate in underdense regions that do not show a significant trace of HI. Furthermore, we show that the neutral gas column N(HI) associated with these OVI absorbers spans nearly five orders of magnitude, and show moderate correlation with N(OVI). Finally, while the number density of OVI absorbers varies substantially from one sightline to another, it also appears to be inversely correlated with the number density of HI absorbers along individual lines of sight.

arXiv comment12 pages. ApJ accepted

References in corpus (38)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• The Cosmic Baryon Budget
• Where are the Baryons?
• Baryons in the Warm-Hot Intergalactic Medium
• Line formation in solar granulation: IV. [O I], OI and OH lines and the photospheric O abundance
• Big-Bang Nucleosynthesis Predictions for Precision Cosmology
• The Opacity of the Lyman Alpha Forest and Implications for Omega_{baryon} and the Ionizing Background
• Time-Dependent Ionization in Radiatively Cooling Gas
• Intervening O VI Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir
• The baryon content of the Universe
• The Deuterium to Hydrogen Abundance Ratio Towards the QSO SDSS1558-0031
• An OVI Baryon Census of the Low-z Warm-Hot Intergalactic Medium
• Physical Properties, Baryon Content, and Evolution of the LyαForest: New Insights from High Resolution Observations at z < 0.4
• On the Physical Origin of OVI Absorption-Line Systems
• Physical Properties and Baryonic Content of Low-Redshift Intergalactic Ly-alpha and O VI Absorption Systems: The PG1116+215 Sight Line
• O VI and Multicomponent H I Absorption Associated with a Galaxy Group in the Direction of PG0953+415: Physical Conditions and Baryonic Content
• The Ionization and Metallicity of the Intervening O VI Absorber at z = 0.1212 in the Spectrum of H1821+643
• Detection of Ne VIII in the Low-Redshift Warm-Hot IGM
• Where Are the Baryons? III: Non-Equilibrium Effects and Observables
• FUSE and STIS Observations of the Warm-Hot Intergalactic Medium towards PG1259+593
• Revealing the Warm-Hot Intergalactic Medium with OVI Absorption
• The Cosmological Density and Ionization of Hot Gas: Oxygen VI Absorption in Quasar Spectra
• Probing the IGM/Galaxy Connection Toward PKS0405-123 I: UV Spectroscopy and Metal-Line Systems
• X-ray Absorption by the Low-redshift Intergalactic Medium: A Numerical Study of the Lambda CDM model
• Probing the Intergalactic Medium with the OVI Forest
• Tracing baryons in the warm-hot intergalactic medium with broad Ly alpha absorption
• Characterizing the Low-Redshift Intergalactic Medium towards PKS1302-102
• The last stand before MAP: cosmological parameters from lensing, CMB and galaxy clustering
• The Origin of a Chemically Enriched lya Absorption System at z=0.167
• Do young galaxies exist in the Local Universe? - Red Giant Branch detection in the metal-poor dwarf SBS 1415+437
• High Metallicity, Photoionised Gas in Intergalactic Large-Scale Filaments
• Absorption-Line Systems and Galaxies in Front of the Second Brightest Quasar, PHL 1811
• Low Redshift Intergalactic Absorption Lines in the Spectrum of HE0226-4110
• Galactic Wind Signatures around High Redshift Galaxies
• The Low-Redshift Lyman Alpha Forest toward PKS 0405-123
• High-Resolution Absorption Spectroscopy of Multi-phase, High-Metallicity Gas Associated with the Luminous Quasar HE 0226-4110
• Associated Absorption Lines in the Radio-Loud Quasar 3C 351: Far-Ultraviolet Echelle Spectroscopy from the Hubble Space Telescope
• The variable super-orbital modulation of Cygnus X-1

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