The Statistical and Physical Properties of the Low Redshift Lyman Alpha Forest Observed with HST/STIS

Abstract

We examine the Ly-alpha absorber population at z<0.3 detected in spectra of the QSOs PG0953+415 and H1821+643 taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. We compare their statistical properties to those in carefully-constructed mock quasar spectra drawn from a cosmological hydrodynamic simulation of a Lambda-CDM universe. We find very good agreement in the column density and b-parameter distributions, down to the smallest observable absorbers with N_HI\approx 10^{12.3} cm^-2. The observed absorber population is complete for N_HI\ga 10^{13} cm^-2, with a column density distribution slope of β=2.04\pm 0.23 and a median b-parameter of 21 km/s above this limit. The intergalactic gas giving rise to these weak absorbers is analogous to that at high redshift, located in diffuse large-scale structures that are highly photoionized by the metagalactic UV flux, though a greater number arise within shock-heated warm gas. The density, temperature, and column density of these absorbers follow similar relationships to those at high redshift, though with substantially larger scatter due to the shock-heated gas. The b-parameters typically have a significant contribution from thermal broadening, which facilitates a measurement of the low-z IGM temperature as traced by Ly-alpha absorbers. From our simulation we estimate T_IGM\sim 5000 K, with an upper limit of 10^4 K, at the mean density. The agreement in predicted and observed amplitude of the column density distributions allows us to measure the HI photoionization rate at z=0.17 to be 10^{-13.3\pm 0.7} s^{-1} (estimated modeling uncertainty), close to predictions based on quasar properties.

17 pages, minor revisions to match published version

Cited by in corpus (70)

• Cosmological Simulations of Intergalactic Medium Enrichment from Galactic Outflows
• The COS-Halos Survey: An Empirical Description of the Metal-Line Absorption in the Low-Redshift Circumgalactic Medium
• Model-independent insights into the nature of the Lyman-alpha forest and the distribution of matter in the universe
• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• The first ultraviolet quasar stacked spectrum at z=2.4 from WFC3
• The Thermal Memory of Reionization History
• A Composite Extreme Ultraviolet QSO Spectrum from the Far Ultraviolet Spectroscopic Explorer
• The COS-Halos Survey: Origins of the Highly Ionized Circumgalactic Medium of Star-Forming Galaxies
• An HST/COS Survey of the Low-Redshift IGM. I. Survey, Methodology, & Overall Results
• The Local Ly-alpha Forest IV: STIS G140M Spectra and Results on the Distribution and Baryon Content of HI Absorbers
• The physical properties of the Ly-Alpha forest at z > 1.5
• Physical Properties, Baryon Content, and Evolution of the LyαForest: New Insights from High Resolution Observations at z < 0.4
• The intergalactic medium over the last 10 billion years I: Lyman alpha absorption and physical conditions
• The Nature and Origin of Low-Redshift O VI Absorbers
• The Column Density Distribution and Continuum Opacity of the Intergalactic and Circumgalactic Medium at Redshift <z>=2.4
• The Ionization and Metallicity of the Intervening O VI Absorber at z = 0.1212 in the Spectrum of H1821+643
• The Photon Underproduction Crisis
• X-Ray Scaling Relations of Galaxy Groups in a Hydrodynamic Cosmological Simulation
• FUSE and STIS Observations of the Warm-Hot Intergalactic Medium towards PG1259+593
• QSO Absorption Systems Detected in Ne VIII: High-Metallicity Clouds with a Large Effective Cross Section
• Lyman-alpha absorption around nearby galaxies
• Probing the IGM/Galaxy Connection Toward PKS0405-123 I: UV Spectroscopy and Metal-Line Systems
• Discovery of a Primitive Damped Lyman alpha Absorber Near an X-ray Bright Galaxy Group in the Virgo Cluster
• Faint AGN and the Ionizing Background
• The Low-z Intergalactic Medium. II. LyB, OVI, and CIII Forest
• The Heavy Element Enrichment of Lyman alpha Clouds in the Virgo Supercluster
• Probing the Intergalactic Medium with the OVI Forest
• A Uniform Analysis of the Ly-alpha Forest at z=0 - 5: V. The extragalactic ionizing background at low redshift
• Tracing baryons in the warm-hot intergalactic medium with broad Ly alpha absorption
• The Simulated HI Sky at low redshift
• The Hot Intergalactic Medium - Galaxy Connection: Two Strong Absorbers in the Sightline Toward PG 1211+143
• On the importance of local sources of radiation for quasar absorption line systems
• A Near-Solar Metallicity, Nitrogen-Deficient Lyman Limit Absorber Associated with two S0 Galaxies
• Intergalactic Lyman continuum photon budget in the past 5 billion years
• The Evolution of Lyman alpha Absorbers in the Redshift Range 0.5<z<1.9
• VoIgt profile Parameter Estimation Routine (VIPER): H I photoionization rate at z<0.5
• Absorption signatures of warm-hot gas at low redshift: Broad HI Lyman-Alpha Absorbers
• Probing the IGM/Galaxy Connection Toward PKS0405-123 III: The Galaxy Survey and Correlations with OVI Absorbers
• Properties of QSO Metal Line Absorption Systems at High Redshifts: Nature and Evolution of the Absorbers and New Evidence on Escape of Ionizing Radiation from Galaxies
• The Imprint of Cosmic Web Quenching on Central Galaxies
• High Metallicity, Photoionised Gas in Intergalactic Large-Scale Filaments
• A New Observational Upper Limit to the Low Redshift Ionizing Background Radiation
• The Power Spectrum of the Lyman-$\alpha$ Forest at z < 0.5
• Simulations of thermally broadened HI Lya absorption arising in the warm-hot intergalactic medium
• Low Redshift Intergalactic Absorption Lines in the Spectrum of HE0226-4110
• Jet Feedback and the Photon Underproduction Crisis in Simba
• The Low-Redshift Lyman Alpha Forest toward PKS 0405-123
• A new z=0 metagalactic UV background limit
• Ultraviolet Line Emission from Metals in the Low-Redshift Intergalactic Medium
• Probing the Size of Low-Redshift Lyman-alpha Absorbers
• A Survey of Analogs to Weak MgII Absorbers in the Present
• Highly-Ionized Oxygen Absorbers in the Intergalactic Medium
• The association between gas and galaxies I: CFHT spectroscopy and pair analysis
• Baryons: What, When and Where?
• Associated Absorption Lines in the Radio-Loud Quasar 3C 351: Far-Ultraviolet Echelle Spectroscopy from the Hubble Space Telescope
• The Astrophysical Consequences of Intervening Galaxy Gas on Fast Radio Bursts
• The Effect of Large-Scale Power on Simulated Spectra of the Lya forest
• The Normalization and Slope of the Dark Matter (Sub-)Halo Mass Function on Sub-Galactic Scales
• A uniform analysis of the Lyman alpha forest at z = 0-5: IV. The clustering and evolution of clouds at z < 1.7
• Efficient adiabatic hydrodynamical simulations of the high-redshift intergalactic medium
• Spectroscopic Analysis of H I Absorption Line Systems in 40 HIRES Quasars
• The Robustness of Cosmological Hydrodynamic Simulation Predictions to Changes in Numerics and Cooling Physics
• The Low-Redshift Lyman Alpha Forest toward 3C 273
• The Lyman-alpha forest at redshifts 0.1 -- 1.6: good agreement between a large hydrodynamic simulation and HST spectra
• Lyman Alpha Flux Power Spectrum and Its Covariance
• Modeling the Void H I Column Density Spectrum
• Can the Low Redshift Lyman Alpha Forest Constrain AGN Feedback Models?
• The Nature and Origin of the Non-Void Lyman alpha Cloud Population
• Lyman Alpha Absorber Correlations and the Bias of the Lyman Alpha Forest
• Line versus Flux Statistics -- Considerations for the Low Redshift Lyman-alpha Forest