H I gas in higher density regions of the intergalactic medium

Abstract

Using H I absorption alone, we attempt to separate H I absorption lines in quasar spectra into two categories; HDLs (Higher Density Lines) and LDLs (Lower Density Lines), and we discuss the difference in their physical properties. We deblend and fit all H I lines with Voigt profiles, and make an unbiased sample of H I lines covering a wide column density range (12 < log N_HI < 19 cm^-2). To reduce the influence of line blending, we simultaneously fit several Lyman series lines. As a result of a two-point correlation analysis, we found that higher column density H I lines are clustering at $\Delta$ v < 200 km/s, while lower ones at $\Delta$ v < 100 km/s. We define HDLs as H I lines with 15 < log N_HI < 19 cm^-2 and all H I lines within +/- 200 km/s of a line with log N_HI > 15 cm^-2, and LDLs as others with 12 < log N_HI < 15 cm^-2. We found that the HDLs have smaller minimum b-values for a given column density than the LDLs. This difference is successfully reproduced by our Hydrodynamic simulation. The LDLs seem to be cool or shock-heated diffuse IGM gas, while the HDLs are likely to be cooler dense gas near to galaxies.

22 pages, 7 figures, accepted for publication in the Astronomical Journal

References in corpus (36)

• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• Galaxies and Intergalactic Matter at Redshift z~3: Overview
• The Lyman Alpha Forest in the Spectra of QSOs
• The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies
• The Deuterium Abundance Towards Q1937-1009
• The cosmological baryon density from the deuterium to hydrogen ratio towards QSO absorption systems: D/H towards Q1243+3047
• Abundances at High Redshifts: the Chemical Enrichment History of Damped Lyman-alpha Galaxies
• The Deuterium Abundance Towards Q1009+2956
• The Deuterium to Hydrogen Abundance Ratio Towards a Fourth QSO: HS0105+1619
• The Cosmological Baryon Density from the Deuterium Abundance at a redshift z = 3.57
• A Multi-Species Model for Hydrogen and Helium Absorbers in Lyman-Alpha Forest Clouds
• The Distribution of Column Densities and b Values in the Lyman-Alpha Forest
• The Relationship Between Galaxies and Low Redshift Weak Lyman alpha Absorbers in the Directions of H1821+643 and PG1116+215
• Intrinsic Properties of the <z>=2.7 Lyman Alpha Forest from Keck Spectra of QSO HS 1946+7658
• The Gaseous Extent of Galaxies and the Origin of Lya Absorption Systems. V. Optical and Near-Infrared Photometry of Lya-absorbing Galaxies at z < 1
• The physical properties of the Ly-Alpha forest at z > 1.5
• The UCSD HIRES/KeckI Damped Lya Abundance Database: I. The Data
• Spectral Analysis of the Lyman Alpha Forest in a Cold Dark Matter Cosmology
• Physical Properties of the Lyman Alpha Forest in a Cold Dark Matter Cosmology
• The Local Lya Forest. III. Relationship between Lya Absorbers and Galaxies, Voids and Superclusters
• The Lyman-Alpha Forest at 1.5 < z < 4
• APM z>4 QSO Survey: Spectra and Intervening Absorption Systems
• Resolving the Lyman-alpha Forest
• The Kinematics of Intermediate Redshift Mg II Absorbers
• Absorption Systems in the Spectra of 66 z > 4 Quasars
• A High Deuterium Abundance in the Early Universe
• High redshift galaxies and the Lyman-alpha forest in a CDM universe
• Lyman Break Galaxies and the Lyman-alpha Forest
• The evolution of the physical state of the IGM
• The clustering properties of the Lyman-alpha clouds
• The Lyman-alpha Forest at z~4: Keck HIRES Observations of Q 0000-26
• QSO 0130-4021: A third QSO showing a low Deuterium to Hydrogen Abundance Ratio
• The Clustering of Intergalactic Metals
• Lyman-Alpha Absorption Systems and the Nearby Galaxy Distribution
• Large-scale Correlation of Mass and Galaxies with the Lyman-alpha Forest Transmitted Flux
• Subaru high resolution spectroscopy of complex metal absorption lines of QSO HS1603+3820

Cited by in corpus (9)

• Evolution of the Intergalactic Opacity: Implications for the Ionizing Background, Cosmic Star Formation, and Quasar Activity
• Colour corrections for high redshift objects due to intergalactic attenuation
• Lyman Limit Systems in Cosmological Simulations
• The Effect of Large-Scale Power on Simulated Spectra of the Lya forest
• Spectroscopic Analysis of H I Absorption Line Systems in 40 HIRES Quasars
• Spectroscopy along Multiple, Lensed Sightlines through Outflowing Winds in the Quasar SDSS J1029+2623
• Tracing the gas at redshift 1.7-3.5 with the Lyman-alpha forest: the FLO approach
• The Lyman-alpha forest at redshifts 0.1 -- 1.6: good agreement between a large hydrodynamic simulation and HST spectra
• The HeII Lyman alpha forest and the thermal state of the IGM