The Observability of Metal Lines Associated with the Lyman-alpha Forest

Abstract

We develop a prescription for characterizing the strengths of metal lines associated with Lyman-alpha forest absorbers (LYFAs) of a given neutral hydrogen column density N_HI and metallicity [Fe/H]. This Line Observability Index (LOX) is line-specific and translates, for weak lines, into a measure of the equivalent width. It can be evaluated quickly for thousands of transitions within the framework of a given model of the Lyman-alpha forest, providing a ranking of the lines in terms of their strengths and enabling model builders to select the lines that should be detectable in observed spectra of a given resolution and signal-to-noise ratio. We compute the LOX for a large number of elements and transitions in two cosmological models of the Lyman-alpha forest at z=3 derived from a hydrodynamic simulation of structure formation, and we discuss how the LOX depends on redshift and on model parameters such as the mean baryonic density and radiation field. We find that the OVI (1032,1038) doublet is the best probe of the metallicity in low column density LYFAs N_{HI} \approx 10^{14.5} cm^{-2}). Metallicities down to [O/H] \sim -3 ([Fe/H] \sim -3.5 with the assumed [O/Fe] ratio) yield OVI absorption features that should be detectable in current high-quality spectra, provided that the expected position of the OVI feature is not contaminated by HI absorption. The strongest transitions in lower ionisation states of oxygen are OV(630), OIV(788), and OIII(833), and are likely to be detected with next generation UV instruments. Of the lines with rest wavelengths λ_r > 1216, which can potentially be observed redwards of the \lya forest, the CIV(1548,1551) doublet is expected to dominate in all LYFAs, regardless of the value of N_HI.

Substantially revised version: larger line database, additional cosmological model analyzed. Accepted for ApJ

References in corpus (6)

• Equation of State of the Photoionized Intergalactic Medium
• Reionization of the Universe and the Early Production of Metals
• Recovery of the Power Spectrum of Mass Fluctuations from Observations of the Lyman-alpha Forest
• The Opacity of the Lyman Alpha Forest and Implications for Omega_{baryon} and the Ionizing Background
• Physical Properties of the Lyman Alpha Forest in a Cold Dark Matter Cosmology
• Metal Lines Associated with Lyman Alpha Absorbers: A Comparison of Theory and Observations

Cited by in corpus (25)

• Cosmological Simulations of Intergalactic Medium Enrichment from Galactic Outflows
• The Low Redshift Lyman Alpha Forest in Cold Dark Matter Cosmologies
• The cosmological baryon density from the deuterium to hydrogen ratio towards QSO absorption systems: D/H towards Q1243+3047
• The Physics of the Intergalactic Medium
• The Power Spectrum of Mass Fluctuations Measured from the Lyman-alpha Forest at Redshift z=2.5
• Metal Enrichment of the Intergalactic Medium in Cosmological Simulations
• The intergalactic medium over the last 10 billion years I: Lyman alpha absorption and physical conditions
• The intergalactic medium over the last 10 billion years II: Metal-line absorption and physical conditions
• Hydrogen and Metal Line Absorption Around Low-Redshift Galaxies in Cosmological Hydrodynamic Simulations
• Characterizing the Warm-Hot IGM at High Redshift: A High Resolution Survey for O VI at z = 2.5
• The detection of oxygen in the low-density intergalactic medium
• Constraining the Metallicity of the Low Density Lyman-alpha Forest Using OVI Absorption
• Extreme Ultraviolet Absorption Lines in LyA Forest Absorbers and the Oxygen Abundance in the Intergalactic Medium
• QSO 0130-4021: A third QSO showing a low Deuterium to Hydrogen Abundance Ratio
• An HST/COS survey of molecular hydrogen in DLAs & sub-DLAs at z < 1: Molecular fraction and excitation temperature
• Pixel correlation searches for OVI in the Lyman alpha forest and the volume filling factor of metals in the Intergalactic Medium at z ~ 2-3.5
• A high resolution study of intergalactic O VI absorbers at z~2.3
• A Search for Oxygen in the Low-Density Lyman-alpha Forest Using the Sloan Digital Sky Survey
• Chemical Abundances and the Metagalactic Radiation Field at High Redshift
• High Metallicity Mg II Absorbers in the z < 1 Lyman alpha Forest of PKS 0454+039: Giant LSB Galaxies?
• MUSEQuBES: The relation between Ly$\alpha$ emitters and C IV absorbers at $z\approx 3.3$
• Multicomponent H2 in DLA at zabs = 2.05: physical conditions through observations and numerical models
• Discovery of a multiphase OVI and OVII absorber in the circumgalactic/intergalactic transition region
• A Survey of Metal Lines at High-redshift (II) : SDSS Absorption Line Studies - OVI line density, space density and gas metallicity at z_abs ~ 3.0
• Trend Filtering -- II. Denoising Astronomical Signals with Varying Degrees of Smoothness