The Detection of Two Distinct High Ionization States in a QSO Lyman Limit Absorption System: Evidence for Hierarchical Galaxy Formation at z ~ 3?

Abstract

We have detected two high ionization phases of gas in the z ~ 2.77 partial Lyman limit system (LLS) towards QSO 1157-3143. We detect the first phase by CIV and SiIV absorption, and the second phase -- which is either warmer or undergoing larger random bulk motions than the first -- via OVI absorption. Both phases of gas are present in similar column density ratios in each of the 5 velocity components, making it appear that this LLS is constructed of 5 very similar building blocks. We find that this system displays some of the properties expected of a hierarchical merging event, although published models may have trouble explaining the SiIV absorption we observe. When different ions show similar velocity structure, we commonly assume that they arise in the same gas, and we compare their column densities to derive the ionization and abundances. For this one absorption system the different ions have similar velocity but they do not arise in the same gas.

9 pages, including 3 figures

References in corpus (1)

• On the Kinematics of the Damped Lyman Alpha Protogalaxies

Cited by in corpus (18)

• Galactic and Circumgalactic OVI and its Impact on the Cosmological Metal and Baryon Budgets at 2<z<3.5
• O VI and Multicomponent H I Absorption Associated with a Galaxy Group in the Direction of PG0953+415: Physical Conditions and Baryonic Content
• The detection of oxygen in the low-density intergalactic medium
• Hot Halos around High Redshift Protogalaxies: Observations of O VI and N V Absorption in Damped Lyman Alpha systems
• C IV absorption in damped and sub-damped Lyman-alpha systems: correlations with metallicity and implications for galactic winds at z~2-3
• Intergalactic HeII absorption towards QSO 1157+3143
• Spectral shape of the UV ionizing background and HeII absorption at redshifts 1.8 < z < 2.9
• The High-Ion Content and Kinematics of Low-Redshift Lyman Limit Systems
• The Surprisingly Constant Strength of O VI Absorbers over Cosmic Time
• Multiphase Plasma in Sub-Damped Lyman Alpha Systems: A Hidden Metal Reservoir
• Inhomogeneous metal enrichment at z \sim 1.9: the Lyman limit systems in the spectrum of the HDF-S quasar
• Spectroscopic Analysis of H I Absorption Line Systems in 40 HIRES Quasars
• Metal abundances and kinematics of quasar absorbers.- I. Absorption systems toward J2233-606
• Probing the warm Inter-Galactic Medium through absorption against Gamma Ray Bursts X-ray afterglows
• The Absorbers Toward CSO 118: Superclustering at {z~3}, or an Intrinsic Absorption Complex?
• Gas Accretion via Lyman Limit Systems
• A high-redshift quasar absorber without CIV - a galactic outflow caught in the act?
• Nature of the background ultraviolet radiation field