THE HIGH-ION CONTENT AND KINEMATICS OF LOW-REDSHIFT LYMAN LIMIT SYSTEMS

• Published in: The Astrophysical journal 2013-12, Vol.778 (2), p.1-16
• Main Authors: Fox, Andrew J, Lehner, Nicolas, Tumlinson, Jason, Howk, J Christopher, Tripp, Todd M, Prochaska, J Xavier, O'Meara, John M, Werk, Jessica K, BORDOLOI, RONGMON, Katz, Neal, Oppenheimer, Benjamin D, Dave, Romeel
• Format: Article
• Language: English
• Subjects: APPROXIMATIONS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BARYONS; COMPARATIVE EVALUATIONS; DETECTION; DISTRIBUTION; GALAXIES; Hubble Space Telescope; HYDROGEN; Kinematics; LINE WIDTHS; MASS; METALLICITY; METALS; Phases; RED SHIFT; Samples; Searching; SPACE; Statistical methods; TELESCOPES
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/778/2/187

We study the high-ion content and kinematics of the circumgalactic medium around low-redshift galaxies using a sample of 23 Lyman limit systems (LLSs) at 0.08 < z < 0.93 observed with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. In Lehner et al., we recently showed that low-z LLSs have a bimodal metallicity distribution. Here we extend that analysis to search for differences between the high-ion and kinematic properties of the metal-poor and metal-rich branches. We find that metal-rich LLSs tend to show higher O VI columns and broader O VI profiles than metal-poor LLSs. The total H I line width ( Delta v sub(90) statistic) in LLSs is not correlated with metallicity, indicating that the HI kinematics alone cannot be used to distinguish inflow from outflow and gas recycling. Among the 17 LLSs with O VI detections, all but two show evidence of kinematic sub-structure, in the form of O VI-H I centroid offsets, multiple components, or both. Using various scenarios for how the metallicities in the high-ion and low-ion phases of each LLS compare, we constrain the ionized hydrogen column in the O VI phase to lie in the range log N(H II) similar to 17.6-20. The O VI phase of LLSs is a substantial baryon reservoir, with M(high-ion) similar to 10 super(8.5-10.9) (r/150 kpc) super(2) M sub([middot in circle]), similar to the mass in the low-ion phase. Accounting for the O VI phase approximately doubles the contribution of low-z LLSs to the cosmic baryon budget.