The High-ion Content and Kinematics of Low-redshift Lyman Limit Systems

Andrew J. Fox, Nicolas Lehner, Jason Tumlinson, J. Christopher Howk, Todd M. Tripp, J. Xavier Prochaska, John M. O'Meara, Jessica K. Werk, Rongmon Bordoloi, Neal Katz, Benjamin D. Oppenheimer, Romeel Davé

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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 (Δv 90 statistic) in LLSs is not correlated with metallicity, indicating that the H I 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) ~ 17.6-20. The O VI phase of LLSs is a substantial baryon reservoir, with M(high-ion) ~ 108.5-10.9 (r/150 kpc)2 M ⊙, 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. Based on observations taken under programs 11508, 11520, 11541, 11598, 11692, 11741, 12025, 12038, and 12466 of the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Original languageEnglish
Pages (from-to)187
JournalAstrophysical Journal
Volume778
Issue number2
DOIs
Publication statusPublished - 13 Nov 2013

Keywords / Materials (for Non-textual outputs)

  • galaxies: halos
  • galaxies: kinematics and dynamics
  • intergalactic medium

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