Kinematics of the O vi circumgalactic medium: Halo mass dependence and outflow signatures

Mason Ng, Nikole M. Nielsen, Glenn G. Kacprzak, Stephanie K. Pointon, Sowgat Muzahid, Christopher W. Churchill, Jane C. Charlton

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14 Scopus citations


We probe the high-ionization circumgalactic medium by examining absorber kinematics, absorber-galaxy kinematics, and average absorption profiles of 31 O vi absorbers from the "Multiphase Galaxy Halos" Survey as a function of halo mass, redshift, inclination, and azimuthal angle. The galaxies are isolated at 0.12 < z gal < 0.66 and are probed by a background quasar within D ≈ 200 kpc. Each absorber-galaxy pair has Hubble Space Telescope images and COS quasar spectra, and most galaxy redshifts have been accurately measured from Keck/ESI spectra. Using the pixel-velocity two-point correlation function (TPCF) method, we find that O vi absorber kinematics have a strong halo mass dependence. Absorbers hosted by ∼L∗ galaxies have the largest velocity dispersions, which we interpret to be that the halo virial temperature closely matches the temperature at which the collisionally ionized O vi fraction peaks. Lower-mass galaxies and group environments have smaller velocity dispersions. Total column densities follow the same behavior, consistent with theoretical findings. After normalizing out the observed mass dependence, we studied absorber-galaxy kinematics with a modified TPCF and found nonvirialized motions due to outflowing gas. Edge-on minor-Axis gas has large optical depths concentrated near the galaxy systemic velocity as expected for bipolar outflows, while face-on minor-Axis gas has a smoothly decreasing optical depth distribution out to large normalized absorber-galaxy velocities, suggestive of decelerating outflowing gas. Accreting gas signatures are not observed owing to "kinematic blurring," in which multiple line-of-sight structures are observed. These results indicate that galaxy mass dominates O vi properties over baryon cycle processes.

Original languageEnglish (US)
Article number66
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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