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The COS-Halos Survey: Rationale, Design, and a Census of Circumgalactic Neutral Hydrogen

Research output: Contribution to journalArticle

  • Jason Tumlinson
  • Christopher Thom
  • Jessica K. Werk
  • J. Xavier Prochaska
  • Todd M. Tripp
  • Neal Katz
  • Romeel Davé
  • Benjamin D. Oppenheimer
  • Joseph D. Meiring
  • Amanda Brady Ford
  • John M. O'Meara
  • Molly S. Peeples
  • Kenneth R. Sembach
  • David H. Weinberg

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Original languageEnglish
Pages (from-to)59
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 17 Oct 2013


We present the design and methods of the COS-Halos survey, a systematic investigation of the gaseous halos of 44 z = 0.15-0.35 galaxies using background QSOs observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. This survey has yielded 39 spectra of z em ~= 0.5 QSOs with S/N ~10-15 per resolution element. The QSO sightlines pass within 150 physical kpc of the galaxies, which span early and late types over stellar mass log M */M ⊙ = 9.5-11.5. We find that the circumgalactic medium exhibits strong H I, averaging ~= 1 Å in Lyα equivalent width out to 150 kpc, with 100% covering fraction for star-forming galaxies and 75% covering for passive galaxies. We find good agreement in column densities between this survey and previous studies over similar range of impact parameter. There is weak evidence for a difference between early- and late-type galaxies in the strength and distribution of H I. Kinematics indicate that the detected material is bound to the host galaxy, such that >~ 90% of the detected column density is confined within ±200 km s-1 of the galaxies. This material generally exists well below the halo virial temperatures at T

    Research areas

  • galaxies: formation, galaxies: halos, intergalactic medium, quasars: absorption lines

ID: 57686011