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

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

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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

Keywords / Materials (for Non-textual outputs)

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


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