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Title:
Probing The Intergalactic Medium-Galaxy Connection At z < 0.5. I. A Galaxy Survey In Qso Fields And A Galaxy-Absorber Cross-Correlation Study
Authors:
Chen, Hsiao-Wen; Mulchaey, John S.
Affiliation:
AA(Department of Astronomy & Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA ), AB(The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA )
Publication:
The Astrophysical Journal, Volume 701, Issue 2, pp. 1219-1242 (2009). (ApJ Homepage)
Publication Date:
08/2009
Origin:
IOP
ApJ Keywords:
cosmology: observations, intergalactic medium, quasars: absorption lines
DOI:
10.1088/0004-637X/701/2/1219
Bibliographic Code:
2009ApJ...701.1219C

Abstract

We present an imaging and spectroscopic survey of galaxies in fields around QSOs HE 0226-4110, PKS 0405-123, and PG 1216+069. The fields are selected to have ultraviolet echelle spectra available, which uncover 195 Lyα absorbers and 13 O\,{\scriptstyle VI} absorbers along the three sightlines. We obtain robust redshifts for 1104 galaxies of rest-frame absolute magnitude MR - 5log h lsim -16 and at projected physical distances ρ lsim 4 h -1 Mpc from the QSOs. Hubble Space Telescope (HST)/WFPC2 images of the fields around PKS 0405-123 and PG 1216+069 are available for studying the optical morphologies of absorbing galaxies. Combining the absorber and galaxy data, we perform a cross-correlation study to understand the physical origin of Lyα and O\,{\scriptstyle VI} absorbers and to constrain the properties of extended gas around galaxies. The results of our study are: (1) both strong Lyα absorbers of \log \,N(\mbox{H\,{\scriptstyle I}})\ge 14 and O\,{\scriptstyle VI} absorbers exhibit a comparable clustering amplitude as emission-line-dominated galaxies and a factor of ≈ 6 weaker amplitude than absorption-line-dominated galaxies on comoving projected distance scales of rp < 3 h -1 Mpc; (2) weak Lyα absorbers of \log \,N(\mbox{H\,{\scriptstyle I}})<13.5 appear to cluster very weakly around galaxies; (3) none of the absorption-line-dominated galaxies at rp <= 250 h -1 kpc has a corresponding O\,{\scriptstyle VI} absorber to a sensitive upper limit of W(1031) lsim 0.03 Å, while the covering fraction of O\,{\scriptstyle VI} absorbing gas around emission-line-dominated galaxies is found to be κ ≈ 64%; and (4) high-resolution images of five O\,{\scriptstyle VI} absorbing galaxies show that these galaxies exhibit disk-like morphologies with mildly disturbed features on the edge. Together, the data indicate that O\,{\scriptstyle VI} absorbers arise preferentially in gas-rich galaxies. In addition, tidal debris in groups/galaxy pairs may be principally responsible for the observed O\,{\scriptstyle VI} absorbers, particularly those of W(1031)>70 mÅ.

Observations reported here were obtained in part at the Magellan telescopes, a collaboration between the Observatories of the Carnegie Institution of Washington, University of Arizona, Harvard University, University of Michigan, and Massachusetts Institute of Technology.

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