Probing The Intergalactic Medium-Galaxy Connection At z < 0.5. I. A Galaxy Survey In Qso Fields And A Galaxy-Absorber Cross-Correlation Study
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 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 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(H I) ≥ 14 and O 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(H 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 VI absorber to a sensitive upper limit of W(1031) lsim 0.03 Å, while the covering fraction of O VI absorbing gas around emission-line-dominated galaxies is found to be κ ≈ 64%; and (4) high-resolution images of five O VI absorbing galaxies show that these galaxies exhibit disk-like morphologies with mildly disturbed features on the edge. Together, the data indicate that O VI absorbers arise preferentially in gas-rich galaxies. In addition, tidal debris in groups/galaxy pairs may be principally responsible for the observed O 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.- Publication:
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The Astrophysical Journal
- Pub Date:
- August 2009
- DOI:
- 10.1088/0004-637X/701/2/1219
- arXiv:
- arXiv:0906.3293
- Bibcode:
- 2009ApJ...701.1219C
- Keywords:
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- cosmology: observations;
- intergalactic medium;
- quasars: absorption lines;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 27 journal-style pages, 15 figures