PROBING THE INTERGALACTIC MEDIUM/GALAXY CONNECTION. V. ON THE ORIGIN OF Ly{alpha} AND O VI ABSORPTION AT z < 0.2

Journal Article · Thu Oct 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/740/2/91; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21587371

Prochaska, J Xavier ^[1]; Weiner, B ^[2]; Chen, H -W ^[3]; Mulchaey, J ^[4]; Cooksey, K ^[5]

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1. Department of Astronomy and Astrophysics and UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
2. Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)
3. Department of Astronomy, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States)
4. Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101 (United States)
5. MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-611, Cambridge, MA 02139 (United States)

We analyze the association of galaxies with Ly{alpha} and O VI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z{sub em} = 0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho} = 300 h{sup -1}{sub 72} kpc: 33/37 of our L > 0.01 L* galaxies show Ly{alpha} equivalent width W{sup Ly{alpha}} {>=} 50 mA. Galaxies of all luminosity L > 0.01 L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at {approx}10{sup 10.5{+-}0.3} M{sub sun} for a constant N{sub H} = 10{sup 19} cm{sup -2}. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W{sup Ly{alpha}} > 300 mA) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W{sup Ly{alpha}} = 30-300 mA occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of {approx}400 h{sup -1}{sub 72} kpc. Regarding O VI, we observe a near unity covering fraction to {rho} = 200 h{sup -1}{sub 72} kpc for L > 0.1 L* galaxies and to {rho} = 300 h{sup -1}{sub 72} kpc for sub-L* (0.1 L* < L < L*) galaxies. Similar to our Ly{alpha} results, stronger O VI systems (W{sup 1031} > 70 mA) arise in the virialized halos of L > 0.1 L* galaxies. Unlike Ly{alpha}, the weaker O VI systems (W{sup 1031} {approx} 30 mA) arise in the extended CGM of sub-L* galaxies. The majority of O VI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L {approx} 0.3 L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.

• OSTI ID: 21587371
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 740; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
COSMIC RADIO SOURCES
ELEMENTS
GALAXIES
IMPACT PARAMETER
INTERGALACTIC SPACE
LYMAN LINES
NONMETALS
OXYGEN
QUASARS
SORPTION
SPACE