A MULTIPHASE ABSORBER CONTAINING O VI AND BROAD H I DIRECTLY TRACING 10{sup 6} K PLASMA AT LOW REDSHIFT TOWARD HE 0153-4520

Journal Article · Sun Apr 10 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/731/1/14· OSTI ID:21574791

Savage, B D; Narayanan, A; Wakker, B P ^[1]; Lehner, N ^[2]

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1. Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States)
2. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States)

Observations of the QSO HE 0153-4520 (z{sub em} = 0.450) with the Cosmic Origins Spectrograph (COS) from 1134 to 1796 A with a resolution of {approx}17 km s{sup -1} and a signal-to-noise ratio per resolution element of 20-40 are used to study a multiphase partial Lyman limit system (LLS) at z = 0.22601 tracing both cool and hot gas. Far-Ultraviolet Spectroscopic Explorer observations of the Lyman limit break yield log N(H I) = 16.61 (0.12, -0.17). The observed UV absorption lines of H I {lambda}{lambda}1216 to 926, C III, C II, N III, N II, Si III, and Si II imply the existence of cool photoionized gas in the LLS with log U = -2.8 {+-} 0.1 and log N(H) = 19.35 {+-} 0.18, log n{sub H} = -2.9 {+-} 0.2, log T = 4.27 {+-} 0.02, log (P/k) = 1.75 {+-} 0.17, and log L (kpc) = 0.70 {+-} 0.25. The abundances are [X/H] = -0.8 (+0.3, -0.2) for N, Si, and C, but the result is sensitive to the assumed shape of the ionizing background radiation field. The multiphase system has strong O VI and associated broad Ly{alpha} absorption (BLA) with log N(O VI) = 14.21 {+-} 0.02, b(O VI) = 37 {+-} 1 km s{sup -1}, log N(H I) = 13.70 (+0.05, -0.08), b(H I) = 140 (+14, -16) km s{sup -1} and b(H I)/b(O VI) = 3.9 {+-} 0.4. The O VI does not arise in the cool photoionized gas of the LLS. The O VI and BLA imply the direct detection of thermally broadened absorption by hot gas with log T = 6.07 (+0.09, -0.12), [O/H] = -0.28 (+0.09, -0.08), and log N(H) = 20.41 (+0.13, -0.17). The absorber probably occurs in the circumgalactic environment (halo) of a foreground galaxy. The very high sensitivity of UV absorption line spectroscopy to O VI and thermally broadened H I Ly{alpha} now permits the direct detection of hot gas with log T > 6, a determination of the abundance of O/H, and log N(H) in low-redshift intergalactic medium absorption line systems.

• OSTI ID: 21574791
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 731; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ABUNDANCE
ELECTROMAGNETIC RADIATION
ELEMENTS
FAR ULTRAVIOLET RADIATION
GALAXIES
NONMETALS
OXYGEN
RADIATIONS
SORPTION
ULTRAVIOLET RADIATION