B. Savage, N. Lehner, A. Narayanan
Observations of the QSO HE 0226-4110 (zem = 0.495) with the Cosmic Origins
Spectrograph (COS) from 1134 to 1796 {\AA} with a resolution of ~17 km s-1 and
signal-to- noise (S/N) per resolution element of 20 to 40 are used to study the
multi-phase absorption system at z = 0.20701 containing O VI and Ne VIII. The
system was previously studied with lower S/N observations with FUSE and STIS.
The COS observations provide more reliable measures of the H I and metal lines
present in the system and reveal the clear presence of broad Lyman {\alpha}
(BLA) absorption with b = 72(+13, -6) km s-1 and logN(H I) = 13.87\pm0.08.
Detecting BLAs associated with warm gas absorbers is crucial for determining
the temperature, metallicity and total baryonic content of the absorbers. The
BLA is probably recording the trace amount of thermally broadened H I in the
collisionally ionized plasma with log T ~5.7 that also produces the O VI and Ne
VIII absorption. The total hydrogen column in the collisionally ionized gas,
logN(H) ~ 20.1, exceeds that in the cooler photoionized gas in the system by a
factor of ~22. The oxygen abundance in the collisionally ionized gas is [O/H] =
-0.89\pm0.08\pm0.07. The absorber probably occurs in the circumgalactic
environment (halo) of a foreground L = 0.25L* disk galaxy with an impact
parameter of 109h70-1 kpc identified by Mulchaey & Chen (2009).
View original:
http://arxiv.org/abs/1111.1697
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