Luca Zappacosta, Fabrizio Nicastro, Yair Krongold, Roberto Maiolino
We report a detection of an absorption line at ~44.8 {\AA} in a > 500 ks
Chandra HRC-S/LETG X-ray grating spectrum of the blazar H 2356-309. This line
can be identified as intervening CV-K{\alpha} absorption, at z\approx0.112,
produced by a warm (logT = 5.1 K) intergalactic absorber. The feature is
significant at a 4.2{\sigma} level, with a 0.2% chance detection probability.
We estimate an equivalent hydrogen column density of log N_H=19.05 (Z/Zsun)^-1
cm^-2. Unlike other previously reported FUV/X-ray metal detections of warm-hot
intergalactic medium (WHIM), this CV absorber lies in a region with locally low
galaxy density, at ~2.2 Mpc from the closest galaxy at that redshift, and
therefore is unlikely to be associated with an extended galactic halo. We
instead tentatively identify this absorber with a genuine WHIM system
permeating a large-scale, 30 Mpc extended, filament of galaxies crossing the
sightline at z\approx0.112.
View original:
http://arxiv.org/abs/1202.5237
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