| Type |
Journal Article |
| Names |
Anand Narayanan, Blair D. Savage, Bart P. Wakker, Charles W. Danforth, Yangsen Yao, Brian A. Keeney, J. Michael Shull, Kenneth R. Sembach, Cynthia S. Froning, James C. Green |
| Publication |
The Astrophysical Journal |
| Volume |
730 |
| Issue |
1 |
| Pages |
15 |
| Date |
March 1, 2011 |
| URL |
http://adsabs.harvard.edu/abs/2011ApJ...730...15N |
| Library Catalog |
NASA ADS |
| Abstract |
We report on the detection of Ne VIII in the Hubble Space
Telescope/Cosmic Origins Spectrograph (COS) spectrum of the intervening
absorption system at z = 0.495096 toward PKS 0405–123 (z
em = 0.5726). The high signal-to-noise COS spectrum also
covers absorption from H I, C III, O III, O IV, and O VI associated with
this multiphase system. The Ne VIII is detected with high significance
in both lines of the doublet, with integrated column densities of log
Na (Ne VIII 770) = 13.96 ± 0.06 and log Na
(Ne VIII 780) = 14.08 ± 0.07. We find the origin of Ne VIII
consistent with collisionally ionized gas at T ~ 5 ×
105 K with a large baryonic column density of N(H) ~
1019-1020 cm–2. The metallicity
in the Ne VIII gas phase is estimated to be [Ne/H] ~–0.6 ±
0.3 dex. The intermediate ions such as C III, O III, O IV, and H I are
consistent with photoionization in lower ionization gas at T ~
104 K. The O V and O VI in this absorber can have
contributions from both the photoionized and collisionally ionized gas
phases. The absorber is at |Δv| = 180 km s–1
systematic velocity and ρ = 110h –1 70
kpc projected separation from an MR = –19.6 galaxy of
extended morphology. The collisionally ionized gas at T ~ 5 ×
105 K detected in Ne VIII and O VI points to an origin in
multiphase gas embedded in the hot halo of the galaxy, or in a nearby
WHIM structure. The high-sensitivity UV spectroscopy afforded by COS has
opened up new opportunities for discovering large reservoirs of missing
baryons in the low-z universe through the detection of Ne VIII systems.
Based on observations with the NASA/ESA Hubble Space Telescope, obtained
at the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., under NASA
contract NAS 05-26555, and the NASA-CNES/ESA Far-Ultraviolet
Spectroscopic Explorer mission, operated by the Johns Hopkins
University, supported by NASA contract NAS 05-32985. |
| Tags |
Galaxies: Halos, intergalactic medium, quasars: absorption lines, quasars: individual: PKS 0405–123, ultraviolet: general |