Astronomy and Astrophysics – Astrophysics
Scientific paper
2000-03-20
Astrophys.J.534:L1-L5,2000
Astronomy and Astrophysics
Astrophysics
Accepted for publication in the Ap.J. Letters, 7 pages, 3 figures
Scientific paper
10.1086/312644
FUV echelle spectroscopy of the radio-quiet QSO H1821+643 (z = 0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) at 7 km/s resolution, reveals 4 definite O VI absorption line systems and one probable O VI absorber at 0.15 < z(abs) < 0.27. The four definite O VI absorbers are located near galaxies and are highly displaced from the quasar in redshift; these are likely intervening systems unrelated to the background QSO. In the case of the strong O VI system at z(abs) = 0.22497, multiple components are detected in Si III and O VI as well as H I Lyman series lines, and the differing component velocity centroids and b-values firmly establish that this is a multiphase absorption system. A weak O VI absorber is detected at z(abs) = 0.22637, i.e., offset by ~340 km/s from the z(abs) = 0.22497 system. Lya absorption is detected at z(abs) = 0.22613, but no Lya absorption is significantly detected at 0.22637. Other weak O VI absorbers at z(abs) = 0.24531 and 0.26659 and the probable O VI system at 0.21326 have widely diverse O VI/H I column density ratios with N(O VI)/N(H I) ranging from <=0.14+/-0.03 to 5.2+/-1.2. The number density of O VI absorbers with rest equivalent width > 30 mA in the H1821+643 spectrum is remarkably high, dN/dz ~48, with a high (90%) confidence that it is greater than 17. We conservatively estimate that the cosmological mass density of the O VI systems Omega_b(O VI) > 0.0008/h_75. With an assumed metallicity of 1/10 solar and a conservative assumption that the fraction of oxygen in the O VI ionization stage is 0.2, we obtain Omega_b(O VI) > 0.004/h_75. This is comparable to the combined cosmological mass density of stars and cool gas in galaxies and X-ray emitting gas in galaxy clusters at low redshift.
Jenkins Edward B.
Savage Blair. D.
Tripp Todd M.
No associations
LandOfFree
Intervening O VI Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Intervening O VI Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Intervening O VI Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-392225