Hubble/COS Observations of Intergalactic Gas Toward PKS 0405-123

Type Conference Paper
Names J. Michael Shull, C. Danforth, C. Froning, J. Green, B. Keeney, J. Stocke, Y. Yao, B. Savage, A. Narayanan, K. Sembach
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #215, #464.21
Volume 42
Pages 502
Date January 1, 2010
Library Catalog NASA ADS
Abstract We present an overview of far-UV Hubble Space Telescope observations (1150-1780 A, at 17 km/s resolution) taken by the Cosmic Origins Spectrograph (COS) of the QSO PKS 0405-123 at redshift zem = 0.5726 and FUV flux 3.5x10-14 erg/s/cm2/A. This spectrum illustrates the the power of COS for studying metal-enriched gas between the galaxies, distributed throughout the multiphase intergalactic medium (IGM). We used 7 orbits with 9 FP-split positions, obtained S/N = 35-45 over much of the G130M band (1150-1440 A), and detected numerous absorption features of hydrogen (Lya, Lyb) and heavy-element probes of metallicity. Ions that can be studied include lines (O VI, N V, Ne VIII) sensitive to hot gas produced by strong shocks produced in gravitational inflows to the Cosmic Web, in circumgalactic gas, and in galactic winds. The high S/N allows a search for broad Ly-alpha possibly associated with O VI in hot gas (105 to 106 K). This sight line also intercepts a high-velocity cloud seen in Si III at 110-170 km/s (LSR) and b = -37.55 in the Galactic halo. In the absorption system at z = 0.495, the Ne VIII doublet (770.41, 780.32 A) shifts into the COS band, allowing us to probe the warm-hot IGM at log T = 5.5-6.0, several times deeper than previous (STIS) studies (Prochaska et al. 2004; Howk et al. 2009). In other posters, members of the COS science team describe the detection of O VI absorbers at redshifts z = 0.16710, 0.18292, 0.36156, 0.36332, and 0.49501, including a Lyman Limit system at z = 0.16710 with log N(HI) = 16.45 +/- 0.05. The high S/N observations allow us to measure important ions previously not detected and to evaluate the kinematical relationships and physical conditions among the detected ions.
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