%0 Generic %1 Meiring2012 %A Meiring, Joseph D. %A Tripp, Todd M. %A Werk, Jessica K. %A Howk, Christopher %A Jenkins, Edward B. %A Prochaska, Jason X. %A Lehner, Nicholas %A Sembach, Kenneth R. %D 2012 %K absorption collision qso systems %T Qso absorption systems detected in ne viii: Evidence for high-metallicity, multiphase gas far from galaxies %U http://arxiv.org/abs/1201.0939 %X Using high signal-to-noise spectra (S/N 30) taken with the Cosmic Origins Spectrograph (COS) of the z=0.9754 quasar PG1148+549, we report on the physical conditions of Ne VIII + OVI absorption line systems at z=0.6838, 0.7015, 0.7248. At these redshifts, absorption lines from multiple ionization stages of oxygen (O II, O III, O IV, O VI) are available to constrain the ionization and physical conditions of the gas. A single-phase model with only photoionization or collisional ionization fails to reproduce the observed column density ratios. Even with extreme modifications to the ionizing background, single-phase photoionzation models fail to produce enough Ne VIII. We thus conclude that the O VI and Ne VIII are produced via collisional ionization. The metallicities of these systems are determined to be O/H >-0.5, higher than the typically assumed value for O VI absorbers of O/H-1.0. Densities of n(H) 10^-4 cm-3 are determined for the photoionized phase, indicating that these systems reside in regions of overdensity \Delta 80. The collisionally ionized component of the gas traced by O VI and Ne VIII bears temperatures of T10^5.7 K. We determine the redshift density of Ne VIII absorbers dN/dz 7 (+7,-3), similar to the redshift density of O VI absorbers of comparable equivalent width to these systems. Based on the redshift density and galaxy luminosity function at z\sim0.7, we estimate the cross section radius of the O VI + Ne VIII absorbers to be \sim70-150 kpc. We find a star forming \simLgalaxy at the redshift of the zabs=0.7248 system, at an impact parameter of 217 kpc.

@misc{Meiring2012, abstract = { Using high signal-to-noise spectra (S/N 30) taken with the Cosmic Origins Spectrograph (COS) of the z=0.9754 quasar PG1148+549, we report on the physical conditions of Ne VIII + OVI absorption line systems at z=0.6838, 0.7015, 0.7248. At these redshifts, absorption lines from multiple ionization stages of oxygen (O II, O III, O IV, O VI) are available to constrain the ionization and physical conditions of the gas. A single-phase model with only photoionization or collisional ionization fails to reproduce the observed column density ratios. Even with extreme modifications to the ionizing background, single-phase photoionzation models fail to produce enough Ne VIII. We thus conclude that the O VI and Ne VIII are produced via collisional ionization. The metallicities of these systems are determined to be [O/H] >-0.5, higher than the typically assumed value for O VI absorbers of [O/H]\sim -1.0. Densities of n(H) \sim 10^-4 cm-3 are determined for the photoionized phase, indicating that these systems reside in regions of overdensity \Delta \sim 80. The collisionally ionized component of the gas traced by O VI and Ne VIII bears temperatures of T\sim 10^5.7 K. We determine the redshift density of Ne VIII absorbers dN/dz \sim 7 (+7,-3), similar to the redshift density of O VI absorbers of comparable equivalent width to these systems. Based on the redshift density and galaxy luminosity function at z\sim0.7, we estimate the cross section radius of the O VI + Ne VIII absorbers to be \sim70-150 kpc. We find a star forming \simL\star galaxy at the redshift of the zabs=0.7248 system, at an impact parameter of 217 kpc. }, added-at = {2012-01-05T20:36:00.000+0100}, author = {Meiring, Joseph D. and Tripp, Todd M. and Werk, Jessica K. and Howk, Christopher and Jenkins, Edward B. and Prochaska, Jason X. and Lehner, Nicholas and Sembach, Kenneth R.}, biburl = {https://www.bibsonomy.org/bibtex/2e190582a05b6b140a162403eb0493563/miki}, description = {[1201.0939] Qso absorption systems detected in ne viii: Evidence for high-metallicity, multiphase gas far from galaxies}, interhash = {125415089cbfa76d110c1ba73510f2b4}, intrahash = {e190582a05b6b140a162403eb0493563}, keywords = {absorption collision qso systems}, note = {cite arxiv:1201.0939 Comment: 14 pages, submitted to ApJ, comments welcome}, timestamp = {2012-01-05T20:36:00.000+0100}, title = {Qso absorption systems detected in ne viii: Evidence for high-metallicity, multiphase gas far from galaxies}, url = {http://arxiv.org/abs/1201.0939}, year = 2012 }