We have obtained new observations of the partial Lyman limit absorber at z _ { abs } = 0.93 towards quasar PG 1206+459 , and revisit its chemical and physical conditions .
The absorber , with N ( \mbox { H { \sc i } } ) \sim 10 ^ { 17.0 } cm ^ { -2 } and absorption lines spread over \gtrsim 1000 km s ^ { -1 } in velocity , is one of the strongest known O vi absorbers at \log N ( { \mbox { O { \sc vi } } } ) = 15.54 \pm 0.17 .
Our analysis makes use of the previously known low- ( e.g .
Mg ii ) , intermediate- ( e.g .
Si iv ) , and high-ionization ( e.g. , C iv , N v , Ne viii ) metal lines along with new HST / COS observations that cover O vi , and an HST / ACS image of the quasar field .
Consistent with previous studies , we find that the absorber has a multiphase structure .
The low-ionization phase arises from gas with a density of \log ( n _ { H } / cm ^ { -3 } ) \sim - 2.5 and a solar to super-solar metallicity .
The high-ionization phase stems from gas with a significantly lower density , i.e . \log ( n _ { H } / cm ^ { -3 } ) \sim - 3.8 , and a near-solar to solar metallicity .
The high-ionization phase accounts for all of the absorption seen in C iv , N v , and O vi .
We find the the detected Ne viii , reported by ( ) , is best explained as originating in a stand-alone collisionally ionized phase at T \sim 10 ^ { 5.85 } ~ { } K , except in one component in which both O vi and Ne viii can be produced via photoionization .
We demonstrate that such strong O vi absorption can easily arise from photoionization at z \gtrsim 1 , but that , due to the decreasing extragalactic UV background radiation , only collisional ionization can produce large O vi features at z \sim 0 .
The azimuthal angle of \sim 88 ^ { \circ } of the disk of the nearest ( 68 ~ { } kpc ) luminous ( 1.3 L _ { * } ) galaxy at z _ { gal } = 0.9289 , which shows signatures of recent merger , suggests that the bulk of the absorption arises from metal enriched outflows .