Title: Understanding the strong intervening OVI absorber at z$_{abs}$ ~0.93 towards PG1206+459 Show Chinese title

Title: 理解PG1206+459星系方向红移z$_{abs}$~0.93处的强OVI吸收线

Abstract: We have obtained new observations of the partial Lyman limit absorber at \zabs$=0.93$ towards quasar PG~1206+459, and revisit its chemical and physical conditions. The absorber, with $ N(HI) \sim 10^{17.0}$ ~\sqcm\ and absorption lines spread over $\gtrsim$1000~\kms\ in velocity, is one of the strongest known OVI absorbers at $\log N(OVI)=$15.54$\pm$0.17. Our analysis makes use of the previously known low-(e.g. \MgII), intermediate-(e.g. SiIV), and high-ionization (e.g., CIV, NV, NeVIII) metal lines along with new $HST/$COS observations that cover OVI, 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 $\log (n_{\rm H}/\rm cm^{-3})\sim-2.5$ and a solar to super-solar metallicity. The high-ionization phase stems from gas with a significantly lower density, i.e. $\log (n_{\rm H}/\rm cm^{-3}) \sim-3.8$, and a near-solar to solar metallicity. The high-ionization phase accounts for all of the absorption seen in CIV, NV, and OVI. We find the the detected \NeVIII, reported by \cite{Tripp2011}, is best explained as originating in a stand-alone collisionally ionized phase at $T\sim10^{5.85}~\rm K$, except in one component in which both OVI and NeVIII can be produced via photoionization. We demonstrate that such strong OVI absorption can easily arise from photoionization at $z\gtrsim1$, but that, due to the decreasing extragalactic UV background radiation, only collisional ionization can produce large OVI features at $z\sim0$. The azimuthal angle of $\sim88$\degree\ of the disk of the nearest ($\rm 68~kpc$) luminous ($1.3L_*$) galaxy at $z_{\rm gal}=0.9289$, which shows signatures of recent merger, suggests that the bulk of the absorption arises from metal enriched outflows. Show Chinese abstract

Abstract: 我们获得了类星体 PG~1206+459 方向上的部分Lyman极限吸收线\zabs $=0.93$ 的新观测结果，并重新审视了其化学和物理条件。 该吸收体具有$ N(HI) \sim 10^{17.0}$至\sqcm 的吸收线，并且在速度上分布在$\gtrsim$的 1000 至\kms 范围内，是已知最强的 OVI 吸收体之一，位于$\log N(OVI)=$15.54$\pm$0.17。 我们的分析利用了之前已知的低（例如\MgII ）、中间（例如 SiIV), and high-ionization (e.g., CIV, NV, NeVIII) metal lines along with new $HST/$COS observations that cover OVI, 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 $\log (n_{\rm H}/\rm cm^{-3})\sim-2.5$ and a solar to super-solar metallicity. The high-ionization phase stems from gas with a significantly lower density, i.e. $\log (n_{\rm H}/\rm cm^{-3}) \sim-3.8$, and a near-solar to solar metallicity. The high-ionization phase accounts for all of the absorption seen in CIV, NV, and OVI. We find the the detected \NeVIII , reported by \cite{Tripp2011}, is best explained as originating in a stand-alone collisionally ionized phase at $T\sim10^{5.85}~\rm K$, except in one component in which both OVI and NeVIII can be produced via photoionization. 我们证明了如此强烈的OVI吸收可以很容易地由$z\gtrsim1$处的光致电离产生，但由于星系际紫外背景辐射的下降，在$z\sim0$处只有碰撞电离才能产生较大的OVI特征。最近（$\rm 68~kpc$）发光（$1.3L_*$）星系盘的方位角角度$\sim88$\degree 在$z_{\rm gal}=0.9289$处显示出近期合并的迹象，这表明大部分吸收来自金属富集的外流。