论文标题
具有非常大的C IV等效宽度的发光类星体的性质
The Nature of Luminous Quasars with Very Large C IV Equivalent Widths
论文作者
论文摘要
我们报告了10个具有较大C IV等效宽度（EW> 150 A）的10个发光射电Quiet类星体的完整样本的结果。对于8/10，我们进行了Chandra快照观测。我们发现，除了增强的C IV线EW外，其He II和Mg II线得到了增强，但C III]线却没有。它们的X射线发射比其紫外线亮度所预期的要强大。此外，这些大的C IV EW类星体显示出小的C IV蓝光，可能是低埃丁顿的比率，这表明它们是“极低的特征向量1（EV1）”的类星体。辐射压缩压缩（RPC）光电离模型的平均过量He II EW具有较难的AOX电离频谱。但是，这些结果并不能很好地再现C IV，Mg II和C III] EWS或观察到的高C IV/MG II比的增强模式。 RPC计算表明，C IV/MG II线比是一个有效的金属性指标，具有亚极性金属气体和硬电离连续体的模型可很好地再现所有四种紫外线的增强模式。我们发现类星体中的C IV/MG II线比通常与过量的X射线发射相关。极高的EV1类星体的特征是高金属性和抑制X射线发射。与气体金属性和X射线发射有关的基本机制尚不清楚，但可能与辐射压力驱动的磁盘风相关，这些磁盘在高金属性下得到增强，因此减少冠状X射线发射的质量负载。
We report results for a complete sample of ten luminous radio-quiet quasars with large C IV equivalent widths (EW > 150 A). For 8/10 we performed Chandra snapshot observations. We find that, in addition to the enhanced C IV line EW, their He II and Mg II lines are enhanced, but the C III] line is not. Their X-ray emission is substantially stronger than expected from their ultraviolet luminosity. Additionally, these large C IV EW quasars show small C IV blueshifts and possibly low Eddington ratios, suggesting they are "extreme low Eigenvector 1 (EV1)" quasars. The mean excess He II EW is well-matched by Radiation Pressure Compression (RPC) photoionization models, with the harder aox ionizing spectrum. However, these results do not reproduce well the enhancement pattern of the C IV, Mg II, and C III] EWs, or the observed high C IV/Mg II ratio. RPC calculations indicate that the C IV/Mg II line ratio is an effective metallicity indicator, and models with sub-Solar metallicity gas and a hard ionizing continuum reproduce well the enhancement pattern of all four ultraviolet lines. We find that the C IV/Mg II line ratio in quasars is generally correlated with the excess X-ray emission. Extremely high EV1 quasars are characterized by high metallicity and suppressed X-ray emission. The underlying mechanism relating gas metallicity and X-ray emission is not clear, but may be related to radiation-pressure driven disk winds, which are enhanced at high metallicity, and consequent mass loading reducing coronal X-ray emission.
