类星体发射线与吸收线红移的趋势拟合
Fitting trends in quasar emission and absorption line redshifts
AI总结：
本研究针对类星体发射线与吸收线红移的系统趋势，基于MgII和CIV吸收线数据建立了可预测对应最低吸收线红移的线性模型，模型拟合度优异，为类星体相关研究提供了可靠的参考工具。
AI中文摘要：
类星体的光谱由少量发射线和大量吸收线组成，发射线的波长被相似的红移量移动，吸收线的波长则被不同的红移量移动，因此每个类星体都有一个发射线红移，且所有吸收线红移均小于发射线红移。Katz等人在2016年指出，大样本类星体的观测吸收线红移（$z_{abs}$）相对于发射线红移（$z_{em}$）的分布存在系统趋势：$z_{em}$增大时，探测到的最低$z_{abs}$单调增大，他们据此推断发射线和吸收线均形成于类星体中。本研究聚焦于对观测到的$z_{em} \rightarrow z_{abs}$分布的系统趋势进行建模，选取大样本类星体的单电离镁（MgII）和三重电离碳（CIV）吸收线红移数据开展分析。研究发现，给定$z_{em}$时，定义MgII吸收线红移最低值的数据点包络（记为$z_{MgIImodel}$）满足关系$z_{MgIImodel} = (0.418 \pm 0.008) z_{em} - (0.482 \pm 0.02)$，其决定系数$R^2$为0.99，该模型可用于预测任意$z_{em}$对应的预期最低MgII吸收线红移；同时，研究还得到了任意$z_{em}$对应的预期最低CIV吸收线红移的类似模型，即$z_{CIVmodel} = 0.845 (\pm 0.0002) z_{em} - 0.153 (\pm 0.0006)$。
英文摘要：
The spectrum of a quasar consists of a few emission lines whose wavelengths are shifted by similar redshifts and numerous absorption lines whose wavelengths are shifted by different redshifts. Hence each quasar is characterised by an emission line redshift and the absorption lines redshifts are all less than the emission line redshift. The distribution of observed absorption line redshifts ($z_{abs}$) with respect to emission line redshift ($z_{em}$) for a large sample of quasars shows a systematic trend as pointed out by \citet{2016arXiv160901593K}. They noticed that increase in $z_{em}$ is accompanied by a monotonic increase in the lowest detected value of $z_{abs}$ and inferred that the emission and absorption lines were all formed in the quasar. This study focuses on modeling the systematic trend in the observed $z_{em} \rightarrow z_{abs}$ distribution. We considered the redshift data of absorption lines of singly ionized magnesium (denoted by MgII) and triply ionized carbon (denoted by CIV) for a large sample of quasars. We find that the envelope of data points defining the lowest value of the MgII absorption line redshift (which we denote by $z_{MgIImodel}$) for a given $z_{em}$ satisfies $z_{MgIImodel} = (0.418 \pm 0.008) z_{em} - (0.482 \pm 0.02)$ with an $R^2$ value of 0.99. The model can be used to predict the lowest expected MgII absorption line redshift for any $z_{em}$. We find a similar model for the lowest expected redshift of triply ionized carbon lines for any $z_{em}$ which is $z_{CIVmodel} = 0.845 (\pm 0.0002) z_{em} - 0.153 (\pm 0.0006)$.
