Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample
Chemical abundance of z ~ 6 quasar broad-line regions in the XQR-30 sample
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XQR-30 样本中 z ~ 6 类星体宽线区域的化学丰度
DOI：
10.1093/mnras/stac1001
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发表时间：
2022
影响因子：
4.8
通讯作者：
Cupani, Guido
中科院分区：
文献类型：
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作者：
Lai, Samuel;Bian, Fuyan;Onken, Christopher A.;Wolf, Christian;Mazzucchelli, Chiara;Bañados, Eduardo;Bischetti, Manuela;Bosman, Sarah E. I.;Becker, George;Cupani, Guido
高红移类星体宽线区域的元素丰度追踪了早期宇宙大质量星系核区域的化学演化。本文研究了用VLT/X-shooter和Gemini/GNIRS仪器观测到的25个高红移（5.8 <z< 7.5）类星体的静止坐标系紫外光谱中的金属敏感宽发射线通量比。我们拟合了单个光谱和通过跨类星体属性的分箱产生的复合光谱：热光度，黑洞质量和Civline的蓝移，通过比较我们的高红移类星体和文献中提出的较低红移（2.0 <z< 5.0）结果，发现发射线比率没有红移演变。利用基于云的局部最优发射云光电离模型的金属丰度和发射线通量比之间的关系，我们发现宽发射线的可观测性质与金属丰度至少为太阳2-4倍的气体云的发射一致。我们的高红移测量也证实了Civemission线的蓝移与其等效宽度相关，这会影响对Civemission线归一化的线比。当占Civblueshift，我们发现，休息帧紫外线发射线通量比不相关的黑洞质量或热光度明显。
The elemental abundances in the broad-line regions of high-redshift quasars trace the chemical evolution in the nuclear regions of massive galaxies in the early Universe. In this work, we study metallicity-sensitive broad emission-line flux ratios in rest-frame UV spectra of 25 high-redshift (5.8 <z< 7.5) quasars observed with the VLT/X-shooter and Gemini/GNIRS instruments, ranging overin black hole mass andin bolometric luminosity. We fit individual spectra and composites generated by binning across quasar properties: bolometric luminosity, black hole mass, and blueshift of the Civline, finding no redshift evolution in the emission-line ratios by comparing our high-redshift quasars to lower redshift (2.0 <z< 5.0) results presented in the literature. Usingcloudy-based locally optimally emitting cloud photoionization model relations between metallicity and emission-line flux ratios, we find the observable properties of the broad emission lines to be consistent with emission from gas clouds with metallicity that are at least 2–4 times solar. Our high-redshift measurements also confirm that the blueshift of the Civemission line is correlated with its equivalent width, which influences line ratios normalized against Civ. When accounting for the Civblueshift, we find that the rest-frame UV emission-line flux ratios do not correlate appreciably with the black hole mass or bolometric luminosity.