BLACK HOLE MASS ESTIMATES AND EMISSION-LINE PROPERTIES OF A SAMPLE OF REDSHIFT z

DOI：

10.1088/0004-637x/790/2/145

发表时间：

2013-11

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

G. de Rosa;B. Venemans;R. Decarli;M. Gennaro;R. Simcoe;M. Dietrich;B. Peterson;F. Walter;S. Frank;R. McMahon;P. Hewett;D. Mortlock;C. Simpson

我们给出了在UKIDSS-LAS和Vista-Viking调查中发现的迄今仅有的四个z&gt；6.5类星体的光学和近红外光谱分析。我们的数据集由新的甚大望远镜/X-Shooter和麦哲伦/FIRE观测组成。这些是最好的光学/近红外光谱数据，很可能是使用当前6-10米的设备为z&gt；6.5样品获得的。我们估算了黑洞(BH)质量、艾丁顿比、Si IV/C IV、C III]/C IV和Fe II/Mg II发射线通量比。我们使用一个程序进行光谱建模，该程序允许我们推导出连续统分量的概率分布，并获得根据连续统模型的基本分布加权的类星体属性。Z&gt；6.5类星体表现出与红移较低的同类星体相同的发射特性。Z&gt；6.5类星体拥有质量为109M∼的BHS，它们在接近爱丁顿光度(<☉(LBol/LEdd)>=−.4±0.2)，这与对4.0&lt；z&lt；6.5类星体的观测结果一致。通过将Si IV/C IV和C III]/C IV通量比与在z∼6和2⩽z⩽4.5时光度匹配的样品的结果进行比较，我们没有发现线比随宇宙时间演化的证据。我们将测量的Fe II/mg II通量比与对4.0&lt；z&lt；6.4源的测量结果进行了比较。使用一致的程序对这两个样品进行分析。没有证据表明Fe II/Mg II通量比在z=7和z=4之间演化。在Fe II/Mg II跟踪Fe/Mg丰度比的假设下，这意味着在大爆炸后的第一个∼0.8Gyr的类星体主机中存在主要的化学富集幕。

We present the analysis of optical and near-infrared spectra of the only four z > 6.5 quasars known to date, discovered in the UKIDSS-LAS and VISTA-VIKING surveys. Our data set consists of new Very Large Telescope/X-Shooter and Magellan/FIRE observations. These are the best optical/NIR spectroscopic data that are likely to be obtained for the z > 6.5 sample using current 6–10 m facilities. We estimate the black hole (BH) mass, the Eddington ratio, and the Si iv/C iv, C iii]/C iv, and Fe ii/Mg ii emission-line flux ratios. We perform spectral modeling using a procedure that allows us to derive a probability distribution for the continuum components and to obtain the quasar properties weighted upon the underlying distribution of continuum models. The z > 6.5 quasars show the same emission properties as their counterparts at lower redshifts. The z > 6.5 quasars host BHs with masses of ∼109 M☉ that are accreting close to the Eddington luminosity (〈log(LBol/LEdd)〉 = −0.4 ± 0.2), in agreement with what has been observed for a sample of 4.0 < z < 6.5 quasars. By comparing the Si iv/C iv and C iii]/C iv flux ratios with the results obtained from luminosity-matched samples at z ∼ 6 and 2 ⩽ z ⩽ 4.5, we find no evidence of evolution of the line ratios with cosmic time. We compare the measured Fe ii/Mg ii flux ratios with those obtained for a sample of 4.0 < z < 6.4 sources. The two samples are analyzed using a consistent procedure. There is no evidence that the Fe ii/Mg ii flux ratio evolves between z = 7 and z = 4. Under the assumption that the Fe ii/Mg ii traces the Fe/Mg abundance ratio, this implies the presence of major episodes of chemical enrichment in the quasar hosts in the first ∼0.8 Gyr after the Big Bang.

BLACK HOLE MASS ESTIMATES AND EMISSION-LINE PROPERTIES OF A SAMPLE OF REDSHIFT z > 6.5 QUASARS

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