arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0903.3947astro-ph.CO
收藏

Sub-parsec超大质量双星类星体:在z<1时的期望

Sub-parsec supermassive Binary Quasars: expectations at z<1

M. Volonteri, J. M. Miller, M. Dotti

摘要:

我们调查的理论预期检测超大质量的双黑洞,可以确定为亚秒差距发光类星体。到目前为止,只有两个候选人已被选定的样本包括17,500来源选择斯隆数字巡天(SDSS)类星体目录在z<0.70(Boroson & Lauer 2009)在这封信中,我们使用的组装和成长的超大质量黑洞(SMBH)在分级宇宙学的统计和观测研究的二进制类星体在亚秒差距的分离。我们的目标是双重的:(1)测试这种稀少的双星数量是否与SMBH合并速率的理论预测一致,(2)在更高的红移和更低的通量水平上提供额外的预测。我们确定在一个完整的,体积有限的样本中预期的二进制文件的累积数量。受Boroson & Lauer(2009)的启发,我们将SDSS类星体光度切割(M_i<-22)应用于我们的理论样本,推导出可观测双星分数的上限。我们发现,sub-parsec类星体二进制本质上是罕见的。我们的最佳模型预测了在z<0.7时,距离小于10^4史瓦西半径(v_orb>2000 km/s)的约0.01 deg^-2亚秒差距的二元类星体,这代表了我们的理论样本中未吸收类星体的约6x 10 ^-4。在一个完整的样本约10,000源,因此,我们预测的上限约10亚秒差距的二进制类星体。双星的数量随着红移的增加而迅速增加。随着SMBH双星质量的减少,寿命的减少表明,降低光度阈值不会导致可检测的亚秒差距双星类星体数量的显着增加。

英文摘要:

We investigate the theoretical expectations for detections of supermassive binary black holes that can be identified as sub-parsec luminous quasars. To-date, only two candidates have been selected in a sample comprising 17,500 sources selected from the Sloan Digital Sky Survey (SDSS) Quasar Catalog at z<0.70 (Boroson & Lauer 2009) In this Letter, we use models of assembly and growth of supermassive black holes (SMBHs) in hierarchical cosmologies to study the statistics and observability of binary quasars at sub-parsec separations. Our goal is twofold: (1) test if such a scarce number of binaries is consistent with theoretical prediction of SMBH merger rates, and (2) provide additional predictions at higher redshifts, and at lower flux levels. We determine the cumulative number of expected binaries in a complete, volume limited sample. Motivated by Boroson & Lauer (2009), we apply the SDSS Quasar luminosity cut (M_i<-22) to our theoretical sample, deriving an upper limit to the observable binary fraction. We find that sub-parsec quasar binaries are intrinsically rare. Our best models predict ~0.01 deg^-2 sub-parsec binary quasars with separations below ~10^4 Schwarzschild radii (v_orb>2000 km/s) at z<0.7, which represent a fraction ~6x10^-4 of unabsorbed quasars in our theoretical sample. In a complete sample of ~10,000 sources, we therefore predict an upper limit of ~10 sub-parsec binary quasars. The number of binaries increases rapidly with increasing redshift. The decreasing lifetime with SMBH binary mass suggests that lowering the luminosity threshold does not lead to a significant increase in the number of detectable sub-parsec binary quasars.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑