Chandra Observations of the QSO Pair Q2345+007: Binary or Massive Dark Lens?
Chandra Observations of the QSO Pair Q2345+007: Binary or Massive Dark Lens?
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QSO 对的钱德拉观测 Q2345 007：二元还是大质量暗透镜？
DOI：
10.1086/340051
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
Christopher D. Smith
中科院分区：
文献类型：
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作者：
P. Green;C. Kochanek;A. Siemiginowska;Dong;M. Markevitch;J. Silverman;A. Dosaj;B. Jannuzi;Christopher D. Smith
宽（7.“3）分离的类星体对Q2345+ 007 A，B（z = 2.15）的组成部分具有迄今为止（Steidel &萨金特）发现的最惊人的相似光谱，但没有检测到透镜质量，使该系统成为已知的大质量（~1014 M）暗物质透镜系统的最佳候选者。在这里，我们提出的结果，从65 ks钱德拉观测，旨在调查它是否是一个二元类星体或引力透镜。我们没有发现（0.5- 2keV）通量极限为2 × 10-15 ergscm-2s-1的透镜星系团的X射线证据，这与仅对约化重子分数的透镜一致。使用钱德拉X射线观测的类星体本身，连同新的和公布的光学测量，我们使用观测到的发射性质的类星体之间的进一步测试的透镜和二进制的假设。假设与图像相似的视线吸收，我们发现它们的X射线连续谱斜率是不一致的（ΓA = 2.30和ΓB = 0.83），它们的X射线与光通量比也是如此。B遭受足以解释这些光谱差异的本征吸收的概率可以忽略不计。我们提出了新的光学证据，对通量比是可变的，所以在透镜的情况下的时间延迟可能会导致一些差异。然而，在单个类星体中，整体光谱能量分布的足够大的变化是罕见的。这里所有的新证据都强烈支持二元解释。因此，Q2345+007可能代表了已知的由相互作用触发但尚未合并的明亮活动星系核的最高红移例子。
The components of the wide (7.″3) separation quasar pair Q2345+007A,B (z = 2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent) yet no detected lensing mass, making this system the best candidate known for a massive (~1014 M☉) dark matter lens system. Here we present results from a 65 ks Chandra observation designed to investigate whether it is a binary quasar or a gravitational lens. We find no X-ray evidence for a lensing cluster to a (0.5-2 keV) flux limit of 2 × 10-15 ergs cm-2 s-1, which is consistent with lensing only for a reduced baryon fraction. Using the Chandra X-ray observations of the quasars themselves, together with new and published optical measurements, we use the observed emission properties of the quasars for further tests between the lens and binary hypotheses. Assuming similar line-of-sight absorption to the images, we find that their X-ray continuum slopes are inconsistent (ΓA = 2.30 and ΓB = 0.83) as are their X-ray-to-optical flux ratios. The probability that B suffers intrinsic absorption sufficient to account for these spectral differences is negligible. We present new optical evidence that the flux ratio of the pair is variable, so the time delay in a lens scenario could cause some of the discrepancies. However, adequately large variations in overall spectral energy distribution are rare in individual QSOs. All new evidence here weighs strongly toward the binary interpretation. Q2345+007 thus may represent the highest redshift example known of an interaction-triggered but as-yet unmerged luminous active galactic nucleus.