A Robust Determination of the Time Delay in 0957+561A, B and a Measurement of the Global Value of Hubble's Constant
A Robust Determination of the Time Delay in 0957+561A, B and a Measurement of the Global Value of Hubble's Constant
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DOI：
10.1086/304147
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发表时间：
1996-10
期刊：
影响因子：
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通讯作者：
T. Kundić;E. Turner;W. Colley;J. Gott;J. Rhoads;J. Rhoads;Yun Wang;L. Bergeron;L. Bergeron;K. Gloria;D. Long;S. Malhotra;J. Wambsganss
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作者：
T. Kundić;E. Turner;W. Colley;J. Gott;J. Rhoads;J. Rhoads;Yun Wang;L. Bergeron;L. Bergeron;K. Gloria;D. Long;S. Malhotra;J. Wambsganss
1996年，用阿帕奇点天文台(APO)3.5m望远镜对引力透镜系统0957+561a，B在g波段和r波段进行了连续的光度监测，发现在早期论文预测的精确时间，在拖尾(B)图像光曲线上有一个尖锐的g带事件。这一预测是根据在前导(A)图像中对1995年期间事件的观察和415天的差异时间延迟作出的。这一成功证实了所谓的短延迟，而在近540天的延迟中没有任何这样的功能，就排除了该系统的“长延迟”，从而解决了一个长期存在的争议。对我们的光曲线数据的一系列统计分析得出了417±3天(95%的可信区间)的最佳拟合延迟，并表明该结果对于分析技术、数据子样本和假设的两条光曲线的参数关系的变化相当稳健。最近在透镜系统(由一个星系和一个星系团组成)建模方面的改进使我们能够使用Refsdal方法推导出哈勃常数H0的全局值(z=0.36)，这是一种简单而直接的(单步)距离确定方法，基于实验验证和安全理解的物理和几何学。结果是H0=±13公里S-1 Mpc-1(Ω=1)，其中95%的可信区间主要是由于仍然存在的透镜模型的不确定性。然而，令人放心的是，现有的透镜质量分布观测过度约束了模型，从而提供了对其有效性的内部一致性检查。我们认为，这种河外距离尺度的测定(在1σ时精确度为10%)现在在统计和系统不确定度方面与基于更传统技术的测定具有相当的质量。最后，我们简要讨论了利用引力透镜改进H0测定的前景，以及0957+561a，B光曲线的其他一些可能的含义和用途。
Continued photometric monitoring of the gravitational lens system 0957+561A, B in the g and r bands with the Apache Point Observatory (APO) 3.5 m telescope during 1996 shows a sharp g-band event in the trailing (B) image light curve at the precise time predicted in an earlier paper. The prediction was based on the observation of the event during 1995 in the leading (A) image and on a differential time delay of 415 days. This success confirms the so-called short delay, and the absence of any such feature at a delay near 540 days rejects the “long delay” for this system, thus resolving a long-standing controversy. A series of statistical analyses of our light-curve data yield a best-fit delay of 417 ± 3 days (95% confidence interval) and demonstrate that this result is quite robust against variations in the analysis technique, data subsamples, and assumed parametric relationship of the two light curves. Recent improvements in the modeling of the lens system (consisting of a galaxy plus a galaxy cluster) allow us to derive a value of the global value (at z = 0.36) of Hubble's constant H0 using Refsdal's method, a simple and direct (single-step) distance determination based on experimentally verified and securely understood physics and geometry. The result is H0 = 64 ± 13 km s-1 Mpc-1 (for Ω = 1), where this 95% confidence interval is dominantly due to remaining lens model uncertainties. However, it is reassuring that available observations of the lensing mass distribution overconstrain the model and thus provide an internal consistency check on its validity. We argue that this determination of the extragalactic distance scale (10% accurate at 1 σ) is now of comparable quality, in terms of both statistical and systematic uncertainties, to those based on more conventional techniques. Finally, we briefly discuss the prospects for improved H0 determinations using gravitational lenses, and some other possible implications and uses of the 0957+561A, B light curves.