COSMOGRAIL：GRAvItational镜片VII的宇宙学监测。从WFI J2033-4723得到的时间延迟和哈勃常数
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VII. Time delays and the Hubble constant from WFI J2033-4723
摘要：
引力透镜类星体可以用来绘制透镜星系的质量分布图，并通过测量类星体图像之间的时间延迟来估计哈勃常数H0。本文报道了四重成像类星体WFI J2033 - 4723（z = 1.66）中两个独立时间延迟的测量结果。我们的数据包括R波段的图像与瑞士1.2米欧拉望远镜位于拉西拉和1.3米SMARTS望远镜位于Cerro Tololo。在2004年3月至2007年5月的3年监测期间，光变曲线有218个独立的历元，平均每4天进行一次观测。我们使用三种不同的技术测量时间延迟，我们得到Dt（B-A）= 35.5 +-1.4天（3.8%）和Dt（B-C）= 62.6 + 4.1/-2.3天（+6.5%/-3.7%），其中A是接近的合并图像对的合成。在对时间延迟进行校正后，我们发现R波段的通量比为F_A/F_B = 2.88 ± 0.04，F_A/F_C = 3.38 ± 0.06，F_A1/F_A2 = 1.37 ± 0.05，在三年的时间尺度上没有微透镜变化的证据。然而，这些通量比不同意在类星体发射线的测量，这表明存在较长期的微透镜。我们对H0的估计与一致值一致：透镜星系的非参数模型预测H0 = 67 + 13/-10 km s-1 Mpc-1，而单等温球模型得出H0 = 63 + 7/-3 km s-1 Mpc-1（68%置信水平）。更复杂的透镜模型，使用复合德Vaucouleurs加上NFW星系的质量配置文件显示扭曲的质量等值线在透镜星系，做非参数模型。由于所有模型都需要显著的外部剪切，这表明透镜是WFI J2033 - 4723视场中看到的星系群的成员。
英文摘要：
Gravitationally lensed quasars can be used to map the mass distribution in lensing galaxies and to estimate the Hubble constant H0 by measuring the time delays between the quasar images. Here we report the measurement of two independent time delays in the quadruply imaged quasar WFI J2033-4723 (z = 1.66). Our data consist of R-band images obtained with the Swiss 1.2 m EULER telescope located at La Silla and with the 1.3 m SMARTS telescope located at Cerro Tololo. The light curves have 218 independent epochs spanning 3 full years of monitoring between March 2004 and May 2007, with a mean temporal sampling of one observation every 4th day. We measure the time delays using three different techniques, and we obtain Dt(B-A) = 35.5 +- 1.4 days (3.8%) and Dt(B-C) = 62.6 +4.1/-2.3 days (+6.5%/-3.7%), where A is a composite of the close, merging image pair. After correcting for the time delays, we find R-band flux ratios of F_A/F_B = 2.88 +- 0.04, F_A/F_C = 3.38 +- 0.06, and F_A1/F_A2 = 1.37 +- 0.05 with no evidence for microlensing variability over a time scale of three years. However, these flux ratios do not agree with those measured in the quasar emission lines, suggesting that longer term microlensing is present. Our estimate of H0 agrees with the concordance value: non-parametric modeling of the lensing galaxy predicts H0 = 67 +13/-10 km s-1 Mpc-1, while the Single Isothermal Sphere model yields H0 = 63 +7/-3 km s-1 Mpc-1 (68% confidence level). More complex lens models using a composite de Vaucouleurs plus NFW galaxy mass profile show twisting of the mass isocontours in the lensing galaxy, as do the non-parametric models. As all models also require a significant external shear, this suggests that the lens is a member of the group of galaxies seen in field of view of WFI J2033-4723.
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