arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.13996astro-ph.COastro-ph.GA
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微透镜效应对引力时间延迟观测策略的影响

Impact of Microlensing on Observational Strategies for Gravitational Time Delay Measurements

Kai Liao

摘要:

微透镜效应不仅使光变曲线在本征光变曲线的基础上增加了额外的放大倍数,而且使光变曲线在时间域上发生了移动,使得强透镜活动星系核图像之间的实际时间延迟在发射区的$\sim$日光交叉时间尺度上发生了变化。微透镜引起的时间延迟如果不计在内,将使强透镜时间延迟宇宙照相产生偏差。然而,由于磁盘大小和磁盘模型的不确定性,影响很难准确估计。在这项工作中,我们研究了如何减少偏差与设计的观察策略的基础上,一个标准的磁盘模型。我们发现长时间的图像监测可以减轻影响,因为它平均的微透镜的时间滞后地图由于源相对于透镜星系的椭圆运动。此外,蓝色波段的图像对应于较小的磁盘大小,因此也有利于时间延迟测量。我们进行了模拟的基础上PG 1115+080类透镜类星体。结果表明,具有20年光变曲线的$\sim40\%$可以减小微透镜引起的时延色散,而u波段相对于r波段的色散减小了$\sim75\%$。然而,这种影响在任何情况下都不能完全消除。还需要进一步的研究,以适当地将其纳入推断准确的哈勃常数。

英文摘要:

Microlensing not only brings extra magnification lightcurves on top of the intrinsic ones but also shifts them in time domain, making the actual time-delays between images of strongly lensed active galactic nucleus change on the $\sim$ day(s) light-crossing time scale of the emission region. The microlensing-induced time-delays would bias strong lens time-delay cosmography if uncounted. However, due to the uncertainties of the disk size and the disk model, the impact is hard to accurately estimate. In this work, we study how to reduce the bias with designed observation strategy based on a standard disk model. We find long time monitoring of the images could alleviate the impact since it averages the microlensing time-lag maps due to the peculia motion of the source relative to the lens galaxy. In addition, images in bluer bands correspond to smaller disk sizes and therefore benefit time-delay measurements as well. We conduct a simulation based on a PG 1115+080-like lensed quasar. The results show the time-delay dispersions caused by microlensing can be reduced by $\sim40\%$ with 20-year lightcurves while u band relative to r band reduces $\sim75\%$ of the dispersions. Nevertheless, such an effect can not be totally eliminated in any cases. Further studies are still needed to appropriately incorporate it in inferring an accurate Hubble constant.

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