AI 中文总结
本研究分析星系团透镜化双黑洞引力波的时间延迟和放大率分布，发现其长延迟尾部被现有先验抑制，但微透镜影响小，需专用搜索管线。
AI 中文摘要
强引力透镜引力波（GW）通常利用包括时间延迟和放大率比分布在内的种群先验进行搜索，以抑制误报。当前LIGO、Virgo和KAGRA（LVK）搜索主要采用以星系尺度透镜校准的先验；然而，这些先验可能会惩罚星系团产生的较长的时间延迟，而星系团可能贡献10%--20%的透镜事件。星系团成员星系也可能扰动宏透镜势并改变图像放大率。我们研究了由星系团透镜化的双黑洞引力波的时间延迟和放大率比分布，以及微透镜系统效应。在全透镜样本中，星系团透镜的中位时间延迟约为76天，而星系透镜为6.9天。在LVK O4灵敏度下施加信噪比阈值ρ>8后，中位数分别为15.4天和0.24天。探测到的星系团样本保留了长延迟尾部，9.1%的图像对延迟超过365天，3.3%超过1000天，因此基于星系的时间延迟先验会抑制星系团透镜对。相比之下，尽管星系团成员星系拓宽了全星系团样本的放大率比分布，但在O4灵敏度下，探测到的星系团和星系透镜样本非常相似，表明候选选择中的偏差很小。星系团透镜通常也产生较弱的微透镜畸变：只有约0.8%的单图像失配超过M=0.03，而4.8%超过参数估计阈值1.35/ρ^2。因此，对于大多数星系团透镜事件，微透镜效应是次要的，主要原因是图像通常形成在离最亮星系团星系较远的地方，那里的恒星密度低且由星系团内光主导，尽管附近的卫星星系可以局部增强它。这些结果激励了专门用于引力波透镜搜索的星系团透镜管线。
英文摘要
Strongly lensed gravitational waves (GWs) are commonly searched for using population priors, including time-delay and magnification-ratio distributions, to suppress false alarms. Current LIGO, Virgo, and KAGRA (LVK) searches mainly adopt priors calibrated with galaxy-scale lenses; however, these may penalize the longer time delays produced by galaxy clusters, which could contribute 10%--20% of lensed events. Cluster member galaxies may also perturb the macro-lens potential and alter image magnifications. We investigate the time-delay and magnification-ratio distributions of binary black hole GWs lensed by galaxy clusters, together with microlensing systematics. In the full lensed sample, the median time delay is about 76 days for cluster lenses, compared with 6.9 days for galaxy lenses. After imposing an SNR threshold of $ρ>8$ at LVK O4 sensitivity, the medians are 15.4 and 0.24 days. The detected cluster sample retains a long-delay tail, with 9.1% of image pairs delayed by more than 365 days and 3.3% by more than 1000 days, so galaxy-based time-delay priors can suppress cluster-lensed pairs. By contrast, although cluster member galaxies broaden the magnification-ratio distribution of the full cluster sample, the detected cluster- and galaxy-lensing samples are very similar at O4 sensitivity, suggesting little bias in candidate selection. Cluster lenses also generally produce weak microlensing distortions: only about 0.8% of single-image mismatches exceed ${\cal M}=0.03$, while 4.8% exceed the parameter-estimation threshold $1.35/ρ^2$. Thus, microlensing is subdominant for most cluster-lensed events, mainly because images often form far from the brightest cluster galaxy, where the stellar density is low and dominated by intracluster light, although nearby satellites can locally enhance it. These results motivate a dedicated cluster-lensing pipeline for GW lensing searches.
Comments17 pages, 6 figures, submitted to PRD
