We use the gravitational wave signals from binary black hole merger events observed by LIGO and Virgo to reconstruct the underlying mass and spin distributions of the population of merging black holes. We reconstruct the population using the mixture model framework VAMANA using observations in GWTC-2 occurring during the first two observing runs and the first half of the third run (O1, O2, and O3a). Our analysis identifies a structure in the chirp mass distribution of the observed population. Specifically, we identify peaks in the chirp mass distribution at 8, 14, 26, and 45 M _⊙ and a complementary structure in the component mass distribution with an excess of black holes at masses of 9, 16, 45, and 57 M _⊙. Intriguingly, for both the distributions, the location of subsequent peaks are separated by a factor of around two and there is a lack of mergers with chirp masses of 10–12 M _⊙. The appearance of multiple peaks is a feature of a hierarchical merger scenario when, due to a gap in the black hole mass spectrum, a pile-up occurs at the first peak followed by mergers of lower mass black holes to hierarchically produce higher mass black holes. However, cross-generation merger peaks and observations with high spins are also predicted to occur in such a scenario that we are not currently observing. The results presented are limited in measurement accuracy due to small numbers of observations but if corroborated by future gravitational wave observations these features have far-reaching implications.

我们使用 LIGO 和 Virgo 观测到的双黑洞合并事件的引力波信号来重建合并黑洞群的基本质量和自旋分布。我们使用混合模型框架 VAMANA 重建种群，使用 GWTC-2 中发生在前两次观察运行和第三次运行的前半部分（O1、O2 和 O3a）的观察结果。我们的分析确定了观察到的群体的啁啾质量分布中的结构。具体来说，我们确定了 8、14、26 和 45 M _⊙处的啁啾质量分布中的峰值以及分量质量分布中的互补结构，其中在质量为_9、16、45和 57 M _⊙处有过量的黑洞. 有趣的是，对于这两种分布，后续峰的位置相隔约 2 倍，并且缺乏 10-12 M _⊙啁啾质量的合并。多个峰的出现是分层合并场景的一个特征，当由于黑洞质谱的间隙，在第一个峰处发生堆积，随后是低质量黑洞的合并，以分层产生更高质量的黑洞. 然而，在我们目前没有观察到的情况下，预计也会出现跨代合并峰值和高自旋观测。由于观测数量少，所呈现的结果在测量精度方面受到限制，但如果未来的引力波观测得到证实，这些特征将具有深远的影响。