恒星级双黑洞的自旋大小随质量演化：来自引力波数据的证据
The spin magnitude of stellar-mass binary black holes evolves with the mass: evidence from gravitational wave data
AI总结：
本研究利用O3引力波目录和层级贝叶斯模型发现BBH自旋大小随质量升高而增大，并在40–50倍太阳质量处发生种群转变，支持层级并合形成通道。
摘要：
恒星级双黑洞（BBHs）的质量与自旋之间的关系，已被认为是致密天体存在多种形成通道的确凿证据。由孤立双星恒星前身星形成的第一代黑洞（BHs）预计具有近乎对齐的小自旋，而由层级并合产生的第n代BBHs预计具有不对齐且更高的自旋。利用第三次观测运行O3（GWTC-2.1和GWTC-3）的数据，我们采用层级贝叶斯方法，对BBH质量与自旋之间可能的相关性进行了全面研究。我们使用参数化模型，这些模型要么叠加独立的BBH种群，要么显式建模质量—自旋相关性。我们揭示了BBH的归一化自旋大小与质量之间存在相关性的强有力证据。这种相关性可以解释为从低质量时低自旋的BBH种群向更高质量时更高自旋的转变。尽管高质量处的自旋大小分布缺乏稳健约束，但我们发现强有力的证据表明，两个具有不同自旋分布的BBH种群之间的转变应发生在40–50倍太阳质量处。特别地，我们发现质量高于40–50倍太阳质量的BBH种群应约占总体种群的2%，其自旋大小χ在0.7附近达到峰值，这与最新、最先进的BBH起源模拟中由层级并合形成的第n代BBHs所占比例一致。
英文摘要：
The relation between the mass and spin of stellar-mass binary black holes (BBHs) has been proposed to be a smoking gun for the presence of multiple formation channels for compact objects. First-generation black holes (BHs) formed by isolated binary stellar progenitors are expected to have nearly aligned small spins, while nth-generation BBHs resulting from hierarchical mergers are expected to have misaligned and higher spins. Leveraging data from the third observing run O3 (GWTC-2.1 and GWTC-3), we employ hierarchical Bayesian methods to conduct a comprehensive study of possible correlations between the BBH masses and spins. We use parametric models that either superpose independent BBH populations or explicitly model a mass-spin correlation. We unveil strong evidence for a correlation between normalized spin magnitudes and masses of BBHs. The correlation can be explained as a transition from a BBH population with low spins at low masses and higher spins for higher masses. Although the spin magnitude distribution at high masses lacks robust constraints, we find strong evidence that a transition between two BBH populations with different spin distributions should happen at 40-50 $M_{\odot}$. In particular, we find that the population of BBHs above 40-50 $M_{\odot}$ should compose the $\sim 2 \%$ of the overall population, with a spin magnitude $χ$ peaking around 0.7, consistently with the fraction of nth-generation BBHs formed by hierarchical mergers in the latest state-of-the-art BBH genesis simulations.
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