[论文解读] Cosmic Cousins: Identification of a Subpopulation of Binary Black Holes Consistent with Isolated Binary Evolution

Jaxen Godfrey, B. Edelman+1 more|arXiv (Cornell University)|Apr 3, 2023

Pulsars and Gravitational Waves Research被引用 5

一句话总结

本研究利用具有离散隐变量的分层贝叶斯推断，从LVK的GWTC-3目录中识别出一个具有孤立双星演化特征的质量与自旋特性的双黑洞性质子群。该研究发现一个约10 M⊙的显著低质量峰，自旋幅值较小（a_peak = 0.16⁺⁰.¹⁹₋₀.¹⁶），自旋-轨道对齐倾向明显，占双黑洞（BBH）群体的82%，为孤立形成机制提供了有力证据。

ABSTRACT

Observations of gravitational waves (GWs) from merging compact binaries have become a regular occurrence. The continued advancement of the LIGO-Virgo-KAGRA (LVK) Collaboration detectors have now produced a catalog of over 90 such mergers, from which we can begin to uncover the formation history of merging compact binaries. In this work, we search for subpopulations in the LVK's third gravitational wave transient catalog (GWTC-3) by incorporating discrete latent variables in the hierarchical Bayesian inference framework to probabilistically assign each BBH observation into separate categories associated with distinctly different population distributions. By incorporating formation channel knowledge within the mass and spin correlations found in each category, we find an over density of mergers with a primary mass of $\sim10 M_\odot$, consistent with isolated binary formation. This low-mass subpopulation has a spin magnitude distribution peaking at $a_\mathrm{peak}=0.16^{0.19}_{-0.16}$, exhibits spins preferentially aligned with the binary's orbital angular momentum, is constrained by $15^{+0.0}_{-1.0}$ of our observations, and contributes $82\%^{+8.0\%}_{-16\%}$ to the overall population of BBHs. Additionally, we find that the component of the mass distribution containing the previously identified $35M_\odot$ peak has spins consistent with the $10M_\odot$ events, with $99\%$ of primary masses less than $m_{1,99\%} = 49^{+25}_{-8.1} M_\odot$, providing an estimate of the lower edge of the theorized pair instability mass gap. This work is a first step in gaining a deeper understanding of compact binary formation and evolution, and will provide more robust conclusions as the catalog of observations becomes larger.

研究动机与目标

• 识别LVK的GWTC-3目录中90个双黑洞性质合并事件内，具有独特形成特征的子群。
• 确定观测到的质量与自旋相关性是否指向孤立双星演化，而非动力学形成。
• 使用具有离散隐变量的分层贝叶斯推断，基于质量与自旋分布，对每个BBH的概率归属进行形成通道分类。
• 利用所识别子群的自旋与质量约束，估算对对不稳定超新星质量间隙下限的限制。
• 为未来对紧凑双星目录的群体水平分析提供一个框架，超越预先分类。

提出的方法

• 应用具有离散隐变量的分层贝叶斯推断框架，根据质量与自旋特性将BBH划分为不同子群。
• 使用结合参数与非参数成分的混合模型，从GWTC-3数据中推断群体分布。
• 通过将子群特性（如自旋幅值、对齐性）与孤立双星演化物理机制关联，整合形成通道知识。
• 使用GWInferno Python库实现推断框架，并处理质量与自旋参数间的不确定性传播。
• 通过模型比较与后验预测检验，验证子群识别结果并评估模型拟合度。
• 将孤立峰模型扩展，以评估35 M⊙质量峰是否与10 M⊙子群共享自旋特征。

实验结果

研究问题

• RQ1 是否存在一个在统计上显著的BBH子群，其质量与自旋特性与孤立双星演化一致？
• RQ2 所识别的低质量BBH子群的自旋幅值与对齐分布为何？
• RQ3 BBH群体中35 M⊙质量峰是否与10 M⊙子群共享自旋特征，暗示其具有相同的形成机制？
• RQ4 能否利用自旋与质量数据对对不稳定超新星质量间隙的下限施加约束？
• RQ5 与基于质量或潮汐参数的先验分类相比，使用离散隐变量如何提升子群识别效果？

主要发现

• 识别出一个具有10⁺⁰.⁹⁵₋₀.⁸³ M⊙主峰质量的显著BBH子群，与孤立双星演化一致。
• 该子群的自旋幅值峰值为a_peak = 0.16⁺⁰.¹⁹₋₀.¹⁶，表明自旋幅值较小。
• 该子群表现出强烈的自旋-轨道对齐偏好，15⁺⁰.⁰₋₁.⁰的观测值被分配至该组。
• 10 M⊙子群占总BBH群体的82%⁺⁸.⁰%₋₁⁶%，表明其为占主导地位的形成通道。
• 35 M⊙质量峰在自旋特征上与10 M⊙子群一致，其中99%的主星质量低于49⁺²⁵₋⁸.¹ M⊙。
• 35 M⊙峰主星质量分布的99百分位数估计为49⁺²⁵₋⁸.¹ M⊙，为对不稳定质量间隙提供了下限估计。