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arXiv 2209.06978astro-ph.HEgr-qc
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随心所欲地旋转:LIGO-Virgo-KAGRA双星黑洞自旋倾斜分布的测量(缺乏)

Spin it as you like: the (lack of a) measurement of the spin tilt distribution with LIGO-Virgo-KAGRA binary black holes

Salvatore Vitale, Sylvia Biscoveanu, Colm Talbot

摘要:

虽然通过分析最新的LVK星表GWTC-3已经对黑洞有了很多了解,但对黑洞自旋方向的天体物理分布的测量仍然是难以捉摸的。这通常通过测量每个黑洞自旋和轨道角动量之间的倾斜角($\cosτ$)的余弦来探测,$\cosτ=+1$是完美的对齐。Abbott等人将$\cosτ$分布建模为各向同性分量和高斯分量的混合,平均值固定为+1,宽度从数据中测量。我们想验证数据是否需要在$\cosτ=+1$处存在这样的峰。我们使用各种替代模型的天体物理倾斜分布和测量他们的参数使用LVK GWTC-3目录。我们发现,a)增强LVK模型,使得高斯的平均值$μ$不固定在+1,返回强烈依赖于先验的结果。如果我们允许$μ>+1$,那么得到的天体物理$\cosτ$分布在+1处达到峰值,看起来是线性的,而不是高斯分布。如果我们约束$-1\leq μ\leq+1$,则高斯分量在$μ=0.48^{+0.46}_{-0.99}$(中值和90%对称可信区间)处达到峰值。另外两个2组分混合物模型产生的$\cosτ$分布具有以$0.19^{+0.22}_{-0.18}$为中心的宽峰或跨越范围[-0.5,+1]的平台,在+1处没有明显的峰。b)我们所考虑的所有模型都同意这样一个事实,即在-1附近没有多余的黑洞倾斜。c)虽然产生了完全不同的后验,但这项工作中考虑的模型具有在误差条内相同的贝叶斯证据。我们的结论是,目前的数据集是没有足够的信息来得出任何独立于模型的自旋倾斜的天体物理分布的结论,除了有没有多余的自旋与负对齐倾斜。

英文摘要:

While much has been learned about black holes by analyzing the latest LVK catalog, GWTC-3, a measurement of the astrophysical distribution of the black hole spin orientations remains elusive. This is usually probed by measuring the cosine of the tilt angle ($\cosτ$) between each black hole spin and the orbital angular momentum, $\cosτ=+1$ being perfect alignment. Abbott et al. has modeled the $\cosτ$ distribution as a mixture of an isotropic component and a Gaussian component with mean fixed at +1 and width measured from the data. We want to verify if the data require the existence of such a peak at $\cosτ=+1$. We use various alternative models for the astrophysical tilt distribution and measure their parameters using the LVK GWTC-3 catalog. We find that a) Augmenting the LVK model such that the mean $μ$ of the Gaussian is not fixed at +1 returns results that strongly depend on priors. If we allow $μ>+1$ then the resulting astrophysical $\cosτ$ distribution peaks at +1 and looks linear, rather than Gaussian. If we constrain $-1\leq μ\leq+1$ the Gaussian component peaks at $μ=0.48^{+0.46}_{-0.99}$ (median and 90% symmetric credible interval). Two other 2-component mixture models yield $\cosτ$ distributions that either have a broad peak centered at $0.19^{+0.22}_{-0.18}$ or a plateau that spans the range [-0.5, +1], without a clear peak at +1. b) All of the models we considered agree on the fact that there is no excess of black hole tilts at around -1. c) While yielding quite different posteriors, the models considered in this work have Bayesian evidences that are the same within error bars. We conclude that the current dataset is not sufficiently informative to draw any model-independent conclusions on the astrophysical distribution of spin tilts, except that there is no excess of spins with negatively aligned tilts.

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