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arXiv 2105.08930gr-qc
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利用折叠数据和完整协方差矩阵对 Advanced LIGO 前两次观测运行得到的持续引力波上限

Upper limits on persistent gravitational waves using folded data and the full covariance matrix from Advanced LIGO$'$s first two observing runs

Deepali Agarwal, Jishnu Suresh, Sanjit Mitra, Anirban Ain

AI总结:

本文利用 Advanced LIGO O1、O2 折叠数据和完整像素间 Fisher 信息矩阵进行持续定向引力波无模型搜索,未发现 SGWB 信号,所得 95% 上限与 LVC 结果一致。

摘要:

由近邻宇宙中的天体物理源产生的随机引力波背景(SGWB)很可能是各向异性的。地面激光干涉探测器已针对所有主要数据采集运行给出了 SGWB 各向异性的上限。然而,由于对像素间噪声协方差矩阵进行数值求逆存在挑战——而这对于设定上限是必要的——以往的搜索通过球谐基来考虑地图中的角度关联,因为在该基中正则化相对更容易。不过,这种方法更适合延展源。此外,在两种不同基中生成的上限地图看起来并不相同。尽管这些上限在统计误差范围内可能一致,但仍有必要检验:如果在像素基中使用完整噪声协方差矩阵,结果是否仍保持一致。在这里,我们使用完整的像素间 Fisher 信息矩阵来创建 SGWB 各向异性的上限地图。我们首先利用 Advanced LIGO 第一次(O1)和第二次(O2)观测运行的折叠数据,对持续的、有方向的引力波源执行无模型搜索,并表明结果与 LIGO-Virgo Collaboration(LVC)发表的上限一致。随后,我们利用奇异值分解和贝叶斯正则化方案,探索了多种处理像素间 Fisher 信息矩阵的方法。我们没有在数据中发现任何 SGWB 信号的证据,并且上限在统计误差范围内与 LVC 结果一致。通过注入研究,我们表明它们都是有效的 95% 上限;也就是说,在不到 5% 的像素中,某一像素内的上限会低于注入的信号强度。

英文摘要:

The stochastic gravitational-wave background (SGWB) created by astrophysical sources in the nearby Universe is likely to be anisotropic. Upper limits on SGWB anisotropy have been produced for all major data-taking runs by the ground-based laser interferometric detectors. However, due to the challenges involved in numerically inverting the pixel-to-pixel noise covariance matrix, which is necessary for setting upper limits, the searches accounted for angular correlations in the map by using the spherical harmonic basis, where regularization was relatively easier. This approach is better suited though for extended sources. Moreover, the upper-limit maps produced in the two different bases are seemingly different. While the upper limits may be consistent within statistical errors, it was important to check whether the results would remain consistent if the full noise covariance matrix was used in the pixel basis. Here, we use the full pixel- to-pixel Fisher information matrix to create upper-limit maps of SGWB anisotropy. We first perform an unmodeled search for persistent, directional gravitational-wave sources using folded data from the first (O1) and second (O2) observing runs of Advanced LIGO and show that the results are consistent with the upper limits published by the LIGO-Virgo Collaboration (LVC). We then explore various ways to account for the pixel-to-pixel Fisher information matrix using singular-value decomposition and Bayesian regularization schemes. We do not find evidence for any SGWB signal in the data and the upper limits are consistent with the LVC results within statistical errors. Through an injection study, we show that they are all valid 95\% upper limits, that is, the upper limit in a pixel is less than the injected signal strength in less than 5\% of the pixels.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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