The NANOGrav 15 yr Data Set: Search for Anisotropy in the Gravitational-wave Background

The NANOGrav 15 yr Data Set: Search for Anisotropy in the Gravitational-wave Background
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DOI：
10.3847/2041-8213/acf4fd
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发表时间：
2023-06
期刊：
The Astrophysical Journal Letters
影响因子：
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通讯作者：
G. Agazie;A. Anumarlapudi;A. Archibald;Z. Arzoumanian;P. Baker;B. Bécsy;L. Blecha;A. Brazier;P. Brook;S. Burke-Spolaor;J. A. Casey-Clyde;M. Charisi;S. Chatterjee;T. Cohen;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;M. DeCesar;P. Demorest;T. Dolch;B. Drachler;E. Ferrara;W. Fiore;E. Fonseca;G. Freedman;E. Gardiner;N. Garver-Daniels;P. Gentile;J. Glaser;D. Good;K. Gültekin;J. Hazboun;R. Jennings;A. Johnson;Megan L. Jones;A. Kaiser;D. Kaplan;L. Kelley;M. Kerr;J. Key;N. Laal;M. Lam;W. Lamb;T. Joseph W. Lazio;N. Lewandowska;Tingting Liu;D. Lorimer;Jing Luo;R. Lynch;Chung-Pei Ma;D. Madison;A. McEwen;J. McKee;M. Mclaughlin;N. McMann;B. W. Meyers;C. Mingarelli;A. Mitridate;C. Ng;D. Nice;S. Ocker;K. Olum;T. Pennucci;B. Perera;N. Pol;H. Radovan;S. Ransom;P. Ray;J. Romano;S. C. Sardesai;A. Schmiedekamp;C. Schmiedekamp;K. Schmitz;L. Schult;B. Shapiro-Albert;X. Siemens;J. Simon;M. Siwek;I. Stairs;D. Stinebring;K. Stovall;A. Susobhanan;J. Swiggum;S. Taylor;J. E. Turner;C. Unal;M. Vallisneri;S. Vigeland;H. Wahl;C. Witt;O. Young
G. Agazie;A. Anumarlapudi;A. Archibald;Z. Arzoumanian;P. Baker;B. Bécsy;L. Blecha;A. Brazier;P. Brook;S. Burke-Spolaor;J. A. Casey-Clyde;M. Charisi;S. Chatterjee;T. Cohen;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;M. DeCesar;P. Demorest;T. Dolch;B. Drachler;E. Ferrara;W. Fiore;E. Fonseca;G. Freedman;E. Gardiner;N. Garver-Daniels;P. Gentile;J. Glaser;D. Good;K. Gültekin;J. Hazboun;R. Jennings;A. Johnson;Megan L. Jones;A. Kaiser;D. Kaplan;L. Kelley;M. Kerr;J. Key;N. Laal;M. Lam;W. Lamb;T. Joseph W. Lazio;N. Lewandowska;Tingting Liu;D. Lorimer;Jing Luo;R. Lynch;Chung-Pei Ma;D. Madison;A. McEwen;J. McKee;M. Mclaughlin;N. McMann;B. W. Meyers;C. Mingarelli;A. Mitridate;C. Ng;D. Nice;S. Ocker;K. Olum;T. Pennucci;B. Perera;N. Pol;H. Radovan;S. Ransom;P. Ray;J. Romano;S. C. Sardesai;A. Schmiedekamp;C. Schmiedekamp;K. Schmitz;L. Schult;B. Shapiro-Albert;X. Siemens;J. Simon;M. Siwek;I. Stairs;D. Stinebring;K. Stovall;A. Susobhanan;J. Swiggum;S. Taylor;J. E. Turner;C. Unal;M. Vallisneri;S. Vigeland;H. Wahl;C. Witt;O. Young
中科院分区：
其他
文献类型：
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作者：
G. Agazie;A. Anumarlapudi;A. Archibald;Z. Arzoumanian;P. Baker;B. Bécsy;L. Blecha;A. Brazier;P. Brook;S. Burke-Spolaor;J. A. Casey-Clyde;M. Charisi;S. Chatterjee;T. Cohen;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;M. DeCesar;P. Demorest;T. Dolch;B. Drachler;E. Ferrara;W. Fiore;E. Fonseca;G. Freedman;E. Gardiner;N. Garver-Daniels;P. Gentile;J. Glaser;D. Good;K. Gültekin;J. Hazboun;R. Jennings;A. Johnson;Megan L. Jones;A. Kaiser;D. Kaplan;L. Kelley;M. Kerr;J. Key;N. Laal;M. Lam;W. Lamb;T. Joseph W. Lazio;N. Lewandowska;Tingting Liu;D. Lorimer;Jing Luo;R. Lynch;Chung-Pei Ma;D. Madison;A. McEwen;J. McKee;M. Mclaughlin;N. McMann;B. W. Meyers;C. Mingarelli;A. Mitridate;C. Ng;D. Nice;S. Ocker;K. Olum;T. Pennucci;B. Perera;N. Pol;H. Radovan;S. Ransom;P. Ray;J. Romano;S. C. Sardesai;A. Schmiedekamp;C. Schmiedekamp;K. Schmitz;L. Schult;B. Shapiro-Albert;X. Siemens;J. Simon;M. Siwek;I. Stairs;D. Stinebring;K. Stovall;A. Susobhanan;J. Swiggum;S. Taylor;J. E. Turner;C. Unal;M. Vallisneri;S. Vigeland;H. Wahl;C. Witt;O. Young

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北美纳赫兹引力波天文台（NANOGrav）报告了在其15年数据集中存在各向同性纳赫兹引力波背景（GWB）的证据。然而，如果GWB是由吸入超大质量黑洞双星（SMBHB）系统的人口产生的，那么背景被预测为各向异性的，这取决于这些系统在本地宇宙中的分布和SMBHB人口的统计特性。在这项工作中，我们使用多种方法和基础来描述GWB功率在天空中的分布，以寻找GWB中的各向异性。我们没有发现明显的各向异性的证据。通过将角功率分布建模为球谐函数的总和（其中系数不一定总是在任何地方产生正功率），我们发现偶极各向异性水平的贝叶斯95%上限为（Cl =1/Cl =0）<27%。这类似于在处处为正功率的约束下导出的上限，表明偶极子可能接近数据通知机制。相比之下，在较高的球谐多极子的各向异性的约束强烈优先主导。我们还得到保守估计的各向异性预期从随机分布的SMBHB系统使用天体物理模拟条件的各向同性GWB推断在15年的数据集，并表明，该数据集具有足够的灵敏度，以探测大部分的预测水平的各向异性。最后，我们强调的机遇和挑战，在脉冲星定时阵列数据中寻找各向异性。
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has reported evidence for the presence of an isotropic nanohertz gravitational-wave background (GWB) in its 15 yr data set. However, if the GWB is produced by a population of inspiraling supermassive black hole binary (SMBHB) systems, then the background is predicted to be anisotropic, depending on the distribution of these systems in the local Universe and the statistical properties of the SMBHB population. In this work, we search for anisotropy in the GWB using multiple methods and bases to describe the distribution of the GWB power on the sky. We do not find significant evidence of anisotropy. By modeling the angular power distribution as a sum over spherical harmonics (where the coefficients are not bound to always generate positive power everywhere), we find that the Bayesian 95% upper limit on the level of dipole anisotropy is (C l=1/C l=0) < 27%. This is similar to the upper limit derived under the constraint of positive power everywhere, indicating that the dipole may be close to the data-informed regime. By contrast, the constraints on anisotropy at higher spherical-harmonic multipoles are strongly prior dominated. We also derive conservative estimates on the anisotropy expected from a random distribution of SMBHB systems using astrophysical simulations conditioned on the isotropic GWB inferred in the 15 yr data set and show that this data set has sufficient sensitivity to probe a large fraction of the predicted level of anisotropy. We end by highlighting the opportunities and challenges in searching for anisotropy in pulsar timing array data.