The NANOGrav 11 Year Data Set: Pulsar-timing Constraints on the Stochastic Gravitational-wave Background
The NANOGrav 11 Year Data Set: Pulsar-timing Constraints on the Stochastic Gravitational-wave Background
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DOI：
10.3847/1538-4357/aabd3b
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发表时间：
2018-01
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通讯作者：
Z. Arzoumanian;P. Baker;A. Brazier;S. Burke-Spolaor;S. Chamberlin;S. Chatterjee;B. Christy;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;M. DeCesar;P. Demorest;T. Dolch;J. Ellis;R. Ferdman;E. Ferrara;W. Folkner;E. Fonseca;N. Garver-Daniels;P. Gentile;R. Haas;J. Hazboun;E. Huerta;K. Islo;Glenn Jones;Megan L. Jones;D. Kaplan;V. Kaspi;M. Lam;T. Lazio;L. Levin;A. Lommen;D. Lorimer;J. Luo;R. Lynch;D. Madison;M. Mclaughlin;S. McWilliams;C. Mingarelli;C. Ng;D. Nice;R. Park;T. Pennucci;N. Pol;S. Ransom;P. Ray;Alexander Rasskazov;X. Siemens;J. Simon;R. Spiewak;I. Stairs;D. Stinebring;K. Stovall;J. Swiggum;S. Taylor;M. Vallisneri;R. V. Haasteren;S. Vigeland;Weiwei Zhu
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作者：
Z. Arzoumanian;P. Baker;A. Brazier;S. Burke-Spolaor;S. Chamberlin;S. Chatterjee;B. Christy;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;M. DeCesar;P. Demorest;T. Dolch;J. Ellis;R. Ferdman;E. Ferrara;W. Folkner;E. Fonseca;N. Garver-Daniels;P. Gentile;R. Haas;J. Hazboun;E. Huerta;K. Islo;Glenn Jones;Megan L. Jones;D. Kaplan;V. Kaspi;M. Lam;T. Lazio;L. Levin;A. Lommen;D. Lorimer;J. Luo;R. Lynch;D. Madison;M. Mclaughlin;S. McWilliams;C. Mingarelli;C. Ng;D. Nice;R. Park;T. Pennucci;N. Pol;S. Ransom;P. Ray;Alexander Rasskazov;X. Siemens;J. Simon;R. Spiewak;I. Stairs;D. Stinebring;K. Stovall;J. Swiggum;S. Taylor;M. Vallisneri;R. V. Haasteren;S. Vigeland;Weiwei Zhu
我们在北美纳赫兹引力波天文台（nanogravity）最新发布的11年数据集中寻找各向同性随机引力波背景（GWB）。虽然我们没有发现GWB存在的证据，但我们对超大质量黑洞（SMBH）双星、衰变宇宙弦网络和原始GWB的数量进行了限制。我们首次发现GWB约束对所使用的太阳系星历（SSE）模型敏感，SSE误差可以模拟GWB信号。我们开发了一种弥合系统SSE差异的方法，产生了第一个对SSE误差具有鲁棒性的脉冲星定时阵列（PTA）约束。因此，我们对频率为f = 1 yr−1的基准f−2/3幂律谱和脉冲星间相关性建模的AGWB < 1.45 × 10−15的gw应变幅度设定了95%的上限。这比使用相同程序计算的nanogravity 9年限制提高了约2倍。以前的PTA对GWB的上限（以及它们的天体物理学和宇宙学解释）将需要根据SSE系统误差进行修订。我们使用我们的约束来描述星系核心的恒星质量密度、SMBH双星的偏心率以及SMBH -星系隆起尺度关系对GWB的综合影响。我们使用最近的模拟来约束宇宙弦张力，得到了Gμ < 5.3 × 10 - 11的se边缘95%上限，比已发表的nanogravity 9年约束好2倍。我们的原始GWB能量密度的sse边缘95%上限（对于辐射主导的后暴胀宇宙）是ΩGWB(f) h2 < 3.4 × 10−10。
We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a GWB, we place constraints on a population of inspiraling supermassive black hole (SMBH) binaries, a network of decaying cosmic strings, and a primordial GWB. For the first time, we find that the GWB constraints are sensitive to the solar system ephemeris (SSE) model used and that SSE errors can mimic a GWB signal. We developed an approach that bridges systematic SSE differences, producing the first pulsar-timing array (PTA) constraints that are robust against SSE errors. We thus place a 95% upper limit on the GW-strain amplitude of AGWB < 1.45 × 10−15 at a frequency of f = 1 yr−1 for a fiducial f−2/3 power-law spectrum and with interpulsar correlations modeled. This is a factor of ∼2 improvement over the NANOGrav nine-year limit calculated using the same procedure. Previous PTA upper limits on the GWB (as well as their astrophysical and cosmological interpretations) will need revision in light of SSE systematic errors. We use our constraints to characterize the combined influence on the GWB of the stellar mass density in galactic cores, the eccentricity of SMBH binaries, and SMBH–galactic-bulge scaling relationships. We constrain the cosmic-string tension using recent simulations, yielding an SSE-marginalized 95% upper limit of Gμ < 5.3 × 10−11—a factor of ∼2 better than the published NANOGrav nine-year constraints. Our SSE-marginalized 95% upper limit on the energy density of a primordial GWB (for a radiation-dominated post-inflation universe) is ΩGWB(f) h2 < 3.4 × 10−10.