Black-Hole Spin Precession and its Astrophysical Implications

引力是自然界的四种基本力之一，由爱因斯坦的广义相对论描述。 广义相对论最极端的预言之一是黑洞的存在，黑洞是一种紧凑的物体，其引力如此强烈，甚至连光都无法逃脱。在这样一个极端的状态下研究重力提供了一个最有希望的机会来更多地了解这种基本力。广义相对论的另一个预测，即双黑洞发射引力波，拉伸和挤压时空，最近被NSF资助的激光干涉引力波天文台（LIGO）证实。 黑洞可以用它们的质量和自旋来描述，但是双黑洞的自旋通常与它们的轨道平面不重合，就像地球的自转轴和它绕太阳的轨道之间的23度不重合一样。广义相对论导致黑洞旋转改变方向或进动;这种进动在LIGO观测到的引力波中留下了可检测的特征。该奖项支持对黑洞自旋进动的研究，以及它可以在多大程度上受到LIGO等引力波探测器的限制。这项工作有助于科学家解释LIGO的观测结果，从而更好地理解引力和黑洞的天体物理起源。PI和合作者还将开发一个交互式虚拟现实模拟进动黑洞和它们发出的引力波，这将在网上免费提供，并通过德克萨斯大学达拉斯现有的外展网络在当地公共图书馆和博物馆展示。这项计划的目的，是全面了解双黑洞自旋与轨道角动量之间的错位的成因和影响。人口合成代码将被用来探索如何初始自旋失调取决于天体物理学黑洞形成的各个方面，如质量转移，潮汐对齐，超新星反冲。这些代码产生的自旋分布将从黑洞形成，直到他们开始发射可检测的引力波使用PI的新开发的技术，有效地计算自旋旋进的inspiral时标。一旦二进制进入LIGO等地面探测器的灵敏度范围，LIGO算法库套件中的公开代码将用于生成波形，并分析确定自旋进动的二进制黑洞参数可以如何估计现实的信噪比。PI和合作者还将执行和分析数值相对论模拟，以评估黑洞合并前最终轨道中自旋进动的后牛顿预测的可靠性。这项研究为天体物理模型选择提供了基础，结合了许多事件对自旋失调的约束，以区分黑洞形成的天体物理模型，例如球状星团中的动态形成（自旋应该是各向同性的）与恒星双星的形成（应该表现出对齐自旋的趋势）。最后一个专题将考虑黑洞形成和合并之间的自旋进动如何影响对最终黑洞质量、自旋和引力反冲的预测。 该项目对LIGO观测到的恒星质量黑洞和在星系巡天中寻找的在空间或运动学上偏离其宿主星系的反冲类星体都有影响。

Gravity is one of the four fundamental forces of nature and is described by Einstein's theory of general relativity. One of the most extreme predictions of general relativity is the existence of black holes, compact objects whose gravity is so intense that not even light can escape from them. Investigating gravity in such an extreme regime provides one of the most promising opportunities to learn more about this fundamental force. Another prediction of general relativity, that binary black holes emit gravitational waves that stretch and squeeze spacetime, was recently confirmed by the NSF-funded Laser Interferometer Gravitational-wave Observatory (LIGO). Black holes are fully described by their masses and spins, but the spins of binary black holes are generally misaligned with their orbital plane, much like the 23 degree misalignment between the Earth's rotation axis and its orbit about the Sun responsible for the seasons. General relativity causes black-hole spins to change direction or precess; this precession leaves detectable signatures in the gravitational waves observed by LIGO. This award supports studies on black-hole spin precession and the extent to which it can be constrained by gravitational-wave detectors like LIGO. This work helps scientists to interpret LIGO observations and thus better understand gravity and the astrophysical origin of black holes responsible for their spin misalignments. The PI and collaborators will also develop an interactive virtual-reality simulation of precessing black holes and the gravitational waves they emit which will be available free online and presented at local public libraries and museums through existing outreach networks of the University of Texas at Dallas. These simulations help the public virtually experience the effects of gravitational waves and enhance public interest and support for science research and education.This goal of this proposal is to provide a comprehensive picture of the origin and implications of misalignments between binary black-hole spins and their orbital angular momentum. Population-synthesis codes will be used to explore how initial spin misalignments depend on various aspects of astrophysical black-hole formation like mass transfer, tidal alignment, and supernova recoils. The spin distributions generated by these codes will be evolved from black-hole formation until they begin to emit detectable gravitational waves using the PI's newly developed technique for efficiently calculating spin precession on the inspiral timescale. Once the binaries enter the sensitivity band of ground-based detectors like LIGO, publicly available codes in the LIGO Algorithm Library Suite will be used to generate waveforms and analyze how well the binary black-hole parameters that determine spin precession can be estimated for realistic signal-to-noise ratios. The PI and collaborators will also perform and analyze numerical-relativity simulations to assess the reliability of post-Newtonian predictions for spin precession in the final orbits before black-hole merger. This research provides the basis for astrophysical model selection, combining constraints on spin misalignments from many events to distinguish astrophysical models of black-hole formation, such as dynamical formation in a globular cluster (for which spins should be isotropic) versus formation from stellar binaries (which should exhibit a tendency towards aligned spins). The final project will consider how spin precession between black hole formation and merger affects predictions for final black-hole masses, spins, and gravitational recoils. This project has implications both for the stellar-mass black holes observed by LIGO and recoiling quasars spatially or kinematically offset from their host galaxies sought in galaxy surveys.