Supermassive black holes, accretion discs, stellar dynamics and tidal disruptions

巨大的黑洞存在于大多数，也许是所有星系的中心。黑洞的质量与它们的宿主星系的性质非常相关，这表明这两个星系群的形成是有联系的。此外，星系是由较小的星系合并而成的。我建议研究在星系合并过程中形成的黑洞双星（BBH）的命运。我打算回答BBH是合并还是在次秒差分隔处停滞。研究小组将专注于(i)恒星的潮汐破坏和（ii）富气环境中BBH的演化，从秒差距分离开始，直到它们达到引力波驱动阶段。根据周围气体的热力学，包括在气体中形成的恒星的影响，我们将计算过程中潮汐破坏的速率，以及双星在不同阶段的衰变速率。一旦BBH达到100个史瓦西半径的距离，轨道就会由于引力波的发射和双星与盘的解耦而衰减。然而，一些气体预计仍会被黑洞束缚。我们将研究这种气体的演化，并在BBH合并之前预测其电磁发射的强度。这将增加其引力波探测的科学产出。我们还计划对上述模拟进行后处理，以确定揭示黑洞存在的观测特征。这些预测将在当前和即将到来的时域和光谱大天空调查中指导对此类系统的电磁搜索至关重要。这将使我们能够对大质量黑洞种群的起源和演化施加严格的限制。

Massive black holes exist at the centre of most, perhaps all galaxies. The masses of the black holes are very well correlated with the properties of their host galaxies, suggesting that the formation of both populations are linked. Moreover, galaxies form hierarchically, from the merger of smaller galaxies. I propose to study the fate of the black hole binaries (BBH) formed during galaxy mergers. I plan to answer whether the BBH merge or stall at sub-parsec separations. The research group will focus on (i) tidal disruptions of stars and (ii) the evolution of BBH in gas-rich environments, from parsec separations, but also until they reach the gravitational-wave-driven phase. We will calculate the rate tidal disruptions in the process and also of decay of the binary at different stages, depending on the thermodynamics of the surrounding gas, including the effect of the stars formed in this gas. Once the BBH reaches separations of the order of a hundred Schwarzschild radii, the orbit decays due to the emission of gravitational waves and the binary decouples from the disc. However, some gas is expected to remain bound to the black holes. We will study the evolution of this gas and predict the strength of its electromagnetic emission just before the BBH coalesce. This will increase the scientific output of its gravitational wave detection. We also plan on a post-processing of the simulations described above, to identify observational features that reveal the presence of BBHs. These predictions will be crucial in guiding electromagnetic searches for such systems in current and upcoming time-domain and spectral large-sky surveys. This would allow us to put stringent limits on the origin and evolution of the massive black hole population.