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arXiv · 2310.16896

Observational Signatures of Supermassive Black Hole Binaries

Daniel J. D'Orazio·Maria Charisi
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Abstract

Despite solid theoretical and observational grounds for the pairing of supermassive black holes (SMBHs) after galaxy mergers, definitive evidence for the existence of close (sub-parsec) separation SMBH binaries (SMBHBs) approaching merger is yet to be found. This chapter reviews techniques aimed at discovering such SMBHBs in galactic nuclei. We motivate the search with a brief overview of SMBHB formation and evolution, and the gaps in our present-day theoretical understanding. We then present existing observational evidence for SMBHBs and discuss ongoing efforts to provide definitive evidence for a population at sub-parsec orbital separations, where many of the aforementioned theoretical gaps lie. We conclude with future prospects for discovery with electromagnetic (primarily time-domain) surveys, high-resolution imaging experiments, and low-frequency gravitational-wave detectors.

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Daniel J. D'Orazio, Maria Charisi. 2023-10-25. Observational Signatures of Supermassive Black Hole Binaries. https://arxiv.org/abs/2310.16896

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