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Observational Signatures of Supermassive Black Hole Binaries

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arxiv 2310.16896 v2 pith:K7LRWANO submitted 2023-10-25 astro-ph.HE astro-ph.CO

Observational Signatures of Supermassive Black Hole Binaries

classification astro-ph.HE astro-ph.CO
keywords evidenceobservationalsmbhbstheoreticalbinariesblackdefinitivegaps
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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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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Cited by 16 Pith papers

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