Electromagnetic counterparts to massive black-hole mergers

Abstract

The next two decades are expected to open the door to the first coincident detections of electromagnetic (EM) and gravitational-wave (GW) signatures associated with massive black-hole (MBH) binaries heading for coalescence. These detections will launch a new era of multimessenger astrophysics by expanding this growing field to the low-frequency GW regime and will provide an unprecedented understanding of the evolution of MBHs and galaxies. They will also constitute fundamentally new probes of cosmology and would enable unique tests of gravity. The aim of this Living Review is to provide an introduction to this research topic by presenting a summary of key findings, physical processes and ideas pertaining to EM counterparts to MBH mergers as they are known at the time of this writing. We review current observational evidence for close MBH binaries, discuss relevant physical processes and timescales, and summarize the possible EM counterparts to GWs in the precursor, coalescence, and afterglow stages of a MBH merger. We also describe open questions and discuss future prospects in this dynamic and quick-paced research area.

Quasars with Periodic Variability: Capabilities and Limitations of Bayesian Searches for Supermassive Black Hole Binaries in Time-domain Surveys

“…Previous studies have demonstrated a link between AGNs and galaxy mergers; this follows naturally from the idea that the mergers bring significant amounts of gas to the central regions of the postmerger galaxies, which may actively accrete onto the SMBHs, triggering AGN activity (Goulding et al 2018). Similarly, binaries are expected to be surrounded by significant amounts of gas, which can give rise to bright quasar-like electromagnetic emission (Armitage & Natarajan 2002;Tanaka et al 2012;Bogdanovic et al 2022).…”

“…GWs in this frequency band can be detected by pulsar timing arrays (PTAs), and offer one of the only direct probes to SMBHBs at close (roughly milliparsec) separations (Burke-Spolaor et al 2019;Taylor et al 2019). Electromagnetic observations can also infer the existence of a SMBHB, and provide a unique probe of the binary's environment (Bogdanovic et al 2022). The detection of GWs along with associated electromagnetic counterparts will mark the beginning of multimessenger astrophysics in the low-frequency regime (Kelley et al 2019a).…”

General Relativistic Magnetohydrodynamic Simulations of Accretion Disks Around Tilted Binary Black Holes of Unequal Mass

“…In fact, for steady accretion from a magnetized disk, the spin will re-lax to χ 0.9 [59]. As pointed out in [60], GW observations from merging SMBHBHs are required to impose tight constraints on their spin.…”

Radiación de agujeros negros acretantes: problemas micro- y macrofísicos

“…Estos sistemas se formarían en el centro de galaxias que sufrieron una fusión previa, donde puede haber abundantes cantidades de gas (Begelman et al, 1980;Mayer et al, 2007;Escala et al, 2004Escala et al, , 2005Merritt, 2004;Merritt, 2006;Dotti et al, 2007;Volonteri, 2010;Dotti et al, 2009;Shi et al, 2012;Sesana & Khan, 2015;Mirza et al, 2017;Khan et al, 2019;Tiede et al, 2020;Springel et al, 2005;Chapon et al, 2013). Es razonable esperar, luego, que las fusiones de SMBH se conviertan en fuentes multimensajero de GW y ondas electromagnéticas (Bogdanović et al, 2022). Futuras observaciones simultáneas de estos dos tipos de radiación mensajera podrán brindar información relevante para comprender la evolución de los SMBH en el contexto de la evolución de las galaxias, de la formación de estructura a gran escala del Universo, así como brindar luz sobre la física de la acreción en situaciones muy distintas a las que se dan en un AGN simple.…”

“…Además, dado que la tasa de acreción en el radio de Bondi escala como M 2 , con M la masa total del sistema binario, para condiciones fijas en el medio interestelar vecino, un SMBHB puede acretar grandes cantidades de gas, formando un flujo de acreción brillante como sucede en un AGN. Es razonable esperar, luego, que las fusiones de SMBH se conviertan en fuentes multimensajero de GW y ondas electromagnéticas (Bogdanović et al, 2022). Futuras observaciones simultáneas de estos dos tipos de radiación mensajera podrán brindar información relevante para comprender la evolución de los SMBH en el contexto de la evolución de las galaxias, de la formación de estructura a gran escala del Universo, así como brindar luz sobre la física de la acreción en situaciones muy distintas a las que se dan en un AGN simple.…”