Περίληψη :
While black hole binary systems are being detected through Gravitational Waves across different orders of magnitude of mass, their host environments are yet to be identified. This is because the association between each binary and the galaxy in which it inspirals is made challenging by the large uncertainty in the localisation of the source. After presenting the first observational constraints on the formation path for binaries of stellar-mass black holes detected by the LIGO-Virgo-KAGRA collaboration, I will show new results regarding the investigation on the host environments of supermassive black hole binaries. Pulsar timing arrays (PTAs) are in fact approaching the sensitivity required to resolve, for the first time, gravitational wave signals from individual supermassive black hole (SMBH) binaries. I will show how the posterior probability function of binary parameters inferred by the standard GW analysis can be converted into distributions of apparent magnitudes of the host galaxy in the infrared (IR) and optical bands. Such distributions can be used to inform host searches regarding which galaxies are the most likely, and therefore the ones on which to focus investigations of archival or new data aimed to find explicit electromagnetic signatures of the presence of a SMBH binary. I will discuss how we found that the host galaxies of all binaries that are detectable by a PTA with a baseline of 20 years are above the threshold for the WISE and SuperCOSMOS surveys if they lie outside the Milky Way plane, while 2MASS becomes incomplete for hosts of binary systems more massive than 10^9.8M⊙ at a luminosity distance from Earth greater than 1 Gpc.
