Gravitational waves from resolvable massive black hole binary systems and observations with Pulsar Timing Arrays

Massive black holes are key components of the assembly and evolution of cosmic Structures. and a number Of Surveys are Currently oil going or planned to probe the demographics of these objects and to gain insight into the relevant physical processes. Pulsar Timing Arrays (PTAs) Currently provide the only means to observe gravitational radiation from massive black hole binary systems with masses 107 M(D. The whole cosmic population produces a stochastic background that Could be detectable with upcoming PTAs. Sources Sufficiently Close and/or massive generate gravitational radiation that significantly exceeds the level of the background and Could be individually resolved. We consider a wide range of massive black hole binary assembly scenarios, investigate the distribution of the main physical parameters of the sources, Such Lis masses and redshift, and explore the consequences for PTAs observations. Depending oil the specific massive black hole populations model. We estimate that oil average at least one resolvable source produces timing residuals ill the range similar to 5-50ns. PTAs, and ill Particular the future Square Kilometre Array, call plausibly detect these unique systems, although the events are likely to be rare. These observations Would naturally complement oil the high-mass end of the massive black hole distribution function future Surveys carried Out by the Laser Interferometer Space Antenna.