Expected properties of the first gravitational wave signal detected with pulsar timing arrays

Understand

In this paper we attempt to investigate the nature of the first gravitational wave (GW) signal to be detected by pulsar timing arrays (PTAs): will it be an individual, resolved supermassive black hole binary (SBHB), or a stochastic background made by the superposition of GWs produced by an ensemble of SBHBs? To address this issue, we analyse a broad set of simulations of the cosmological population of SBHBs, that cover the entire parameter space allowed by current electromagnetic observations in an unbiased way.

• For each simulation, we construct the expected GW signal and identify the loudest individual sources.
• We then employ appropriate detection statistics to evaluate the relative probability of detecting each type of source as a function of time for a variety of PTAs; we consider the current International PTA, and speculate into the era of the Square Kilometre Array.
• The main properties of the first detectable individual SBHBs are also investigated.