Pulsar timing arrays and the challenge of massive black hole binary astrophysics

TL;DR

Pulsar timing arrays aim to detect nanohertz gravitational waves from supermassive black hole binaries, providing insights into their population, environment, and evolution, with current efforts progressing towards potential future detections.

Contribution

This paper reviews the expected gravitational wave signals from SMBH binaries, their dependence on astrophysical factors, and the current status and future prospects of PTA observations.

Findings

Current PTA efforts are advancing towards detection.

The GW signal depends on SMBH population and environment.

Future observations could reveal SMBH binary properties.

Abstract

Pulsar timing arrays (PTAs) are designed to detect gravitational waves (GWs) at nHz frequencies. The expected dominant signal is given by the superposition of all waves emitted by the cosmological population of supermassive black hole (SMBH) binaries. Such superposition creates an incoherent stochastic background, on top of which particularly bright or nearby sources might be individually resolved. In this contribution I describe the properties of the expected GW signal, highlighting its dependence on the overall binary population, the relation between SMBHs and their hosts, and their coupling with the stellar and gaseous environment. I describe the status of current PTA efforts, and prospect of future detection and SMBH binary astrophysics.