The astrophysics of nanohertz gravitational waves

By S. Burke-Spolaor, S. Taylor. The Astronomy and Astrophysics Review, 2018

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Pulsar timing array (PTA) collaborations in North America, Australia, and Europe, have been exploiting the exquisite timing precision of millisecond pulsars over decades of observations to search for correlated timing deviations induced by gravitational waves (GWs). PTAs are sensitive to the frequency band ranging just below 1 nanohertz to a few tens of microhertz. The discovery space of this band is potentially rich with populations of inspiraling supermassive black hole binaries, decaying cosmic string networks, relic post-inflation GWs, and even non-GW imprints of axionic dark matter. This article aims to provide an understanding of the exciting open science questions in cosmology, galaxy evolution, and fundamental physics that will be addressed by the detection and study of GWs through PTAs. The focus of the article is on providing an understanding of the mechanisms by which PTAs can address specific questions in these fields, and to outline some of the subtleties and difficulties in each case. The material included is weighted most heavily toward the questions which we expect will be answered in the near-term with PTAs; however, we have made efforts to include most currently anticipated applications of nanohertz GWs.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/170f960d3c85daf07ca9d225d1a9f3d5fd1d1121

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Citations in the corpus

The NANOGrav 15 yr Data Set: Constraints on Supermassive Black Hole Binaries from the Gravitational-wave Background (2023, background): “…coherent deviations in the times of arrival (TOAs) of pulsar signals, PTAs can observe a stochastic gravitational-wave background (GWB) from the superposition of many unresolved binaries, as well as individually resolved sources on top of the background (Burke-Spolaor et al. 2019; Taylor 2021).”
Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar Timing Array (2023, background): “…may include supermassive black hole binary (SMBHB) systems (e.g. Rajagopal & Romani 1995; Wyithe & Loeb 2003; Sesana 2013; Ravi et al. 2015; Burke-Spolaor et al. 2019), primordial quantum fluctuations amplified by inflation (e.g. Grishchuk 2005; Lasky et al. 2016), cosmic strings (e.g.…”
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background (2023, background): “If all contributing SMBHBs evolve purely by loss of circular orbital energy to gravitational radiation, the resultant GWB spectrum is well described by a simple f−2/3 characteristic-strain power law (Phinney 2001).”