title: Detectability of Gravitational Waves from High-Redshift Binaries.
abstract: Recent nondetection of gravitational-wave backgrounds from pulsar timing arrays casts further uncertainty on the evolution of supermassive black hole binaries. We study the capabilities of current gravitational-wave observatories to detect individual binaries and demonstrate that, contrary to conventional wisdom, some are, in principle, detectable throughout the Universe. In particular, a binary with rest-frame mass ≳10^{10}M_{⊙} can be detected by current timing arrays at arbitrarily high redshifts. The same claim will apply for less massive binaries with more sensitive future arrays. As a consequence, future searches for nanohertz gravitational waves could be expanded to target evolving high-redshift binaries. We calculate the maximum distance at which binaries can be observed with pulsar timing arrays and other detectors, properly accounting for redshift and using realistic binary waveforms.
authors.affiliation: Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122, Australia.
authors.forename: Pablo A
authors.initials: PA
authors.lastname: Rosado
authors.affiliation: Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Victoria 3800, Australia.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Lasky
authors.affiliation: Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, Victoria 3800, Australia.
authors.forename: Eric
authors.initials: E
authors.lastname: Thrane
authors.affiliation: School of Physics, University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Xingjiang
authors.initials: X
authors.lastname: Zhu
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Ilya
authors.initials: I
authors.lastname: Mandel
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Alberto
authors.initials: A
authors.lastname: Sesana