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Brian Cahill's picture

For the first time, the local nanohertz gravitational-wave landscape has been predicted as part of research carried out during an MSCA project by MCAA Member Chiara Mingarelli. In a Nature Astronomy paper entitled "The local nanohertz gravitational-wave landscape from supermassive black hole binaries", she found that there should be about 91 local massive galaxies (or ~2%) hosting supermassive black hole binaries in the pulsar timing array band, and that 7 (or 0.1%) of local supermassive black hole binaries will never merge! Since this work is based on real galaxies, instead of simulated populations, galaxies are ranked in terms of the likeliest to host supermassive black hole binaries in the pulsar timing array band. Surprisingly, M87, which hosts a 4 billion solar mass supermassive black hole, is not #1 on our list of supermassive black hole binaries candidates. The binary it would host would be so massive that it would zoom through the nanohertz GW band, where pulsar timing arrays operate The hero here is M104, the Sombrero Galaxy, which is massive enough to host a detectible supermassive black hole binary, but not so massive that it zooms through the pulsar timing array band. Chiara also did a comprehensive study of when we should expect to detect the first merging supermassive black hole binaries with pulsar timing arrays, and found that AT LEAST one will be detectible in 10 years. In the spirit of open access and transparency, all of codes are made public and available on @github, as are the 75,000 monte carlo realizations I did of the local Universe. Yours to explore! https://github.com/ChiaraMingarelli/nanohertz_GWs

A previous version of this work is available on the arXiv, https://arxiv.org/abs/1708.03491