How to Detect an Astrophysical Nanohertz Gravitational-Wave Background
Creators: name: Bécsy, Bence
name: Cornish, Neil J.
name: Meyers, Patrick M.
name: Kelley, Luke Zoltan
name: Agazie, Gabriella
name: Anumarlapudi, Akash
name: Archibald, Anne M.
name: Arzoumanian, Zaven
name: Baker, Paul T.
name: Blecha, Laura
name: Brazier, Adam
name: Brook, Paul R.
name: Burke-Spolaor, Sarah
name: Casey-Clyde, J. Andrew
name: Charisi, Maria
name: Chatterjee, Shami
name: Chatziioannou, Katerina
name: Cohen, Tyler
name: Cordes, James M.
name: Crawford, Fronefield
name: Cromartie, H. Thankful
name: Crowter, Kathryn
name: DeCesar, Megan E.
name: Demorest, Paul B.
name: Dolch, Timothy
name: Ferrara, Elizabeth C.
name: Fiore, William
name: Fonseca, Emmanuel
name: Freedman, Gabriel E.
name: Garver-Daniels, Nate
name: Gentile, Peter A.
name: Glaser, Joseph
name: Good, Deborah C.
name: Gültekin, Kayhan
name: Hazboun, Jeffrey S.
name: Hourihane, Sophie
name: Jennings, Ross J.
name: Johnson, Aaron D.
name: Jones, Megan L.
name: Kaiser, Andrew R.
name: Kaplan, David L.
name: Kerr, Matthew
name: Key, Joey S.
name: Laal, Nima
name: Lam, Michael T.
name: Lamb, William G.
name: Lazio, T. Joseph W.
name: Lewandowska, Natalia
name: Littenberg, Tyson B.
name: Liu, Tingting
name: Lorimer, Duncan R.
name: Luo, Jing
name: Lynch, Ryan S.
name: Ma, Chung-Pei
name: Madison, Dustin R.
name: McEwen, Alexander
name: McKee, James W.
name: McLaughlin, Maura A.
name: McMann, Natasha
name: Meyers, Bradley W.
name: Mingarelli, Chiara M. F.
name: Mitridate, Andrea
name: Ng, Cherry
name: Nice, David J.
name: Ocker, Stella Koch
name: Olum, Ken D.
name: Pennucci, Timothy T.
name: Perera, Benetge B. P.
name: Pol, Nihan S.
name: Radovan, Henri A.
name: Ransom, Scott M.
name: Ray, Paul S.
name: Romano, Joseph D.
name: Sardesai, Shashwat C.
name: Schmiedekamp, Ann
name: Schmiedekamp, Carl
name: Schmitz, Kai
name: Shapiro-Albert, Brent J.
name: Siemens, Xavier
name: Simon, Joseph
name: Siwek, Magdalena S.
name: Fiscella, Sophia V. Sosa
name: Stairs, Ingrid H.
name: Stinebring, Daniel R.
name: Stovall, Kevin
name: Susobhanan, Abhimanyu
name: Swiggum, Joseph K.
name: Taylor, Stephen R.
name: Turner, Jacob E.
name: Unal, Caner
name: Vallisneri, Michele
name: van Haasteren, Rutger
name: Vigeland, Sarah J.
name: Wahl, Haley M.
name: Witt, Caitlin A.
name: Young, Olivia
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Analysis of pulsar timing data have provided evidence for a stochastic gravitational wave background in the nHz frequency band. The most plausible source of such a background is the superposition of signals from millions of supermassive black hole binaries. The standard statistical techniques used to search for such a background and assess its significance make several simplifying assumptions, namely: i) Gaussianity; ii) isotropy; and most often iii) a power-law spectrum. However, a stochastic background from a finite collection of binaries does not exactly satisfy any of these assumptions. To understand the effect of these assumptions, we test standard analysis techniques on a large collection of realistic simulated datasets. The dataset length, observing schedule, and noise levels were chosen to emulate the NANOGrav 15-year dataset. Simulated signals from millions of binaries drawn from models based on the Illustris cosmological hydrodynamical simulation were added to the data. We find that the standard statistical methods perform remarkably well on these simulated datasets, despite their fundamental assumptions not being strictly met. They are able to achieve a confident detection of the background. However, even for a fixed set of astrophysical parameters, different realizations of the universe result in a large variance in the significance and recovered parameters of the background. We also find that the presence of loud individual binaries can bias the spectral recovery of the background if we do not account for them.
description: 14 pages, 8 figures, version matching published paper