The NANOGrav 15-year Data Set: Search for Anisotropy in the Gravitational-Wave Background
Abstract
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has reported evidence for the presence of an isotropic nanohertz gravitational wave background (GWB) in its 15 yr dataset. However, if the GWB is produced by a population of inspiraling supermassive black hole binary (SMBHB) systems, then the background is predicted to be anisotropic, depending on the distribution of these systems in the local Universe and the statistical properties of the SMBHB population. In this work, we search for anisotropy in the GWB using multiple methods and bases to describe the distribution of the GWB power on the sky. We do not find significant evidence of anisotropy, and place a Bayesian upper limit on the level of broadband anisotropy such that . We also derive conservative estimates on the anisotropy expected from a random distribution of SMBHB systems using astrophysical simulations conditioned on the isotropic GWB inferred in the 15-yr dataset, and show that this dataset has sufficient sensitivity to probe a large fraction of the predicted level of anisotropy. We end by highlighting the opportunities and challenges in searching for anisotropy in pulsar timing array data.
Keywords
Cite
@article{arxiv.2306.16221,
title = {The NANOGrav 15-year Data Set: Search for Anisotropy in the Gravitational-Wave Background},
author = {Gabriella Agazie and Akash Anumarlapudi and Anne M. Archibald and Zaven Arzoumanian and Paul T. Baker and Bence Bécsy and Laura Blecha and Adam Brazier and Paul R. Brook and Sarah Burke-Spolaor and J. Andrew Casey-Clyde and Maria Charisi and Shami Chatterjee and Tyler Cohen and James M. Cordes and Neil J. Cornish and Fronefield Crawford and H. Thankful Cromartie and Kathryn Crowter and Megan E. DeCesar and Paul B. Demorest and Timothy Dolch and Brendan Drachler and Elizabeth C. Ferrara and William Fiore and Emmanuel Fonseca and Gabriel E. Freedman and Emiko Gardiner and Nate Garver-Daniels and Peter A. Gentile and Joseph Glaser and Deborah C. Good and Kayhan Gültekin and Jeffrey S. Hazboun and Ross J. Jennings and Aaron D. Johnson and Megan L. Jones and Andrew R. Kaiser and David L. Kaplan and Luke Zoltan Kelley and Matthew Kerr and Joey S. Key and Nima Laal and Michael T. Lam and William G. Lamb and T. Joseph W. Lazio and Natalia Lewandowska and Tingting Liu and Duncan R. Lorimer and Jing Luo and Ryan S. Lynch and Chung-Pei Ma and Dustin R. Madison and Alexander McEwen and James W. McKee and Maura A. McLaughlin and Natasha McMann and Bradley W. Meyers and Chiara M. F. Mingarelli and Andrea Mitridate and Cherry Ng and David J. Nice and Stella Koch Ocker and Ken D. Olum and Timothy T. Pennucci and Benetge B. P. Perera and Nihan S. Pol and Henri A. Radovan and Scott M. Ransom and Paul S. Ray and Joseph D. Romano and Shashwat C. Sardesai and Ann Schmiedekamp and Carl Schmiedekamp and Kai Schmitz and Levi Schult and Brent J. Shapiro-Albert and Xavier Siemens and Joseph Simon and Magdalena S. Siwek and Ingrid H. Stairs and Daniel R. Stinebring and Kevin Stovall and Abhimanyu Susobhanan and Joseph K. Swiggum and Stephen R. Taylor and Jacob E. Turner and Caner Unal and Michele Vallisneri and Sarah J. Vigeland and Haley M. Wahl and Caitlin A. Witt and Olivia Young},
journal= {arXiv preprint arXiv:2306.16221},
year = {2023}
}
Comments
19 pages, 11 figures; submitted to Astrophysical Journal Letters as part of Focus on NANOGrav's 15-year Data Set and the Gravitational Wave Background. For questions or comments, please email [email protected]