Constraints on Supermassive Black Hole Binaries from the Lack of Resolvable Sources in the NANOGrav 15-yr Dataset
Year: 2026
Type: preprint
Abstract: Pulsar timing arrays (PTAs) have found evidence of a gravitational wave background (GWB) consistent with a population of supermassive black hole binaries (SMBHBs), but have not yet resolved a continuous wave (CW) from an individual binary. We present the first SMBHB population constraints incorporating PTA upper limits on CWs, based on the NANOGrav 15-year (NG15) data. Using semi-analytic models to generate simulated populations, we calculate each sample's GWB likelihood by free spectral comparison and CW nondetection (nCW) likelihoods by (1) mapping each realization's highest CW signal-to-noise ratio (S/N) to a detection probability and (2) counting the fraction of realizations without a binary close enough that NG15 would have detected it. CW nondetection favors populations in which many lower-mass sources, rather than a few ultramassive ones, dominate the GWB. This information is complementary to that provided by the GWB amplitude, breaking the degeneracy between the masses and number of binaries required to reproduce the observed spectrum. Relative to GWB-only constraints, the joint posteriors favor higher galaxy merger rates, lower $M_\mathrm{BH}$-$M_\mathrm{bulge}$ scatter, shorter binary lifetimes, and steeper small-separation hardening. The most detectable sources in the S/N-weighted joint posterior have chirp masses $\sim 10^{9.6} M_\odot$, luminosity distances $\sim$1300 Mpc, and frequencies $\sim$6 nHz, while the nCW-only constraints favor lower frequencies, coinciding with the NG15 4 nHz candidate. These constraints will tighten if CW nondetection continues.
Source: arXiv (Cornell University)
Authors: Gardiner, Emiko C., Gültekin, Kayhan, Turgeon, Philippe, Bécsy, Bence, Blecha, Laura, Agarwal, Nikita, Agazie, Gabriella, Anumarlapudi, Akash, Archibald, Anne M., Arzoumanian, Zaven, Ashok, Anjana, Baier, Jeremy G., Baker, Paul T., Brazier, Adam, Brook, Paul R., Burke-Spolaor, Sarah, Burnette, Rand, Case, Robin, Casey-Clyde, J. Andrew, Charisi, Maria, Chatterjee, Shami, Cohen, Tyler, Cordes, James M., Cornish, Neil J., Crawford, Fronefield, Cromartie, H. Thankful, Crowter, Kathryn, DeCesar, Megan E., Demorest, Paul B., Deng, Heling, Dey, Lankeswar, Dolch, Timothy, Doskoch, Graham M., Ferrara, Elizabeth C., Fiore, William, Fonseca, Emmanuel, Freedman, Gabriel E., Garver-Daniels, Nate, Gentile, Peter A., Gersbach, Kyle A., Glaser, Joseph, Good, Deborah C., Gundersen, Aiden, Harris, C. J., Hazboun, Jeffrey S., Jennings, Ross J., Johnson, Aaron D., Jones, Megan L., Kaplan, David L., Sreekumar, Anala Kavumkandathil, Kelley, Luke Zoltan, Kerr, Matthew, Key, Joey S., Laal, Nima, Lam, Michael T., Lamb, William G., Larsen, Bjorn, Lazio, T. Joseph W., Lewandowska, Natalia, Liu, Tingting, Lorimer, Duncan R., Luo, Jing, Lynch, Ryan S., Ma, Chung-Pei, Madison, Dustin R., Martsen, Ashley, Matt, Cayenne, McEwen, Alexander, McKee, James W., McLaughlin, Maura A., McMann, Natasha, Meyers, Bradley W., Meyers, Patrick M., Miles, Matthew T., Mingarelli, Chiara M. F., Mitridate, Andrea, Ng, Cherry, Nice, David J., Nichols, Shania A., Ocker, Stella Koch, Oliver, Daniel J., Olum, Ken D., Pennucci, Timothy T., Perera, Benetge B. P., Petrov, Polina, Pol, Nihan S., Radovan, Henri A., Ransom, Scott M., Ray, Paul S., Romano, Joseph D., Runnoe, Jessie C., Saffer, Alexander, Sardesai, Shashwat C., Schmiedekamp, Ann, Schmiedekamp, Carl, Schmitz, Kai, Schult, Levi, Shapiro-Albert, Brent J., Siemens, Xavier, Simon, Joseph, Fiscella, Sophia V. Sosa, Stairs, Ingrid H., Stinebring, Daniel R., Stovall, Kevin, Susobhanan, Abhimanyu, Swiggum, Joseph K., Taylor, Jacob, Taylor, Stephen R., Thompson, Mercedes S., Turner, Jacob E., Vallisneri, Michele, van Haasteren, Rutger, Verbiest, Joris P. W., Vigeland, Sarah J., Wahl, Haley M., Wilson, Kevin P., Witt, Caitlin A., Wright, David, Young, Olivia
Institutions: University of California, Berkeley, University of Michigan, University of Florida, West Virginia University, Newcastle University, Goddard Space Flight Center, Oregon State University, Widener University, Cornell University, Montana State University, Franklin & Marshall College, University of British Columbia, George Mason University, National Radio Astronomy Observatory, Columbia University, FORTH Institute of Astrophysics, Foundation for Research and Technology Hellas, Vanderbilt University, University of Wisconsin–Milwaukee, University of Washington Bothell, Search for Extraterrestrial Intelligence, Yale University, Georgia State University, University of Toronto, Union College, ETH Zurich, Institute for Particle Physics and Astrophysics, Flatiron Institute, Imperial College London, Lafayette College, California Institute of Technology, Carnegie Institution for Science, Carnegie Observatories, Tufts University, Eötvös Loránd University, Arecibo Observatory, Texas Tech University, University of Puerto Rico-Mayaguez, United States Naval Research Laboratory, Naval Research Laboratory Space Science Division, University of Birmingham
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Gordon and Betty Moore Foundation, Vanderbilt University, California Institute of Technology, Texas Tech University, Canadian Institute for Advanced Research, Oregon State University, Flatiron Health, European Commission, University of Toronto, Eötvös Loránd Tudományegyetem, Jet Propulsion Laboratory, College of Science, Oregon State University, Natural Sciences and Engineering Research Council of Canada, Science and Technology Facilities Council, Office of Naval Research
Awards: NANOGrav@UPRM: Growing and Characterizing the NANOGrav Gravitational-Wave Detector, The First Multi-Messenger Study of Supermassive Black Hole Growth, CAREER: Unveiling the Nanohertz GW Discovery Landscape by Broadening Participation In Multi-Messenger Astrophysics, G2500807902, Enabling multi-messenger science with pulsar timing arrays, G2676722403, CAREER: More Accurate Galaxy Merger Rates to Propel Studies of Gravitational Waves and Star Formation in Galaxy Mergers, AccelNet-Implementation: The International Pulsar Timing Array, WoU-MMA: Pulsar Timing Arrays Around the World CHIME in on Gravitational Waves, WOU-MMA: Probing Supermassive Binary Black Holes with Pulsar Timing Arrays, G3653412478, Collaborative Research: Building the Next-Generation NANOGrav Pulsar Timing Array with the DSA-2000, Astrophysics at the University of Birmingham - Consolidated grant 2022-2025, RII Track-1: Gravitational Wave Astronomy and the Appalachian Freshwater Initiative, Graduate Research Fellowship Program (GRFP), G5429681523, Improving NANOGrav Gravitational Wave Detection, G5805864723, Collaborative research: Completing the most sensitive low-frequency survey for radio pulsars and transients, Collaborative Research: Building the Next-Generation NANOGrav Pulsar Timing Array with the DSA-2000, Toward Robust Models of Supermassive Black Hole Binary Populations for the Low-Frequency Gravitational Wave Era, G7484881787, WoU-MMA: Multi-messenger Titans: Probing The Dynamics & Environments Of Supermassive Binary Black Holes, G830101876, Kavli Institute for Theoretical Physics
OpenAlex ID: W7214802133