The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background
Gabriella AgazieCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAAkash AnumarlapudiCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAAnne M. ArchibaldNewcastle University, NE1 7RU, UKZaven ArzoumanianX-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USAP. T. BakerDepartment of Physics and Astronomy, Widener University, One University Place, Chester, PA 19013, USAB. BécsyDepartment of Physics, Oregon State University, Corvallis, OR 97331, USALaura BlechaPhysics Department, University of Florida, Gainesville, FL 32611, USAAdam BrazierCornell Center for Advanced Computing, Cornell University, Ithaca, NY 14853, USAPaul R. BrookInstitute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UKSarah Burke-SpolaorCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USARand BurnetteDepartment of Physics, Oregon State University, Corvallis, OR 97331, USARobin CaseDepartment of Physics, Oregon State University, Corvallis, OR 97331, USAMaria CharisiDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USAShami ChatterjeeCornell Center for Astrophysics and Planetary Science and Department of Astronomy, Cornell University, Ithaca, NY 14853, USAKaterina ChatziioannouDivision of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USAB. D. CheeseboroCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USASiyuan ChenKavli Institute for Astronomy and Astrophysics, Peking University, Beijing, 100871, People's Republic of ChinaTyler CohenDepartment of Physics, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801, USAJ. M. CordesCornell Center for Astrophysics and Planetary Science and Department of Astronomy, Cornell University, Ithaca, NY 14853, USANeil J. CornishDepartment of Physics, Montana State University, Bozeman, MT 59717, USAF. CrawfordDepartment of Physics and Astronomy, Franklin & Marshall College, P.O. Box 3003, Lancaster, PA 17604, USAH. T. CromartieCornell Center for Astrophysics and Planetary Science and Department of Astronomy, Cornell University, Ithaca, NY 14853, USAKathryn CrowterDepartment of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, CanadaCurt CutlerDivision of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USAMegan E. DeCesarGeorge Mason University, resident at the Naval Research Laboratory, Washington, DC 20375, USADallas DeGanDepartment of Physics, Oregon State University, Corvallis, OR 97331, USAPaul B. DemorestNational Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801, USAHeling DengDepartment of Physics, Oregon State University, Corvallis, OR 97331, USATimothy DolchDepartment of Physics, Hillsdale College, 33 E. College Street, Hillsdale, MI 49242, USABrendan DrachlerLaboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, Rochester, NY 14623, USAJustin A. EllisE. C. FerraraCenter for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, MD 20771, USAWilliam FioreCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAEmmanuel FonsecaCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAGabriel E. FreedmanCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USANate Garver-DanielsCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAPeter A. GentileCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAKyle A. GersbachDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USAJoseph GlaserCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USADeborah C. GoodCenter for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USAKayhan GültekinDepartment of Astronomy and Astrophysics, University of Michigan, Ann Arbor, MI 48109, USAJeffrey S. HazbounDepartment of Physics, Oregon State University, Corvallis, OR 97331, USASophie HourihaneDivision of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USAKristina IsloCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USARoss J. JenningsCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAAaron D. JohnsonCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAMegan L. JonesCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAAndrew R. KaiserCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAD. L. KaplanCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USALuke Zoltan KelleyDepartment of Astronomy, University of California, Berkeley, 501 Campbell Hall #3411, Berkeley, CA 94720, USAM. KerrSpace Science Division, Naval Research Laboratory, Washington, DC 20375-5352, USAJ. S. KeyUniversity of Washington Bothell, 18115 Campus Way NE, Bothell, WA 98011, USATonia C. KleinCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USANima LaalDepartment of Physics, Oregon State University, Corvallis, OR 97331, USAMichael T. LamLaboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, Rochester, NY 14623, USAWilliam G. LambDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USAT. Joseph W. LazioJet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USAN. LewandowskaDepartment of Physics, State University of New York at Oswego, Oswego, NY, 13126, USAT. B. LittenbergNASA Marshall Space Flight Center, Huntsville, AL 35812, USATingting LiuCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAA. N. LommenDepartment of Physics and Astronomy, Haverford College, Haverford, PA 19041, USAD. R. LorimerCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAJing LuoDepartment of Astronomy & Astrophysics, University of Toronto, 50 Saint George Street, Toronto, ON M5S 3H4, CanadaRyan S. LynchChung‐Pei MaDepartment of Astronomy, University of California, Berkeley, 501 Campbell Hall #3411, Berkeley, CA 94720, USADustin R. MadisonDepartment of Physics, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USAM. A. MattsonCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAAlexander McEwenCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAJames W. McKeeCentre of Excellence for Data Science, Artificial Intelligence and Modelling (DAIM), University of Hull, Cottingham Road, Kingston-upon-Hull, HU6 7RX, UKM. A. McLaughlinCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USANatasha McMannDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USABradley W. MeyersDepartment of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, CanadaP. M. MeyersDivision of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USAChiara M. F. MingarelliCenter for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USAAndrea MitridateDeutsches Elektronen-Synchrotron DESY, Notkestr. 85, D-22607 Hamburg, GermanyPriyamvada NatarajanBlack Hole Initiative, Harvard University, 20 Garden Street, Cambridge, MA 02138, USACherry NgDunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON M5S 3H4, CanadaD. J. NiceDepartment of Physics, Lafayette College, Easton, PA 18042, USAStella Koch OckerCornell Center for Astrophysics and Planetary Science and Department of Astronomy, Cornell University, Ithaca, NY 14853, USAKen D. OlumInstitute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155, USATimothy T. PennucciInstitute of Physics and Astronomy, Eötvös Loránd University, Pázmány P.s. 1/A, 1117 Budapest, HungaryBenetge B. P. PereraArecibo Observatory, HC3 Box 53995, Arecibo, PR 00612, USAPolina PetrovDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USANihan S. PolDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USAH. A. RadovanDepartment of Physics, University of Puerto Rico, Mayagüez, PR 00681, USAS. M. RansomNational Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USAPaul S. RaySpace Science Division, Naval Research Laboratory, Washington, DC 20375-5352, USAJoseph D. RomanoDepartment of Physics, Texas Tech University, Box 41051, Lubbock, TX 79409, USAShashwat C. SardesaiCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAAnn SchmiedekampDepartment of Physics, Penn State Abington, Abington, PA 19001, USACarl SchmiedekampDepartment of Physics, Penn State Abington, Abington, PA 19001, USAKai SchmitzInstitute for Theoretical Physics, University of Münster, D-48149 Münster, GermanyLevi SchultDepartment of Physics and Astronomy, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235, USABrent J. Shapiro-AlbertCenter for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USAXavier SiemensCenter for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, P.O. Box 413, Milwaukee, WI 53201, USAJoseph SimonDepartment of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USAMagdalena S. SiwekCenter for Astrophysics, Harvard University, 60 Garden St., Cambridge, MA 02138, USAI. H. StairsDepartment of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, CanadaDaniel R. StinebringDepartment of Physics and Astronomy, Oberlin College, Oberlin, OH 44074, USAKevin StovallNational Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801, USA
2023en
ABI
Annotatsiya
Abstract We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings–Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 10 14 , and this same model is favored over an uncorrelated common power-law spectrum model with Bayes factors of 200–1000, depending on spectral modeling choices. We have built a statistical background distribution for the latter Bayes factors using a method that removes interpulsar correlations from our data set, finding p = 10 −3 (≈3 σ ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of interpulsar correlations yields p = 5 × 10 −5 to 1.9 × 10 −4 (≈3.5 σ –4 σ ). Assuming a fiducial f −2/3 characteristic strain spectrum, as appropriate for an ensemble of binary supermassive black hole inspirals, the strain amplitude is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:msup> </mml:math> (median + 90% credible interval) at a reference frequency of 1 yr −1 . The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings–Downs correlations points to the gravitational-wave origin of this signal.
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