Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries

Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries Yifan Chen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6898268/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Feb, 2026 Read the published version in Nature Astronomy → Version 1 posted You are reading this latest preprint version Abstract The detection of a stochastic gravitational wave background by pulsar timing arrays suggests the presence of a supermassive black hole binary population. Although the observed spectrum generally matches predictions for orbital evolution driven by gravitational-wave emission in circular orbits, there is a preference for a spectral turnover at the lowest observed frequencies, which may point to a significant hardening phase transitioning from early environmental influences to later stages dominated by gravitational-wave emission. In the vicinity of these binaries, the ejection of stars or dark matter particles through gravitational three-body slingshots efficiently extracts orbital energy, leading to a low-frequency turnover in the spectrum. We model how the gravitational-wave spectrum depends on the initial inner galactic profile prior to scouring by binary ejections, accounting for a range of initial binary eccentricities. By analyzing the NANOGrav 15-year data, we find that a parsec-scale galactic center density of around $10^6,M_\odot/\mathrm{pc}^3$ is favored across most of the parameter space, shedding light on environmental effects that shape black hole evolution and the combined matter density near galaxy centers. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/General relativity and gravity Physical sciences/Physics/Astronomy and astrophysics/Compact astrophysical objects Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 05 Feb, 2026 Read the published version in Nature Astronomy → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6898268","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":488437812,"identity":"e619f5aa-76ef-4c48-bef4-8aae5a549534","order_by":0,"name":"Yifan Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIiWNgGAWjYDACZsYHICoByDpArBZmA6gWtgSirYFp4TEgToPBcWbGzwUMdnn80j3fHvzcYWO3vf2MAcPHPbW4tRxmZpaewZBcLDnn7HbD3jNpyXPO5Bgwznh2HI8W/gPSPAwHEjfcyN0mwdt2OFmCIS2BmefAMby2/AZp2X8j55nkX5AW/mcEtbBBbJHIYZMG2mInIZF8AKilBqcWSaAWax6D5MQZN9LMpGXb0hIkJB4fODjjwAGcWvjOH2a+zVNhl9g/I/mZ5Ns2G3sJ/sTGBx8O1OHUogA2DSlGEhuABFDwME4t8g1oAvZQGrcto2AUjIJRMOIAAAbuVD0HnmYvAAAAAElFTkSuQmCC","orcid":"","institution":"Niels Bohr Institute","correspondingAuthor":true,"prefix":"","firstName":"Yifan","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2025-06-15 12:30:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6898268/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6898268/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41550-026-02782-0","type":"published","date":"2026-02-05T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":102397377,"identity":"9239edf0-5c45-412b-828b-6bb023a22871","added_by":"auto","created_at":"2026-02-11 10:16:18","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":565774,"visible":true,"origin":"","legend":"Article File","description":"","filename":"GalacticTomographyPTANAv1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6898268/v1_covered_9f79996f-fb25-4056-9ff5-dee0f31e06b0.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Galaxy Tomography with the Gravitational Wave Background from Supermassive Black Hole Binaries","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6898268/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6898268/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The detection of a stochastic gravitational wave background by pulsar timing arrays suggests the presence of a supermassive black hole binary population. Although the observed spectrum generally matches predictions for orbital evolution driven by gravitational-wave emission in circular orbits, there is a preference for a spectral turnover at the lowest observed frequencies, which may point to a significant hardening phase transitioning from early environmental influences to later stages dominated by gravitational-wave emission. In the vicinity of these binaries, the ejection of stars or dark matter particles through gravitational three-body slingshots efficiently extracts orbital energy, leading to a low-frequency turnover in the spectrum. We model how the gravitational-wave spectrum depends on the initial inner galactic profile prior to scouring by binary ejections, accounting for a range of initial binary eccentricities. 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