Prevalent Mpc-scale lobes around quasars at cosmic noon revealed by Faraday rotation measures

Prevalent Mpc-scale lobes around quasars at cosmic noon revealed by Faraday rotation measures | 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 Prevalent Mpc-scale lobes around quasars at cosmic noon revealed by Faraday rotation measures Renyue Cen, Gang Li, Russell Taylor, Dongzi Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8356590/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Giant radio lobes spanning tens of kiloparsecs to several megaparsecs are observed around quasars and are classified as FRI and FRII radio galaxies locally. In this work, we investigate, for the first time, the environments of high-redshift quasars during the cosmic noon using Faraday rotation measures. Through a statistical cross-correlation between foreground quasars and background rotation measure sources, we detect a significant rotation measure excess within about 1.5 megaparsecs of quasar positions. The excess amounts to 3.42±0.63 radians per square meter, with a local statistical significance of 3.38σ, indicating the presence of substantial magnetic fields. This rotation measure excess is accompanied by increased scatter in rotation measure values around quasars—approximately 10.47±3.43 radians per square meter—which shows a power-law dependence on the intersection path length. This dependence is consistent with a magnetic field coherence length on the order of 100 kiloparsecs. Monte Carlo simulations show that the observed rotation measure excess can be reproduced if most quasars possess linear sizes on the order of one megaparsec, in striking agreement with the known sizes of local giant Fanaroff–Riley type II radio lobes. We derive a typical line-of-sight magnetic field strength of about 3.87 microgauss, with asymmetric uncertainties of roughly +1.46 and −1.44 microgauss, assuming an electron density of 10 -4 per cubic centimeter. Two profound implications follow from this discovery. First, all or a large fraction of quasars at cosmic noon undergo at least one episode that inflates giant radio lobes into the surrounding medium; these lobes persist for timescales comparable to the contemporary Hubble time or are episodically re-energized. Second, large-scale active galactic nucleus feedback in the form of magnetic energy from such powerful radio lobes may provide a significant external feedback mechanism, regulating gas accretion onto galaxies in the extended environment around massive, lobe-hosting galaxies. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Astrophysical magnetic fields Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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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-8356590","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":604571237,"identity":"4f744d27-1091-4980-8f59-875da1b0e5ab","order_by":0,"name":"Renyue Cen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIiWNgGAWjYFAD9gYGAyDF2EC8Fp4DJGuRSABThLWYt/cek+apsJMzl3z+oJiHwUZ2wwHmZw/waZE5cy5NmudMsrHl7IQEYx6GNOMNB9jMDfA6RyLHTJq37UDihtsJB4BaDiduOMDDJoFXi/wboJZ/B+o33DzYANTynwgtEjxALQ0HEgxuMDMAtRwgQgtPjrHlnGPJhhvOpDEYzjFINp55mM0Mvxb2M4Y33tTYyRscP/7M4E2FnWzf8eZneLUAAQtMAZsBODKZCagHKfkAYzwgrHgUjIJRMApGIgAAHSpCrjZpKcIAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-8531-9536","institution":"Zhejiang University","correspondingAuthor":true,"prefix":"","firstName":"Renyue","middleName":"","lastName":"Cen","suffix":""},{"id":604571238,"identity":"558bce1d-dc93-464c-9e49-e54205be21bf","order_by":1,"name":"Gang Li","email":"","orcid":"","institution":"Zhejiang University","correspondingAuthor":false,"prefix":"","firstName":"Gang","middleName":"","lastName":"Li","suffix":""},{"id":604571239,"identity":"842ef473-75b4-4cbd-9c6a-4229205ba0bd","order_by":2,"name":"Russell Taylor","email":"","orcid":"","institution":"University of Cape Town","correspondingAuthor":false,"prefix":"","firstName":"Russell","middleName":"","lastName":"Taylor","suffix":""},{"id":604571240,"identity":"2323265c-f956-456e-9215-9a9f25214310","order_by":3,"name":"Dongzi Li","email":"","orcid":"","institution":"Department of Astronomy, Tsinghua University","correspondingAuthor":false,"prefix":"","firstName":"Dongzi","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-12-14 08:01:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8356590/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8356590/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107867626,"identity":"aa139a40-ba62-4b83-9096-7f868c989a04","added_by":"auto","created_at":"2026-04-27 06:57:23","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3971444,"visible":true,"origin":"","legend":"Article File","description":"","filename":"RMmanuscriptNA.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8356590/v1_covered_a5ec82a6-c936-4133-a5d2-a080d942599a.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Prevalent Mpc-scale lobes around quasars at cosmic noon revealed by Faraday rotation measures","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8356590/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8356590/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Giant radio lobes spanning tens of kiloparsecs to several megaparsecs are observed around quasars and are classified as FRI and FRII radio galaxies locally. In this work, we investigate, for the first time, the environments of high-redshift quasars during the cosmic noon using Faraday rotation measures. Through a statistical cross-correlation between foreground quasars and background rotation measure sources, we detect a significant rotation measure excess within about 1.5 megaparsecs of quasar positions. The excess amounts to 3.42±0.63 radians per square meter, with a local statistical significance of 3.38σ, indicating the presence of substantial magnetic fields. This rotation measure excess is accompanied by increased scatter in rotation measure values around quasars—approximately 10.47±3.43 radians per square meter—which shows a power-law dependence on the intersection path length. This dependence is consistent with a magnetic field coherence length on the order of 100 kiloparsecs. Monte Carlo simulations show that the observed rotation measure excess can be reproduced if most quasars possess linear sizes on the order of one megaparsec, in striking agreement with the known sizes of local giant Fanaroff–Riley type II radio lobes. We derive a typical line-of-sight magnetic field strength of about 3.87 microgauss, with asymmetric uncertainties of roughly +1.46 and −1.44 microgauss, assuming an electron density of 10\u003csup\u003e-4\u003c/sup\u003e per cubic centimeter. Two profound implications follow from this discovery. First, all or a large fraction of quasars at cosmic noon undergo at least one episode that inflates giant radio lobes into the surrounding medium; these lobes persist for timescales comparable to the contemporary Hubble time or are episodically re-energized. Second, large-scale active galactic nucleus feedback in the form of magnetic energy from such powerful radio lobes may provide a significant external feedback mechanism, regulating gas accretion onto galaxies in the extended environment around massive, lobe-hosting galaxies.","manuscriptTitle":"Prevalent Mpc-scale lobes around quasars at cosmic noon revealed by Faraday rotation measures","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-27 06:55:18","doi":"10.21203/rs.3.rs-8356590/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2374c56f-9048-40ee-a62a-db449d3c03dc","owner":[],"postedDate":"April 27th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":64340500,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Astrophysical magnetic fields"},{"id":64340501,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters"}],"tags":[],"updatedAt":"2026-04-27T06:55:18+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-27 06:55:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8356590","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8356590","identity":"rs-8356590","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}