Neutral Atomic Hydrogen in a Star-forming Galaxy 7 Billion Years Ago

Neutral Atomic Hydrogen in a Star-forming Galaxy 7 Billion Years Ago | 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 Neutral Atomic Hydrogen in a Star-forming Galaxy 7 Billion Years Ago Graham Lawrie, Roger Deane, Tariq Blecher, Danail Obreschkow, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7806857/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Neutral atomic hydrogen (HI) constitutes a key phase of the cosmic baryon cycle, bridging the ionised circumgalactic medium and the star-forming molecular gas. Yet, nearly 75 years after its discovery, direct views of HI through its 21 cm emission line remain largely confined to the nearby Universe. Indirect measurements and statistical analyses indicate little evolution in the comoving HI density over the past 10 billion years, in stark contrast to the order-of-magnitude decline in the cosmic star-formation rate density over the same epoch. Resolving this tension requires direct HI measurements in individual, representative galaxies at earlier times. Here we report a detection of HI 21 cm emission from the Dragon Arc, a gravitationally lensed main-sequence star-forming galaxy at z=0.725, observed 6.6 billion years in the past with the MeerKAT radio telescope. The inferred intrinsic HI mass, M HI =10 9.66 +0.16 -0.19 M sun , and velocity width of 205 +66 -48 km/s are consistent with expectations from scaling relations for local star-forming galaxies. The resulting HI depletion time of 1.2 +1.0 -0.6 Gyr is significantly shorter than the ~5-10 Gyr, measured locally for comparable galaxies. This indicates that the galaxy must rapidly replenish its atomic gas reservoir to remain on the star-forming main sequence. This detection demonstrates that strong gravitational lensing, combined with modern cm-wave facilities, can now reveal the HI reservoirs of typical galaxies well beyond the local Universe, opening a new path toward statistical samples that will directly trace the evolution of the cosmic atomic gas supply. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Cosmology Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Under Review 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7806857","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":526605150,"identity":"cf678add-cd5a-480e-bf3c-39148da77c65","order_by":0,"name":"Graham Lawrie","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-2043-4346","institution":"University of the Witwatersrand","correspondingAuthor":true,"prefix":"","firstName":"Graham","middleName":"","lastName":"Lawrie","suffix":""},{"id":526605151,"identity":"90dcb299-951d-48e4-b5a8-e245e09e0c77","order_by":1,"name":"Roger Deane","email":"","orcid":"https://orcid.org/0000-0003-1027-5043","institution":"Wits University / University of Pretoria","correspondingAuthor":false,"prefix":"","firstName":"Roger","middleName":"","lastName":"Deane","suffix":""},{"id":526605152,"identity":"a46035c2-9ef9-421c-8ab5-659d99cb783b","order_by":2,"name":"Tariq Blecher","email":"","orcid":"","institution":"South African Radio Astronomy Observatory","correspondingAuthor":false,"prefix":"","firstName":"Tariq","middleName":"","lastName":"Blecher","suffix":""},{"id":526605153,"identity":"d7c60545-71bc-4bef-b48f-f297749574ad","order_by":3,"name":"Danail Obreschkow","email":"","orcid":"","institution":"University of Western Australia","correspondingAuthor":false,"prefix":"","firstName":"Danail","middleName":"","lastName":"Obreschkow","suffix":""},{"id":526605154,"identity":"c8e37aeb-945c-4ba1-8276-25bc1205c74c","order_by":4,"name":"Ian Heywood","email":"","orcid":"","institution":"SKA Observatory","correspondingAuthor":false,"prefix":"","firstName":"Ian","middleName":"","lastName":"Heywood","suffix":""},{"id":526605156,"identity":"db7ca7fc-3d84-4ef9-86a0-b3f3afc58e91","order_by":5,"name":"Shilpa Ranchod","email":"","orcid":"","institution":"Max-Planck-Institute fur Radioastronomie","correspondingAuthor":false,"prefix":"","firstName":"Shilpa","middleName":"","lastName":"Ranchod","suffix":""}],"badges":[],"createdAt":"2025-10-08 10:30:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7806857/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7806857/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":94986201,"identity":"df10018d-3570-4bfd-ab17-e6a1b8979f08","added_by":"auto","created_at":"2025-11-03 07:00:03","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6206398,"visible":true,"origin":"","legend":"Article File","description":"","filename":"Abell370lensedHI.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7806857/v1_covered_ecf19ea7-4566-4f86-a625-11a65f2a0265.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Neutral Atomic Hydrogen in a Star-forming Galaxy 7 Billion Years Ago","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"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":"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-7806857/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7806857/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Neutral atomic hydrogen (HI) constitutes a key phase of the cosmic baryon cycle, bridging the ionised circumgalactic medium and the star-forming molecular gas. Yet, nearly 75 years after its discovery, direct views of HI through its 21 cm emission line remain largely confined to the nearby Universe. Indirect measurements and statistical analyses indicate little evolution in the comoving HI density over the past 10 billion years, in stark contrast to the order-of-magnitude decline in the cosmic star-formation rate density over the same epoch. Resolving this tension requires direct HI measurements in individual, representative galaxies at earlier times. Here we report a detection of HI 21 cm emission from the Dragon Arc, a gravitationally lensed main-sequence star-forming galaxy at z=0.725, observed 6.6 billion years in the past with the MeerKAT radio telescope. The inferred intrinsic HI mass, M\u003csub\u003eHI\u003c/sub\u003e=10\u003csup\u003e9.66\u003csup\u003e+0.16\u003c/sup\u003e\u003csub\u003e-0.19\u003c/sub\u003e\u003c/sup\u003e M\u003csub\u003esun\u003c/sub\u003e, and velocity width of 205\u003csup\u003e+66\u003c/sup\u003e\u003csub\u003e-48\u003c/sub\u003ekm/s are consistent with expectations from scaling relations for local star-forming galaxies. The resulting HI depletion time of 1.2\u003csup\u003e+1.0\u003c/sup\u003e\u003csub\u003e-0.6\u003c/sub\u003e Gyr is significantly shorter than the ~5-10 Gyr, measured locally for comparable galaxies. This indicates that the galaxy must rapidly replenish its atomic gas reservoir to remain on the star-forming main sequence. This detection demonstrates that strong gravitational lensing, combined with modern cm-wave facilities, can now reveal the HI reservoirs of typical galaxies well beyond the local Universe, opening a new path toward statistical samples that will directly trace the evolution of the cosmic atomic gas supply.","manuscriptTitle":"Neutral Atomic Hydrogen in a Star-forming Galaxy 7 Billion Years Ago","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-30 02:48:55","doi":"10.21203/rs.3.rs-7806857/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"68908e07-cd73-4935-9a86-57711fd42bf3","owner":[],"postedDate":"October 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":55974462,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters"},{"id":55974463,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Cosmology"}],"tags":[],"updatedAt":"2025-12-22T22:05:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-30 02:48:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7806857","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7806857","identity":"rs-7806857","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}