Gas Accretion versus BH Merger driven Growth Modes of Central Supermassive Black Holes and Implications for the Little Red Dots

Gas Accretion versus BH Merger driven Growth Modes of Central Supermassive Black Holes and Implications for the Little Red Dots | 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 Gas Accretion versus BH Merger driven Growth Modes of Central Supermassive Black Holes and Implications for the Little Red Dots Paramita Barai This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7049515/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 We investigate the growth of central supermassive black holes in galaxies, aiming to distinguish between gas accretion versus BH merger-driven growth modes. By performing and analysing cosmological hydrodynamical simulations of $(50 ~ {\rm Mpc})^3$ comoving boxes, we also study how the BH feedback physical parameters affect the coevolution between SMBHs and their host galaxies. Starting as $10^5 M_{\odot}$ seeds, we find that the BHs grow initially via BH mergers to $\sim 10^7 M_{\odot}$. Gas accretion onto the BHs is initially low, then increases with time, and reaches the Eddington rate after $7-9$ Gyrs. The BHs then undergo very fast growth via efficient gas accretion over a period of $600 - 700$ Myr, when the BH mass increases $10^2 - 10^3$ times, causing their predominant growth from $10^7 M_{\odot}$ to $(10^9 - 10^{10}) M_{\odot}$. Taking into account the cosmological gas inflows and outflows, SMBHs do not grow to more than $10^{10} M_{\odot}$ by $z=0$, because of gas depletion from galaxy centers driven by AGN feedback. In terms of SMBH - host galaxy coevolution along the $M_{\rm BH} - M_{\star}$ relation, we find that they initially lie below and thereby move upward toward the relation. We make some physical implications of the growth of high-$z$ Little Red Dots recently observed by JWST: the normal-mass SMBHs had predominantly undergone BH merger driven evolution, whereas the overmassive BHs underwent periods of Eddington-limited or super-Eddington bursts of gas accretion. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Computational astrophysics Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Compact astrophysical objects Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Early universe 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. 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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-7049515","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":493863409,"identity":"187b2ae4-6b95-432e-be69-2bd470a9d169","order_by":0,"name":"Paramita Barai","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYNACAyCWADNseBgYGB8wJBDWYgDTkgbUwmzAkECEHqgWhsMMYC34rDFnP/vw042CP/IM0s3PPvwoOC9jzg7U9vAHbi2WPenG0jkGBoYNMseMZ/YY3Oax7ElmwOswgwNpDCAtjA0SCcYMPEAtBgfyD+DXcv4Z82+gFvsGifTPjH8MzvEYnH9MwJYbaWwgWxIbJHKMmYFW8BjcIOAwyxnP2KxzDIyT22TOFDPLGCQDtTxmOJCQhluLOX8a8+2cP3K2/dLtmxnf/LGzNzifzPjwhw0eh8EYbMiiB3BrQNIyCkbBKBgFowAnAAAXJUlLGbAf/gAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-7031-2331","institution":"National Institute for Astrophysics (INAF)","correspondingAuthor":true,"prefix":"","firstName":"Paramita","middleName":"","lastName":"Barai","suffix":""}],"badges":[],"createdAt":"2025-07-04 21:30:22","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7049515/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7049515/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":91820530,"identity":"a20445b2-448c-4603-bcf8-94a14c546a16","added_by":"auto","created_at":"2025-09-22 07:17:13","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":10259226,"visible":true,"origin":"","legend":"Article File","description":"","filename":"ms.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7049515/v1_covered_239eb2bf-ef61-4ee3-bb62-cb97905d87f1.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Gas Accretion versus BH Merger driven Growth Modes of Central Supermassive Black Holes and Implications for the Little Red Dots","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-7049515/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7049515/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"We investigate the growth of central supermassive black holes in galaxies, \r\naiming to distinguish between gas accretion versus BH merger-driven growth modes. \r\nBy performing and analysing cosmological hydrodynamical simulations of $(50 ~ {\\rm Mpc})^3$ \r\ncomoving boxes, we also study how the BH feedback physical parameters \r\naffect the coevolution between SMBHs and their host galaxies. \r\nStarting as $10^5 M_{\\odot}$ seeds, \r\nwe find that the BHs grow initially via BH mergers to $\\sim 10^7 M_{\\odot}$. \r\nGas accretion onto the BHs is initially low, \r\nthen increases with time, and reaches the Eddington rate after $7-9$ Gyrs. \r\nThe BHs then undergo very fast growth via efficient gas accretion \r\nover a period of $600 - 700$ Myr, when the BH mass increases $10^2 - 10^3$ times, \r\ncausing their predominant growth from $10^7 M_{\\odot}$ to $(10^9 - 10^{10}) M_{\\odot}$. \r\nTaking into account the cosmological gas inflows and outflows, \r\nSMBHs do not grow to more than $10^{10} M_{\\odot}$ by $z=0$, \r\nbecause of gas depletion from galaxy centers driven by AGN feedback. \r\nIn terms of SMBH - host galaxy coevolution along the $M_{\\rm BH} - M_{\\star}$ relation, \r\nwe find that they initially lie below and thereby move upward toward the relation. \r\nWe make some physical implications of the growth of high-$z$ Little Red Dots recently observed by JWST: \r\nthe normal-mass SMBHs had predominantly undergone BH merger driven evolution, \r\nwhereas the overmassive BHs underwent periods of \r\nEddington-limited or super-Eddington bursts of gas accretion.","manuscriptTitle":"Gas Accretion versus BH Merger driven Growth Modes of Central Supermassive Black Holes and Implications for the Little Red Dots","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-22 07:08:55","doi":"10.21203/rs.3.rs-7049515/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":"c7b74e6c-50ff-4f8d-baf8-60e87cad19ee","owner":[],"postedDate":"September 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":52450479,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters"},{"id":52450480,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Computational astrophysics"},{"id":52450481,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Compact astrophysical objects"},{"id":52450482,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Early universe"},{"id":52450483,"name":"Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Cosmology"}],"tags":[],"updatedAt":"2025-09-22T07:08:55+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-22 07:08:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7049515","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7049515","identity":"rs-7049515","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}