Unveiling Extended Components of ‘Little Red Dots’ in Rest-Frame Optical

Unveiling Extended Components of ‘Little Red Dots’ in Rest-Frame Optical | 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 Unveiling Extended Components of ‘Little Red Dots’ in Rest-Frame Optical Xuheng Ding, Yiyang Zhang, Lilan Yang, Erini Lambrides, Hollis Akins, and 24 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7884438/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 Recent JWST observations have revealed a population of red, compact, high-redshift objects called “Little Red Dots” (LRD), whose host components have remained largely unconstrained, possibly due to their extreme compactness. Current morphological studies have been limited by small samples, as well as by insufficient imaging depth, which may not allow reliable separation between point-like and extended components, leaving the existence and properties of extended components in LRD largely unconstrained. Here, we perform the image stacking analysis of 217 LRDs in four NIRCam bands, representing the largest and homogeneous sample observed from COSMOS-Web survey to date. Our results reveal an unambiguous detection of faint extended emission in the F444W band, with a typical size of ~200 parsecs and magnitude of 27.7 AB at z 6.5. We perform four-band photometric SED fitting based on galaxy templates and derive a stellar mass of 8.91+-~0.1 logM_sun. Given this stellar mass, the host galaxy is compact, i.e., ~2.5 times smaller than star-forming populations at similar mass, and the typical black hole mass of LRDs is elevated by ~1.5 dex above the local MBH-M* relation. This work provides direct observational evidence for the existence of LRD host galaxies and offers crucial insights into the growth of the host galaxy and the co-evolution of galaxies and their black holes within the first billion years after the Big Bang. Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Galaxies and clusters Physical sciences/Astronomy and planetary science/Astronomy and astrophysics/Early universe 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-7884438","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":540901786,"identity":"616933b2-4ae7-48ba-ac86-ec31b4c612d7","order_by":0,"name":"Xuheng Ding","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxElEQVRIiWNgGAWjYDCCw0DM2GDDYADi8JCgJY0ULQfAWg6ToIXvOO/h17w7zidul0hgfPC2jUHenJAWycN8aZYzz9xO3DkjgdlwbhuD4c4GAloMDvOYGXxsu5274UYCmzRvG0OCwQFitCS2nQNpYf9NrBbjBx/bDoBtYSZKiyTQFsaZbcn1G848bJacc07CcAMhLXznzxh/5m2zMzY4nnzww5syG3mCtgABmwSEZmwAEhKE1QMB8weilI2CUTAKRsHIBQDOMEQ8ExtTsgAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-8917-2148","institution":"Wuhan University","correspondingAuthor":true,"prefix":"","firstName":"Xuheng","middleName":"","lastName":"Ding","suffix":""},{"id":540901787,"identity":"7691d001-0402-4fc9-b34d-f4c21c89bc50","order_by":1,"name":"Yiyang Zhang","email":"","orcid":"","institution":"Wuhan University","correspondingAuthor":false,"prefix":"","firstName":"Yiyang","middleName":"","lastName":"Zhang","suffix":""},{"id":540901788,"identity":"72243fab-911f-4855-9ed5-6a96200ab91e","order_by":2,"name":"Lilan Yang","email":"","orcid":"","institution":"Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA","correspondingAuthor":false,"prefix":"","firstName":"Lilan","middleName":"","lastName":"Yang","suffix":""},{"id":540901789,"identity":"faeb4371-d1fb-46c7-b79d-ae72c5af7474","order_by":3,"name":"Erini Lambrides","email":"","orcid":"https://orcid.org/0000-0003-3216-7190","institution":"NASA-Goddard Space Flight Center","correspondingAuthor":false,"prefix":"","firstName":"Erini","middleName":"","lastName":"Lambrides","suffix":""},{"id":540901790,"identity":"5722a87e-708e-4483-809a-57135a9c04a8","order_by":4,"name":"Hollis Akins","email":"","orcid":"","institution":"University of Texas - 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Current morphological studies have been limited by small samples, as well as by insufficient imaging depth, which may not allow reliable separation between point-like and extended components, leaving the existence and properties of extended components in LRD largely unconstrained. Here, we perform the image stacking analysis of 217 LRDs in four NIRCam bands, representing the largest and homogeneous sample observed from COSMOS-Web survey to date. Our results reveal an unambiguous detection of faint extended emission in the F444W band, with a typical size of ~200 parsecs and magnitude of ~27.7 AB at z~6.5. We perform four-band photometric SED fitting based on galaxy templates and derive a stellar mass of 8.91+-~0.1 logM_sun. Given this stellar mass, the host galaxy is compact, i.e., ~2.5 times smaller than star-forming populations at similar mass, and the typical black hole mass of LRDs is elevated by ~1.5 dex above the local MBH-M* relation. 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