Little Red Dots and Supermassive Black Hole Seed Formation in Ultralight Dark Matter Halos

[2601.21676] Little Red Dots and Supermassive Black Hole Seed Formation in Ultralight Dark Matter Halos Skip to main content Search Submit Donate Log in Astrophysics > Astrophysics of Galaxies arXiv:2601.21676 (astro-ph) [Submitted on 29 Jan 2026 ( v1 ), last revised 25 Aug 2026 (this version, v3)] Title: Little Red Dots and Supermassive Black Hole Seed Formation in Ultralight Dark Matter Halos Authors: Dongsu Bak , Jae-Weon Lee View PDF HTML (experimental) Abstract: We explore a possible mechanism for the formation of supermassive black hole (SMBH) seeds at the centers of ultralight dark matter (ULDM) halos in the early Universe. We investigate the conditions under which high-redshift baryonic gas, strongly confined by central solitonic cores of the halos, undergoes direct and monolithic collapse. The solitonic core sets characteristic mass and length scales for the confined baryons. Once the confined gas becomes self-gravitating, rapid inflow and shock heating may drive it into a high-temperature and high-density regime favorable for suppressing molecular cooling, without requiring a strong external UV background. We present semi-analytic scaling relations for the halo mass, soliton mass, baryonic core radius, and characteristic thermodynamic state of the gas, parametrizing the possible effects of baryonic contraction. These relations provide order-of-magnitude estimates of the characteristic range of SMBH seed masses as a function of redshift. In this framework, pristine gas clouds satisfying the adopted thermal criterion may avoid efficient fragmentation and undergo rapid central collapse, potentially forming massive black hole seeds with characteristic masses of order $10^5 M_\odot$, while systems below the threshold may form compact star clusters instead. The ULDM particle mass required to reproduce the inferred seed mass scale, $m \simeq O(10^{-22}){\rm eV}$, lies in a range favored by galactic-scale observations, suggesting a possible connection between the characteristic scales of galactic cores and early SMBH seeds. Our estimates indicate that favorable conditions for SMBH seed formation may arise at redshifts $z \gtrsim 10$. Such conditions may be relevant to the young SMBHs inferred in some little red dots, which appear to be embedded in compact, dense, ionized gas. Comments: 12 pages, 3 figures, minor improvements included, further improvements Subjects: Astrophysics of Galaxies (astro-ph.GA) Cite as: arXiv:2601.21676 [astro-ph.GA] (or arXiv:2601.21676v3 [astro-ph.GA] for this version) https://doi.org/10.48550/arXiv.2601.21676 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Dongsu Bak [ view email ] [v1] Thu, 29 Jan 2026 13:09:42 UTC (427 KB) [v2] Sun, 8 Mar 2026 10:32:00 UTC (428 KB) [v3] Tue, 25 Aug 2026 08:23:19 UTC (507 KB) Full-text links: Access Paper: View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.GA < prev | next > new | recent | 2026-01 Change to browse by: astro-ph References & Citations NASA ADS Google Scholar Semantic Scholar export BibTeX citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer ( What is the Explorer? ) Connected Papers Toggle Connected Papers ( What is Connected Papers? ) Litmaps Toggle Litmaps ( What is Litmaps? ) scite.ai Toggle scite Smart Citations ( What are Smart Citations? ) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv ( What is alphaXiv? ) Links to Code Toggle CatalyzeX Code Finder for Papers ( What is CatalyzeX? ) DagsHub Toggle DagsHub ( What is DagsHub? ) GotitPub Toggle Gotit.pub ( What is GotitPub? ) Huggingface Toggle Hugging Face ( What is Huggingface? ) ScienceCast Toggle ScienceCast ( What is ScienceCast? ) Demos Demos Replicate Toggle Replicate ( What is Replicate? ) Spaces Toggle Hugging Face Spaces ( What is Spaces? ) Spaces Toggle TXYZ.AI ( What is TXYZ.AI? ) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower ( What are Influence Flowers? ) Core recommender toggle CORE Recommender ( What is CORE? ) IArxiv recommender toggle IArxiv Recommender ( What is IArxiv? ) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. 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