Connecting the Dots: UV-Bright Companions of Little Red Dots as Lyman-Werner Sources Enabling Direct Collapse Black Hole Formation

Abstract

We compile a sample of 83 Little Red Dots (LRDs) with JWST imaging and find that a substantial fraction ($\sim$43%, rising to $\gtrsim$85% for the most luminous LRDs) host one or more spatially offset, UV-bright companions at projected separations of $0.5\mathrm{kpc}\lesssim \mathrm{d}\lesssim 5\mathrm{kpc}$, with median of $⟨d⟩=1.0\mathrm{kpc}$. This fraction is even higher when smaller spatial scales are probed at high S/N ratio: we show that the two most strongly lensed LRDs known to date, A383-LRD and the newly discovered A68-LRD, both have UV-bright companions at separations of only $d\sim 0.3$ kpc, below the resolution limit of most unlensed JWST samples. We explore whether these ubiquitous red/blue configurations may be physically linked to the formation of LRDs, in analogy with the "synchronized pair" scenario originally proposed for direct-collapse black hole formation. In this picture, ultraviolet radiation from the companions, which typically have modest stellar masses ($M_{\ast }\sim 10^{8-9}{M}_{\odot }$), suppresses molecular hydrogen cooling in nearby gas, allowing nearly isothermal collapse and the formation of extremely compact objects, such as massive black holes or quasi-stars. Using component-resolved photometry and SED modeling, we infer Lyman-Werner radiation fields of $J_{21,LW}\sim 10^{2.5}$-$10^5$ at the locations of the red components, comparable to those required in direct-collapse models, suggesting that the necessary photodissociation conditions are realized in many LRD systems. This framework provides a simple and self-consistent explanation for the extreme compactness and distinctive spectral properties of LRDs, and links long-standing theoretical models for early compact object formation directly to a population now observed with JWST in the early universe.

Published in The Astrophysical Journal Letters

References in corpus (52)

• The NumPy array: a structure for efficient numerical computation
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• EAZY: A Fast, Public Photometric Redshift Code
• Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos
• A population of red candidate massive galaxies ~600 Myr after the Big Bang
• Supermassive black hole formation during the assembly of pre-galactic discs
• Formation of the first nuclear clusters and massive black holes at high redshift
• Fluctuations in the High-Redshift Lyman-Werner Background: Close Halo Pairs as the Origin of Supermassive Black Holes
• Can Supermassive Black Holes Form in Metal-Enriched High-Redshift Protogalaxies ?
• Two populations of metal-free stars in the early Universe
• The Evolution of Supermassive Population III Stars
• Initial mass function of intermediate mass black hole seeds
• Feedback-regulated Super Massive Black Hole Seed Formation
• The critical radiation intensity for direct collapse black hole formation: dependence on the radiation spectral shape
• EIGER I. a large sample of [OIII]-emitting galaxies at $5.3<z<6.9$ and direct evidence for local reionization by galaxies
• Supersonic Gas Streams Enhance the Formation of Massive Black Holes in the Early Universe
• RUBIES: Evolved Stellar Populations with Extended Formation Histories at $z\sim 7-8$ in Candidate Massive Galaxies Identified with JWST/NIRSpec
• Direct collapse black hole formation from synchronized pairs of atomic cooling halos
• The mass function of high redshift seed black holes
• RUBIES: a complete census of the bright and red distant Universe with JWST/NIRSpec
• The JWST-PRIMAL Legacy Survey. A JWST/NIRSpec reference sample for the physical properties and Lyman-$\alpha$ absorption and emission of $\sim 500$ galaxies at $z=5.5-13.4$
• Supermassive Star Formation via Super Competitive Accretion in Slightly Metal-enriched Clouds
• A UV flux constraint on the formation of direct collapse black holes
• Mildly Super-Eddington Accretion Onto Slowly-Spinning Black Holes Explains the X-Ray Weakness of the Little Red Dots
• Does disk fragmentation prevent the formation of supermassive stars in protogalaxies?
• JADES -- The Rosetta Stone of JWST-discovered AGN: deciphering the intriguing nature of early AGN
• A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$
• Forming massive seed black holes in high-redshift quasar host progenitors
• Little red dots as young supermassive black holes in dense ionized cocoons
• Beyond Jcrit: a critical curve for suppression of H2-cooling in protogalaxies
• RUBIES: A Spectroscopic Census of Little Red Dots; All V-Shaped Point Sources Have Broad Lines
• Sizes and Stellar Masses of the Little Red Dots Imply Immense Stellar Densities
• The Birth of Binary Direct-Collapse Black Holes
• Little Red Dots As Late-stage Quasi-stars
• "Little red dots" cannot reside in the same dark matter halos as comparably luminous unobscured quasars
• Little Red Dots Are Nurseries of Massive Black Holes
• Cosmic Outliers: Low-Spin Halos Explain the Abundance, Compactness, and Redshift Evolution of the Little Red Dots
• Rapid formation of a very massive star >50000 $M_{\odot }$ and subsequently an IMBH from runaway collisions. Direct N-body and Monte Carlo simulations of dense star clusters
• Massive Star Formation in Metal-Enriched Haloes at High Redshift
• Lonely Little Red Dots: Challenges to the AGN-nature of little red dots through their clustering and spectral energy distributions
• The warm outer layer of a Little Red Dot as the source of [Fe II] and collisional Balmer lines with scattering wings
• Little Red Dots as Direct-collapse Black Hole Nurseries
• Efficient black hole seed formation in low metallicity and dense stellar clusters with implications for JWST sources
• A Little Red Dot at $\mathbf{z}=7.3$ within a Large Galaxy Overdensity
• Predicting the number density of heavy seed massive black holes due to an intense Lyman-Werner field
• Possible environmental quenching in an interacting little red dot pair at $z\sim 7$
• BlackTHUNDER: Shedding light on a dormant and extreme little red dot at z=8.50
• Investigating the Growth of Little Red Dot Descendants at z<4 with the JWST
• A weak Ly$\alpha$ halo for an extremely bright Little Red Dot: Indications of enshrouded SMBH growth
• Can supermassive stars form in protogalaxies due to internal Lyman-Werner feedback?
• Back to basics: Little Red Dots as galaxies and dust-obscured AGNs in a synthetic NIRCam sky simulated with L-GalaxiesBH
• JWST provides a new view of cosmic dawn: latest developments in studies of early galaxies

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