Little Red Dots Are Nurseries of Massive Black Holes

Abstract

The James Webb Space Telescope (JWST) has revealed a previously unknown population of compact, red galaxies at $z\sim 5$, known as "Little Red Dots" (LRDs). With effective radii of $\sim 100$ pc and stellar masses of $10^9-10^{11}{M}_{\odot }$, a purely stellar interpretation implies extreme central densities, ${\rho }_{\star }\sim 10^4-10^5{M}_{\odot }{\mathrm{pc}}^{-3}$ and in some cases up to $\sim 10^9{M}_{\odot }{\mathrm{pc}}^{-3}$, far exceeding those of globular clusters. At such densities, the dynamical friction time for $10M_{\odot }$ stars in the central $0.1$ pc is $<0.1$ Myr, driving rapid mass segregation. We investigate the dynamical consequences of such an environment using: (i) a Fokker-Planck analysis of long-term core evolution, (ii) an analytical model for the collisional growth of a very massive star (VMS), and (iii) direct $N$-body simulations. All approaches show that runaway collisions produce a VMS with mass $9\times 10^3<M_{\mathrm{VMS}}[M_{\odot }]<5\times 10^4$ within $<1$ Myr. Once the supply of massive stars is depleted, the VMS contracts on a $\sim 8000$ yr Kelvin-Helmholtz timescale and undergoes a general relativistic collapse, leaving a massive black hole of mass $M_{\bullet }\sim 10^4{M}_{\odot }$. We conclude that LRDs are natural nurseries for the formation of heavy black hole seeds via stellar-dynamical processes. This pathway produces seed number densities that far exceed those expected from direct collapse models, and, owing to the dense residual stellar core, can sustain high rates of tidal disruption events.

arXiv commentAccepted for publication in The Astrophysical Journal. 12 pages, 4 figures

References in corpus (50)

• How Massive Single Stars End their Life
• Evolution of binary stars and the effect of tides on binary populations
• A luminous quasar at a redshift of z = 7.085
• In the Beginning: The First Sources of Light and the Reionization of the Universe
• An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
• Compact Remnant Mass Function: Dependence on the Explosion Mechanism and Metallicity
• A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey I: Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6
• Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos
• Estimating Black Hole Masses in Active Galaxies Using the Halpha Emission Line
• Formation of the First Supermassive Black Holes
• A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey II: Discovery of Three Additional Quasars at z>6
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• The formation of massive black holes through collision runaway in dense young star clusters
• The runaway growth of intermediate-mass black holes in dense star clusters
• The Assembly of the First Massive Black Holes
• A population of red candidate massive galaxies ~600 Myr after the Big Bang
• Galactic-Field IMFs of Massive Stars
• Supermassive black hole formation during the assembly of pre-galactic discs
• A Luminous Quasar at Redshift 7.642
• Collapse of Primordial Gas Clouds and the Formation of Quasar Black Holes
• JADES. The diverse population of infant Black Holes at 4<z<11: merging, tiny, poor, but mighty
• Stress Testing $\Lambda$CDM with High-redshift Galaxy Candidates
• Formation of Primordial Supermassive Stars by Rapid Mass Accretion
• Fluctuations in the High-Redshift Lyman-Werner Background: Close Halo Pairs as the Origin of Supermassive Black Holes
• The evolution of runaway stellar collision products
• Collapse of a Rotating Supermassive Star to a Supermassive Black Hole: Fully Relativistic Simulations
• Mass segregation and fractal substructure in young massive clusters: (I) the McLuster code and method calibration
• Quasistars: Accreting black holes inside massive envelopes
• Feedback-regulated Super Massive Black Hole Seed Formation
• PeTar: a high-performance N-body code for modeling massive collisional stellar systems
• BSE versus StarTrack: implementations of new wind, remnant-formation, and natal-kick schemes in NBODY7 and their astrophysical consequences
• RUBIES: Evolved Stellar Populations with Extended Formation Histories at $z\sim 7-8$ in Candidate Massive Galaxies Identified with JWST/NIRSpec
• Evolution of Rotating Supermassive Stars to the Onset of Collapse
• Deciphering the JWST spectrum of a 'little red dot' at $z\sim 4.53$: An obscured AGN and its star-forming host
• Relativistic collapse and explosion of rotating supermassive stars with thermonuclear effects
• Mildly Super-Eddington Accretion Onto Slowly-Spinning Black Holes Explains the X-Ray Weakness of the Little Red Dots
• A new Fokker-Planck approach for relaxation-driven evolution of galactic nuclei
• Very Massive Stars: a metallicity-dependent upper-mass limit, slow winds, and the self-enrichment of Globular Clusters
• Particle-Particle Particle-Tree: A Direct-Tree Hybrid Scheme for Collisional N-Body Simulations
• Size matters: are we witnessing super-Eddington accretion in high-redshift black holes from JWST?
• Simulations predict intermediate-mass black hole formation in globular clusters
• Exploring the AGN Fraction of a Sample of JWST's Little Red Dots at $5<z<8$: Overmassive Black Holes Are Strongly Favored
• Sizes and Stellar Masses of the Little Red Dots Imply Immense Stellar Densities
• The influence of initial mass segregation on the runaway merging of stars
• Cosmic Outliers: Low-Spin Halos Explain the Abundance, Compactness, and Redshift Evolution of the Little Red Dots
• Close stellar encounters at the Galactic Centre I: The effect on the observed stellar populations
• Little Red Dots are Tidal Disruption Events in Runaway-Collapsing Clusters
• Segregation and Collisions in Galactic Nuclei: Rates of Destructive Events Near a Supermassive Black Hole
• Collision-induced mass loss and mass gain on an extremely massive star. An analytical approach and a static proto-globular cluster test-case
• Little Red Dots from Low-Spin Galaxies at High Redshifts

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• Constraints on dynamically-formed massive black holes in Little Red Dots from X-ray non-detections
• Nitrogen enhancement of GN-z11 by metal pollution from supermassive stars
• Back to basics: Little Red Dots as galaxies and dust-obscured AGNs in a synthetic NIRCam sky simulated with L-GalaxiesBH
• Massive star clusters detected by JWST as natural birth places to form intermediate-mass black holes
• Rapid sinking and efficient mergers of supermassive black holes in compact high-redshift galaxies
• (Re)solving the Complex Multiscale Morphology and V-shaped Spectral Energy Distribution of a Newly Discovered Strongly Lensed Little Red Dot in A383
• Mass and Spin Growth of Very Massive Stars in Star Clusters Potentially Associated with Little Red Dots