LRD host galaxies show average metallicity 0.08 Z_sun with narrow stable range, challenging pristine-gas formation models while ruling out typical local AGN.
BlackTHUNDER strikes twice: rest-frame Balmer-line absorption and high Eddington accretion rate in a Little Red Dot at $z=7.04$
11 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
JWST has revealed a population of 'Little Red Dots' (LRDs): compact, red objects at redshifts z=2-9 with 'v'-shaped spectral energy distributions, broad permitted lines, and, often, hydrogen Balmer absorption. We use NIRSpec/IFS data from the BlackTHUNDER survey to study the H$\alpha$ line in the LRD Abell2744-QSO1 at z=7.04, which is a confirmed AGN due to time-variable equivalent width (EW) in its broad emission lines. The H$\alpha$ spectral profile is non-Gaussian, requiring at least two Gaussian components. We also detect a narrow-line Gaussian component, and strong H$\alpha$ absorption (EW relative to the continuum $\sim 22_{-7}^{+12} \mathring{\mathrm{A}}$), confirming a connection between the strong Balmer break and line absorption. The absorber is at rest with respect to broad H$\alpha$, suggesting that the gas cannot be interpreted as an inflow or outflow, forming instead a long-lived structure. Its velocity dispersion is $\sigma_{\rm abs}=110_{-10}^{+20}$ km s$^{-1}$, consistent with the value inferred from the analysis of the Balmer break. Based on H$\alpha$, we infer a black hole mass of log($M_{\rm BH}/{\rm M_\odot}$)=7.2, smaller but close to the previous estimates based on H$\beta$. The Eddington ratio is 0.09. Combining the high signal-to-noise ratio of the narrow H$\alpha$ line with the spectral resolution R=3,700 of the G395H grating, we infer a narrow-line intrinsic dispersion $\sigma_{\rm n}=22_{-6}^{+5}$ km s$^{-1}$, which places a stringent constraint on the black-hole-to-dynamical-mass ratio of this system to be $M_{\rm BH}/M_{\rm dyn}$=0.15-1.2, confirming the overmassive nature of the black hole and potentially leaving little room for a host galaxy.
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Confirmation of 77 new heavily reddened quasars at 1.5 < z < 3.9 with high luminosities and extinctions, showing they are deficient in hot and warm dust relative to blue quasars and supporting a blow-out feedback phase.
LRDs transition from underdense low-halo-mass environments at z>4 to typical galaxy conditions by z~3.5, with halo growth leading to larger sizes and SED changes that explain their disappearance at lower redshifts.
A source 660 million years after the Big Bang is interpreted as a black hole star with a dust-free dense gas atmosphere, implying Little Red Dots have black hole masses overestimated by orders of magnitude.
Five LRDs at z≈2 yield number density ≈7×10^{-6} cMpc^{-3}, confirming a decline from the z≈5 peak but gentler than prior photometric estimates.
JWST data on LRDs and LBDs show AGN-like excitation, strong Lyα with broad components, and X-ray weakness, implying clumpy or equatorial geometries around growing black holes rather than complete gas envelopes.
Bayesian continuum fitting of 66 LRDs shows the BH* model fits ~6% best, rising to ~40% under AGN-disfavoring priors, with most objects stellar/AGN-dominated and possible evolutionary trends.
A homogeneous SDSS survey finds seven low-z AGNs with Balmer absorption at 0.05% rate; modeling shows optically thick Hα with moderate covering factors (0.2-0.6), narrow widths, and association with low metallicity plus high accretion that may retain dense neutral gas.
LRDs require Compton-thick gas at moderate metallicity plus high accretion rates producing weak X-rays to explain their non-detection, implying they are not chemically pristine.
A bias-controlled quasar sample of ~2000 objects demonstrates that the X-ray-to-UV luminosity relation remains constant from redshift 0.7 to 5.
SKAO continuum surveys will detect radio emission from JWST AGN and LRDs and distinguish between Compton-thick absorption, intrinsically weak accretion, and dense gas cocoon scenarios.
citing papers explorer
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The metallicities of little red dot host galaxies: LRDs are metal poor, but not pristine
LRD host galaxies show average metallicity 0.08 Z_sun with narrow stable range, challenging pristine-gas formation models while ruling out typical local AGN.
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Hidden Monsters with SPHEREx I: A goldmine for heavily reddened quasars at cosmic noon
Confirmation of 77 new heavily reddened quasars at 1.5 < z < 3.9 with high luminosities and extinctions, showing they are deficient in hot and warm dust relative to blue quasars and supporting a blow-out feedback phase.
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Why Little Red Dots Disappear at z < 3: Evolution of Number Density and Halo Mass
LRDs transition from underdense low-halo-mass environments at z>4 to typical galaxy conditions by z~3.5, with halo growth leading to larger sizes and SED changes that explain their disappearance at lower redshifts.
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A "Black Hole Star" Reveals the Remarkable Gas-Enshrouded Hearts of the Little Red Dots
A source 660 million years after the Big Bang is interpreted as a black hole star with a dust-free dense gas atmosphere, implying Little Red Dots have black hole masses overestimated by orders of magnitude.
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Little Red Dots at z~2 in EIGER reveal a gentle decline with respect to their peak number density at z~5
Five LRDs at z≈2 yield number density ≈7×10^{-6} cMpc^{-3}, confirming a decline from the z≈5 peak but gentler than prior photometric estimates.
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Little Red and Blue Dots: AGN-excited narrow lines, Lyman-$\alpha$ emission, and resemblance to standard quasars
JWST data on LRDs and LBDs show AGN-like excitation, strong Lyα with broad components, and X-ray weakness, implying clumpy or equatorial geometries around growing black holes rather than complete gas envelopes.
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Between Degeneracy and Evolution: UV-to-optical Insights into the BH$^*$ Model in Little Red Dots
Bayesian continuum fitting of 66 LRDs shows the BH* model fits ~6% best, rising to ~40% under AGN-disfavoring priors, with most objects stellar/AGN-dominated and possible evolutionary trends.
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The Extreme Rarity and Physical Properties of Low-redshift AGNs with Balmer Absorption
A homogeneous SDSS survey finds seven low-z AGNs with Balmer absorption at 0.05% rate; modeling shows optically thick Hα with moderate covering factors (0.2-0.6), narrow widths, and association with low metallicity plus high accretion that may retain dense neutral gas.
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On the quenching of LRD X-ray emission by both Compton-thick gas and high accretion rates
LRDs require Compton-thick gas at moderate metallicity plus high accretion rates producing weak X-rays to explain their non-detection, implying they are not chemically pristine.
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The X-ray-to-UV relation does not evolve in homogeneous quasar samples
A bias-controlled quasar sample of ~2000 objects demonstrates that the X-ray-to-UV luminosity relation remains constant from redshift 0.7 to 5.
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Unveil the nature of JWST-AGN and Little Red Dots with SKAO continuum surveys
SKAO continuum surveys will detect radio emission from JWST AGN and LRDs and distinguish between Compton-thick absorption, intrinsically weak accretion, and dense gas cocoon scenarios.