Lyα observations of Little Red Dots show luminosities and equivalent widths like normal star-forming galaxies but lower Lyα/Hα ratios and extended asymmetric emission, supporting a two-component model with host-scale gas.
The Structure and Evolution of LRDs: Insights from JWST NIRSpec Medium and High Resolution Spectroscopy at $z\sim4$
8 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
We present an analysis of medium/high-resolution JWST/NIRSpec spectra for 11 LRDs at $z \sim 4$. By decomposing the broad and narrow components of the Balmer emission lines, we investigate the connection between line emission and UV/optical continua for the LRD population. We find that the broad H$\alpha$ luminosity strongly correlates with the optical continuum (but not with the UV), indicating a common AGN origin for both. In contrast, the [O III] line strength is correlated with the UV continuum rather than the optical. Using the width and luminosity of the broad H$\alpha$ line, we estimate central black hole masses of $10^6-10^8 M_{\odot}$ accreting at high Eddington ratios, consistent with an early ($\lambda_{\rm Edd} \sim 0.6$), rapid-growth phase of AGN evolution. Assuming a constant mass accretion rate in the framework of slim-disk models, we infer growth timescales of $\sim 10^5-10^7\rm yr$, and suggest LRDs may evolve into narrow-line Seyfert 1 galaxies. Upper limits from our spectra indicate that LRDs exhibit intrinsically weak optical Fe II emission compared to typical AGN. To simultaneously account for the inferred broad-line region size and observed luminosity, we propose a "Clumpy Envelope" model in which the optical emission arises from an extended, clumpy gas with a characteristic radius of tens of light-days. The diversity in observed optical continuum shapes can be explained by radial temperature gradients and self-absorption effects within this structure. Our results demonstrate the power of JWST high-resolution spectroscopy in probing the central engines and physical nature of the LRD population.
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astro-ph.GA 8years
2026 8verdicts
UNVERDICTED 8representative citing papers
High-resolution spectra show Balmer absorption in 4/10 LRDs with blue-shifted velocities and exponential wings, supporting a model of co-located partial-covering gas with inflow/outflow gradients.
LRDs at z~3-7 exhibit an L_Hα,broad-L_bol scaling relation enhanced by a factor of ~40 compared to low-z Type 1 AGN, explained via Cloudy modeling with near-unity covering factor and high column density.
Paschen jumps in Little Red Dots indicate their continua originate from free-bound recombination emission in low-temperature nebular gas rather than thermalized or AGN components.
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.
A sample of 36 spectroscopically confirmed LRDs shows broad-line detections in >90%, spectral variety including Balmer breaks and blackbody fits, H-alpha to 5100A continuum correlation, no redshift evolution, declining space density toward z~2 opposite normal AGNs, and clustering in ~10^11 solar mas
Analysis of Balmer decrements and absorption in little red dots at 2.2<z<6.7 leads to a proposed clumpy torus nuclear structure viewed along polar directions.
Halo-driven transient rapid growth followed by thermodynamic suppression explains over-massive black holes and Little Red Dots as precursors to standard SMBH-galaxy coevolution.
citing papers explorer
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Through the Veil: Ly$\alpha$ Illuminates the Host Galaxies of Little Red Dots
Lyα observations of Little Red Dots show luminosities and equivalent widths like normal star-forming galaxies but lower Lyα/Hα ratios and extended asymmetric emission, supporting a two-component model with host-scale gas.
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OCEANS of Absorption: High-resolution NIRSpec Spectroscopy Reveals Diverse Balmer-line Absorption in Little Red Dots
High-resolution spectra show Balmer absorption in 4/10 LRDs with blue-shifted velocities and exponential wings, supporting a model of co-located partial-covering gas with inflow/outflow gradients.
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A Scaling Relation of LRDs between Broad H$\alpha$ and Bolometric Luminosities: Enhanced Broad H$\alpha$ Emission Relative to Low-$z$ Type 1 AGN
LRDs at z~3-7 exhibit an L_Hα,broad-L_bol scaling relation enhanced by a factor of ~40 compared to low-z Type 1 AGN, explained via Cloudy modeling with near-unity covering factor and high column density.
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Paschen Jumps in Little Red Dots: Evidence for Nebular Continua
Paschen jumps in Little Red Dots indicate their continua originate from free-bound recombination emission in low-temperature nebular gas rather than thermalized or AGN components.
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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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NEXUS: Abundance, Environments, and Spectral Diversity of Little Red Dots from the NIRSpec MSA Sample
A sample of 36 spectroscopically confirmed LRDs shows broad-line detections in >90%, spectral variety including Balmer breaks and blackbody fits, H-alpha to 5100A continuum correlation, no redshift evolution, declining space density toward z~2 opposite normal AGNs, and clustering in ~10^11 solar mas
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ABCD: The Nuclear Structure of the Little Red Dots Revealted through Absorption, Break, Continuum, and Decrement
Analysis of Balmer decrements and absorption in little red dots at 2.2<z<6.7 leads to a proposed clumpy torus nuclear structure viewed along polar directions.
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Halo-driven Origin and Suppression of Over-massive Black Holes and Little Red Dots
Halo-driven transient rapid growth followed by thermodynamic suppression explains over-massive black holes and Little Red Dots as precursors to standard SMBH-galaxy coevolution.