Weekly archive
LRDigestWeekly digests of little red dots and JWST-selected AGN papers, with curated reading notes and archive pages.
654 indexed papers · 430 research notes
JWST multi-epoch imaging identifies PLATE-23a at z=0.688 as a strongly favored Type IIP supernova candidate, with cooling early-time SEDs and late evolution resembling local Type IIP events, while sparse late photometry limits physical inferences.
Husvéth et al. present 22-GHz EVN total-intensity and polarimetric VLBI imaging of the secure z=4.31 quasar J1510+5702 and the redshift-uncertain compact source J1606+3124, sampling rest-frame frequencies above 118 GHz if both published high-redshift values apply. J1510+5702 contains a very compact, polarized core with Tb = (1.08 ± 0.15) × 10^12 K and about 3.5% fractional polarization, implying an equipartition Doppler factor of roughly 22 and directly probing its strongly beamed inner jet. J1606+3124 shows only low-level polarization and, conditional on z=4.56, a lower Tb of (7.4 ± 0.8) × 10^10 K that permits mild boosting but leaves a young compact-source interpretation viable; the key caveat is that its published spectroscopic redshift is uncertain, with a photometric estimate near z=0.9. Together, the measurements demonstrate that 22-GHz cm-VLBI can recover rest-frame millimeter polarization from bright z>4 jet systems.
JWST and ALMA reclassify two z=6.63–6.80, MUV≈−23.5 SHELLQs “quasars” as extreme star-forming galaxies. Their UV wind and broad He II features are better matched by VMS-inclusive population models, although inferred IMF cutoffs remain strongly model dependent.
J2048, a z=0.4332 local little-red-dot analog, is detected at 3 GHz with radio luminosity 1.2×10^41 erg s^-1 and a relatively flat synchrotron-like spectrum, making it far brighter than the previously detected local analog J1047+0739.
Across 27 distinct z=3–9 LRDs, broad Lyα is confined to two previously known sources. Sensitivity-aware demographics give a 10% broad-emitter fraction above 10^42 erg s−1, while narrow Lyα dominates detected profiles.
Across six z=4.95–6.68 little red dots, multi-epoch JWST spectroscopy yields only marginal broad-Hα variability in two objects and no significant continuum changes. The results offer tentative AGN support, but calibration-driven uncertainties and four non-detections preclude a definitive population-level conclusion.
In 20 LRDs, extreme broad Balmer decrements require both dense, optically thick non-Case-B line formation and—when Hα/Hβ exceeds the model ceiling—additional broad-line-region-associated dust, rather than galaxy-wide extinction alone.
This paper tests whether frozen tabular foundation models can deliver full probabilistic quasar photo-z posteriors for the 12-band S-PLUS DR6 survey, where colour-redshift degeneracies and spectroscopic-to-photometric covariate shift make single-value estimates inadequate. Across training sets spanning 500 to 121,626 quasars and comparisons with eight specialised baselines, TabPFN 2.5 is best or statistically tied for best on nearly every density and point-estimation metric, with especially strong gains for small training samples, bright or faint sources, and high-redshift quasars. Its posteriors remain close to nominally calibrated after importance-weighted evaluation intended to emulate the photometric target catalogue, making it a strong default for catalogue-scale quasar redshift inference; the practical limitation is the accelerator-memory cost of inference on large support and target sets. SHAP results further identify WISE W1/W2 as the most informative individual inputs, with UV and optical bands providing useful refinements.
JWST/NIRISS spectroscopy identifies an exceptionally dense z≈3 protocluster around quasar J1652, with 18 robust members, two quiescent galaxies, and position–velocity substructure consistent with—though not proving—a merger of two haloes.
Spatially resolved JWST/MIRI spectroscopy of five nearby AGN links contrasting PAH-ratio trends to AGN irradiation and shock-processing diagnostics. The authors interpret their coexistence as a route to nuclear PAH suppression and to divergent PAH star-formation calibrations.
MeerKLASS counterpart catalogs use an empirically calibrated, mass- and redshift-aware association method to identify 20,400 L-band and 61,633 UHF-band optical/IR hosts at P_true>0.5, while retaining rare spectroscopically confirmed radio quasars to z=6.44.
Modelevsky et al. develop an analytic radiative-transfer framework for Balmer lines produced intrinsically inside static, optically thick, scattering-dominated envelopes, a geometry directly relevant if LRD central engines are hidden by dense gas. Unlike externally broadened, backlit or reflected lines, which generically acquire exponential wings, an extended intrinsic photosphere produces a broken power-law profile, transitioning from v^{-α} to v^{-(α+1)} with 0<α<1; this form fits the Hα profiles of JADES-GN-73488 and JADES-GN-68797. The result offers a line-shape diagnostic for distinguishing intrinsic from extrinsic Thomson broadening in LRDs, although the LTE calculation cannot reproduce the observed high Hα-to-continuum contrast and ultimately requires non-LTE modeling.
In an SDSS broad-line sample at z<0.35, the authors identify nine SED-selected local LRD analogues and infer an abundance of 0.08%, supporting rarity at late times but with important spectral-coverage and contamination caveats.
![Figure 5 from Implications of Broad [O III] 4364 and UV Line Emission in Two Little Red Dots at z ~ 7 - 8](/lrdigest/research/figures/2608.04101v1/figure-5-1.png?v=d97d8fa8c5c52d9f)
Deep JWST/NIRSpec spectra of two z=6.68–8.35 LRDs associate broad [O III] λ4364 with dense gas and mixed stellar/accretion ionization; however, inferred parsec-scale structure relies on temperature and virial assumptions.
Ighina et al. construct an eRASS:1-selected sample of extreme radio quasars by cross-matching eROSITA X-ray sources with RACS radio detections and DELVE optical/NIR dropout candidates, then spectroscopically following up 46 of 68 candidates. They confirm 39 quasars at z>3.5, including 14 new z>4 radio quasars, increasing the population above the same flux limits and area by about 65%. Their X-ray-to-optical and radio-loudness diagnostics identify a predominantly blazar-like subset, whose cumulative z>4 counts agree reasonably well with a fractional IC/CMB X-ray-enhancement model. The resulting uniformly selected sample provides a stronger basis for testing early jetted-SMBH growth and relativistic-jet evolution, although the redshift distribution remains affected by incomplete spectroscopy and blazar-classification choices.
Monte Carlo forecasts predict detectable galaxy-scale lensed LRDs in existing JWST imaging, especially doubles; yet the authors’ model-dependent null probability for the de-duplicated 0.66 deg² footprint remains 8.6%, so non-detection is suggestive rather than decisive.
Multi-epoch JWST/NIRSpec monitoring finds that 17 little red dots have large Balmer decrements but weak month-scale continuum and Hα variability. The authors interpret the variability contrast with ordinary AGNs as evidence for differing broad-line emission and/or ionizing-driver properties.
Using a Soltan-normalized black-hole accretion history and a gas-dynamical upper envelope, the authors find black-hole horizons dominate cosmic entropy production but operate 4–7 dex below their proposed maximum at z=4–12.
VLT/FORS2 spectropolarimetry of the z≈0.1 LRD J1025 finds an intrinsically polarised, nearly grey continuum and a weaker, differently angled broad Hα component. The 48±4° angle offset robustly requires broken axial symmetry, but does not identify its physical cause.
SDSS-V’s Gaia/WISE-informed GUA and Skewt_QSO targeting yields a large, mostly southern extension of spectroscopic quasars with broad physical-property coverage; after controlling redshift–luminosity selection differences, its black-hole and Eddington-ratio distributions agree with SDSS DR16Q.
Among 40 JWST-selected LRDs, 14 show Hα absorption, far exceeding SDSS type-1 AGNs; the compiled absorbers are mostly blueshifted and kinematically narrower, consistent with line-of-sight outflows but not uniquely establishing their fate.
This review argues that SKA radio morphology, spectra and polarimetry, tied to redshift-resolved environmental maps, can turn radio galaxies into statistical cosmic-web probes; its quantitative examples are forecasts and pathfinder benchmarks rather than new SKA measurements.
AESOPICA forward-models JWST broad-line selection in 12 cosmological simulations, finding that selection can yield apparently overmassive AGN from several seed scenarios; very light seeds nevertheless require unusually efficient, intermittently super-Eddington growth in the explored models.
Using GOODS-S JWST SMILES+JADES photometry and CIGALE fits, the authors report that obscured-AGN incidence and infrared contribution rise toward high redshift, but are consistent with no systematic dependence on total infrared luminosity within their uncertainties.
XRISM/Resolve spectroscopy of the z=0.297 quasar cluster H1821+643 measures unusually broad ICM Fe XXV lines, implying substantial non-thermal motions on 20–100 kpc scales. The authors interpret these motions as quasar-feedback coupling, but resonance scattering and sloshing remain relevant alternatives.
JADES-GS 209777 (“the Hatchling”) is a z=3.711 red quasar with exposed broad-line/X-ray emission yet nuclear absorption and multiphase disturbed gas. The authors interpret this combination as a partially cleared, dusty buried-quasar phase.
UMAP applied to 242,327 JWST sources localises spectroscopic LRDs into two colour-linked regions and selects roughly 100 candidates. Against the available spectroscopic subset, the main region attains ~0.78 purity and ~0.82 completeness, but preprocessing disfavors the reddest high-z objects.
DESI-like sparse spectroscopy plus ZTF-like photometry can, in simulations, recover stacked C IV reverberation lags and the input radius–luminosity relation within 1σ. Recovery depends especially on multi-hundred-day spectral baselines; this is feasibility evidence, not a measurement from DESI quasars.
In one extreme z~6 halo, simulations predict that earlier seeding plus mildly super-Eddington growth drives cold, fast, neutral CGM clumps and extended Hα after feedback clears nuclear sightlines; this is a model prediction, not a population measurement.
XMM J130514.64-493311.27 is a soft, recurrent off-nuclear X-ray transient in NGC 4945. Its 2022 XMM-Newton luminosity of about 2.3×10^38 erg s^-1 and disk-like spectrum favor an X-ray binary, while the compact object remains unresolved.
This letter proposes that a dust-poor subset of Little Red Dots are hierarchically nested supermassive stars: magnetic envelope inflation and exposed stellar light reproduce a V-shaped continuum, while a dense inner core supplies broad Balmer emission and hides X-rays.
JWST/NIRSpec and ALMA resolve LID-1166 into two accreting, gas-associated nuclei separated by ~1.5 kpc at z~4.5. The authors interpret the system as an obscured, gas-rich late-stage merger undergoing super-Eddington SMBH growth.
Completeness-corrected JWST/NIRSpec fits indicate strong Hα absorption is common in little red dots (LRDs) but not detected in little blue dots, favoring blueshifted, likely outflowing gas while leaving rest-frame absorption substantially incomplete.
Chandra and Keck/DEIMOS observations identify two obscured, broad-line AGN in the interacting Green Pea system J1622+3521, separated by 8.4 kpc. The authors therefore report a confirmed dual AGN in a compact low-mass Green Pea environment.
The authors argue that supercritical accretion can launch an optically thick LRD outflow whose red photosphere, line broadening, and Balmer-break properties are broadly compatible with observations, while its Balmer decrements remain underpredicted.
Spatially resolved NIRSpec spectroscopy of five z≈5 broad-Hα Little Red Dots supports a two-component morphology: compact red continuum/broad-line cores and generally extended blue continuum/narrow-line regions, while imperfect separation and small-sample limitations preclude a unique physical origin.
JWST/NIRCam colors indicate that median Balmer-break strength declines from 1.5 at z≈3.5 to 1.1 at z≈10, consistent with younger populations at earlier epochs, while extreme breaks may flag dust-obscured, evolved systems including LRDs.
Using X-ray spectra of the single nearby, long-quenched galaxy KUG 1208+386, the authors report a ≈0.07c nuclear ultra-fast outflow. Its ≥3σ trial-corrected line evidence makes feedback in a quiescent host plausible, but not yet a demonstrated maintenance mechanism.
JWST IFU spectroscopy and NIRCam imaging resolve GN-77652 at z=5.229 beside a ≈12-kpc, four-source filament. Its modest internal velocity gradient is modelled as rotation, while the filament’s coherent kinematics and a possible nearby second AGN indicate an assembling, complex environment.
JWST/MIRI resolves dusty point sources across Centaurus A’s warped disc: 928 red infrared-excess objects are consistent with embedded young stellar objects and follow the disc rather than the radio jet, favoring merger-accreted gas as the immediate star-formation reservoir.
Euclid imaging and ground-based spectroscopy identify 31 quasars at 6.6<z<7.8, including 12 at z≥7. The sample reaches M1450=−23.6 and contains a z≈7.77 record-holder, but selection completeness remains unquantified.
MEOW uses JWST/MIRI hot-dust selection over GOODS to identify 16 z≳5 AGN candidates, mostly not previously selected as broad-line AGN. Its luminosity-function comparison suggests an obscured population comparable in abundance to broad-line AGN near log Lbol≈45, but faint-end constraints remain limited.
Long-slit follow-up of 11 Gaia-selected quasar-pair candidates yields six systems classified as dual quasars and three projected quasar pairs; however, lensing remains viable for three of the six nominal duals, requiring sharper imaging or time-domain tests.
EIGER slitless spectroscopy identifies five z=1.93–3.18 little red dots among 19 near-infrared broad-line emitters. Their inferred z≈2 density is ≈7×10⁻⁶ cMpc⁻³, supporting a decline from z≈5, but less sharply than prior photometric work suggested.
This is a proposed ELT/VESPER integral-field program, not a feedback detection: it will map eleven z=1.5–2.5 obscured, starbursting radio AGN to test whether spatially resolved jet–ISM associations coincide with shocks, outflows, and altered star formation.
Medium/high-resolution JWST/NIRSpec spectroscopy of 24 LRDs finds host narrow-line gas is typically metal poor (about 0.08 solar) rather than pristine. The result disfavors pristine-collapse requirements for most objects, while two LRDs approach extremely low abundances.
This paper uses spatially resolved CIGALE SED fitting to separate the ∼1 kpc nuclear core of GN20 from the full 9.9 kpc galaxy, combining JWST NIRCam, MIRI, NIRSpec PRISM pseudo-continuum, HST, and millimeter data. The central result is that the galaxy-wide SED is overwhelmingly star-formation powered, with only a marginal integrated AGN fraction of 0.09 ± 0.02, while the nucleus requires a much stronger AGN contribution of 0.34 ± 0.05 to explain a rest-frame 2.5–3.6 μm mid-infrared excess from torus-heated dust. That means the AGN contributes about one-third of the nuclear infrared luminosity but only about 9% of the total L_IR, naturally explaining why integrated diagnostics and earlier Spitzer limits made the source look starburst-dominated. The broader significance is that GN20 looks like a buried-black-hole case where only JWST-resolution, nuclear-scale decomposition can uncover ongoing early SMBH growth inside an extreme z = 4.055 dusty starburst.
This forecasting study argues that multi-frequency SKAO continuum observations could separate intrinsically weak, Compton-thick, and ionized-cocoon interpretations of radio-faint JWST AGN and LRDs, but it presents sensitivity-based predictions rather than new radio detections.
JWST/NIRSpec slit spectroscopy finds offset peaks in [O III]/Hβ relative to continuum light in 12 CEERS galaxies at 3<z<8. These are candidate off-nuclear ionizing regions, not direct detections of wandering black holes.
The authors propose that Little Red Dots are dense-wind, super-Eddington engines analogous to Type IIn supernova interaction phases, rather than virial broad-line AGN. Their escape-velocity interpretation gives a typical-engine upper limit below 10^5 solar masses.
In one EIGER/J1030 field, five X-ray-undetected broad-line candidates imply an LRD density at z≈2.4 consistent with no decline from z≈7 above Lbol=3×10^44 erg s−1, but the large counting uncertainty and small sample preclude a precise evolutionary constraint.
This analytic study derives relativistic, self-similar shocks during singular-isothermal-sphere collapse to a black hole. In this idealized isothermal model, shocks connect collapsing interiors to several envelope states, reduce central supply relative to smooth collapse, and can release appreciable binding energy.
Modified SHAM populations in Uchuu lightcones reproduce DESI DR2 ELG and QSO number-density evolution and clustering over the fitted redshift ranges, providing reference mocks and bias/occupation diagnostics rather than an independent cosmological constraint.
JWST/MIRI PCA tomography recovers 11.3-μm PAH velocity maps in three of five z~0.1 type-2 quasars; all three show dust-traced outflow kinematics, with molecular-gas residuals consistent with outflow after disk subtraction.
This theoretical study builds non-perturbative curvaton mappings for several potentials and argues that positive non-Gaussianity can yield supermassive primordial-black-hole seeds compatible with μ-distortion limits, offering a proposed—not observationally tested—route to JWST Little Red Dots.
OzSSy1 releases uniform WiFeS spectroscopy, decompositions, and line measurements for 887 southern broad-line AGNs at z<0.1, providing a local reference sample while retaining incompleteness from host dilution at the lowest redshifts.
In SEEDZ high-resolution cosmological simulations, rapidly assembling halos preferentially meet a prescribed central-inflow criterion for heavy seeds. The authors infer that low-metallicity, sustained-accretion SMS candidates are rare, making any Little Red Dot connection conditional on model assumptions.
DESI DR2 measures large-scale clustering for 713,706 quasars at 2.0≤z≤3.5, finding bQ=3.61±0.01 at z̄=2.48 and statistically significant but weak luminosity dependence, challenging a tight luminosity–halo-mass mapping.
SDSS color selection identifies ~1,300 low-redshift “LoRD” quasars whose V-shaped subset resembles LRD spectral energy distributions, but host contamination, unresolved morphology, and weak high-z X-ray limits prevent establishing them as a uniformly faithful analog population.
Across >2 years of photometry and spectroscopy, SN 2019vxm is interpreted as an interaction-powered Type IIn whose UV-to-optical-to-IR evolution and increasingly blueshifted Balmer asymmetry are consistent with a late dust contribution, though its origin remains unresolved.