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
In SDSS-IV/eBOSS, [Ne V] produces a large, high-purity but incomplete AGN sample: detection favors less-obscured, higher-Eddington-ratio nuclei. Stacking indicates many individual non-detections are sensitivity-limited, while [Ne V]/[O III] declines with AGN luminosity.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Narrow-line ratios in roughly 20 high-S/N JWST/NIRSpec LRD spectra challenge a uniformly opaque, unity-covering gas envelope: at least 40% require extreme ionization conditions, while weak He II indicates an ionizing spectrum softer than standard AGN.
In 36 GOODS LRDs/LBDs at z=2.26–7.89, the authors find AGN-like narrow-line excitation, extreme X-ray weakness, and LRD Lyα excess with a broad component resembling Hα. They argue against completely enclosing cocoon geometries, while retaining obscured-LBD interpretations.
For the single z=5.482 Little Red Dot LRD-204851, aligned UV, optical-line, and Lyα structures indicate a narrow bipolar channel extending several kpc. Lyα transfer fitting favors slow expansion, but cannot distinguish an outflow from a quasi-static ionization cone.
KOOLS-IFU maps of NGC 6552 find broad [O III] emission declining with radius but no significant full-sample association between local kinematics and [O III]/Hβ excitation, favoring spatial dynamical structure over a detected excitation–kinematics coupling.
In 412 Stripe 82 Type 2 AGNs, optical RMS variability anticorrelates with several narrow-line luminosities, equivalent widths, and widths. The authors interpret this as variability retaining information about obscured accretion, although controls and photometric-noise limits temper causal inference.
In the J0226+0302 quasar sightline, 73 line-emitting galaxies trace a tentative, 10–40 cMpc enhancement in IGM transmission, while four broad-line AGN show a possible smaller-scale enhancement. The results favor local ionizing-background variations but remain statistically and model limited.
Across six JWST/NIRSpec IFU targets at z=3–9, resolved stellar-population histories associate strong AGN-driven ionized outflows with recent nuclear quenching in the most massive systems, while starburst-driven outflows accompany continued growth in lower-mass galaxies.
UV-to-optical continuum fits to 66 JWST LRDs find BH* configurations in only about 6% of 52 robust broad-prior fits; suppressing AGN light raises this to about 40%, exposing severe model degeneracy rather than establishing BH* prevalence.
Stacked JWST/NIRSpec spectra of roughly 2,500 z=1–10 galaxies yield Te-anchored strong-line metallicity calibrations and MZRs. The authors find declining metallicity with redshift, 50 EMPG candidates, and two broad-Hα Little Red Dots in this metal-poor sample.
In 18,749 DESI-DR1 NLSy1s, stronger Fe II and lower single-epoch virial masses than SDSS-DR17 correspond to a larger inferred super-Eddington fraction. Two mass calibrations preserve the population difference, but virial-mass systematics remain consequential.
JWST/NIRSpec IFU spectroscopy of six z~6 SHELLQs narrow-Lyα candidates finds secure broad Balmer components in two, while extended, largely non-rotating ionized gas characterizes several non-broad-line systems. Broad-line incidence rises sharply with Lyα luminosity.
In 110 z≥4 little red dots, 32 Lyα detections and resolved imaging of 13 higher-redshift systems indicate that escaping Lyα more plausibly traces extended host-scale gas than the compact red/Balmer-line component, although continuum-subtraction and depth limit morphology.
Across 37 z=3–7 LRDs, broad Hα scales tightly with modified-blackbody bolometric luminosity yet is ∼40 times stronger than in low-z Type 1 AGN at fixed Lbol. The authors attribute this to unusually high-covering, high-column broad-line gas.
NEXUS combines JWST imaging and PRISM spectroscopy to census LRDs at z=2.3–7.5. Its 36 confirmed objects are predominantly broad-line sources, while selection calibration, abundance, clustering, and continuum diversity remain limited by contamination, resolution, and sample size.
Cloudy fits show that a host-plus-quasi-star model can reproduce several LRD continuum and hydrogen-line properties, but helium lines, hot dust, and model degeneracy prevent it from uniquely establishing quasi-stars as the explanation.
Spatially resolved JWST, ALMA and KCWI data support a multiphase, minor-axis biconical outflow in the dusty local merger IRAS F01364-1042. The authors infer faster ionized than molecular gas and argue a nuclear starburst can energetically drive it despite an obscured AGN.
Among 14,584 SDSS type-1 AGNs at z<0.35, seven robust Balmer absorbers imply a ∼0.05% incidence. Joint, resolution-aware Balmer fitting finds narrow, generally saturated absorbers; a rare high-Eddington, weak-Fe II subset may be preferentially affected.
JWST/NIRSpec spectroscopy of 14 LRDs separates Balmer emission and absorption, favoring dense broad-line gas over dust as the main origin of elevated broad Balmer decrements. A clumpy, viewing-angle-dependent nuclear geometry is proposed, but velocity-profile fits succeed in only three of five high-S/N sources.
Across a large SDSS–eROSITA quasar sample, bolometric luminosity scales nearly linearly with virial black-hole mass while hard X-rays rise more slowly. The authors argue this disfavors classical Bondi feeding and favors CCA, but redshift covariances and JWST line-based systematics limit interpretation.
Across roughly 100 JWST-selected LRDs, rest-UV emission is redder and about four times more compact than matched star-forming galaxies. Stacked spectral trends and high Fe II/Mg II favor a substantial compact central component, although its physical origin remains model-dependent.
JWST/NIRSpec spectroscopy of one z=4.556 QSO finds a steep far-UV extinction curve, A1500/AV≈8, without a 2175 Å bump. The authors interpret this combination as small silicate grains, but proposed QSO-driven production channels remain untested.
High-resolution JWST/NIRSpec spectra of 10 compact, color-selected LRDs at 3<z<7 recover Balmer absorption in four. The authors argue resolution exposes frequent, diverse excited-hydrogen absorption, but the small, selected sample limits population-level inferences.
This paper searches JWST/NIRSpec archival spectra of 87 massive quenched galaxies at z≈1.5-4.5 and finds [NeV] λ3427 in six, arguing that this coronal line cleanly isolates luminous SMBH accretion in systems where residual star formation is not a viable explanation. Four of the six [NeV] hosts also show broad Hα with FWHM ≳ 4000 km s^-1, implying MBH ≈ 10^8.5-10^9.5 Msun, while the [NeV] luminosities indicate quasar-like power outputs of roughly 10^45-10^46 erg s^-1 and Eddington ratios of about 10-50%. The strongest [NeV] emitters sit in the youngest post-starburst galaxies with Dn4000 ≲ 1.3, whereas older quenched systems lack comparable activity, pointing to intense radiatively efficient black-hole growth that can continue for several hundred Myr after the main quenching event. That timing matters because it links early quenching to delayed but still powerful SMBH growth, and provides a concrete empirical target for models that aim to produce the first massive passive galaxies.
Using AGN-aware fits to JWST spectra, the authors report that non-LRD broad-line AGN shift from elevated observed M_BH/M* above z≈4.5 to the local relation by z≈3.5; LRD host-mass inferences remain substantially less secure.
Using JWST imaging of the lensed A2744 field, this paper defines a sample of 31 sub-0.25 arcsecond compact pairs, or “Double Dots,” and shows their separations are strongly skewed to small values, consistent with most being physical systems rather than chance alignments. The main empirical result is that close pairs are extremely common among known broad-line high-redshift sources in the field: at least 16 of 24 published little red dots and both previously identified high-redshift BLAGNs are double systems, with a median observed separation of 0.15 arcseconds. The authors then show that unresolved companions can materially reshape the observed SED, including washing out the canonical LRD v-shape, and that 2D spectroscopy can place the broad-line emission on either the redder or bluer member of the pair. That makes compact pairing itself a powerful marker of broad-line activity at high redshift and points to merger-driven accretion as a plausible underlying trigger.
A DESI DR1 selection identifies 27 candidate low-redshift LRDs at z=0.2–0.9; near-IR spectra of 18 show broad, highly decremented Balmer lines and unusual continua, supporting—but not independently proving—continuity with high-redshift LRD phenomenology.
For the single z=8.312 galaxy MACS0416-Y1, deep JWST/NIRSpec plus archival IFU/ALMA data support a broad-line AGN interpretation, low metallicity and dust mass ratios, and a spatially non-coincident origin for optical and far-infrared [OIII].