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
Across 304 ZTF optical spectra of 106 H-rich superluminous supernovae, Balmer-line modeling and comparisons support dense circumstellar interaction, but reveal no line morphology unique to SLSNe-IIn; blue-excess objects are typically fainter and favor faster fitted emitting shells.
JWST/MIRI photometry of the lensed z=7.04 Little Red Dot Abell2744-QSO1 finds its red continuum turns over near rest-frame 1 μm, tightening energy-budget constraints but leaving dust reddening versus dense-gas reprocessing unresolved.
This planning paper argues that deep JWST/NIRSpec medium-resolution continuum spectroscopy can turn high-redshift galaxy surveys from emission-line detections into measurements of stellar populations, neutral gas, and kinematics; its empirical EXCELS-based exposure scaling motivates a 1,000-hour survey concept.
At z≈2.5, Hyperion has a higher X-ray AGN fraction than its coeval field, but the ≈2.3σ excess is confined to the densest peaks; its outskirts are statistically consistent with the field.
JWST/NIRSpec CO v=1–0 emission across NGC 3256 S’s outflow base implies that the obscured AGN’s 4.7-μm radiation is anisotropic and likely collimated, though the inferred geometry depends on radiative-transfer assumptions.
This white paper proposes a coordinated, multi-cycle JWST program to determine whether Little Red Dots trace accreting black holes and to separate black-hole seeding signatures from later growth through uniform spectroscopy, imaging, and time-domain data.
This SHARP and MICADO science case sets out a unified, parsec-scale program to measure supermassive-black-hole masses, nuclear-star-cluster kinematics and populations, nuclear structure, and gas-inflow signatures in nearby galaxy nuclei. The central aim is to distinguish in-situ cluster growth, star-cluster infall, and black-hole-driven cusp formation, while mapping the transition from low-mass nuclei where clusters can regulate gas supply and black-hole growth to massive core galaxies shaped by mergers and black-hole binaries. Its key practical result is to define the black-hole-mass and distance regimes in which ELT/SHARP can resolve the sphere of influence and nuclear-cluster scales beyond JWST/NIRSpec capabilities. Nearby systems are explicitly presented as a local physics laboratory rather than direct evolutionary analogues of compact active nuclei at high redshift.
A two-stage, spectroscopy-informed NIRCam classifier finds LRD candidates beyond standard color selections. Held-out recall/precision are 0.92/0.79, while broad Hα in 10 of 13 grating-observed candidates supports—without confirming—the LRD interpretation of many new selections.
For SPURS-GN-2 at z=7.19, broad UV nitrogen-to-carbon lines imply strongly CNO-processed, dense gas; ionization-ordered absorption velocities are interpreted as a near-Eddington, decelerating cocoon flow around a 10^6–10^7 solar-mass black hole.
In 12 z=4.17–5.54 compact broad-line emitters, Lyα is detected in six and is systematically narrower than broad Hα. Host-SED predictions correlate more closely with observed Lyα than nuclear Hα/UV, although excess Lyα permits nuclear emission.
Strong lensing resolves the z=8.297 Little Red Dot “Best Friend” into a <6.8 pc central component and a low-mass host. Its V-shaped central spectrum favors, but does not establish, black-hole activity over an ultradense stellar cluster.
JWST/NIRSpec finds CW-LRD-z10 at zspec=10.361, with a Balmer-limit V-shaped continuum and tentative high-ionization/auroral lines. It is a strong z>10 LRD candidate, but present spectroscopy does not unambiguously establish either broad-line or AGN status.
On a spatially independent DESI DR1 test set, conditional normalizing-flow redshift PDFs generally reconstruct tomographic N(z) better than quantile random forests, especially at high redshift; calibration improves several low-z mean-redshift biases but leaves population-transfer and residual-calibration limitations.
A 104-galaxy JWST composite at mean z=6.50 finds ≈180–200 km s⁻¹ blueshifted interstellar absorption. A simple wind-propagation model places most material only 3–9 proper kpc away, challenging bright [O III]-selected galaxies as the dominant source of widespread intergalactic metals.
A systematic JWST/NIRSpec PRISM search finds 20 broad-Hβ emitters at 7<z<9.5, all photometrically/morphologically consistent with LRDs. Completeness-corrected mass-function evolution and inferred BH accretion density are conditional on broad Hβ being a virial black-hole-mass tracer.
Radiative-transfer fits to 11 JWST little red dots find that a clumpy neutral component can jointly accommodate Hα, Hβ, and Balmer-break constraints where a smooth geometry often cannot, supporting—but not uniquely establishing—multiphase circumnuclear gas.
MINERVA/MIRI identifies el Ascua at z~3.8 as a mid-IR-dominant, X-ray-undetected Compton-thick AGN candidate. UV-to-radio SED fitting indicates rapid black-hole growth and a probable AGN radio excess, but obscuration and radio-loudness remain indirect inferences.
Medium-resolution JWST/NIRSpec spectroscopy of the single z=6.6 galaxy COLA1 links a very young, VMS-favored UV population, extreme nitrogen enrichment, and LRD-like optical Balmer structure; the proposed evolution into an LRD remains model-dependent.
A systematic JWST/NIRSpec search identifies MoM-BL-z10 at z=9.9837 as a candidate broad-line AGN. Its marginal-but-model-preferred broad Hβ enables a virial black-hole estimate, while alternative LRD assumptions shift the inferred mass substantially.
AO-assisted ERIS/SPIFFIER spectroscopy of 34 Gaia Multi-Peak candidates resolves six sub-arcsecond dual AGN and seven lensed quasars, but foreground-star superpositions dominate the non-multiple outcomes and broad-line velocity offsets do not securely measure systemic pair velocities.
Gaia zero-motion selection plus broad-band colours and spectroscopy confirmed 21 quasars among 24 candidates, disproportionately finding BAL quasars in photometrically transitional regions. One low-redshift normal quasar is described as LRD-like, but this is not a high-redshift LRD sample.
Using JWST Paα spectroscopy, the authors find that radio-bright AGNs at z=1.1–1.5 occupy denser ∼1.5 pMpc environments than matched controls; density also correlates with accretion indicators, while environmental Paα luminosity functions are elevated and flatter at the faint end.
In 865 ks of Chandra imaging, no X-ray AGN is detected among 21 confirmed non-quasar members of the z=6.63 J0910−0414 protocluster. The resulting limits do not establish environmental enhancement, but still allow substantial excess activity.
Spectroscopy of two LRD–blue-companion pairs confirms small line-of-sight velocity offsets and young, metal-poor companion starbursts. Orbital modeling favors a merger for Tango and conditionally for Waltz, while the proposed heavy-seed connection remains interpretive.
![Figure 1 from A dust-reddened quasar in a [C II]-luminous host at z=6.55](/lrdigest/research/figures/2610.13758v1/figure-1-1.png?v=19f9cd8ff6225e0c)
JWST and ALMA characterize J1440+0019 as a moderately dust-reddened, rapidly accreting z=6.5488 quasar embedded in a dust-rich, exceptionally [C II]-luminous host; absorption indicates a likely ionized nuclear outflow, but host kinematics remain poorly resolved.
DESI DR1 analysis of 114,754 z≤0.9 type 1 AGNs shows that broad-Balmer profile choice systematically shifts Hβ widths, virial masses, accretion rates, and narrow-line diagnostics, while preserving an apparent continuous NLS1-to-broader-line accretion sequence.
Across 28 luminous quasars at z=5.85–7.56, X-ray continua are systematically steep, yet show no significant dependence on black-hole growth indicators. The inferred spectral shapes could modestly to severely reduce high-redshift survey count rates.
Across 79 H I absorber-selected galaxies at 0.2<z<1.2, the authors combine multiwavelength data to inventory stars and cold gas, finding broadly consistent indirect H I estimators at small impact parameter but environmentally driven scatter and mass-dependent gas fractions.
JWST/MIRI F770W selection and volunteer classifications of 14,657 PRIMER galaxies at 1<z<3 reveal morphology trends unlike optical/near-IR samples, while wavelength-dependent structure and unresolved mid-IR cores complicate physical interpretation.
KCWI and HST reveal that CARLA J0800+4029’s dominant Lyα reservoir is tidal and offset from its radio-loud quasar, while a matched-area quasar-halo limit is 3.4 times lower, consistent with spatially redistributed baryons during cluster assembly.
Multi-epoch HST, Spitzer, and JWST observations identify an unusually luminous, chromatically fading nuclear transient in the z=7.19 quasar GNz7q. Its light-curve, spectroscopic, and infrared-echo properties support—rather than uniquely prove—a tidal-disruption interpretation.
SN Helios is a spectroscopically confirmed, strongly lensed Type II supernova at z=3.34. Its predicted 2–6 yr reappearance could enable time-delay cosmography, but current lens-model spread and the absence of a measured delay preclude an H0 result.
Using JWST mid-infrared IFS of NGC 5728, the authors decompose blended circumnuclear line emission into a star-forming ring and AGN bicone. Stacking twelve tracers yields spatial flux fractions that are stable across tested weighting choices.
![Figure 4 from Search for High-Ionization Nebular Emission (SHINE). I. A Systematically Selected [Ne V] Sample at z > 3 with JWST/NIRSpec PRISM](/lrdigest/research/figures/2609.27130v1/figure-4-1.png?v=1f796e8992092206)
SHINE identifies 25 luminous [Ne V] emitters at z=3.06–9.44 from >9,000 JWST/NIRSpec PRISM galaxies. Their hard-ionization lines favor accretion, but heterogeneous selection and incomplete diagnostic overlap preclude an intrinsic AGN-incidence measurement.
DESI spectroscopy plus 144-MHz LOFAR imaging identifies 83 radio-detected quasars at 4.7<z<6.7, including 26 radio-loud objects. Their UV spectra are broadly similar to non-detections; tentative weak-line excesses and BAL trends remain statistically inconclusive.
In 17 JWST/NIRSpec LRDs at z=2–5, Ca II-triplet absorption is detected in three and marginally in a stack (mean EW ≈−5 Å). The authors interpret it as optically thick gas near the central engine, but absorber location and structure remain unresolved.
LATED uses Lyα-selected sources and three-band Hα/[O III]+Hβ/continuum colours to prioritize extremely metal-poor or Pop III-like candidates at z=1.92–6.60. Tests recover AMORE6 and identify three Abell 2744 candidates, but photometry cannot prove metal-free stars.
Deep JWST/NIRSpec spectra of two luminous LRDs resolve Hα–Hδ absorption near systemic velocity, with higher-order troughs redder and unexpectedly persistent. Broad metal lines and diagnostic ratios favor dense gas, while a stratified failed wind remains an interpretation rather than a detection.
JWST MIRI/Spitzer hydrogen-line measurements in 27 dusty z~1–2 infrared galaxies yield directly inferred nebular attenuation declining from ~3 mag near 2 μm to ~1 mag near 4 μm, yet IR-based SFRs remain ~2.5 times higher.
JWST/NIRSpec IFU spectra identify three z>6 quasars with extreme optical Fe II relative to Hβ, supporting rapid early enrichment while leaving accretion rates and nearby line-emitting structures materially uncertain.
A common low-resolution analysis of YZ Cnc separates outburst-related broad Balmer absorption/composite profiles from quiescent emission-rich spectra, while recurrent Fe II λ5169 is established empirically but its optical-depth interpretation remains unresolved.
A single z=7.03 galaxy–absorber pair links a dusty, intensely star-forming galaxy to unusually strong multiphase metal absorption at 16 kpc. Blueshifted gas is consistent with an outflow, while abundance evidence for Population III enrichment remains suggestive rather than decisive.
Medium-resolution JWST spectra of 13 LRDs link narrow-line Balmer decrements to UV slope and Balmer-break strength, which the authors interpret as host-scale dust reddening of predominantly stellar UV emission; extreme-break, flat-UV LRDs form a distinct subgroup.
DESI DR1 yields 1,993 nitrogen-loud quasars at 1.6<z<4.3 (1.2% of the parent sample). Matched-control comparisons associate nitrogen-loud spectra with narrower broad lines, lower virial masses, and higher inferred Eddington ratios.
Ultra-deep JWST/SPURS rest-UV spectra of four UV-bright Little Red Dots find dense, nitrogen-enhanced, neutral-gas-embedded nuclei and diverse broad-line/wind signatures. The authors infer compact nuclear activity, while stellar and AGN contributions remain degenerate.
Deep JWST/NIRSpec spectra of nine z=3–6 LRDs favor electron-scattering-like broad-line profiles in five cases, implying substantial ionized columns but ∼50% covering fractions; this challenges unity-covering cocoon models while supporting an AGN-related origin.
VIPERS yields 14 compact, LRD-like sources at 0.5<z<1.75 selected through V-shaped photometric slopes and broad lines. Their inferred abundance declines sharply below z~1, while one unresolved X-ray source is consistent with a low-inclination, radiatively efficient disk.
Deep JWST spectroscopy of four z~7 LRDs finds Al-rich, Mg-poor, ~1% solar gas. The authors interpret its globular-cluster-like abundance pattern as hot hydrogen burning by ≥10^4-solar-mass supermassive stars, while saturation and small-sample uncertainties remain.
Near-IR spectroscopy of intermediate-luminosity SHELLQs quasars finds lower median virial black-hole masses and higher Eddington ratios than luminosity-matched z≈1.3 quasars, with 11–22% inferred near/super-Eddington depending on the single-epoch mass calibration.
Photospheric fits to 4 absorption-feature LRDs and 82 archival objects yield predominantly super-Eddington ratios. Coupled quasi-star envelope models place black-hole mass caps below local BH–host expectations, but the inference remains model- and host-prior-dependent.
RUBIES-EGS-9809 is a single, heavily obscured broad-line AGN host at z=5.7 whose resolved Balmer break and declining-SFR SED fit make it a quenching candidate, not a confirmed post-starburst. Outflow signatures make AGN feedback plausible but unproven.
In 3,566 JWST/NIRSpec galaxies at z=3.0–8.1, UV–optical continuum slopes reveal a continuously populated path from star-forming galaxies to LRDs. The authors interpret it as changing host/BH* continuum contributions, while stressing model-dependent mass-ratio limits.
Using Fisher forecasts rather than a detected BAO signal, the authors argue that a future 14,000-deg² infrared spectroscopic survey of Little Red Dots could measure the isotropic standard-ruler distance D_V/r_d to 0.28–0.78% across z=4.5–8.
JWST spectra of the single dusty galaxy AzTEC-1 at z=4.3419 reveal a broad Hα component blueshifted by 1245 km s⁻¹. The authors favor a candidate sub-pc SMBH binary or recoiling SMBH over an ionized outflow, but confirmation requires resolved follow-up.
A WISE pilot search finds two extreme mid-infrared AGN flares, modeled as dust echoes and interpreted as candidate TDEs. Their high inferred energies and contrasting optical/spectroscopic behavior make them promising, but not definitive, disruptions in active nuclei.
Skyfire’s CEERS NIRSpec census finds broad Balmer emission across redder LRDs and somewhat bluer candidates, motivating an expanded continuum-slope selection. The color trend is suggestive of continuity with blue broad-line sources, but uneven targeting prevents a definitive population-unification claim.
Using a redshift-dipole estimator on four DESI DR1 tracers, the authors infer a high-redshift QSO velocity consistent with the CMB dipole. They argue that the much larger DESI number-count dipole is footprint- and selection-related rather than kinematic.
Multi-wavelength follow-up overturns J0109−5424’s proposed high-redshift lens interpretation: Paschen lines place it at z=2.07 as a FeLoBAL quasar. For P170+20, compact imaging and a quasar+M-dwarf spectral fit disfavor, but do not exclude, lensing.
A DJA census identifies 20 compact, blue broad-line emitters at z=4–7. Model-dependent escape fractions imply they provide a modest global ionizing budget at z≈5, while potentially dominating radiation locally over few-Mpc scales.
In 89 LRDs and 191 LBDs, LRDs have more luminous and broader Hα, larger Balmer decrements, and lower [O III]/Hβ. The authors argue these population-level differences strain luminosity-independent orientation alone, while not uniquely establishing a gas-cocoon mechanism.