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
Mock JWST selection in AMBRA suggests LRDs are transient appearances of existing black hole–galaxy systems: dim sources require a gas-enshrouded AGN model, while massive compact hosts yield longer-lived phases. Redshift counts remain model-sensitive.
A 14,000-deg² spectroscopic LRD survey at 4<z<9 is forecast to constrain local, equilateral, and orthogonal primordial non-Gaussianity at σ(fNL)=0.32, 32, and 10, respectively, if modeled clustering, abundance, and covariance assumptions hold.
EPOCHS-DR2 releases a large JWST/NIRCam photometric census at 6.5<zphot<16.5, validated against NIRSpec but explicitly incomplete under its conservative selection. It identifies a small V-shaped-SED LRD subset and high-redshift candidates whose nature requires spectroscopy.
Sub-arcsecond 144 MHz LOFAR imaging resolves both nuclei in one of three high-redshift dual-AGN targets, while a 92-system catalog shows a higher LoTSS detection fraction than matched single AGN; blending and interaction-driven activity remain competing explanations.
JWST identifies 11 ultra-red, mostly resolved galaxies in the z=4.3 SPT2349-56 core. Their extreme concentration and ALMA-constrained low star formation suggest a likely protocluster population transitioning beyond the dusty-starburst phase, pending spectroscopy.
Using relativistic SIDM-halo evolution, the authors argue that pre-reionization, concentrated halos can make stellar-mass seeds and grow them through dark-matter inflow to LRD-like SMBHs by z≈6; late-time fluid-model breakdown makes final masses upper limits.
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.
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.
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.
This analytic PBH-cluster framework claims that runaway mergers can reproduce the LRD SMBH mass function with a 1–10% accretion duty cycle while linking overmassive, compact hosts to seed-driven halo evolution; key gas dynamics remain unmodeled.
RXDF is an approved Roman seven-band, multi-epoch imaging program designed to combine AB≈30 depth with a 678.75 arcmin² full-depth footprint. For LRD science it is prospective: it extends the luminosity–redshift discovery space, but supplies neither an LRD selection nor predicted counts.
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.
An analytic halo-inflow model argues that observed early AGN and, conditionally, little red dots (LRDs) require near-free-fall cold gas supply rather than Bondi–Hoyle inflow; it treats this as an upper-limit fuel budget, not a direct measurement of black-hole accretion.
This modelling study proposes tidal-disruption and quasi-periodic-eruption event rates as population-level probes of LRD black-hole masses. Its predictions depend strongly on assumed stellar cusps, black-hole–stellar-mass relations, and the possibility that most LRDs are obscured.
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.
Among 253 JWST-selected LRDs, only the brightest quartile shows a statistically significant excess of very close blue companions: 18/65 within 0.5–2 kpc. The association supports, but does not establish, synchronized seed formation.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
A BH*-template SED selection yields 241 compact, rest-optical central-engine-dominated candidates over z~1.7–9.3, extending beyond conventional V-shaped LRD criteria; inferred luminosities and Eddington-based masses remain model-dependent.
Using X-ray spectra and infrared-informed absorption priors, the authors infer that Compton-thick AGN comprise 17% of AGN at z=3–6. The revision sharply reduces candidate classifications, but supports no significant redshift evolution in this fraction.
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.
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.
Medium-band NIRCam colors identify 26 red, strong-line galaxies at z=5.01–8.60. Nine unresolved objects evade common Little Red Dot cuts; the authors favor a missed LRD population, but dusty star formation and AGN remain viable alternatives.
Forecasts suggest [Ne V] line-intensity-map–galaxy cross-correlations could statistically recover roughly 10% of cosmic-noon AGN line emission from sources below a CDIM-like direct-detection limit, though inference of the faint emissivity remains luminosity-function dependent.
Using 98 spectroscopic LRDs at 3<z<7, the authors infer growth from low-mass, relatively under-dense haloes at z>4 to environments and halo masses comparable to galaxies by z≈3.5; proposed structural and spectral changes remain interpretive.
A cosmological black-hole/galaxy model interprets z≈5 Little Red Dots as luminous, short super-Eddington nuclear-burst phases of previously seeded black holes. It reproduces the reported number-density shape, but the proposed triggering, seeding mix, and descendants remain model-dependent.
Lumina couples a large radiation-hydrodynamic volume to an empirical SMBH-to-observable prescription, and its authors report simultaneous consistency with high-redshift quasar and LRD luminosity functions and LRD clustering. The agreement depends on assumed LRD demographics and spectral properties.
Using simulation-based inference on a synthetic local AGN population, the authors find an intrinsic Compton-thick fraction of 40±3%. Their radiation-regulated geometry broadly reproduces several X-ray observables, but depends materially on fixed, simplified broad-line-region and torus assumptions.
A DESI DR1 line-selected search identifies eight compact z=0.20–0.44 LRD candidates with broad, steep-decrement Balmer emission, low-excitation spectra, and generally weak multi-year variability, extending detailed LRD tests to the nearby Universe.
For ASPIRE-like JWST clustering at z≈6, mock-based covariances—not Poisson pair-count errors—are needed for calibrated halo-mass inference: Poisson intervals are systematically too narrow because they omit cosmic variance and correlated radial bins.
A forward model treating little red dots as dust-intercepted, inclined counterparts of compact broad-line AGN matches the currently measured UV luminosity function, but dust covering fraction and cloud extinction remain substantially degenerate.
After image decomposition and host-only SED fitting, 36 NIRCam-selected NEP-TDF AGN candidates separate into a likely AGN “branch” and an ambiguous, largely early-type “bridge” near quenching; the reported SFR–AGN-fraction trend is weakly explanatory.
Euclid and IRAC imaging over 0.75 deg² identify 16 compact z>4 LRD/LBD candidates among 233 V-shaped SED sources, extending to brighter, more massive systems whose AGN nature and evolutionary connection to JWST LRDs remain unconfirmed.
Using southern-sky multi-band photometry and quasar-versus-brown-dwarf SED fitting, the authors compile 6,104 z=4.5–7 quasar candidates. Three of six bright, visually screened follow-up targets are confirmed at z>5, but catalog-wide purity remains weakly constrained.
Across ∼48,000 photometric and ∼5,000 spectroscopic galaxies, the authors find LRD-like colour, compactness, and broad-Hα properties vary continuously, arguing that most LRDs are an extreme tail rather than a discrete class; only ∼3% show very strong Balmer breaks.
A broad JADES photometric census finds that extreme-red color cuts recover at most one quarter of compact LRD candidates, so inferred luminosity functions and number-density evolution depend strongly on selection rather than necessarily on population evolution.
Extreme-value sampling of fitted black-hole and stellar mass functions predicts median extreme M_BH/M_* = 0.18–0.35 at z=3.5–8.5 (mean ≈0.24), consistent with supplied JWST high-ratio points but not a population-wide relation.
Across SDSS quasars at 0.2<z<2.4, compact red quasars show an excess near α1.4–3 GHz≈−1 that strengthens with dust extinction. The authors interpret this as wind/jet–ISM shocks during a dusty blow-out phase, but radio spectra alone do not establish that mechanism.
Using JWST/MIRI-selected sources, MEOW infers that obscured AGN become increasingly dominant with redshift: its SED-based luminosity functions imply a 98–99% obscured fraction at z=4.5–6 for luminous AGN, relative to UV type-1 quasars.
Deep JADES medium-band photometry identifies 22 candidate near-pristine starbursts at 2.5<z<6.5 from strong Hα but weak [O III]+Hβ. Their inferred metallicities are photometric, however, and dust, dense gas, or obscured AGN can mimic the selection.
Shin-Uchuu predictions indicate that early halo assembly bias can materially alter LRD clustering interpretations: DCBH hosts should be most biased, whereas low-spin and SIDM channels are weaker for different reasons. Forthcoming LRD cross-correlations could therefore discriminate host selections.
Monte Carlo merger evolution can reduce an assumed 0.8–1.0 dex scatter in the z~6 black-hole–stellar-mass relation to the ~0.3 dex local scatter, but the result depends strongly on merger mass ratios and rates; major mergers alone are insufficient.