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
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.
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.
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.
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.
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.
A reionization-budget calculation argues that, if faint z=3–7 Little Blue Dots are common and leak ionizing radiation efficiently, most cannot be highly super-Eddington: their hard EUV spectra would complete He II reionization earlier than allowed.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
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].
eROSITA-triggered monitoring of HE 1237-2252/J1240−2309 links a changing-look transition to intrinsic accretion-rate recovery and an evolving two-component Balmer-line profile. A diskline-like component strengthens with UV flux, while the proposed corona/illumination mechanism remains interpretive.
Across four optical and three X-ray epochs, J0413-0050 changed from broad Balmer emission in 2004 to an Hβ-free 2021 state and back to broad plus narrow Hβ in 2023. The authors favor changing accretion over obscuration, but X-ray column density is unconstrained.
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.
Fits to three absorbed LRD Hα profiles show that a radially stratified, virialized BLR can reproduce nearly exponential wings without requiring dominant electron scattering; inferred high inclinations also match their large equivalent widths under model assumptions.
JWST/NIRSpec FUV spectroscopy of the single z=7.04 LRD Abell2744-QSO1 resolves extended narrow and unresolved broad Lyα components. The authors interpret broad Lyα/Balmer ratios as evidence for lower-column-density sightlines through otherwise dense, clumpy BLR-scale gas.
In 32 AGN spanning LRDs, LBDs and X-ray detections, broad Hα profiles do not generally require electron scattering: Lorentzian or multi-Gaussian alternatives often fit comparably, while BLR stratification and stacking can generate exponential-looking wings.
High-redshift LRDs and JWST-selected broad-line AGN are X-ray weak relative to broad Hα, plausibly resembling highly accreting local systems; however, predominantly upper-limit-based X-ray constraints leave intrinsic coronal suppression and obscuration unresolved.
Forward-modeling broad-Hα selection in a JADES broad-line AGN sample at z≳4 yields an M_BH–M★ relation consistent in mean with local relations but with 0.63 dex intrinsic scatter, implying diverse early black-hole growth histories.
JWST/NIRSpec follow-up of CEERS extreme emission-line galaxies finds broad-line AGN contamination, but for spectroscopically extreme sources the narrow Hα component dominates. The authors therefore attribute the most extreme nebular emission primarily to young star formation, not AGN.
This modeling study argues that Little Red Dots are high-inclination, dust-reddened counterparts of super-Eddington Little Blue Dots. Anisotropic continua and modest BLR/dust covering factors can reproduce several LRD ensemble observables, but the proposed orientation unification remains model-dependent.
Joint modelling of broad lines and Chandra non-detections for 14 JWST high-redshift broad-line AGNs favors low-mass, highly super-Eddington black holes with over-cooled coronæ over massive, weakly accreting alternatives, but the inference remains model-dependent and bimodal.
A 249-object JWST spectroscopic compilation argues that photometrically selected Little Red Dots are spectroscopically heterogeneous composites of accreting black holes and young stars, but its mass, duty-cycle, and Wolf–Rayet interpretations remain model-dependent.
JWST/NIRCam decomposition detects extended host emission in 9 of 17 broad-Hα AGN at z≈4–6. Separating point-source light can reduce inferred host masses by 1–2 dex, yielding high BH-to-stellar mass ratios, although unresolved compact hosts remain a viable alternative.
JWST/HST observations of the lensed z≈6.87 galaxy A2744-z7DLA reveal damped Lyα absorption plus a statistically preferred broad Hα component, supporting a gas-enshrouded broad-line AGN interpretation while its UV–optical continuum remains predominantly stellar.
Presents a NIRSpec/IFU reduction that exploits the red signal on NRS2 for medium‑resolution gratings, effectively doubling the usable wavelength coverage and recovering Hα beyond the nominal range; the authors also note the exposure‑time trade‑off when using adjacent dispersers. Applied to five z≈2 quasars with reverberation‑mapped MBH, the extended cubes enable joint Hβ–Hα measurements at R≈1000. Hβ‑based single‑epoch masses best match RM, while Hα recipes show ≈0.5 dex larger scatter; for the least‑massive, high‑λEdd object (MBH,RM≈10^7.5 M⊙, λEdd=0.8) all SE estimators overpredict by ~1 dex, suggesting a bias at high accretion. The work delivers the first high‑z SE calibrations from Hβ and Hα for the newfound early‑BH population, with uncertainties still limited by sample size.
THRILS delivers deep JWST/NIRSpec G395M spectroscopy in two pointings, yielding 89 measured redshifts and empirical magnitude thresholds. Its >8-hour integrations expose faint lines inaccessible to shallower EGS spectroscopy, enabling targeted follow-up rather than population-level physical conclusions.
FEADME uniformly fits disk-like Balmer profiles in 237 double-peaked AGN and five TDEs. Authors find broad AGN structural diversity but largely overlapping populations; TDE disks are inferred to be more circular, while an added broad component is often preferred.
A JWST/NIRSpec search of roughly 80,000 spectra identifies 252 broad-line AGN to z=7.2, extending census statistics to fainter, lower-mass systems. The authors find high-redshift objects commonly at inferred Eddington ratios of 0.1–1, subject to heterogeneous depth and line-detection limits.
Two z~3 X-ray AGNs with He I λ10830 absorption indicate dense, broad-line-region-scale circumnuclear gas, but their contrasting obscuration, accretion rates, and outflow signatures provide only a two-object, model-dependent case for an evolutionary sequence.
Final OzDES analysis uses multi-year optical monitoring to calibrate high-redshift BLR radius–luminosity relations from Hβ, Mg II, and C IV reverberation lags, yielding 62 RM black-hole masses and single-epoch estimates for 246 additional AGN.
A DESI–SDSS comparison identifies 97 z>0.9 changing-look quasars with high-ionization broad-line transitions. Their lower Eddington ratios, line–luminosity co-variability, and ∼3-year rest-frame transition times are consistent with—though do not prove—accretion-state changes.
Using two SDSS epochs of the z=0.228 quasar SDSS J0012-1022, the authors argue that an anomalous luminosity–optical-slope change is consistent with phase-dependent obscuration of two accreting black holes. It supports, but does not establish, a sub-parsec binary interpretation.
Multi-epoch SDSS spectroscopy of 1,116 nearby type-1 AGNs finds broad-line Hα/Hβ decreases as individual AGNs brighten. The authors argue continuum-driven BLR radiative-transfer and excitation changes, rather than variable intrinsic dust reddening, predominantly drive this variability.
JWST/MIRI-MRS spectroscopy of four luminous type-1 quasars at z=7.08–7.64 yields mutually consistent broad-line black-hole masses of (4–15)×10^8 M⊙ and directly detects hot-torus emission, without resolving the early-SMBH growth tension.
Stacked JADES Type 1 AGN spectra at z>5 show strong Balmer emission but weak or absent high-ionization lines. Cloudy comparisons disfavour much of the tested sub-Eddington parameter space, motivating—but not uniquely establishing—soft, filtered, or anisotropic ionizing continua.
JWST/HST photometry of the z=2.801, ~12×-lensed AGN SDSSJ2222+2745 resolves a mildly disturbed, moderately dusty host near the low-SFR edge of the main sequence, consistent with—but not proving—a Type II-to-Type I transition.
For 70 JWST broad-line AGN at 3<z<7, the authors infer black holes overmassive relative to local broad-line AGN, with the offset and BH-to-stellar-mass ratio increasing toward high redshift; LRD-rich sample composition contributes substantially.
A 255 ks Chandra study resolves NGC 5005’s soft, extended gas from a faint hard nucleus. The authors infer a lightly absorbed, intrinsically weak AGN whose reported broad Hα line persists at an exceptionally low inferred Eddington ratio.
Ultra-deep JWST/NIRSpec G395M spectroscopy behind Abell S1063 enables a systematic search for faint broad-line nuclei, fitting narrow components with an [O III] λ5007 template and validating the method with mocks. The authors identify ten broad-line AGN at 4.5<z<7.0 (eight secure, two tentative) with broad Hα–based virial masses down to ~10^5.5 Msun; composite galaxy+AGN SEDs yield host masses implying M_BH/M_* ≲ 0.1% and placements consistent with the local M_BH–M_* relation. From these they build a BH mass function that agrees with prior results above ~10^6.5 Msun but shows an excess at ~10^5.5 Msun relative to a Schechter extrapolation. They interpret the low-mass excess as evidence for descendants of direct-collapse seeds in the reionization era.
THRILS spectroscopy of the z~7 Little Red Dot THRILS_46403 (CEERS-10444/RUBIES_49140) reveals bona fide AGN tracers: multiple Fe lines including a 4.5σ [Fe VII] and several [Fe II], plus an auroral [N II] detection at 3.1σ. Three Balmer lines show broad emission with superposed narrow absorption whose small widths and depths imply a partially covering absorber at or beyond the broad-line region. Electron-temperature diagnostics indicate O++ is markedly hotter than N+ across densities, pointing to a powerful, hard central ionizing source. Together these features establish multiply ionized iron emission from an accreting SMBH within the first 800 Myr and suggest direct sight-lines from the disk to gas at or beyond the BLR.
Review draws a line between local narrow-line Seyfert 1s and the newly uncovered z>4 type 1 AGN/LRDs: both host low-mass (∼10^6–10^7 M⊙) black holes accreting near or above Eddington and often show features like steep, variable X-rays and, in a subset, relativistic jets. The authors argue jets can help shed angular momentum in super-Eddington flows, making NLS1s practical analogs for early SMBH growth. Radio examples underscore the wide range from host-dominated star-formation morphologies to blazar-like, large-scale jets. Key caveat: some systematic differences remain, plausibly tied to distinct environments and evolutionary paths at high redshift.
ALPINE-CRISTAL-JWST uses NIRSpec IFU aperture spectra at photometric peaks in 18 z=4.4–5.7 main-sequence galaxies and finds 7 broad-line AGN candidates via Hα, including one robust source (FWHM ≈ 2800 km/s) and six with 600–1600 km/s, two in a merger. Narrow-line diagnostics place these systems within the star-forming locus, so broad-line detection is the only reliable discriminator; the implied broad-line AGN fraction is 5.9–33% and is aided by targeting high-mass hosts. Virial estimates give MBH ≈ 10^6–10^{7.5} M⊙ with Lbol/LEdd ≈ 0.1–1, and candidates lie at or below the local MBH–M* relation, counter to prior JWST reports of overmassive BHs. The work highlights mass-dependent selection effects and points to a substantial, previously missed population of faint, undermassive broad-line AGN at early times.
New NIRSpec/MSA G140H/F070LP data reveal broad Lyα in CANUCS-LRD-z8.6 (z=8.63) centered near systemic (FWHM 1540±260 km/s), implying transmission through a large reionized region. Simple Strömgren modeling of the line shape yields an ionized-bubble radius Rb=1.5^{+0.3}_{-0.2} pMpc and a Lyα escape fraction fesc=11±3%. The intrinsic width is even broader (≈2200±280 km/s), consistent with a BLR in a low-luminosity AGN, while high N IV]/C IV and N IV]/O III] ratios from PRISM indicate nitrogen enrichment. A mild local overdensity (δ≈1.8) suggests neighboring galaxies may help sustain the bubble, linking this LRD to the emerging class of nitrogen-rich systems like GN-z11 and GHZ2/GLASSz12.
JWST/NIRCam imaging and NIRSpec prism spectroscopy of the Bullet‑cluster LRD Bz5.3 (zspec=5.2907) reveal broad Balmer emission plus strong low‑ionization Fe II, O I, and Ca II triplet lines, confirming a bona fide BLR around an accreting SMBH. The work reports the first high‑z detection of the O I λ1304 bump (O I+Si II), alongside prominent O I λ8446 and Ca II λλ8498,8542,8662. A markedly low O I λ1304/λ8446 photon ratio (0.1–0.3) implies internal dust with AV≈0.4–1.0 and points to Lyβ fluorescence as the dominant excitation, consistent with high EW O I λ8446 and weak O I λ7774. Photoionization modeling of O I and Ca II favors multiple BLR gas phases with distinct densities/ionization states, supporting a stratified BLR at early times.