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
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.
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.
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.
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.
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.
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.
Using one lensed, decades-variable little red dot, the authors turn an idealized pulsation period–luminosity–temperature relation into a preliminary, period-limited H0 estimate. Ten-year monitoring could improve statistical precision, but calibration of the relation remains the decisive uncertainty.
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.
Cosmological simulations of compact z≈12.5–14.9 starbursts find centrally concentrated stellar and gas reservoirs. The authors argue that rapid inflow and transport could, under an assumed 10% retained efficiency, assemble conditions for a ∼10^6 M⊙ black hole and an AGN phase.
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.
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.
In MELIORA simulations at z>8.5, the host-to-DCBH UV–optical balance declines over roughly 30 Myr after direct collapse, offering a model-dependent relative age indicator: UV-faint/red LRDs are younger, whereas UV-bright systems have more developed stellar hosts.
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.
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.
This modeling study predicts optical/UV transients when cluster stars strike proposed gaseous LRD envelopes. Red-supergiant impacts on envelopes near the SMBH mass are favored; rates could reach 0.3 yr⁻¹ per compact LRD, but detectability depends critically on low-redshift LRD abundance.
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.
In lensed A2744, a rest-frame red cut identifies most robust ALMA sources while separating luminous, extended dusty star-forming galaxies from compact LRDs; ALMA non-detections of LRDs constrain, but do not alone establish, their dust content.
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.
This theoretical study proposes that rapid, halo-driven accretion produces high-redshift over-massive black holes and possibly Little Red Dots, while virial-shock heating later suppresses growth and moves systems toward local black-hole–stellar-mass scaling.
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].
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.
JWST/MIRI-MRS-informed SED fits to the single z=4.601 Hot DOG W2246-0526 favor an added hot-dust component interpreted as polar dust. This changes inferred AGN luminosity, but its geometry and physical association with an outflow remain model-dependent.
UV-to-optical fitting of one z=3.55 little red dot, The Cliff, admits a BH* envelope plus low-mass, dusty, metal-poor host. The result depends materially on Balmer-absorption and dust prescriptions, while AGN UV leakage remains 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.
JWST/NIRSpec spectra of two z~6.6 ultra-luminous Lyα emitters reveal broad Balmer-line black-hole masses near 2×10^8 M⊙ and double-peaked Lyα, which the authors interpret as brief post-quasar phases inside relic ionised bubbles.
Multi-epoch JWST/NIRSpec spectra of one z~7 little red dot show coordinated continuum, broad-Balmer, and [O III] changes over ~13 rest-frame days. If intrinsic, the variability ties at least some narrow-line gas to the central engine and disfavors complete dense-gas coverage.
Direct cluster simulations suggest that stellar-mass black holes can enter collision-built extremely/supermassive stars in ultra-dense, low-metallicity clusters, creating longer-lived quasi-star-like objects. The authors propose these as faint, companion-rich multiple Little Red Dots, not typical bright LRDs.
A semi-numerical PBH-seeded AGN model predicts that PBH X-ray heating makes cosmic-dawn 21-cm absorption shallower and suppresses power, with outcomes strongly dependent on the assumed PBH mass function and X-ray escape fraction.
Dayal cross-compares astrophysical light (~100 M⊙) and heavy (~10^3–10^5 M⊙) seeds (via DELPHI) with cosmological primordial black holes (10^{0.5–6} M⊙; PHANES) against z≈5–10 observables. The only scenario the data rule out is Eddington-limited accretion onto light seeds; high black hole–to–stellar mass ratios (Mbh/M*≈0.3–1) are achievable with PBHs or heavy seeds under super-Eddington growth. Crucially, only PBHs and Eddington-limited heavy seeds can simultaneously recover the observed Mbh, M*, and extremely low host metallicities (Z≤0.01 Z⊙) at z≈7–10. PBHs also predict a distinctive decline of Mbh/M* with increasing halo mass and occupancy of 10^9–10^11 M⊙ halos, motivating a clustering-based test selecting z≈7 systems with Mbh/M*>0.1 and Lbol≈10^{44–46} erg s⁻¹.
This paper asks whether late pulsational mass loss from supermassive stars can naturally create the compact dense shells inferred around little red dots. The main result is that the final pre-collapse ejection episode can leave behind an optically thick shell on sub-parsec scales, while earlier episodes expand away and become dynamically unimportant for the observed cocoon. The paper matters because it turns the dense-gas requirement of LRDs into a concrete stellar-evolution prediction rather than an external assumption.
Hebe’s strong He II emission can be matched by either a near-maximal Pop III burst or an accreting 10^4–10^5 M⊙ black hole, but the authors favor Pop III stars because the inferred burst mass remains physically plausible.
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.
In 14 JWST LRD spectra, four show >3σ Paschen-continuum breaks, including one 12σ case. The authors interpret these slope changes as hydrogen free-bound emission, favouring low-temperature, minimally reddened nebular continua over fully thermalised continua.
JWST/NIRSpec-IFU spectroscopy of the single z=3.55 Little Red Dot The Cliff yields a very low narrow-line metallicity, Z=0.017±0.004 Z⊙, while broad Hβ-based virial estimates place its black hole above local host-scaling expectations.
Medium-resolution JWST/NIRSpec data spatially separate an LRD-like AGN and its host at z=6.64, revealing exceptionally broad ionised gas consistent with AGN driving but a low inferred mass-loading factor and therefore limited immediate star-formation impact.
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.
Ultra-deep JWST/NIRSpec spectra of two Abell 2744 little red dots resolve a broad Lyα component in z=7.0364 Abell2744-QSO1. The authors argue its comparatively modest shift favors a clumpy, rather than uniform, neutral envelope and an ionized local environment.
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.
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.
Monte Carlo solutions of a Smoluchowski merger model predict three-stage evolution and possible runaway growth in dense primordial-black-hole clusters within the first billion years. The result is a model-dependent route to early massive black-hole seeds, not a direct measurement of little red dots.
A theoretical dark-sector transition model argues that rare false-vacuum domains can collapse into primordial seeds of up to ~10^10 M⊙ for Little Red Dots, with PTA-band gravitational waves as a possible test; it does not fit an LRD sample.
Deep NOEMA observations of three z>6 JWST AGN—two Little Red Dots and one blue Type-I source—yield no significant [C II] or dust-continuum detection, tightening host-galaxy and SED constraints while leaving the physical origin of their [C II] deficit unresolved.
This paper asks whether the newly discussed overmassive black hole galaxies at cosmic dawn can arise naturally from early direct-collapse black-hole formation rather than from a more exotic late-time assembly path. The main result is that a 70,000-solar-mass DCBH formed at very high redshift can grow into a system with the black-hole-to-stellar-mass ratio, metallicity, star-formation rate, and broad spectral properties seen in objects like UHZ1 and GHZ9 by z around 10. The paper matters because it offers a concrete physical channel for the broader JWST overmassive-black-hole population that sits adjacent to the little-red-dot and early-AGN discussion.
A radially resolved analytic framework predicts that stellar collisions can shape compact z≈5–12 clusters: constructive mergers may build very massive stars, whereas destructive encounters near central black holes may create dense gas potentially relevant to Little Red Dots.
A reanalysis of UHZ1’s full Chandra exposure and new MIRI non-detections reduces the evidence for its proposed luminous, Compton-thick direct-collapse black hole: the X-ray excess is marginal and non-persistent, while infrared limits exclude the originally inferred luminosity scale.
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.
This lecture-based review argues that JWST has converted early luminous-quasar studies from rest-UV, ground-based inference to rest-optical spectroscopy and resolved host/environment measurements, while supporting—within virial-estimator uncertainty—the pre-JWST Mg II black-hole mass scale.
Stellar-evolution calculations suggest rapidly accreting supermassive stars can undergo relativistic collapse into long-lived quasi-stars whose cool, luminous envelopes overlap Little Red Dot optical properties across modeled metallicities; the LRD interpretation remains model-dependent rather than a direct identification.
In 18 z≈3–7 broad-Hα emitters, Balmer cores progress from narrow emission to P-Cygni-like and absorption-dominated profiles as UV–optical colour reddens. The authors interpret this as changing envelope column density and optical depth, not purely dynamical line broadening.
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.