654 indexed papers · 430 research notes

Research archive

2025-08-22 · 2508.16795v1

On the Variability Features of Active Galactic Nuclei in Little Red Dots

Shuying Zhou, Mouyuan Sun, Zijian Zhang, et al.

Applies the CHAR (corona-heated disk reprocessing) model to the Tee et al. (2025) 22-object LRD sample to interpret their multi-epoch photometry. Finds that the measured |Δm| is dominated by photometric uncertainties; within CHAR the non-detections are consistent with either AGN light fractions ≲30% or intrinsically luminous AGN whose fractional variability is small. Simulations specify what it would take to break this degeneracy: ≈200 LRDs, two epochs separated by ≥2 years (observed frame), and σ_phot ≤0.07 mag. If variability still fails to appear, it would point to accretion modes unlike those of low‑z quasars, offering independent constraints on what powers LRDs.

LRD variability v-shaped SED simulation high-z

2025-08-21 · 2508.15905v1

Glimmers in the Cosmic Dawn. III. On the Photometrically Determined Black Hole Mass to Stellar Mass Relation Across Cosmic Time

Alice R. Young, Matthew J. Hayes, Alberto Saldana-Lopez, et al.

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Photometric SED decomposition of 121 variability-selected HUDF nuclei using HST+JWST (0.2–4.8 μm) isolates stellar and AGN components and estimates MBH from L5100 via local scalings. AGN contributions are significant in 26 sources across 0<z<7, including a zphot=6.74 object with a lower limit log10(MBH/M⊙)>7.36. In the MBH–M* plane, low‑z sources align with local relations while higher‑z systems—and two z<1 dwarf hosts flagged as IMBH candidates—are increasingly overmassive. A NIRISS‑confirmed BL‑AGN exemplifies successful recovery, with the AGN providing ≈95% of the flux in at least one band, underscoring accelerated early BH growth relative to hosts.

variability overmassive BH high-z

2025-08-20 · 2508.14897v1

Little Red Dots as Direct-collapse Black Hole Nurseries

Elia Cenci, Melanie Habouzit

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Preliminary MELIORA cosmological simulations implement a direct-collapse BH formation model that tracks Lyman–Werner irradiation and halo inflow rates to test whether newborn heavy seeds can resemble Little Red Dots. The simulated population of newly formed DCBHs drops sharply at z<6 as inflows wane, mirroring the observed emergence-and-decline trend of LRDs. DCBH birth coincides with a strong gas-compaction event and a short, bright AGN phase lasting ~200 Myr, after which the first Pop III stars appear and the AGN fades. If LRDs trace this nursery phase, their weak X-ray and hot-dust signatures follow naturally from the scenario.

LRD BH seeds simulation high-z X-ray

2025-08-19 · 2508.14164v1

The implications of overmassive black holes at $z > 5$ for quasar and black hole growth

Judah Luberto, Steven R. Furlanetto

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Analyzing recent JWST reports of ~100× overmassive black holes at z>5, the authors show that if such BHs are common, the global black hole mass density at z≈5 would already rival today’s value—unless the overmassive systems are rare or accrete with very high radiative efficiencies (implying rapid spin). Tracking representative z≈5 detections forward using average growth rates from modern models keeps them overmassive relative to the local Mbh–M⋆ relation. To land within the local scatter by z≈0, these BHs must grow at least an order of magnitude more slowly than expected. This creates tension with the rapid early growth needed to assemble them and complicates standard expectations for quasar feedback on galaxies.

overmassive BH high-z QSO demographics

2025-08-19 · 2508.14155v1

Little Red Dots and their Progenitors from Direct Collapse Black Holes

Junehyoung Jeon, Boyuan Liu, Volker Bromm, et al.

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Using the A-SLOTH semi-analytic framework, the authors generate a DCBH-seeded SMBH population and benchmark it against Little Red Dot (LRD) demographics and spectra. Heavy (DCBH) seeds reproduce the observed LRD BH mass functions, number densities, and host-halo trends better than stellar-remnant seeds. For the most extreme early LRDs (e.g., MoM-BH*-1), DCBH scenarios with either strong dust attenuation or dense, dust-free gas can match the distinctive V-shaped, Balmer-break–dominated SEDs, whereas even super-Eddington growth on light seeds cannot. The work points to gas metallicity as a crucial observable, beyond BH-to-stellar mass ratios, to pin down LRD progenitors.

LRD BH seeds simulation demographics v-shaped SED high-z

2025-08-19 · 2508.13541v1

Little Red reionization factories

Fan Zhang

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Proposes Little Red Dots as “reionization factories,” where a Weyl-curvature–driven Cosmic Tide funnels intergalactic HI into colliding streams that shock, compress, and trigger rapid starbursts whose LyC reionizes hydrogen. In this picture, hot HII escapes along interstitial directions, so reionization proceeds via outflowing plasma rather than requiring extreme photon escape fractions. The model predicts a gas-dominated rest‑optical continuum—HII bremsstrahlung with a minimum‑timescale red cutoff and an IR rollover from opacity—while the UV is stellar, naturally producing strong Balmer breaks. It also anticipates narrow+broad Balmer components and slightly shifted Balmer absorption from bulk‑moving n=2 HI, with a proof‑of‑concept SED fit to J1025+1402; the scenario is explicitly speculative.

LRD reionization nebular continuum high-z

2025-08-18 · 2508.12599v1

SMILES Data Release II: Probing Galaxy Evolution during Cosmic Noon and Beyond with NIRSpec Medium-Resolution Spectra

Yongda Zhu, Nina Bonaventura, Yang Sun, et al.

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SMILES DR2 releases medium-resolution NIRSpec MSA spectra for 166 GOODS-S/HUDF galaxies spanning 0<z<7.5, with a strong emphasis on cosmic noon (z~1–3). Using the G140M/F100LP and G235M/F170LP settings to provide contiguous ~1–3 µm coverage (split near 1.8 µm), the team delivers reduced 1D/2D spectra, robust redshifts, emission-line catalogs (GELATO) and pPXF fits for quiescents, plus ancillary SED results. The dataset is tuned to capture rest‑optical diagnostics for dusty and obscured systems, enabling work on AGN, multi‑phase outflows, excitation, and metallicity in environmental context. Public HLSP availability makes this a ready benchmark set for cosmic‑noon black‑hole growth and ISM studies.

spectroscopy obscured AGN outflows JWST AGN

2025-08-14 · 2508.10986v1

Population III star formation near high-redshift active galactic nuclei

Ethan M. Fisk, Madeline A. Marshall, Phoebe R. Upton Sanderbeck, et al.

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Cosmological radiation‑hydrodynamical simulations test quasar SEDs (near‑UV to hard X‑ray) impinging from 10–1000 kpc onto a neighboring halo and quantify how AGN radiation regulates primordial collapse. X‑rays keep the free‑electron fraction high, catalyzing H2 despite LW dissociation, so collapse is delayed until ≲10^7 Msun of pristine gas accumulates—yielding a massive Pop III cluster for the weaker two fields and a DCBH for the strongest. Runaway collapse occurs at z ≃ 24.99, 15.46, and 12.63 (A→C), directly tying radiation intensity to later collapse and larger available gas reservoirs. Predicted He II 1640 luminosities match the GN‑z11 Pop III candidate and should be detectable with NIRSpec to z ≈ 15, outlining an AGN‑proximity pathway to luminous Pop III clusters or early DCBH seeds.

BH seeds simulation X-ray high-z spectroscopy

2025-08-13 · 2508.09749v1

A dual AGN at z = 5.4 associated with a Lyman-alpha Nebula in the Center of a Cosmic Filament

Qiong Li, Christopher J. Conselice, Qiao Duan, et al.

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A systematic JWST search flags a spectroscopically confirmed close pair at z≈5.4 (G1: JADES 32751; G2: JADES 32927) with 1.7″ (10.4 pkpc) separation; both components show AGN signatures. NIRSpec PRISM (G1) and NIRCam/F444W grism from FRESCO (G2) reveal rest‑optical line ratios consistent with AGN on BPT diagnostics, with SED fits preferring AGN+SF templates and high‑ionization features strengthening the case. VLT/MUSE maps a >22 kpc Lyα nebula around G2 whose morphology and high Lyα escape fraction point to anisotropic AGN photoionization and an outflow. The pair sits in an overdense filament/protocluster node at z∼5.4, hinting that dual AGNs may be more common at early times than simulations predict and offering a clean probe of CGM feedback during early black‑hole growth.

JWST AGN high-z spectroscopy outflows demographics

2025-08-12 · 2508.08768v1

Impact of Resonance, Raman, and Thomson Scattering on Hydrogen Line Formation in Little Red Dots

Seok-Jun Chang, Max Gronke, Jorryt Matthee, et al.

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The authors run 3D Monte Carlo radiative transfer to test how resonance, Raman, and Thomson scattering sculpt Balmer lines in Little Red Dots. Resonance scattering in an n=2–populated H I medium drives strong departures from Case B and distinct Hα vs Hβ shapes, but Hβ is funneled into Paα, preventing broad Hβ wings. Raman scattering of higher Lyman-series emission can explain Hα/Hβ wing-width ratios ≳1.28, whereas Ramanization of a UV continuum is disfavored by the near-constant FWHM across transitions. Thomson scattering with Te≈10^4 K and electron column ≈10^24 cm−2 reproduces the ≳1000 km s−1 wings and implies virial BH masses can be overestimated by ≳10 if widths are taken at face value.

LRD broad Balmer simulation overmassive BH spectroscopy

2025-08-11 · 2508.08460v1

MAGAZ3NE: Far-IR and Radio Insights into the Nature and Properties of Ultramassive Galaxies at $z\gtrsim3$

Wenjun Chang, Gillian Wilson, Ben Forrest, et al.

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Adds ten FIR-to-radio passbands to the MAGAZ3NE UV–NIR catalogs and performs UV–radio SED fits for two ultramassive galaxies, COS-DR3-195616 (z=3.255) and COS-DR1-209435 (z=2.481), revising earlier classifications. The full SEDs show 195616 is unobscured and quenching with a largely depleted molecular-gas reservoir, while 209435 is a heavily obscured, actively star-forming UMG with a long depletion timescale. The authors forecast that 209435 will grow by 0.34 dex to log(M⋆/M⊙)=11.72 over 0.72 Gyr and present multi-pronged evidence for AGN in both systems, with feedback likely linked to gas depletion in 195616 but not yet suppressing star formation in 209435. The work demonstrates how FIR–radio constraints prevent UV–NIR-only misclassification and sharpen the AGN–quenching picture for ultramassive galaxies at early times.

obscured AGN radio high-z

2025-08-04 · 2508.02792v1

Luminous Mid-IR Selected Obscured Quasars at Cosmic Noon in SDSS Stripe82 II: Spectroscopic Diversity and Broad H$α$ Emissions

Ben Wang, Yuzo Ishikawa, Joseph F. Hennawi, et al.

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Survey of 24 WISE W4–bright, optically faint/red SDSS Stripe 82 candidates confirms 23 luminous Type‑2 quasars at z = 0.88–3.49 using Gemini/GNIRS plus Keck/LRIS and KCWI spectra. About one‑third (8/23) unexpectedly show broad Hα (FWHM > 2000 km/s) while sharing SEDs with JWST “little red dots,” marking them as lower‑z analogues of heavily obscured broad‑line AGN. The sample also exhibits relatively weak [O III] λ5007 given their high bolometric luminosities, and the authors construct a new Type‑2 QSO composite spectrum. Results demonstrate that simple mid‑IR plus extreme r−W4 color selection efficiently recovers a spectroscopically diverse obscured quasar population at cosmic noon, informing SMBH growth demographics that connect to the LRD population.

QSO obscured AGN broad Balmer spectroscopy low-z demographics

2025-08-02 · 2508.01372v1

A Nitrogen-rich AGN Powering a Large Ionizing Bubble at z=8.63

Takahiro Morishita, Massimo Stiavelli, Charlotte A. Mason, et al.

arXiv abstract

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.

LRD broad-line AGN reionization spectroscopy high-z

2025-08-01 · 2508.00774v1

A Novel Formation Channel for Supermassive Black Hole Binaries in the Early Universe via Primordial Black Holes

Saiyang Zhang, Boyuan Liu, Volker Bromm

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High-resolution hydrodynamics around ∼10^6 M⊙ primordial black holes show that accretion-driven LW fields plus strong baryon–DM streaming (v_bχ ≳ 0.8 σ_bχ) push gas onto an atomic-cooling track and trigger collapse in the PBH wake. The collapsing clouds sustain inflow rates ≳0.01–0.1 M⊙ yr⁻¹, enabling ∼10^5 M⊙ supermassive stars that rapidly form direct-collapse BHs at z ∼ 20–10. These secondary DCBHs pair with the primary PBH to yield in-situ SMBH binaries with initial q ≈ O(0.1) at ∼10 pc separations. The channel predicts compact, LRD-like sources and low-frequency GW emitters accessible to JWST/ALMA and LISA/TianQin.

BH seeds simulation high-z stellar envelope LRD

2025-07-31 · 2508.00209v1

Accretion disc reverberation mapping in a high-redshift quasar

F. Pozo Nuñez, E. Bañados, S. Panda, et al.

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Six months of medium-band photometric reverberation mapping on the MPG/ESO 2.2 m captured inter-band lags in the z=2.66 quasar QSO J0455-4216, isolating continuum windows with ~7% variability and day-scale micro-variations. GPCC-derived lags follow a wavelength-dependent delay spectrum consistent with an SS73 thin disc plus lamp-post, placing the ultraviolet-emitting outermost radius at 3.02(+0.33/−0.57) light-days (~500 AU). Transfer-function modeling shows the light curves are disc-dominated, with only minor diffuse BLR continuum allowed; large DCE fractions oversmooth the variability. This delivers the first direct disc-size measurement at this redshift for an ~9×10^8 M⊙ black hole, validating thin-disc expectations and enabling faster high‑z mass estimates.

QSO variability high-z

2025-07-31 · 2508.00057v1

Discovery of a Little Red Dot candidate at $z\gtrsim10$ in COSMOS-Web based on MIRI-NIRCam selection

Takumi S. Tanaka, Hollis B. Akins, Yuichi Harikane, et al.

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Using COSMOS-Web’s joint NIRCam–MIRI imaging, the authors conduct the first targeted search for little red dots beyond z≈10, leveraging F770W to isolate the V‑shaped SED signature and cull Balmer‑break contaminants. They uncover one robust source, CW-LRD-z10, with zphot=10.5(+0.7/−0.6), MUV=−19.9(+0.1/−0.2), compact morphology, a clear V‑shaped SED, and an F115W non‑detection consistent with an LRD at z∼10. From this single detection they infer a number density at MUV≈−20 of 1.2(+2.7/−1.0)×10⁻⁶ Mpc⁻³ mag⁻¹, implying the LRD fraction rises with redshift to ≈3% at z∼10. If confirmed, this points to LRDs as a common early population potentially tied to the first SMBH growth; deep spectroscopy is still required to secure the redshift and nature of CW-LRD-z10.

LRD v-shaped SED high-z demographics compact red

2025-07-31 · 2507.23774v1

Lord of LRDs: Insights into a "Little Red Dot" with a low-ionization spectrum at z = 0.1

Xihan Ji, Francesco D'Eugenio, Ignas Juodžbalis, et al.

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A nearby LRD analog is uncovered: the broad-line AGN SDSS J102530.29+140207.3 at z=0.1 shows the hallmark V-shaped SED, broad Balmer emission (FWHM 1000–2000 km/s), and deep Balmer absorption. New GTC optical spectra reveal a G–K-giant-like continuum with a clear CH G-band and unusually deep low-ionization absorption, plus a series of [Fe II] emission lines; similar [Fe II] features are identified in a JWST-selected LRD at z=2.26. Multi-epoch data show small but significant Hα variability, and NuSTAR confirms extreme X-ray weakness consistent with Compton-thick obscuration (NH>10^24 cm^-2). Together these point to a dense, complex nuclear environment that reproduces LRD hallmarks locally and informs early black-hole growth, though the strength of the ionic/atomic/molecular absorptions remains challenging for standard stellar/AGN models.

LRD v-shaped SED broad Balmer obscured AGN X-ray low-z

2025-07-30 · 2507.23066v1

SHELLQs-JWST perspective on the intrinsic mass relation between supermassive black holes and their host galaxies at z > 6

John Silverman, Junyao Li, Xuheng Ding, et al.

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Using nine SHELLQs quasars at 6.18<z<6.4 with NIRCam host detections and NIRSpec Balmer-line M_BH, the authors infer the intrinsic M_BH–M_* relation via forward modeling that accounts for selection and measurement systematics, with the slope fixed to 1.61 and acknowledging parameter degeneracies. The sample (log M_BH≈8–9; log M_*≈9.5–11) is consistent with a non-evolving relation but with markedly larger intrinsic scatter, σ≈0.80 dex. The preferred model implies an active UV-unobscured AGN fraction of ~2.3% at z≈6 and predicts many lower-mass AGN soon to be found. An overmassive normalization is disfavored, as it would require unrealistically small scatter (~0.22 dex) and a very low AGN fraction (~0.6%).

QSO high-z spectroscopy demographics JWST AGN

2025-07-29 · 2507.22206v1

The X-ray Link Between High Eddington Ratio Dust-Obscured Galaxies (DOGs) and Hot DOGs

Fan Zou, W. N. Brandt, Elena Gallo, et al.

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Targets seven high-λEdd DOGs and combines new, deeper Chandra exposures with archival X-ray data to measure line-of-sight obscuration. Finds these systems are typically buried: 6/7 have N_H ≳ 10^23 cm^-2 and 3/7 are Compton-thick (N_H ≳ 10^24 cm^-2), with observed X-rays strongly suppressed relative to the mid-IR relation. Placing the sources on the λEdd–N_H plane shows they overlap the regime occupied by Hot DOGs. Authors argue both populations trace a post-merger phase where rapidly accreting SMBHs are enshrouded by dust-rich gas.

obscured AGN X-ray super-Eddington

2025-07-29 · 2507.22014v1

Little Red Dots as self-gravitating discs accreting on supermassive stars: Spectral appearance and formation pathway of the progenitors to direct collapse black holes

Lorenz Zwick, Christopher Tiede, Lucio Mayer

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Models little red dots as supermassive stars fed by massive self‑gravitating discs assembled in gas‑rich major mergers, reproducing the V‑shaped SED as two blackbodies and attributing Balmer broadening to disc rotation—without invoking extra AGN, stellar, or dust components. MCMC fits to two representative LRDs (J0647‑1045 and COS‑756434) yield sub‑Eddington disc accretion and SMS masses of a few ×10^6 Msun with physically motivated parameters. The framework predicts a luminosity cut‑off of order few ×10^44 erg/s and ties the observed redshift distribution of LRDs to merger rates, matching current trends. Acknowledged caveat: reproducing the absolute abundance of LRDs remains challenging, though the fits are robust to observed diversity.

LRD stellar envelope BH seeds v-shaped SED broad Balmer simulation

2025-07-28 · 2507.21230v1

Can high-redshift AGN observed by JWST explain the EDGES absorption signal?

Alexandra Nelander, Christopher Cain, Jordan C J DSilva, et al.

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Tests whether a high‑z radio‑loud AGN population—calibrated to JWST UV luminosity functions and extrapolated to z≈20—can provide the excess radio background needed for the EDGES 78 MHz absorption. Matching the EDGES depth requires that essentially all UV‑bright sources down to M_UV ≳ −15 are radio‑loud AGN, with the UV number density declining by ≤1.5 dex from z=10→20, and an X‑ray escape fraction ≲1% to avoid pre‑heating that erases the trough. Only an extremely shallow UVLF evolution can achieve the amplitude, and reproducing the trough’s sharp edges and flat bottom demands fine‑tuned redshift dependence of the UVLF, AGN UV fraction, and X‑ray leakage. Verdict: physically possible but implausible given the extreme requirements.

radio reionization JWST AGN high-z X-ray demographics

2025-07-28 · 2507.20684v1

A deep dive down the broad-line region: permitted OI, CaII and FeII emission in an AGN Little Red Dot at z=5.3

Roberta Tripodi, Maruša Bradač, Francesco D'Eugenio, et al.

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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.

LRD broad-line AGN broad Balmer spectroscopy high-z

2025-07-23 · 2507.17833v1

Not-quite-primordial black holes seeded by cosmic string loops

Bryce Cyr

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This work builds an improved, unified framework for the halo mass function seeded by cosmic string loops, treating arbitrary loop-velocity distributions and capturing both spherical and filamentary growth. From this mass function, it isolates halos that meet direct-collapse conditions at high redshift, producing black-hole seeds of ~10^4–10^5 Msun. For reasonable string parameters, the predicted seed abundance reproduces the observed number density of JWST’s Little Red Dots, offering a non-Gaussian small-scale route to early SMBH growth. Because loop formation lacks large acoustic waves, the scenario avoids CMB spectral-distortion bounds, and a velocity–tension phase diagram (including fragmentation into “beads”) clarifies where this channel dominates.

BH seeds simulation LRD high-z demographics

2025-07-23 · 2507.17738v1

Beyond the Dot: an LRD-like nucleus at the Heart of an IR-Bright Galaxy and its implications for high-redshift LRDs

Pierluigi Rinaldi, George H. Rieke, Zihao Wu, et al.

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The authors present WISEA J123635.56+621424.2 (“the Saguaro”) at z=2.0145 in GOODS‑North as an LRD analog: a compact, LRD‑like nucleus with a face‑on spiral host and a clear V‑shaped nuclear SED from NIRSpec. Redshifting the system to z≈7 renders the host undetectable via surface‑brightness dimming, reproducing a canonical LRD appearance and implying many high‑z LRDs could be visible galactic nuclei embedded in extended hosts. A stack of rest‑UV images for 99 photometrically selected LRDs reveals faint diffuse emission and mild radial growth with redshift, consistent with galaxy size evolution. A simple analytic model shows surface‑brightness dimming alone can explain the compact morphology, arguing LRDs are a short‑lived, AGN‑dominated phase rather than a distinct population.

LRD v-shaped SED JWST AGN demographics

2025-07-22 · 2507.16921v1

ALMA survey of a massive node of the Cosmic Web at $z\sim 3$. II. A dynamically cold and massive disk galaxy in the proximity of a hyperluminous quasar

A. Pensabene, S. Cantalupo, W. Wang, et al.

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High-resolution (∼0.3″) ALMA Band-3 CO(4–3) and 3‑mm continuum mapping of the MQN01 node isolates a massive companion, MQN01‑QC, ∼10 kpc and −300 km s⁻¹ from the hyperluminous quasar CTS G18.01 (z=3.251). Kinematic modeling of the cold gas yields a dynamical mass of 2.5×10^11 M⊙ within ≈4 kpc and a dynamically cold disk with Vrot/σ≈11, establishing the first quasar companion confirmed as a massive rotating disk at this epoch. Despite the proximity, the disk shows no clear tidal disturbances, while the quasar’s CO(4–3) profile exhibits a broad blueshifted wing consistent with a powerful molecular outflow or interaction. The system suggests dynamically cold disks can persist even in dense, early cosmic‑web nodes and hints the quasar may be a satellite in an incipient merger.

luminous quasar ALMA/mm outflows high-z

2025-07-21 · 2507.15556v1

Signatures of Exploding Supermassive PopIII Stars at High Redshift in JWST, EUCLID and Roman Space Telescope

Cédric Jockel, Kyohei Kawaguchi, Sho Fujibayashi, et al.

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Semi-analytic models, anchored to stellar-evolution and GR collapse simulations, follow ejecta–CSM shocks from exploding supermassive Pop III stars to predict light curves, spectra, and photometry. The events peak at ~10^45–10^47 erg/s and last 10–200 yr in the source frame (observed 250–3000 yr), yielding quasi-persistent variability indistinguishable from little red dots/AGN on 0.5–9(1+z) yr baselines. Bright explosions should be detectable in long-wavelength JWST filters to z≤20 at 24–26 mag, with pulsating SMSs to z≤15; Euclid and Roman reach z<11–12. Deep fields could constrain the event rate to ~10^-11 Mpc^-3 yr^-1 and yield several hundred (Euclid) to dozens (Roman) detections, directly testing heavy-seed SMBH pathways.

BH seeds simulation high-z variability LRD

2025-07-17 · 2507.13489v1

The $z=7.08$ quasar ULAS J1120+0641 May Never Reach a "Normal" Black Hole to Stellar Mass Ratio

Meredith A. Stone, George H. Rieke, Jianwei Lyu, et al.

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JWST/NIRCam narrow–medium–wide imaging selects [O III] 5007 emitters at z≈7.08 around ULAS J1120+0641 across two 4.4 arcmin² fields, revisiting a site previously deemed underdense. The team finds 22 candidates near the quasar redshift, demonstrating a strong overdensity relative to field expectations, and sums the stellar+gas masses of the host plus neighbors with incompleteness corrections to estimate the merger-fed growth budget. Even if the black hole ceases accretion, the system is projected to retain an elevated MBH/M* ≳2.5% by z=0, far above the local relation. This implies some descendants could hide as quiescent black holes in faint galaxies at low redshift.

luminous quasar high-z overmassive BH reionization

2025-07-16 · 2507.12618v1

Supermassive Stars Match the Spectral Signatures of JWST's Little Red Dots

Devesh Nandal, Abraham Loeb

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First-principles synthetic spectra for non-rotating, metal-free supermassive stars (up to 10^6 M⊙) are used to test whether LRDs are direct photospheres of SMSs. The model’s luminosity at 4050 Å (Lλ ≈ 1.7×10^44 erg s^-1 μm^-1) and NLTE physics reproduce hallmark LRD traits—a V-shaped Balmer break and strong Hβ emission with other Balmer lines in absorption—with wind/macroturbulent broadening matching observed profiles. Quantitative fits to sources at z=7.76 and z=3.55 include an Hβ width match for MoM‑BH*-1 to within 4%, offering a self-consistent alternative to multi-component obscured AGN. A luminosity-dependent visibility window of ~10^4 yr for the brightest systems and 10^5–10^6 yr for objects 1–2 dex fainter implies LRDs may capture brief, pre-collapse stages of SMBH progenitors.

LRD stellar envelope BH seeds v-shaped SED broad Balmer high-z

2025-07-14 · 2507.10674v1

BASS. XLIX. Characterization of highly luminous and obscured AGNs: local X-ray and [NeV]$λ$3426 emission in comparison with the high-redshift Universe

Alessandro Peca, Michael J. Koss, Kyuseok Oh, et al.

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A BAT-selected local analog set of 21 highly luminous, obscured Seyfert 1.9–2 AGN at z<0.6 (log L_X,2–10keV>44.6) is modeled with NuSTAR, XMM-Newton, Suzaku, and Chandra to recover N_H, Γ, intrinsic L_X, covering factor, Fe Kα, and [NeV] λ3426. The sample is highly variable: 82% vary overall (73% in 2–10 keV flux; 33% in line-of-sight N_H), and 6/12 with M_BH estimates fall in the N_H–λ_Edd “forbidden region,” where they also show enhanced N_H variability/outflow signatures—consistent with a clearing phase. [NeV] λ3426 is detected in 85% and, when renormalized to the same [OIII] peak, is significantly stronger than in JWST-selected z=2–9 narrow-line AGN. These local benchmarks calibrate [NeV]-based obscured AGN searches and frame expectations for future high‑z X-ray follow-up.

obscured AGN X-ray low-z variability outflows spectroscopy

2025-07-14 · 2507.10659v1

The Discovery of Little Red Dots in the Local Universe: Signatures of Cool Gas Envelopes

Xiaojing Lin, Xiaohui Fan, Zheng Cai, et al.

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Reports three SDSS-selected local little red dots at z=0.1–0.2 with LBT/MODS and Magellan/FIRE follow-up, showing the same hallmarks as high‑z LRDs: compact morphologies, V‑shaped UV–optical SEDs with declining NIR continua, broad H/He lines, full Balmer+Paschen series, and minimal variability. All display blue‑shifted He I absorption; two show Hα and Na D absorption, and two have abundant narrow [Fe II]; J1025+1402 (The Egg) further exhibits extreme Na D, K I, and Ca II triplet absorption consistent with a cool (~5000 K), metal‑enriched envelope. Line diagnostics point to AGN‑powered, metal‑poor narrow lines with little dust, very high‑density inner regions for the broad lines (or unusual dust), and [Fe II] from dense gas between them; two targets are X‑ray non‑detections and WISE photometry implies only weak dust (T ~10^2–10^3 K). The authors propose a largely thermalized cool‑gas envelope plus an extended, high‑density outflow to unify these features, positioning local LRDs as resolvable analogs of early BH growth.

LRD low-z v-shaped SED broad Balmer stellar envelope outflows

2025-07-12 · 2507.09085v1

Little Red Dots As Late-stage Quasi-stars

Mitchell C. Begelman, Jason Dexter

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Begelman and Dexter propose that JWST “Little Red Dots” are late-stage quasi-stars: black holes embedded in massive envelopes accreting at super‑Eddington rates once the BH exceeds ~10% of the total mass. In this regime the models predict mass‑insensitive global properties, yielding reddish continua with a pronounced Balmer break and Balmer lines broadened primarily by electron scattering rather than Doppler motions. The enormous electron columns naturally quench X‑rays, while BHs grow roughly linearly in time; late-stage objects with MBH ≳10^6 Msun should dominate the quasi-star population. Given lifetimes of only tens of Myr yet high observed LRD number densities, the authors argue most SMBHs likely pass through this quasi‑star/LRD phase.

LRD stellar envelope super-Eddington broad Balmer X-ray

2025-07-11 · 2507.08929v1

Ruling out dominant electron scattering in Little Red Dots' Rosetta Stone using multiple hydrogen lines

Matilde Brazzini, Francesco D'Eugenio, Roberto Maiolino, et al.

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Targets the LRD “Rosetta Stone” GN-28074 (z=2.26) and tests whether broad Balmer/Paβ wings are dominated by wavelength-independent electron scattering. Using JWST/NIRSpec MSA medium-resolution data (∼1.7 hr), the authors compare Hα, Hβ, and Paβ profiles in velocity space and find mismatched wing shapes, contrary to the electron-scattering prediction of identical profiles. Joint fits with Gaussian BLR components plus exponential scattering wings cannot simultaneously match all three lines with physically plausible parameters. Result: dominant electron scattering around the BLR is ruled out for GN-28074, arguing against a universal systematic BH-mass overestimation in LRDs.

LRD broad Balmer spectroscopy

2025-07-11 · 2507.08298v1

Obscured and unobscured X-ray AGNs I: Host galaxy properties

Carlos G. Bornancini, Gabriel A. Oio, Georgina Coldwell

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X-ray selected AGNs from zCOSMOS (0.5<z<0.9) are split by obscuration (NH) and excitation (log[OIII]/Hβ>0.5) to compare host properties. Unobscured sources show a clearer rise of the ionization index O32=[OIII]/[OII] with L2–10 keV than obscured ones, while high-excitation obscured AGNs reach higher X-ray luminosities on average. High-excitation systems also have elevated R23, implying lower gas metallicities reminiscent of z~4–6 galaxies. λsBHAR positively correlates with NH, O32, and R23, linking high specific accretion to harder radiation fields in less enriched environments.

obscured AGN X-ray spectroscopy demographics low-z

2025-07-10 · 2507.07380v1

AT2019cmw: A highly luminous, cooling featureless TDE candidate from the disruption of a high mass star in an early-type galaxy

Jacob L. Wise, Daniel A. Perley, Nikhil Sarin, et al.

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This paper presents dense optical/UV monitoring plus X-ray and radio follow-up of the ZTF nuclear transient AT2019cmw (z=0.519), which reached an extraordinary peak bolometric luminosity of ~10^45.6 erg s^-1. Spectra remained featureless while the continuum cooled steadily from ~30 kK to ~10 kK over the first ~300 days, supporting a classification as a luminous, “featureless” TDE in an early-type host. Deep non-detections in X-ray and radio constrain on-axis jets and any visible inner accretion disk. Light-curve modeling (cooling-envelope, with a reprocessing-outflow alternative) favors the disruption of a tens-of-solar-masses star by an SMBH, hinting at localized nuclear star formation despite the quiescent host.

variability X-ray radio low-z

2025-07-09 · 2507.07190v1

The Balmer Break and Optical Continuum of Little Red Dots from Super-Eddington Accretion

Hanpu Liu, Yan-Fei Jiang, Eliot Quataert, et al.

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Semi-analytic atmospheres plus radiative-transfer show that super-Eddington flows can reproduce LRDs’ red rest-optical continua and Balmer breaks without dust or an external absorbing shell. A cool, low-density photosphere (ρ < 10^{-9} g cm^{-3}) creates a strong opacity jump at the Balmer limit, yielding a break even at T_eff ≈ 5000 K. Thin disks match the color only with a fine-tuned inner truncation giving T_eff ~ 5000 K, whereas a geometrically thick, quasi-spherical flow naturally produces T_eff ≈ 4000–6000 K largely insensitive to Ṁ (Hayashi-line-like). The resulting continua agree with current LRD spectra and motivate predictions for future super-Eddington simulations.

LRD super-Eddington broad Balmer

2025-07-09 · 2507.07171v1

Little Red Dots from Small-Scale Primordial Black Hole Clustering

Borui Zhang, Wei-Xiang Feng, Haipeng An

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Proposes LRD heavy seeds as runaway-merger products of primordial black holes initially clustered by small-scale long–short mode coupling. Monte Carlo solutions of the Smoluchowski equation yield merger timescales sufficient to assemble 10^5–10^8 Msun SMBHs within the first Gyr while evading CMB distortion limits. The scenario predicts a distinctive stochastic gravitational-wave background and high birth spins inherited from cluster tidal torques. Interpretation assumes LRDs host obscured AGN.

LRD BH seeds simulation high-z obscured AGN

2025-07-09 · 2507.07160v1

Empirical Calibration of Na I D and Other Absorption Lines as Tracers of High-Redshift Neutral Outflows

Lorenzo Moretti, Sirio Belli, Gwen C. Rudie, et al.

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A cleverly aligned system lets the authors directly calibrate neutral outflow tracers: a massive quiescent galaxy J1439B at z=2.4189 sits 38 kpc from the sightline to QSO J1439+1117, where its outflow appears as a sub-DLA enabling an H I column density measurement. New Magellan/FIRE spectra detect Na I D, Mg II, Mg I, and Fe II in the quasar spectrum and tie their column densities to N(H I), delivering empirical conversions usable for JWST-selected neutral outflows. The Na I calibration is just ~30% below the Milky Way relation commonly assumed at high z, supporting large neutral mass outflow estimates relevant to quenching. In contrast, applying the local Mg II calibration would err by an order of magnitude, likely due to dust depletion variations.

outflows high-z spectroscopy

2025-07-08 · 2507.06339v1

High-Resolution Optical IFU Spectroscopy of the Complex Galaxy Merger II Zw 096

C. Riesco, E. Treister, G. Venturi, et al.

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Using VLT/MUSE in both NFM and WFM, this work resolves II Zw 096 into three or more interacting galaxies and maps ionized-gas morphology, kinematics, and excitation across the system. Velocity fields show rotation with strong deviations and widespread shocks, consistent with a collapsing small-group scenario and intense star formation. A compact D1 knot (≤175 pc) that contributes 40–70% of the IR luminosity shows strong multiwavelength evidence for a heavily obscured AGN. Multi-component fits to Hα+[N II] and continuum mapping clarify the internal structure and current merger stage.

obscured AGN low-z spectroscopy

2025-07-07 · 2507.05381v1

Escape fractions from unattenuated Ly$α$ emitters around luminous $z>6$ quasars

Minghao Yue, Anna-Christina Eilers, Jorryt Matthee, et al.

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JWST/NIRSpec-MSA spectroscopy in the J0100+2802 and J1148+5251 fields measures Lyα for 50 galaxies at 6<z<7 (median M_UV=−19.97), including 15 within Δv<2500 km s−1 of the quasars. Galaxies in the quasar proximity zones show clear blue-side Lyα flux and higher equivalent widths than similar-redshift field galaxies, implying little to no evolution in the LAE fraction from z≈6.4 to z≈5. Using the low IGM opacity near the quasars, the authors infer an average Lyα escape fraction of 0.14±0.04 at ⟨z⟩≈6.4. This supports reionization scenarios with low LyC escape in luminous galaxies (f_esc^LyC≲0.1), suggesting bright galaxies contribute modestly to the ionizing budget.

luminous quasar high-z reionization spectroscopy

2025-07-07 · 2507.05354v1

JWST MIRI/MRS observations of hot molecular gas in an AGN host galaxy at Cosmic Noon

D. Kakkad, V. Mainieri, Takumi S. Tanaka, et al.

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Using JWST/MIRI MRS, the authors detect ro‑vibrational H2 in the z≈2.2 X‑ray AGN cid_346, measuring 1‑0 S(1) (and S(0)) and inferring a hot H2 mass of ≈8×10^5 M⊙. They map hot molecular emission and CO(3‑2) to >10 kpc, and NIRCam imaging reveals two nearby satellites at ≈3.3 and 7.4 kpc, pointing to an interacting environment. The hot phase is 10^5–10^6× less massive than the cold reservoir, but the authors argue H2 ro‑vibrational lines effectively trace locally heated/shocked gas where CO may be faint. Ionized gas shows [O III] extension and a blue wing toward the SE, consistent with outflow activity shaping the multiphase medium.

JWST AGN X-ray outflows ALMA/mm spectroscopy

2025-07-05 · 2507.04011v1

Investigating the Growth of Little Red Dot Descendants at z<4 with the JWST

Jean-Baptiste Billand, David Elbaz, Fabrizio Gentile, et al.

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Using CEERS imaging, the authors select z<4 “post-LRD” candidates by requiring a compact, very red core plus a blue star-forming envelope, then model inner/outskirts with stellar-only SED fits and single-Sérsic morphologies. The sample shows LRD-like cores with M* ~1e10 Msun, Σ* ~1e11 Msun kpc^-2, and compact sizes about 1 kpc below the size–mass relation, while adding an extended young component; their number density at z=3±0.5 (~10^-4.15 Mpc^-3) matches that of LRDs at 5<z<7, indicating an evolutionary link. Outskirts mass fraction and size increase toward lower redshift (≈250 pc at z=5 to ≈600 pc at z=3), as the core stays red/compact and the hallmark V-shaped SED fades, consistent with growth by cold accretion. This offers an explanation for the apparent decline of LRD counts at lower z, with the caveat that it assumes a single evolutionary path and stellar-only modeling.

LRD compact red v-shaped SED demographics

2025-07-04 · 2507.03230v1

Little Red Dots from Ultra-Strongly Self-Interacting Dark Matter

M. Grant Roberts, Lila Braff, Aarna Garg, et al.

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Proposes ultra-strongly self-interacting dark matter (uSIDM) as a route to rapid gravothermal core collapse in early halos, yielding massive black hole seeds (≳10^5 Msun) by z≳5 that can power Little Red Dots. Builds a semi-analytic framework tracking halo evolution, collapse redshifts z_coll, and the SMBH mass function with stochastic growth via a log-normal Eddington ratio and finite duty cycle. Finds that uSIDM reproduces LRD abundance, compactness, and characteristic BH masses, with a z≈5 SMBH mass function matching LRD data and SIDM merger-tree results, especially at m_BH≳10^7 Msun. Implies LRDs could be incisive tracers of non-gravitational dark sector physics and that early SMBH assembly may depart from CDM expectations.

LRD BH seeds simulation high-z obscured AGN

2025-07-02 · 2507.02058v1

On the rapid growth of SMBHs in high-z galaxies: the aftermath of Population III.1 stars

Mahsa Sanati, Julien Devriendt, SergioMartin-Alvarez, et al.

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High-resolution zoom-in simulations with Pop III.1 progenitor preheating follow 10^5 Msun seeds through a suite of AGN feedback modes (Eddington-limited thermal; non-Eddington thermal, kinetic, and radiative). Across all models the seeds grow efficiently to ~10^7 Msun by z≈8, with growth largely unimpeded by feedback; the radiative case shows brief super-Eddington bursts that launch fast, mass-loaded outflows (>2500 km s^-1) to ~50 kpc and slightly suppress stellar mass. The simulated systems resemble JWST moderate-luminosity quasars, yielding overmassive BHs, dynamical masses ~10^9.5 Msun, and short-lived high Eddington fractions. This argues that early AGN feedback coexists with rapid SMBH build-up while exporting energy and metals deep into the CGM/IGM.

simulation BH seeds high-z super-Eddington outflows reionization

2025-07-02 · 2507.01952v1

The Lockman-SpReSO project. Spectroscopic analysis of Type 1 AGN

Castalia Alenka Negrete, Hector J. Ibarra-Medel, Erika Benitez, et al.

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First optical–UV spectral analysis of 30 faint (mB=19.6–21.8) Type 1 AGN from the Lockman‑SpReSO survey spanning 0.33<z<4.97, using Quasar Main Sequence–based deblending of the principal UV/optical broad‑line regions. Derived ranges are 44.85<log Lbol<47.87, 7.59<log MBH<9.80, and −1.70<log REdd<0.56; 18 high‑z sources fall in Population B, with a few A/B1/B1+ at low z, and none are extreme accretors. CIV c(1/2) indicates modest winds (941 to −1587 km s−1) and the Baldwin effect shows a slope of −0.23±0.03, consistent with comparable samples. Twelve spectra overlap with SDSS DR17 and show no variability, providing a stable benchmark for FIR/X‑ray–selected quasar demographics.

broad-line AGN spectroscopy X-ray QSO

2025-07-02 · 2507.01355v1

The birth of young radio jets in changing-look AGN: a population study

Sufia Birmingham, Charlotte Ward, Kristina Nyland, et al.

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A population study of 474 spectroscopically confirmed changing-look AGN tracks their radio behavior with ASKAP VAST and VLASS to test whether optical state changes spawn newborn radio jets. Across 20 VAST-detected CLAGN, the authors see no Mrk 590– or 1ES 1927+654–like radio fading within ~10 years of the changing-look epoch, and for six low‑z, high‑mass objects they rule out a Mrk 590–like flare. Population-wide, CLAGN show higher VAST/VLASS detection and 1 GHz variability rates but lower radio‑loud fractions than a control AGN sample, and VLA SEDs plus Magellan spectra do not support a link to VLASS sources that transitioned from radio‑quiet to radio‑loud. The results imply enhanced accretion episodes often stir compact radio activity but rarely mirror the decadal jet turn‑on channel seen in RL-transition systems, constraining when and how young radio jets are born.

radio variability broad Balmer broad-line AGN spectroscopy

2025-06-30 · 2507.00129v1

Lya2pcf: an efficient pipeline to estimate two- and three-point correlation functions of the Lyman-$α$ forest

Josue De-Santiago, Rafael Gutiérrez-Balboa, Gustavo Niz, et al.

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Lya2pcf introduces a GPU-optimized pipeline for three-dimensional two- and three-point correlation measurements of the Lyman-α forest, including the standard distortion matrix and covariance estimation. Applied to SDSS DR16 and a DESI Year-5 mock, it achieves substantial computational speedups over PICCA, most notably for the 2PCF and its distortion matrix. The code delivers the first large-sample anisotropic 3PCF measurement for all triangle configurations out to 80 Mpc/h, with signal-to-noise above one for many bins. This demonstrates that higher-order Lyα statistics are ready for inclusion in Stage IV cosmological inference.

QSO high-z

2025-06-30 · 2506.24128v1

Beneath the Surface: >85% of z>5.9 QSOs in Massive Host Galaxies are UV-Faint

R. J. Bouwens, E. Banados, R. Decarli, et al.

arXiv abstract

Ranks 190 z>5.9 QSOs by host mass using ALMA [CII] luminosity as a gas/host-mass proxy, boosted by CISTERN cycle-10 coverage of UV-faint sources, and defines “massive hosts” at L[CII]>1.8x10^9 Lsun. From the resulting UV-luminosity distribution and [CII] luminosity functions, only ~3% of massive-host QSOs are UV-bright (Muv<-26) while >85% are UV-faint (Muv>-24.5). At Muv≈-23 the median extrapolated log10(MBH/Msun)=8.1±0.4, implying UV-bright QSOs host SMBHs ~15x more massive than typical massive-host systems at z~6. This points to most SMBH growth in massive galaxies being missed by UV-bright QSO selections; spectroscopy is still needed to confirm the MBH interpretation.

QSO high-z ALMA/mm demographics

2025-06-27 · 2506.22416v1

Cosmology from Planck CMB Lensing and DESI DR1 Quasar Tomography

R. de Belsunce, A. Krolewski, S. Chiarenza, et al.

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Cross-correlating Planck PR4 (NPIPE) CMB lensing maps with 1.22M DESI DR1 spectroscopic quasars over 7,200 deg², the authors perform three-bin quasar–lensing tomography at z≈1.44, 2.27, and 2.75. A joint fit to quasar auto- and quasar×lensing power spectra, with an Ωm prior from DESI DR1 BAO, yields σ8=0.929(+0.059/−0.074) and S8=0.922(+0.059/−0.073), with detections of the cross and auto signals at S/N=21.7 and 27.2, respectively. The inferred growth amplitude is ≈1.5σ higher than ΛCDM predictions from Planck primary CMB, providing a high‑z, matter‑era check on structure formation. Combining with the Planck PR4 and ACT DR6 lensing auto-spectra, they obtain a sound-horizon-free H0=69.1(+2.2/−2.6) km s⁻¹ Mpc⁻¹ via sensitivity to the matter–radiation equality scale.

QSO

2025-06-26 · 2506.21658v1

Euclid and Roman with JWST Could Reveal Quasars at up to $z \sim$ 15

Muhammad A. Latif, Daniel J. Whalen

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Normalizing a thin-disk+corona spectrum to a J1120-like quasar grown in the Smidt et al. (2018) simulation, the authors predict continuum NIR AB magnitudes from z = 6–15 in Euclid, Roman, and JWST bands. They find Euclid can photometrically select such SMBHs to z ≈ 11 (Wide), z ≈ 13 (Deep), and z ≈ 14 (Ultra Deep), while Roman reaches z ≈ 14.5 in Y/J/H and its F213 band extends selection to z ≈ 18. JWST’s sensitivity enables spectroscopic redshift confirmation to z ≈ 15 and even detects ≳10^6 M⊙ BHs accreting near Eddington. This Euclid/Roman discovery plus JWST follow-up pipeline could inventory early SMBHs (including analogs of UHZ1 and GHZ9) and discriminate their growth channels beyond z > 10.

QSO luminous quasar high-z BH seeds simulation

2025-06-26 · 2506.20896v1

Blowing star formation away in AGN Hosts (BAH) -- IV: Feeding and feedback in 3C 293 observed with JWST NIRSpec

Maitê S. Z. de Mellos, Rogemar A. Riffel, Gabriel L. Souza-Oliveira, et al.

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JWST/NIRSpec IFU mapping of 3C 293’s inner ~2 kpc separates the gas into a rotating disk (σ ~100 km s−1), a blueshifted broad outflow (σ ~250 km s−1), and a very broad ionized outflow (σ ~640 km s−1). H2 2.12 μm, [Fe II] 1.64 μm, and Paα trace multiphase flows through heavy dust (A_V up to ~35), with H2 inflow along dust lanes at Ṁ_in ~4×10−4 M⊙ yr−1. Peak outflow rates reach 0.08±0.02 M⊙ yr−1 (hot H2) and 6.5±1.7 M⊙ yr−1 (ionized), and the jet-driven outflow carries ≈5% of the radio-jet power—sufficient to suppress star formation. The stellar field is a rotating disk whose kinematic center is offset by ~0.5 arcsec from the NIR continuum peak, consistent with a disturbed, post-merger nucleus.

JWST AGN outflows obscured AGN radio spectroscopy low-z

2025-06-25 · 2506.20634v1

The VLA Frontier Fields Survey: A 6GHz High-resolution Radio Survey of Abell 2744

Esteban A. Orozco, Eric F. Jiménez-Andrade, Eric J. Murphy, et al.

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Ultra-deep 6 GHz VLA imaging of Abell 2744 (z=0.307) reaches ≈1 µJy beam−1 at 0.82″, yielding 93 detections, 46 with optical/NIR counterparts spanning z=0.15–3.55 (median z=0.93; median M⋆≈2.3×10^10 M⊙). Radio-inferred SFRs exceed UV–NIR estimates by roughly an order of magnitude, pointing to heavily obscured star formation missed by rest-UV/optical tracers. No individual radio counterparts are found for the z≈6 Little Red Dots; stacking sets a stringent 3σ limit of L6 GHz < 4.1×10^39 erg s−1. The survey also assembles 22 μ≳2 lensed systems, enabling sub-arcsecond probes of main-sequence galaxies at z∼1–2.

radio LRD high-z

2025-06-24 · 2506.19589v1

Black Holes in the Red-sequence Elliptical Galaxies at Redshifts $\sim 0.7-2.5$: Not Dark Energy Source but Remanants of Little Red Dots

Lei Lei, Ze-Fan Wang, Yi-Ying Wang, et al.

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Uses a JWST-selected set of very high‑z AGNs in red‑sequence ellipticals to test black‑hole cosmological coupling via the MBH–M* fundamental plane. The sample aligns with the local relation and yields a posterior on the coupling strength that rejects the “BHs as dark energy” scenario at >10σ, contradicting earlier claims of strong coupling. Simulations and data further show that low‑accretion Little Red Dots can evolve into the z≈0.7–2.5 red‑sequence ellipticals hosting relatively low‑mass BHs, eliminating the need for cosmological coupling. This links JWST LRD demographics to later ETG BH masses while removing BHs as a viable dark‑energy source.

LRD JWST AGN demographics high-z simulation

2025-06-23 · 2506.18993v1

Direct Collapse Pre-supermassive Black Hole Objects as Ly$α$ Emitters

Yang Luo, Isaac Shlosman

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The authors post-process a direct-collapse pre-SMBH inflow–outflow geometry with a Monte Carlo Lyα transfer that includes photon destruction and two-photon emission, finding that a radiatively driven shell plus a biconical polar funnel enables substantial escape. The emergent Lyα is highly anisotropic and line shapes depend on funnel opening angle and outer column density, yielding strong asymmetry with an extended red tail and measurable peak shifts/cuspiness. The escaping fraction can exceed 95% for a z=10 pre-SMBH object, with only the red wing detectable. Such sources are in principle reachable with NIRSpec/MOS in ~10^4 s at 10σ, and their line profiles provide a diagnostic to separate them from high-z galaxies and quasars.

BH seeds high-z outflows simulation

2025-06-22 · 2506.18112v1

Peering into the heart of darkness with VLBA : Radio Quiet AGN in the JWST North Ecliptic Pole Time-Domain Field

Payaswini Saikia, Ramon Wrzosek, Joseph Gelfand, et al.

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A 4.8 GHz VLBA snapshot survey of the JWST NEP Time-Domain Field targeted 106 VLA-selected radio sources and detected 12 compact emitters at 3.3 μJy rms and 4 mas resolution. The detections show pc-scale (<40 pc) structure with high VLBA/VLA flux ratios and Tb >10^5 K, and flatter spectra (α > −0.5) correlate with higher compactness—consistent with synchrotron from AGN coronae or low-power jets. Star formation contributes <50% of the VLBA flux in most cases, with several cores essentially AGN-driven; eight have JWST/NIRCam counterparts in predominantly early-type, bulge-dominated hosts, and WISE colors separate compact AGN/intermediate disks from extended SF galaxies. Comparing SCUBA-2 850 μm SFRs to new JWST-based estimates reveals discrepancies, underscoring JWST’s leverage to disentangle black-hole–driven radio cores from host-galaxy star formation.

radio

2025-06-21 · 2506.17641v1

Dark Bondi Accretion Aided by Baryons and the Origin of JWST Little Red Dots

Wei-Xiang Feng, Hai-Bo Yu, Yi-Ming Zhong

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Proposes an SIDM-driven seeding pathway for JWST little red dots in which gravothermal core collapse, sped up by central baryons, makes a tiny seed that grows first via baryonic Eddington accretion and then rapidly through dark Bondi inflow of SIDM. Demonstrates that black holes can reach ~10^7 Msun within ~500 Myr after the formation of ~10^9 Msun halos at z≈4–11, with most of the final mass supplied by dark matter rather than gas. Fluid simulations with and without a Plummer-fit baryonic potential show that baryons substantially shorten the collapse timescale and establish conditions for efficient dark-sector Bondi growth. The framework naturally explains the overmassive BH-to-stellar ratios in LRDs and links them to SIDM cross sections consistent with galaxy-scale structure data.

LRD BH seeds overmassive BH simulation high-z

2025-06-19 · 2506.16145v1

Measurements of the z=4-10 X-ray Luminosity Function: the high space density of moderate-luminosity, obscured AGN

C. L. Barlow-Hall, J. Aird

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The authors measure the z=4–10 X-ray luminosity function at intermediate luminosities by combining UltraVISTA-selected COSMOS2020 galaxies with Chandra COSMOS imaging, using both blind detections and forced X-ray extraction (21 blind + 11 extracted). They find AGN space densities that exceed low‑z XLF extrapolations: consistent at z=4–5, but ~10× higher at z=5–7 and potentially up to ~220× at z=7–10. The sample indicates a dominantly obscured early AGN population with an obscured fraction of 0.982(+0.007/−0.008), and correcting for this further boosts the inferred densities. These results bridge bright-end quasar counts and JWST detections of faint AGN, implying a larger fraction of early galaxies hosted rapidly growing SMBHs than previously thought.

X-ray obscured AGN demographics high-z

2025-06-17 · 2506.14896v1

Overmassive Black holes live in compact galaxies in the early Universe

Yuxuan Wu, Tao Wang, Daizhong Liu, et al.

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Uniform ALMA [CII] 158 μm size measurements for a curated sample of 22 z≈6 quasars show their hosts are systematically compact, with a median Re≈1.58 kpc versus 2.26 kpc for main-sequence SFGs measured in the same line. The hosts also have elevated MBH/M* and, for the most compact systems, reduced cold-gas content and sizes akin to massive quiescent galaxies at z≈4–5. Simple evolution over a gas-depletion timescale moves them toward the local MBH–M* relation as stellar mass builds. The compact, gas-poor subset likely marks the late stage of rapid BH growth and are prime progenitors of the first quiescent galaxies.

luminous quasar QSO overmassive BH ALMA/mm high-z demographics

2025-06-17 · 2506.14870v1

JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at z = 5

Francesco D'Eugenio, Ignas Juodžbalis, Xihan Ji, et al.

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Reports a broad-line Little Red Dot at z=5.077 (JADES-GS+033223.41-275404.5/159717) with NIRSpec MSA+IFU, revealing multi-component Hα including two broad Gaussians. A virial black hole mass of log(MBH/M⊙)=7.65 and a narrow [O III] λ5007-based dynamical mass of log(Mdyn/M⊙)=9.1 imply a BH overmassive relative to its host. The source sits in a 7-kpc pool of ionized gas with three neighbors (a satellite, a possible satellite/gas cloud, and a tentatively detected spatially detached outflow). A deep rest-frame Hα absorber (deeper than the continuum; v=-13 km s−1, σ=120 km s−1) appears in G395H but not G395M, with tentative EW variability over two rest-frame months (2.6σ), underscoring resolution- and time-dependent incidence of absorbers in LRDs.

LRD broad Balmer overmassive BH spectroscopy outflows variability

2025-06-16 · 2506.13945v1

Euclid: The potential of slitless infrared spectroscopy: A z=5.4 quasar and new ultracool dwarfs

E. Bañados, V. Le Brun, S. Belladitta, et al.

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Euclid NISP slitless spectra demonstrate blind, space-based identification of both high‑z quasars and their chief photometric contaminants, ultracool dwarfs. The team reports a bright z=5.404 quasar, EUCL J181530.01+652054.0, flagged by strong broad CIII] and MgII in RGE (1206–1892 nm) with CIV/CIII] also in BGE (926–1366 nm) and confirmed by LBT optical data. It is a high‑excitation BAL quasar detected by LOFAR at 144 MHz (L144≈4×10^25 W/Hz), with Lbol≈3×10^12 Lsun and MBH≈3.4×10^9 Msun—an unexpectedly luminous find within only ~20 deg2. Cross-correlation of NISP spectra likewise yields new ultracool dwarfs (e.g., T3 EUCL J002516.31+491618.5; M6 EUCL J174429.80+672728.1), underscoring RGE’s ability to uncover bright quasars at z~5.5 and z>7 where photometric selection struggles.

luminous quasar QSO high-z spectroscopy radio

2025-06-16 · 2506.13852v1

Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies

William McClymont, Sandro Tacchella, Xihan Ji, et al.

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Using THESAN-ZOOM zoom-ins, the authors assign black-hole masses by assuming the M_BH–M_dyn relation is fundamental and then compare to JWST-selected AGN and JADES host properties at z>3. This simple prescription reproduces the observed distribution of “overmassive” black holes relative to local M_BH–M_* relations, with M_BH/M_* declining from ~0.1 at M_*≈10^6 Msun to ~0.01 at M_*≈10^10.5 Msun. The trend naturally follows the high dark-matter and gas fractions of low-mass galaxies—f_DM and f_gas decrease with M_* and show little evolution to z≈3—yielding small M_*/M_dyn and thus large apparent BH offsets; Prospector-inferred f_gas for 48,022 JADES galaxies (3<z<9) agrees with the simulations. A caveat is that BH growth and feedback are not modeled live, so full BH–galaxy co-evolution is not captured.

overmassive BH simulation high-z