654 indexed papers · 430 research notes

Research archive

2025-04-14 · 2504.10581v1

Massive Black Hole Seed Formation in Strong X-ray Environments at High Redshift

Kazutaka Kimura, Kohei Inayoshi, Kazuyuki Omukai

Semi-analytic merger-tree modeling with observationally calibrated X-ray irradiation (guided by HERA’s 21 cm non-detections) shows that strong X-ray backgrounds boost H2 formation, steering most overdense halos off the classic direct-collapse path. Including baryonic streaming motion preserves an atomic-cooling route in a subset of cases, still yielding massive seeds. The model predicts seeds with M_BH ≳ 10^4 Msun by z ≃ 15 and an abundance ≈10^-4 Mpc^-3, sufficient to account for SMBHs verified by JWST spectroscopy at 3<z<6. X-ray ionization prevents formation of extremely overmassive BHs comparable to their hosts, while establishing BH-to-stellar mass ratios ≃0.01–0.1 at seeding.

BH seeds simulation high-z reionization X-ray

2025-04-14 · 2504.10573v1

High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties

L. Ighina, A. Caccianiga, A. Moretti, et al.

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Cross-matching RACS-low (888 MHz) with DES and Pan-STARRS, the authors selected 45 bright radio/optical-dropout candidates (S_888MHz>1 mJy, z_mag<21.3) over 16,000 deg^2 and spectroscopically confirmed 24 new quasars, 13 at 4.5<z<5 and 11 at z>5. Including comparable literature objects, the z>5 RACS set reaches 33 powerful radio quasars with νL_1.4GHz≈10^41.5–10^44.4 erg s^-1 and is ~90% complete at the stated flux and magnitude limits. Multi-band radio plus new X-ray coverage (Chandra, uGMRT, MeerKAT, ATCA) reveal predominantly flat spectra (22 with −0.5<α_r<0.5) and X-ray luminosities exceeding coronal expectations. The combined evidence points to many blazar-like, jet-aligned systems, delivering a bright, homogeneous anchor sample for population studies of early SMBH growth.

QSO radio high-z spectroscopy X-ray luminous quasar

2025-04-10 · 2504.08039v1

Bridging Quasars and Little Red Dots: Insights into Broad-Line AGNs at $z=5-8$ from the First JWST COSMOS-3D Dataset

Xiaojing Lin, Xiaohui Fan, Feige Wang, et al.

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From the first 10% (≈127 arcmin²) of COSMOS-3D NIRCam grism WFSS, the team identifies 13 broad-line AGNs at z=5–8 via Hα/Hβ, including a z=7.646 Hβ source at F444W=23.6, among the brightest z>7.5 BL AGN. Most (10/13) show reddened optical continua with β_opt>0, while three have quasar-like SEDs that are less blue than unobscured QSOs; two objects have 7.7–18 μm MIRI points constraining rest-NIR, and no significant F115W UV variability is seen over Δt_rest≈60 days. The Hα luminosity functions at z≈5–6 hint at evolution relative to z≈4–5. An Hβ LF at z∼8 implies number densities ~100× above UV-selected quasar LFs, pointing to a populous bridge between UV-bright quasars and LRD-like BL AGN.

JWST AGN broad-line AGN high-z spectroscopy demographics broad Balmer

2025-04-09 · 2504.07196v1

Joint Survey Processing. III. Compact Oddballs in the COSMOS Field -- Little Red Dots and Transients

Yu-Heng Lin, Andreas L. Faisst, Ranga-Ram Chary, et al.

arXiv abstract

HST/ACS G800L grism follow-up of seven compact, 8000 Å–dropout COSMOS point sources tests the faint z≈6 AGN candidate pool. Only one object (772319) is detected in multiple bands with a V-shaped, LRD-like SED and is ~3 mag brighter than typical JWST LRDs; no Lyα or other common lines appear in the grism. From the non-detections they place an upper limit on the AGN UV luminosity function of Φ=1.1×10^-7 Mpc^-3 mag^-1 at M_UV=−21. The remaining sources show F814W vs Subaru i+z flux mismatches not attributable to emission lines, implying long-lived transients with observed-frame decay timescales ≤6 years and highlighting transient contamination of faint-AGN searches.

LRD v-shaped SED high-z spectroscopy demographics

2025-04-04 · 2504.03848v1

Large-scale surveys of the quasar proximity effect

Rupert A. C. Croft, Patrick Shaw, Ann-Marsha Alexis, et al.

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Develops a CDM halo-model framework for the quasar proximity effect that explicitly includes overdense quasar environments and fits individual Lyα spectra for the radiation-equality radius r_eq and large-scale quasar bias b_q, validated on the ASTRID hydrodynamic simulation. Demonstrates that r_eq can be recovered without bias from a single spectrum with 25–50% statistical uncertainty. Scaling to DESI-sized samples enables precise measurements of the UV background intensity and its redshift evolution. Using the Uchuu simulation, shows that proximity-effect measurements could map spatial UV radiation fluctuations and measure their power spectrum on 100–1000 h−1 Mpc scales, making the radiation field a cosmological observable alongside density.

QSO reionization simulation high-z spectroscopy

2025-04-04 · 2504.03551v1

JADES: comprehensive census of broad-line AGN from Reionization to Cosmic Noon revealed by JWST

Ignas Juodžbalis, Roberto Maiolino, William M. Baker, et al.

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Using JADES spectroscopy, the authors assemble a uniform census of 34 broad-line (Type 1) AGN spanning 1.5<z<9 with virial black-hole masses of 10^6–10^9 M⊙ and bolometric luminosities down to 10^43 erg s^-1, generally at sub-Eddington rates (<0.5 L_Edd). These AGN are typically in low-mass (M⋆≈10^8 M⊙) hosts whose black holes are overmassive relative to the local M_BH–M⋆ relation yet consistent with the local M_BH–σ⋆ relation, enabling a view of how these scalings emerge across cosmic time. The team shows that standard narrow-line diagnostics would miss many counterparts—especially at low metallicity or with attenuated/soft ionizing continua—complicating Type 2 selection. They also find strong cosmic-variance sensitivity in the UV luminosity function and rule out electron/Balmer scattering as the origin of broad Balmer components, arguing BH masses are not severely overestimated.

broad-line AGN JWST AGN broad Balmer demographics overmassive BH high-z

2025-04-03 · 2504.02683v1

Probing patchy reionisation with JWST: IGM opacity constraints from the Lyman-$α$ forest of galaxies in legacy extragalactic fields

Romain A. Meyer, Guido Roberts-Borsani, Pascal Oesch, et al.

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Using public JWST/NIRSpec PRISM spectra of z≈4–7 galaxies, the authors detect the Gunn–Peterson trough in stacked galaxy spectra and derive the first galaxy-based IGM Lyα opacity measurements, plus intrinsic Lyβ opacity at 5<z<6. The galaxy-based opacities agree with state-of-the-art quasar Lyman-α forest constraints and will sharpen as JWST samples grow. In GOODS-South, a z=5.8–5.9 overdensity of galaxies and Lyα emitters coincides with an anomalously low Lyα IGM opacity, directly linking local large-scale structure to an over-ionised IGM patch. The required photo-ionisation rate can be produced by galaxies down to M_UV≲−10 if log10⟨ξion fesc⟩≈25 (e.g., log10 ξion=25.4 with fesc=0.4).

reionization spectroscopy high-z

2025-04-02 · 2504.01852v1

Deciphering the Nature of Virgil: An Obscured AGN Lurking Within an Apparently Normal Lyman-α Emitter During Cosmic Reionization

Pierluigi Rinaldi, Pablo G. Pérez-González, George H. Rieke, et al.

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JWST/MIRI imaging plus deep NIRSpec/PRISM place the LAE “Virgil” at z=6.6379 and reveal Little Red Dot–like photometry with an extreme color F444W−F1500W=2.84±0.04, and a strongly rising mid-IR SED. SED fits across multiple codes favor an obscured AGN whose IR slope and UV excess resemble blue-excess HotDOGs. The host shows subsolar metallicity, low–moderate dust, and high ionization/electron temperature; UV and Hα SFRs suggest Virgil is entering or fading a burst. High‑z line‑ratio diagnostics (e.g., O32–R23, Ne3O2) nominally flag AGN, though this is ambiguous after accounting for redshift evolution; a tentative broad Hα improves residuals only marginally, while the new 15 μm data strengthen the AGN case and highlight MIRI’s leverage on early black‑hole growth.

LRD obscured AGN JWST AGN high-z spectroscopy reionization

2025-03-31 · 2504.00172v1

Evidence for evolutionary pathway-dependent black hole scaling relations

Jonathan H. Cohn, Emmanuel Durodola, Quinn O. Casey, et al.

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This letter benchmarks secure dynamical black hole masses in a z~2 lensed quiescent galaxy and six local red‑nugget relics against recent 4<z<11 AGN, quasar, and Little Red Dot samples on the M_BH-M_star and M_BH-sigma_* planes. The relics and the z~2 quiescent system land on both the local bulge M_BH-M_star relation and the 4<z<7 Pacucci et al. relation, while luminous QSOs and broad-line AGN follow Pacucci et al. more closely and LRDs scatter across all three; on M_BH-sigma_* most sources sit above the local median except the lensed system. The authors argue the bulge relation was already in place at high z and that differing evolutionary pathways—compact-core assembly by z~2 followed by dry-merger stellar-mass growth versus ongoing BH and star formation in AGN—govern positions on scaling planes. Given large systematics in single‑epoch high‑z masses, they emphasize dynamical detections in relics and strongly lensed galaxies as a complementary, less biased probe of early scaling relations.

LRD overmassive BH demographics high-z low-z

2025-03-31 · 2503.23710v1

Formation of the Little Red Dots from the Core-collapse of Self-interacting Dark Matter Halos

Fangzhou Jiang, Zixiang Jiang, Haonan Zheng, et al.

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Using Monte Carlo merger trees, the authors model black hole seeding via gravothermal core-collapse in self-interacting dark matter halos and their subsequent growth at early times. Collapse occurs in rare, high-concentration halos at a characteristic mass scale set by the velocity-dependent cross section, naturally producing seeds early enough to explain compact, galaxy-poor little red dots. With simple growth assumptions and a 100% duty cycle, the model reproduces the observed LRD black hole mass function for σ0m ~ 30 cm^2 g^-1 and ω ~ 80 km s^-1, consistent with independent local constraints. If σ0m or ω are higher, the resulting overproduction at one end of the mass function can be mitigated by a reduced duty cycle or lower Eddington ratios, suggesting high‑z BH demographics as a probe of SIDM physics.

LRD BH seeds simulation demographics high-z

2025-03-25 · 2503.19915v1

A New Hope for Obscured AGN: The PRIMA-NewAthena Alliance

Luigi Barchiesi, F. J. Carrera, C. Vignali, et al.

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Simulation-driven forecast of a full obscured-AGN census using the far-IR PRIMA plus X-ray NewAthena, built on X-ray background synthesis models and Deep/Wide survey layouts. PRIMA dominates for heavily obscured and Compton-thick accretors, yielding an expected 7500 CT-AGN detections per square degree, while NewAthena preferentially recovers the most luminous, unobscured, and moderately obscured sources. Together they out-perform past IR efforts—PRIMA alone delivers ~60× Herschel source counts over the same area—and enable a precise BHAD history to z≈8. The alliance is pitched as the cleanest route to reveal the true CT-AGN contribution to cosmic BH growth.

obscured AGN simulation X-ray demographics high-z

2025-03-20 · 2503.16600v1

A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$

Anna de Graaff, Hans-Walter Rix, Rohan P. Naidu, et al.

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JWST/NIRSpec+NIRCam+MIRI data on The Cliff, a luminous Little Red Dot at z=3.55, reveal an extreme Balmer break—about twice stronger than any previously seen at high-z—alongside broad Hα (FWHM∼1500 km s⁻¹) and He I emission but no significant metal lines. Stellar-population solutions (even with steep dust or IMF tweaks) fail, and their formal M*∼10^10.5 M⊙ with re∼40 pc would imply implausibly high stellar-collision rates. The spectra and continuum are instead best matched by a “black hole star” configuration: a powerful central ionizing source embedded in dense, absorbing gas that imprints the Balmer edge and Hα absorption while favoring an intrinsically red continuum over heavy dust. This makes The Cliff compelling evidence that at least some LRDs are not ultra-dense galaxies but compact, accretion-powered nuclei shrouded by dense gas.

LRD broad Balmer stellar envelope super-Eddington spectroscopy high-z

2025-03-20 · 2503.16596v1

A "Black Hole Star" Reveals the Remarkable Gas-Enshrouded Hearts of the Little Red Dots

Rohan P. Naidu, Jorryt Matthee, Harley Katz, et al.

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JWST/NIRSpec spectroscopy of the point-like source MoM-BH*-1, observed ~660 Myr after the Big Bang, reveals an enormous Balmer break, broad multi-peaked Hβ, and deep Balmer-line absorption. The authors model it as a “black hole star”: a supermassive black hole enshrouded by extremely dense, turbulent, dust-free gas whose atmosphere imprints the break and absorption while dominating the observed light; narrow [OIII] and residual UV are attributed to a faint host. The data are well matched by a simple Cloudy setup that reproduces the break strength, Balmer EWs, UV faintness, and MIRI continuum, with line ratios consistent with high densities that can collisionally suppress [OIII] and a hint of variability reinforcing the SMBH interpretation. They further argue that Little Red Dots can be explained as BH*s embedded in comparably bright hosts, implying current LRD black hole masses—derived with steep dust corrections and standard scaling relations—may be overestimated by orders of magnitude.

LRD BH seeds super-Eddington stellar envelope broad Balmer high-z

2025-03-20 · 2503.16595v1

Little red dots as young supermassive black holes in dense ionized cocoons

V. Rusakov, D. Watson, G. P. Nikopoulos, et al.

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Using the highest-S/N JWST/NIRSpec spectra of LRD-like broad-line sources, the authors show that Balmer-line wings are exponential and symmetric, as expected from electron scattering in a compact, Compton-thick ionized cocoon. Convolving a narrow Doppler core with this scattering kernel yields intrinsic widths of only a few hundred km/s, implying black holes of ~10^5–10^7 M⊙ accreting near the Eddington limit within light‑day–scale gas with mild outflows. Accounting for scattering lowers previous mass estimates by ~2 dex and naturally explains LRD traits, including very weak X-ray/radio via nebular reprocessing. This reframes LRDs as young, rapidly growing SMBHs rather than overmassive quasars for their hosts.

LRD broad Balmer nebular continuum super-Eddington high-z

2025-03-18 · 2503.14739v1

DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha Forest

DESI Collaboration, M. Abdul-Karim, J. Aguilar, et al.

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DESI DR2 doubles the Lyα-forest dataset over DR1, analyzing both the Lyα auto-correlation and the Lyα–QSO cross-correlation from >820k quasar spectra and >1.2M quasar positions. It delivers sub‑percent BAO distances at zeff=2.33: 1.1% radial and 1.3% transverse, for 0.65% isotropic precision, measuring DH/rd=8.632±0.098(stat)±0.026(sys) and DM/rd=38.99±0.52(stat)±0.12(sys). The team details analysis upgrades, validation on improved synthetic data, and refined DLA identification. Motivated by nonlinear BAO shift studies, they include—for the first time in Lyα BAO—a dedicated systematic error term, strengthening high‑z expansion constraints.

QSO high-z spectroscopy

2025-03-14 · 2503.11611v1

A Census of the Most Obscured Galaxy Nuclei over Cosmic Time to be revealed by PRIMA

Fergus R. Donnan, Dimitra Rigopoulou, Ismael García-Bernete, et al.

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Concept study for the 1.8 m far‑IR PRIMA mission shows how to census the most buried galaxy nuclei across cosmic time. PRIMAger (25–235 um) photometry captures rest‑frame 9.8 um silicate absorption from z=2–7, enabling color selections that recover local CONs and scale to high z. FIRESS low‑resolution (R~100) spectroscopy to z~7 would detect PAHs, ice bands, and warm‑gas diagnostics even when high‑ionization lines are quenched, yielding redshifts and column densities. Simulations plus local (U)LIRG templates (NGC 4418 vs NGC 7714) suggest large, confusion‑mitigated yields in 1500 h/deg^2 surveys, making PRIMA pivotal for the obscured phase of SMBH growth.

obscured AGN demographics high-z

2025-03-13 · 2503.10958v1

Dot to dot: high-$z$ little red dots in $M_{\rm bh}$-$M_{\rm \star}$ diagrams with galaxy-morphology-specific scaling relations

Alister W. Graham, Igor V. Chilingarian, Dieu D. Nguyen, et al.

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Places high‑z little red dots onto morphology‑aware Mbh–M★ diagrams alongside compact stellar systems and local galaxy sequences. With 2023–2024 masses, LRDs are not NSCs (NSCs have higher Mbh/M★); the least‑massive LRDs overlap UCD‑like Mbh and M★, and the full LRD set spans from UCDs to primaeval S0s, while spirals and merger‑built ETGs sit at higher M★. Low‑z AGN align with the quasi‑quadratic/steeper relations defined by local disc galaxies with direct black‑hole masses, emphasizing morphology in coevolution. As 2025 mass updates arrive, placements may shift, potentially bringing LRDs closer to NSCs/UCDs/green‑peas.

LRD overmassive BH demographics high-z

2025-03-11 · 2503.08779v1

Seeding Cores: A Pathway for Nuclear Star Clusters from Bound Star Clusters in the First Billion Years

Fred Angelo Batan Garcia, Massimo Ricotti, Kazuyuki Sugimura

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Cosmological RHD zoom-ins of a dwarf progenitor with a variable, cloud-scale SFE (calibrated on AU-scale RMHD) produce burstier star formation, a richer massive cluster population, and higher total stellar mass than constant-SFE runs. Dense clouds reach up to ~80% SFE, yielding bound star clusters (Σ~10^2–10^4 M_sun pc^-2, r<=3 pc) with a flat mass function (dN/dlogM ∝ M^Γ, Γ≈−0.4); the most massive (10^4–10^5 M_sun) assemble via mergers and show 0.05–0.1 dex metallicity spreads. A nuclear star cluster is seeded by z≈8.7 and grows to ~2.4×10^5 M_sun, with 83% of its mass built through cluster mergers, reaching ~20% of the galaxy’s stellar mass. This early, merger-driven NSC pathway provides a natural route to SMBH seeding and links to the compact “little red dots” population at z≳5.

simulation BH seeds high-z

2025-03-10 · 2503.07074v1

JWST ASPIRE: How Did Galaxies Complete Reionization? Evidence for Excess IGM Transmission around ${\rm [O\,{\scriptstyle III}]}$ Emitters during Reionization

Koki Kakiichi, Xiangyu Jin, Feige Wang, et al.

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ASPIRE cross-correlates [O III] emitters from NIRCam/F356W grism with Lyα-forest pixels in five z>6.5 QSO fields (5.4<z<6.5). It finds 2σ excess Lyα transmission at ~20–40 cMpc around [O III] emitters (z=5.86) with small-scale absorption, implying highly ionized bubbles around galaxies embedded in overdense environments. Comparing to THESAN, the signal points to >50 cMpc ionized regions and a stronger UV background supplied by unseen faint galaxies; the observed [O III] sources near individual transmission spikes cannot by themselves maintain the ionization even if all hosted AGN with 100% LyC escape. Simulations underpredict the excess transmission, hinting at larger bubbles or stronger UV/temperature fluctuations, with current uncertainties dominated by cosmic variance.

reionization high-z spectroscopy simulation

2025-03-07 · 2503.05537v1

Little Red Dots as the Very First Activity of Black Hole Growth

Kohei Inayoshi

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Using 341 Little Red Dots (39 with spectroscopic redshifts) compiled from JWST surveys, this paper models their occurrence across cosmic time. The counts peak at z ~ 6–8 and fall steeply by z < 4, well described by a log‑normal distribution interpreted as the first one or two accretion episodes of newborn seed black holes. Dense circumnuclear gas naturally explains broad Balmer-line absorption, X‑ray weakness, and brief super‑Eddington bursts that yield overmassive BHs relative to local relations. Summing recurrent episodes reproduces the global AGN abundance evolution ∝ (1+z)^(−5/2) and provides an analytic form for the LRD redshift dependence for future tests.

LRD BH seeds super-Eddington overmassive BH demographics high-z

2025-03-05 · 2503.03870v1

The Convergence of Heavy and Light Seeds to Overmassive Black Holes at Cosmic Dawn

Haojie Hu, Kohei Inayoshi, Zoltan Haiman, et al.

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A semi-analytic growth model tied to dark-matter halo assembly follows M_BH/M_star for both heavy and light seeds under feedback-limited, episodic super-Eddington accretion. Despite mass loss in winds, the ratio first increases and then converges to a universal ~0.1–0.3 set by the balance between nuclear gas feeding and star-formation efficiency, forming an attractor in the M_BH–M_star plane. On this attractor, overmassive BHs grow more slowly than their hosts while undermassive seeds catch up rapidly, erasing seed-memory by z~4–6. The model predicts that 10^5–10^6 Msun BHs at higher redshift that deviate from this trend would reveal their birth conditions.

overmassive BH BH seeds super-Eddington simulation high-z

2025-03-05 · 2503.03431v1

Self-Consistent JWST Census of Star Formation and AGN activity at z=5.5-13.5

Jordan C. J. D'Silva, Simon P. Driver, Claudia D. P. Lagos, et al.

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Combining ≈400 arcmin^2 of JWST imaging from PEARLS, CEERS, NGDEEP, JADES, and PRIMER, this work jointly fits galaxy and AGN components with EAZY+ProSpect for ≈3.9k galaxies at z=5.5–13.5 to build SMF, SFRF, and AGNLF in four bins. Integrating these functions shows a ~1 dex rise in the CSFH from z≈13.5→5.5, while the CAGNH also increases and tentatively does so more rapidly, implying early SMBH accretion can outpace stellar mass growth. The results are stitched to z<5 measurements to provide a continuous, self-consistent census spanning >13 Gyr. This anchors the early coevolution picture and constrains the AGN contribution around reionization.

JWST AGN demographics high-z reionization

2025-03-03 · 2503.01945v1

No [CII] or dust detection in two Little Red Dots at z$_{\rm spec}$ > 7

Mengyuan Xiao, Pascal A. Oesch, Longji Bing, et al.

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Two z_spec > 7 Little Red Dots in FRESCO GOODS-N (ID9094, ID2756) show v‑shape colors, compact morphologies, and broad Hβ (FWHM 2280±490 and 1070±240 km/s), marking them as Type‑I AGN candidates. Deep NOEMA follow-up finds no [CII] 158 μm or 1.3 mm continuum; a DSFG interpretation would have yielded strong detections (>16σ [CII] and >3σ 1.3 mm for ID9094; >5σ [CII] for ID2756). Using the 3σ FIR limits in UV–FIR SED fitting (with/without AGN) and comparison to the L_[CII]–SFR_tot relation, the data favor an AGN contribution, as a dust‑only model would require unusually high dust temperatures. The work shows FIR non‑detections can discriminate AGN‑dominated LRDs from DSFG impostors at z > 7, though a purely dusty origin cannot be fully excluded.

LRD v-shaped SED broad Balmer ALMA/mm spectroscopy high-z

2025-03-02 · 2503.00998v1

Tentative detection of neutral gas in a Little Red Dot at $z=4.46$

Hollis B. Akins, Caitlin M. Casey, John Chisholm, et al.

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ALMA Band 3/4/5 spectroscopy targets CO(7–6) and [CI](2–1) in three Little Red Dots at z=3.10, 4.46, and 7.04, finding no CO and no far-IR continuum, implying conservative molecular gas limits ≲1–5×10^10 Msun. A2744-45924 (z=4.4655) shows a tentative 4.9σ [CI](2–1) line with a narrow FWHM ~80 km s−1. The [CI]-inferred dynamical mass is ≲10^10 Msun for conservative size assumptions, well below the local MBH–Mdyn relation and an order of magnitude under SED-based stellar mass. If confirmed, this points to LRD hosts unlike massive, gas-rich quasar hosts and lends weight to a non-stellar origin for the Balmer break.

LRD ALMA/mm spectroscopy high-z

2025-02-27 · 2502.20550v1

JWST's PEARLS: A z=6 quasar in a train-wreck galaxy merger system

Madeline A. Marshall, Rogier A. Windhorst, Giovanni Ferrami, et al.

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JWST/NIRSpec IFU prism data (0.6–5.3 μm, R≈100) on the z=5.89 quasar NDWFS J1425+3254 capture rest-UV/optical lines and spatially resolve its host environment. Broad Hα and Hβ yield MBH≈1.4×10^9 M⊙ and Lbol/LEdd≈0.3, while [O III] exposes a quasar-driven outflow with v≈6050 km s−1 and an ionized outflow rate ≈1650 M⊙ yr−1. The cube maps a “train-wreck” triple merger: an older, massive NE companion (M⋆≈3.6×10^11 M⊙, age≈65 Myr) linked to the host by a gas bridge, plus a very young SE companion (age≈6.7 Myr, M⋆≈1.9×10^10 M⊙) with ongoing star formation. These results argue for merger-triggered early SMBH growth; a likely foreground z=1.135 galaxy may modestly lens the quasar (1<μ<2; <0.75 mag).

luminous quasar QSO high-z broad Balmer outflows spectroscopy

2025-02-25 · 2502.18310v1

High-velocity outflows in [OIII] emitters at z=2.5-9 from JWST NIRSpec medium-resolution spectroscopy

Ryan A. Cooper, Karina I. Caputi, Edoardo Iani, et al.

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From the full JADES NIRSpec R~1000 sample of 1087 [O III] 5007 emitters at z=2.5–9, the authors flag 40 galaxies with clear blue-side line broadening, of which 34 are robust ionized outflow candidates and 6 may reflect rotating clumps. The outflows occur mostly in star-forming systems (~65% starbursts) spanning log10(M*/Msun)=7.5–11, and include two type-2 AGN candidates plus one little red dot. They measure a median outflow velocity of 531(+146/−159) km/s and a global incidence of 3.4%, higher velocities and lower incidence than prior work, attributed to R1000 resolution and stricter selection. No v_out–M* or SFR correlations are found; v_out/v_esc has a median 0.77 (generally bound), while mass loading anti-correlates with M* up to ~10^10 Msun, exceeding unity in many M*<10^9 Msun galaxies.

outflows spectroscopy high-z demographics

2025-02-18 · 2502.12538v1

Bridging Theory and Observations: Insights into Star Formation Efficiency and Dust Attenuation in $z > 5$ Galaxies

Daisuke Toyouchi, Hidenobu Yajima, Andrea Ferrara, et al.

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Radially resolved disk-evolution modeling links gas inflow, star formation, outflows, enrichment, and dust to reproduce z>5 galaxy sizes, stellar masses, SFRs, metallicities, and dust-to-stellar mass ratios. The model finds SFE f_* governed by inflow–SF–outflow equilibrium with f_* ≲ 20% for M_h ~10^11–10^12 Msun down to z=5, enabling intrinsic M_UV ≲ −22 and a dust-free z≈12 UV LF consistent with observations. Yet the same galaxies are predicted to be extremely opaque (τ_1500 ≳ 10), which would depress the UV LF below the observed counts. The tension motivates mechanisms that lower effective attenuation, such as dust evacuation from star-forming regions or preferentially large grains.

high-z simulation

2025-02-11 · 2502.07875v1

Investigating photometric and spectroscopic variability in the multiply-imaged Little Red Dot A2744-QSO1

Lukas J. Furtak, Amy R. Secunda, Jenny E. Greene, et al.

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Exploiting the three lensed images of the z=7.045 LRD A2744-QSO1 with 22 yr (observer; 2.7 yr rest) delays, the authors test variability using two NIRSpec epochs and multi-epoch NIRCam. Magnification-insensitive EWs of broad Hα and Hβ vary by up to 18±3% and 22±8%, respectively, over 875 d (2.4 yr) in the rest frame, coherently across images. No significant broadband photometric variability is detected beyond ≈0.3 mag systematics, so the EW changes cannot yet be tied to line- versus continuum-driven variability. A DRW model for MBH≈4×10^7 M⊙ matches the sparse sampling, bolstering the AGN interpretation and motivating continued monitoring.

LRD variability broad Balmer broad-line AGN spectroscopy high-z

2025-02-07 · 2502.05048v1

A prevalent population of normal-mass central black holes in high-redshift massive galaxies

Junyao Li, Yue Shen, Ming-Yang Zhuang

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From a galaxy-selected parent sample of 52 massive systems at z≈3–5, the authors use JWST/NIRSpec medium–high resolution spectra to search the Hα+[N II]+[S II] region for broad components (FWHM>1000 km/s), identifying 13 moderate-luminosity BLAGNs. Virial Hα masses and AGN luminosities place these sources on the local M_BH–M_* relation with an average M_BH/M_*≈0.1%, contrasting with previously JWST-selected overmassive LDs and quasars. Back-tracing indicates limited evolution in this mean ratio to z≈6, implying that a prevalent population of “normal” SMBHs was already in place within the first Gyr. Host SEDs show prominent Balmer/4000 Å breaks and red continua, suggesting many of these massive galaxies are already quenching, so assembling massive quiescents need not require overmassive black holes.

broad-line AGN high-z spectroscopy

2025-02-06 · 2502.03742v1

Radio emission from little red dots may reveal their true nature

Muhammad A. Latif, Ammara Aftab, Daniel J. Whalen, et al.

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Using the black-hole fundamental plane alongside star-formation radio scaling, the authors predict continuum fluxes for little red dots (LRDs) across BH mass, X-ray luminosity, SFR, and redshift (≈3–7). They find AGN radio fluxes are typically 10–100× the host stellar contribution at 3–8 GHz, and that a ≥500 nJy detection above 2 GHz at z ≥ 5 or ≥2000 nJy at z = 3–4 would be a clear AGN signature if SFR < 30 M⊙/yr. The analysis implies most LRDs are radio-quiet AGN, consistent with current survey non-detections. Forecasts show ngVLA and SKA could confirm typical LRD AGN in ~10–100 hr integrations, providing a dust-robust discriminator between starbursts and accretion.

LRD radio high-z X-ray

2025-02-06 · 2502.03683v1

AGN ruled out as the dominant source of cosmic reionization

Danyang Jiang, Linhua Jiang, Shengxiu Sun, et al.

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JWST GOODS-S/N imaging is used to build a highly complete z=7.15–7.75 sample and decompose each source into a point-source (AGN) and extended component in F115W and F150W, yielding 93 faint AGNs down to M_UV ≈ −15. From the PSF-only UV magnitudes they measure the faint-end AGN UV luminosity function and integrate a 1–4 Ryd SED with f_esc=1 to set an absolute upper bound on AGN ionizing emissivity. The cumulative result is that AGNs provide at most one third of the LyC photon budget at z≈7.5, with the contribution dominated by the lowest-luminosity bins. This effectively rules out AGNs as the dominant drivers of reionization, implying galaxies supply most ionizing photons during the EoR.

reionization JWST AGN high-z demographics

2025-01-29 · 2501.17925v1

Possible environmental quenching in an interacting little red dot pair at $z\sim7$

Rosa M. Mérida, Gaia Gaspar, Marcin Sawicki, et al.

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CANUCS NIRCam imaging behind Abell 370 reveals a compact z∼7 group with two little red dots only 3.3 kpc apart plus three satellites. SEDs show strong Balmer breaks implying recent (~100 Myr) quenching in the LRDs, while the satellites are consistent with a recent-onset (~100 Myr), ongoing burst. Modeling suggests a dust-free AGN produces the UV excess in LRD1 (with the optical dominated by an obscured post‑starburst and a subdominant AGN), and LRD2 is more ambiguous; in this picture the LRDs are massive (~10^10 M⊙, AV>1 mag) and the satellites are lower-mass (10^8–10^9 M⊙) with low attenuation. The tight configuration points to interaction-driven environmental bursting and quenching during reionization.

LRD high-z JWST AGN

2025-01-23 · 2501.14026v1

Luminous Mid-IR Selected Type-2 Quasars at Cosmic Noon in SDSS Stripe82 I: Selection, Composite Photometry, and Spectral Energy Distributions

Ben Wang, Joseph F. Hennawi, Zheng Cai, et al.

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WISE W4>5 mJy selection in SDSS Stripe 82 yielded 24 candidates, with GNIRS (all) plus LRIS (18/24) confirming 23 luminous Type‑2 QSOs at 0.88<z<2.99, including 12 at z>2. Multi‑band photometry (DESI Legacy, PS1, UKIDSS, Spitzer, WISE) enables rest‑frame 0.1–10 μm composite photometry and AGNfitter SEDs. The IR is torus‑dominated with average L_torus ≈10^46.84 erg s−1; inferred L_bol spans 10^46.28–10^47.49 erg s−1 and Eddington masses ~10^8.18–10^9.39 M⊙, and the sample is redder with brighter tori than earlier Type‑2 SEDs. Their SED shapes closely resemble JWST “little red dots,” highlighting mid‑IR selection as an efficient path to luminous z>2 Type‑2s; a key open point is the origin of the rest‑UV/optical light (scattered, stellar, or a reddened disk).

obscured AGN QSO luminous quasar spectroscopy high-z

2025-01-22 · 2501.13082v1

BlackTHUNDER -- A non-stellar Balmer break in a black hole-dominated little red dot at $z=7.04$

Xihan Ji, Roberto Maiolino, Hannah Übler, et al.

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BlackTHUNDER analyzes JWST NIRSpec-IFU plus archival MSA data of the triply imaged lensed LRD Abell2744-QSO1 at z=7.04, confirming a smooth Balmer break and a broad Hβ from the BLR. The narrow Hβ dispersion gives M_dyn < 4×10^8 Msun, capping the stellar contribution to <10% of the optical continuum and favoring a non-stellar Balmer break produced by an AGN continuum filtered by very dense (n_H ~ 10^10 cm^-3), nearly dust-free gas likely in/around the BLR; a tentative 3σ Hβ absorption appears in the R2700 spectrum. The black hole is overmassive relative to both stellar and dynamical masses, with hints of variability and an initial reverberation-mapping attempt. This picture alleviates the extreme stellar-density problem for LRDs and may generalize to similar V-shaped continua.

LRD v-shaped SED broad Balmer overmassive BH spectroscopy high-z

2025-01-22 · 2501.12567v1

Exploring quasar evolution with proximate molecular absorbers: Insights from the kinematics of highly ionized nitrogen

R. Cuellar, P. Noterdaeme, S. Balashev, et al.

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X-shooter spectroscopy of 13 z≈2.5–3.3 quasars with proximate H2+HI absorbers finds NV in 9/13 (70%), far exceeding intervening DLA (~10%) and generic proximate (~30%) rates. High-ionization lines show blue-extended, broader kinematics decoupled from the neutral/low-ionized profiles, and NV/SiIV varies with velocity such that blueshifted components require higher ionization parameters. Redshifted systems lack NV and are interpreted as infall pre-feedback, while blueshifted proximate H2 systems trace outflow phases that can reach neutral/molecular gas. The authors argue that ionization state—not a fixed velocity threshold—should define “associated” versus “intervening” classifications.

QSO outflows spectroscopy high-z

2025-01-21 · 2501.12449v1

Intervening nuclear obscuration changing the X-ray look of the $z\approx6$ QSO CFHQS J164121+375520

Fabio Vito, William Nielsen Brandt, Andrea Comastri, et al.

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The authors re-monitor the z=6.025 QSO CFHQS J164121+375520 (J1641) with Chandra and rest‑UV imaging in 2022–2024 after a dramatic X-ray dimming seen between 2018 and 2021. J1641 is now detected only in the hard 2–7 keV band, while its soft 0.5–2 keV flux has faded by >20× relative to 2018, establishing it as an X‑ray changing‑look quasar at z>6. They attribute the transition to intervening, ongoing Compton‑thick obscuration along our line of sight—potentially a thickened inner disk/failed wind or an occultation by dust‑free sub‑pc clouds—with the near‑constant rest‑UV light curve supporting obscuration over intrinsic fading. Catching such events in the reionization era offers a new handle on how rapidly growing SMBHs are fueled and shrouded.

QSO high-z X-ray obscured AGN variability

2025-01-16 · 2501.09585v1

New Methods of Identifying AGN in the Early Universe using Spectroscopy and Photometry in the JWST Era

Flor Arevalo Gonzalez, Titanilla Braun, James Trussler, et al.

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This paper stress-tests UV-line diagnostics and NIRCam SED selection to find early AGN, showing that classic optical BPT/VO87 fail in low-metallicity regimes. Using photoionization grids, the most effective discriminants emerge as (CIII]+CIV)/HeII λ1640, CIII]/HeII λ1640, and the EW of HeII λ1640, with HeII λ1640/Hβ also separating AGN from star-formers when dust is low. Applied to three JADES/NIRSpec sources (IDs 9422, 18846, 10058975), the diagnostics are promising but current spectra blend HeII λ1640 with OIII] λλ1661,1666 and optical lines are unreliable, limiting firm AGN claims. An EAZY-based NIRCam SED search flags one strong candidate with strong UV emission, and the authors argue longer integrations—especially at z>6—are needed to cleanly deblend key lines.

JWST AGN spectroscopy high-z demographics

2025-01-09 · 2501.05512v1

JWST NIRCam simulations and observations of AGN ionization cones in cosmic noon galaxies

Sophie Lebowitz, Kevin Hainline, Stéphanie Juneau, et al.

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Simulating JWST/NIRCam narrow- and medium-band [O III] maps at z≈2–3 using MUSE datacubes of nine nearby AGN, the authors show NIRCam can recover classic ionization-cone morphologies. They then apply this to 27 known AGN in GOODS-S (z=2.4–3.4), identifying six systems with [O III]+Hβ morphologies consistent with cones and characteristic NLR sizes of 1–2.5 kpc. The simulations quantify how cosmological dimming and instrument noise bias high‑z NLR size measurements low, depressing the local NLR size–AGN luminosity relation by about a factor of two. This establishes a practical medium-band imaging path to select cone candidates and calibrate NLR size trends at cosmic noon.

JWST AGN high-z simulation low-z

2025-01-09 · 2501.04912v1

Another piece to the puzzle: radio detection of a JWST detected AGN candidate

Anniek J. Gloudemans, Kenneth J. Duncan, Anna-Christina Eilers, et al.

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Deep 0.144–3 GHz maps across COSMOS, GOODS-N, and GOODS-S are mined for radio counterparts to ~700 JWST-selected AGN candidates (including LRDs). Only PRIMER-COS 3866 at z=4.66 is individually detected; its spectrum (α=−0.76+0.11−0.09), modest radio-loudness (R≈0.5), and Tb≳10^3 K remain consistent with either AGN or star-formation power. Stacks of spectroscopic and photometric subsamples yield non-detections with 3σ limits L1.4GHz<8.6×10^39 erg s−1 and L1.3GHz<1.3×10^39 erg s−1, still compatible with local L_X–L_Hα and L_X–L_R relations. The authors argue present radio depths are insufficient to label the population radio-weak and forecast SKA/ngVLA detections within hours to enable brightness-temperature tests that separate AGN from starbursts.

JWST AGN radio X-ray demographics high-z

2025-01-08 · 2501.04770v1

Lyman Alpha Forest - Halo Cross-Correlations in Effective Field Theory

Anton Chudaykin, Mikhail M. Ivanov

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This paper develops a redshift-space EFT for Lyα forest cross-correlations with biased tracers and delivers one-loop full-shape power-spectrum predictions. Tested on Sherwood hydrodynamic simulations at z=2.8 with massive and light halo catalogs, the model jointly fits the Lyα auto, halo auto, and Lyα–halo cross spectra. Adding the cross term significantly tightens constraints on Lyα and halo EFT parameters relative to auto-only fits. The combined model attains percent-level accuracy for the cross-spectrum up to k_max=1 h Mpc^{-1}, improving over prior analytic approaches and enabling precision DESI-era Lyα–quasar analyses.

QSO simulation high-z

2025-01-07 · 2501.04085v1

The Cosmic Evolution Early Release Science Survey (CEERS)

Steven L. Finkelstein, Micaela B. Bagley, Pablo Arrabal Haro, et al.

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CEERS is a 77.2 hr ERS survey in the EGS that uses coordinated, overlapping NIRCam/MIRI imaging, NIRSpec low–medium resolution spectroscopy, and NIRCam slitless grism data to validate efficient extragalactic mapping. From ~90 arcmin^2 of NIRCam imaging it uncovered large samples of z ≳ 10 galaxies and secured >1000 spectra, including dozens at 6<z<10, enabling redshifts and rest‑optical line diagnostics that probe star formation and supermassive black hole growth. The program also quantifies the first bulge, bar, and disk structures at z>3 and leverages MIRI mid‑IR emission to trace dust‑obscured star formation and black‑hole accretion at z~1–3. As a legacy, CEERS releases processed data with detailed reduction notes and reproducible notebooks.

spectroscopy high-z demographics