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2025-08-19 · 2508.13541v1

Little Red reionization factories

Fan Zhang

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

2025-07-31 · 2508.00209v1

Accretion disc reverberation mapping in a high-redshift quasar

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

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.

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.

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.

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.

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%).

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.

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.

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.

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.

2025-07-23 · 2507.17833v1

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

Bryce Cyr

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.

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.

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.

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.

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.

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.

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.

2025-07-16 · 2507.12618v1

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

Devesh Nandal, Abraham Loeb

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.

2025-07-09 · 2507.07171v1

Little Red Dots from Small-Scale Primordial Black Hole Clustering

Borui Zhang, Wei-Xiang Feng, Haipeng An

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.

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.

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.

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.

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.

2025-07-04 · 2507.03230v1

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

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

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

2025-06-23 · 2506.18993v1

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

Yang Luo, Isaac Shlosman

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.

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

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.

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

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.

2025-06-17 · 2506.14896v1

Overmassive Black holes live in compact galaxies in the early Universe

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

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.

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.

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.

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.

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.

2025-06-06 · 2506.06418v1

The Identification of Two JWST/NIRCam-Dark Starburst Galaxies at $z=6.6$ with ALMA

Fengwu Sun, Jinyi Yang, Feige Wang, et al.

Two extreme, dust-enshrouded starbursts at z=6.6 are identified in ASPIRE quasar fields: they are bright in ALMA 1.2 mm continuum and [C II] 158 µm, yet essentially disappear in JWST/NIRCam (F356W >28 AB). SEDs anchored to ALMA fluxes imply heavier obscuration than Arp 220 and star formation rates of ≃80–250 M⊙ yr⁻¹. Their inferred star-formation histories make them plausible progenitors of massive quiescent galaxies at z≳4 and descendants of UV-luminous z>10 systems, with an abundance as high as n≈10⁻⁵⋅⁵ Mpc⁻³ under a light halo-occupation model (~30% of those comparison populations). A key caveat is that number densities come from quasar-companion fields; analogous z∼8 systems may remain undetected (“JWST-dark”) at current survey depths.

2025-06-05 · 2506.05459v1

RUBIES: A Spectroscopic Census of Little Red Dots; All V-Shaped Point Sources Have Broad Lines

Raphael E. Hviding, Anna de Graaff, Tim B. Miller, et al.

RUBIES delivers uniform NIRSpec PRISM+G395M spectroscopy for ~1500 z>3.1 sources, identifying 80 broad-Balmer emitters, including 28 (35%) at z>6. A coherent subpopulation of 36 shows v-shaped UV–to–optical continua with dominant rest‑optical point sources; these are defined as spectroscopic LRDs, the largest such sample to date. The key result is that every v‑shaped point source exhibits broad Balmer lines, tying continuum shape, compact morphology, and AGN kinematics together. Photometric LRD searches recover only 50–62% of these to F444W<26.5, implying current color cuts miss many due to faint rest‑UV, comparatively bluer rest‑optical colors, or uncertain photo‑z.

2025-06-04 · 2506.04350v1

JWST Insights into Narrow-line Little Red Dots

Zijian Zhang, Linhua Jiang, Weiyang Liu, et al.

Using NIRSpec medium/high-resolution data and line-free photometry, the authors isolate five narrow-line LRDs at z≈5 (H-alpha FWHM ≈250 km/s; one ≈475 km/s) from 32 LRDs with H-alpha coverage, and show that about 20% of color-selected LRD candidates fake a V-shape continuum via strong lines. Relative to normal star-forming galaxies, these objects have higher H-alpha widths and luminosities but smaller equivalent widths. SED fits allow either dusty, compact, high-M* and high-SFR galaxies or low-mass AGN with MBH≈10^5–10^6 Msun, plausibly in an early, super-Eddington phase; the BHs are slightly overmassive vs MBH–M* yet consistent/undermassive vs MBH–sigma and MBH–Mdyn within large errors. Nearly half of high‑z broad-line AGN show V‑shape SEDs, underscoring that LRD-like photometry does not uniquely imply broad-line activity.

2025-06-04 · 2506.04004v1

Lonely Little Red Dots: Challenges to the AGN-nature of little red dots through their clustering and spectral energy distributions

María Carranza-Escudero, Christopher J. Conselice, Nathan Adams, et al.

Builds a 124-object little red dot sample at z≈3–10 from CEERS, NEP‑TDF, JADES, and JEMS, then tests SED fits with and without AGN components using BIC. Despite lower χ² when adding AGN templates, BIC generally prefers non‑AGN SEDs, especially when MIRI photometry is included. KS tests of projected environments show LRDs occupy sparser neighborhoods than comparison galaxies, and abundance matching yields conservative halo-mass upper limits. Together these point to most LRDs being compact galaxies or forming star clusters rather than AGN‑dominated, while allowing for a mixed population.

2025-06-03 · 2506.03244v1

Cosmic Outliers: Low-Spin Halos Explain the Abundance, Compactness, and Redshift Evolution of the Little Red Dots

Fabio Pacucci, Abraham Loeb

Proposes that Little Red Dots are the visible outcomes of galaxies forming in the extreme low-spin tail of the halo angular-momentum distribution, using Mo–Mao–White scaling to link halo spin to compact disk sizes. Assuming progenitors in the lowest ~1% of spins at z ~ 5 reproduces both the observed number densities and compact effective radii of ~80–300 pc, without requiring a choice between BH- or star-dominated power. The observed redshift trend arises from the competition between an increasing compact-halo fraction and cosmological surface-brightness dimming, yielding an “LRDs Era” at 4 < z < 8; at z < 4 they are bright but rare, while at z > 8 they are common but faint. Agreement with current counts, plus excess small-scale clustering and spectral signs of extreme core densities, supports the low-spin origin.

2025-06-03 · 2506.03121v1

EIGER VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization

Daichi Kashino, Simon J. Lilly, Jorryt Matthee, et al.

Using the full EIGER program, the authors assemble 948 [O III]λ5008 emitters (−21.4≲MUV≲−17.2) at 5.33<z<6.97 from deep NIRCam 3.5 μm slitless spectroscopy along six quasar sightlines and cross-correlate them with Lyα/Lyβ transmission in high-resolution quasar spectra. They find a strong redshift evolution: overdense regions at z<5.50 show suppressed transmission and excess absorption within ~8 cMpc, while at 5.70<z<6.15 the transmission is enhanced on intermediate (~5–20 cMpc) scales, with a transitional regime between. Mock catalogs without galaxy–IGM coupling show these signals are unlikely by chance. The results support inside-out reionization, where local radiation around clustered galaxies dominates early and is later overtaken by a rising UV background that sets the IGM ionization state.

2025-05-28 · 2505.22567v1

A black hole in a near-pristine galaxy 700 million years after the Big Bang

Roberto Maiolino, Hannah Uebler, Francesco D'Eugenio, et al.

JWST/NIRSpec-IFS dissects the triply imaged Little Red Dot Abell2744-QSO1 at z=7.04, isolating the narrow Hβ to map line ratios. [OIII]5007 is exceptionally weak—[OIII]/Hβn ≈ 0.6 within r<150 pc and <0.32 at 150–300 pc—implying Z ≈ 8×10^-3 Z⊙ centrally and Z<6×10^-3 Z⊙ in the extended gas, while broad Balmer lines/variability yield MBH ≈1.5×10^7 M⊙ in a host with Mdyn ≈10^7.1–10^8 M⊙. This places a massive black hole in an almost pristine, very low-mass galaxy only ~700 Myr post-Big Bang. The chemistry and mass budget strain heavy-seed or super‑Eddington growth paths, motivating alternatives such as primordial black-hole seeds that remain to be fully tested.

2025-05-26 · 2505.20439v1

The Properties of Little Red Dot Galaxies in the ASTRID Simulation

Patrick LaChance, Rupert A. C. Croft, Tiziana Di Matteo, et al.

Using the ASTRID cosmological simulation, the authors generate mock NIRCam-like views at z=5–8 and identify 17 systems that meet little red dot color-plus-size cuts. These ASTRID LRDs are massive, compact, and dusty—log(M*/Msun)≥9.7, log(MBH/Msun)≥6.8, r_half,*=325–620 pc, with F444W attenuation >1.25—and are bright at F444W=23.5–25.5. Their recent quenching and a dust-obscured AGN produce a steep rest-optical red slope while UV light is star-dominated, pointing to an AGN-feedback-driven miniquenching phase. Lower-mass/fainter galaxies lack sufficient central dust, and many highest-Eddington BH hosts are not LRDs because high SFRs and low attenuation yield flatter spectra; the paucity of low-mass LRDs may partly reflect limited resolution.

2025-05-26 · 2505.20393v1

NEXUS: A Spectroscopic Census of Broad-line AGNs and Little Red Dots at $3\lesssim z\lesssim 6$

Ming-Yang Zhuang, Junyao Li, Yue Shen, et al.

Using NIRCam/WFSS F322W2+F444W in the central 100 arcmin² of NEXUS, the team secures a spectroscopic census of 23 BLAGNs at 3≲z≲6, 15 of which satisfy Little Red Dot criteria. The sample spans L(Hα)≈10^{42.2}–10^{43.7} erg s⁻¹, M_BH≈10^{6.3}–10^{8.4} M_⊙, and λ_Edd≈0.1–1 (median 0.4); about half of the LRDs show strong Balmer absorption indicating dense gas near the emission region. Most LRDs reveal extended (hundreds of parsec) rest-UV/optical host emission that significantly or dominantly contributes to the UV, explaining the characteristic UV upturn, and the LRD number density is ≈10⁻⁵ cMpc⁻³ with a mild decline toward lower z. Small-scale (≲1 cMpc) cross-correlations give a BLAGN bias of ~3.3 and halo masses of a few×10¹¹ h⁻¹ M_⊙, while LRD clustering appears overly strong for their space density, hinting at excess small-scale clustering; the single-epoch M_BH and λ_Edd carry large systematics.

2025-05-21 · 2505.15923v1

Discovery and characterization of 25 new quasars at 4.6 < z < 6.9 from wide-field multi-band surveys

Silvia Belladitta, Eduardo Bañados, Zhang-Liang Xie, et al.

Targeted optical/IR/radio selections across wide-area surveys yield 25 new luminous quasars at 4.6<z<6.9 (six at z≥6.5; M1450 −25.4 to −27.0), plus new spectra for six independently discovered z>6.5 sources. Three are strong radio emitters, including a z=4.71 object with blazar-like traits (flat spectrum, radio-loudness ~1000, multi-frequency variability) and an SRG/eROSITA X-ray detection (f0.2–2.3 keV ≈1.3×10^−13 erg s^−1 cm^−2). NIR spectroscopy for seven 6.3<z<6.9 quasars gives MgII-based black hole masses of 10^8.58–10^9.14 Msun and Eddington ratios 0.74–2.2, with one source showing an extreme CIV–MgII velocity offset of ~9000 km s^−1. The sample also includes three HiBALs, one with a potential 48,000 km s^−1 outflow, expanding the rare jetted/outflowing quasar census that constrains early SMBH growth and feedback.

2025-05-19 · 2505.12719v1

Composite spectrum of Little Red Dot from a standard inner disk and an unstable outer disk

Chenxuan Zhang, Qingwen Wu, Xiao Fan, et al.

Builds SEDs for 29 broad-line LRDs and finds uniformly V-shaped continua with a narrow break around ν_b ≃ 10^{14.96±0.06} Hz (λ ≈ 2600–3800 Å). Models the SEDs as a composite of an inner standard thin disk plus an outer gravitationally unstable disk (Q≈1) that self-regulates to T≈2000–4000 K, naturally producing the near-IR/optical bump without invoking extreme dust. MCMC fits anchored by MBH from broad lines reproduce individual SEDs, including UNCOVER 25119 and PRIMER 33823 (whose MIRI 4.9–27.9 μm points trace the bump). Allowing for dense gas to explain strong Balmer breaks suppresses intrinsic optical–UV by only ≲2–3×, implying most LRDs are sub-Eddington and intrinsically weak.

2025-05-14 · 2505.09703v1

SCUBADive II: Searching for $z>4$ Dust-Obscured Galaxies via F150W-Dropouts in COSMOS-Web

Sinclaire M. Manning, Jed McKinney, Katherine E. Whitaker, et al.

SCUBADive II systematically compiles 60 F150W-dropout, far-IR–bright galaxies in COSMOS-Web by cross-matching JWST non-detections at 1.5 μm with SCUBA-2 and ALMA counterparts, motivated by the benchmark AzTECC71. A core subset of 16 AzTECC71-like sources shows faint F444W (>24 mag) and no COSMOS2020 IDs. SED fits give ⟨SFR⟩=550+500−360 M⊙ yr⁻1 and ⟨log10(M⋆)⟩=11.2+0.5−0.4, with offsets indicating they are not unusually elevated above the star-forming main sequence. Crucially, such heavily obscured systems constitute roughly 20% across mass bins and could account for up to 60% of the z>4 high-mass end (log10 M⋆>11), quantifying a major, previously missed component of the early galaxy census.

2025-05-14 · 2505.09669v1

Chandra Rules Out Super-Eddington Accretion Models For Little Red Dots

Andrea Sacchi, Akos Bogdan

Stacks Chandra data for 55 JADES/NGDEEP-selected little red dots in the 7 Ms CDF-S, reaching ~390 Ms effective exposure, yet finds no soft- or hard-band signal. The resulting flux limits translate to bolometric luminosities more than an order of magnitude below those inferred from JWST, directly ruling out current super-Eddington SED models tailored for LRDs. The non-detections are instead consistent only with extreme obscuration, requiring NH ≳ 10^25 cm^-2. The authors therefore argue the SMBHs in LRDs are likely less massive and/or less luminous than currently claimed.

2025-05-14 · 2505.09542v1

A weak Ly$α$ halo for an extremely bright Little Red Dot: Indications of enshrouded SMBH growth

Alberto Torralba, Jorryt Matthee, Gabriele Pezzulli, et al.

Deep VLT/MUSE mapping around the ultra-luminous LRD A2744-45924 (z=4.464, μ=1.8; L_Hα≈10^44 erg s^-1) reveals a modest, spatially offset Lyα halo with exponential scale length ≈5.7 pkpc and a narrow line (FWHM 270±15 km s^-1) whose flux is only 7% of Hα. Compact N IV] λ1486 coincides with the point-like Hα seen by JWST, while the far-UV continuum centroid shifts with the Lyα offset. The authors argue Hα traces the AGN whereas Lyα is powered by star formation; four neighboring Lyα halos (Δz<0.02, Δr<100 pkpc) show no luminosity excess indicative of AGN illumination. Altogether this points to a dense, near-unity covering-factor cocoon that shrouds the SMBH, suppressing UV/ionizing escape and signaling enshrouded early black-hole growth.

2025-05-13 · 2505.08870v1

Galaxies in the Epoch of Reionization Are All Bark and No Bite -- Plenty of Ionizing Photons, Low Escape Fractions

Casey Papovich, Justin W. Cole, Weida Hu, et al.

Using JWST imaging plus NIRSpec/prism spectra for hundreds of galaxies at 4.5<z<9 from JADES and CEERS, the authors fit joint stellar+nebular SEDs with f_esc as a free parameter to infer both ξ_ion and the ionizing escape fraction. They find ξ_ion rises toward higher redshift and fainter UV luminosity with ~0.3 dex scatter, while the population-averaged escape fractions remain low: ⟨f_esc⟩ ≈ 2.6±1.4% at 6<z<9 and 6.5±2.2% at 4.5<z<6, with little evolution. Propagating these distributions through reionization models yields x_e≈0.5 at z≈5.3–5.8 for M_UV<−16 (possibly late vs. QSO constraints), but consistent timing (x_e≈0.5 at z≈6.0–8.1) once galaxies down to M_UV<−14 are included. Bottom line: EoR galaxies make plenty of ionizing photons, yet low f_esc—likely tied to dense gas and bursty SFHs—keeps most of them trapped.

2025-05-11 · 2505.06965v1

Black Hole Envelopes in Little Red Dots

Daisaburo Kido, Kunihito Ioka, Kenta Hotokezaka, et al.

Proposes that little red dots host super-Eddington black holes wrapped in a massive, optically thick envelope that gravitationally confines otherwise destructive winds, effectively making outflows a no-go. The envelope radiates near the system Eddington limit with a photosphere at 5000–7000 K, naturally producing the red optical continuum and the hallmark V-shaped SED while explaining weak X-ray/radio and low short-term variability. A sustained ISM infall of ~1 M_sun/yr feeds the envelope, and a photospheric radius ~0.01 pc sets year-scale variability, linking LRD nuclear structure to Hayashi-limit physics. The envelope both regulates feedback and provides a reservoir enabling rapid early BH growth.

2025-05-09 · 2505.06359v1

JWST/NIRSpec Observations of High Ionization Emission Lines in Galaxies at High Redshift

Mengtao Tang, Daniel P. Stark, Adèle Plat, et al.

Deep NIRSpec R=2700 spectroscopy of 53 new z>4 galaxies, plus a census of 851 archival spectra, is used to track high-ionization UV lines. The team reports narrow NV λ1240 in two systems—CEERS‑7902 (z=6.98; an LRD with broad Hβ) and CEERS‑1025 (z=8.72; narrow-line)—while CIV and He II are absent, yielding extreme NV/CIV and NV/He II. The inferred incidence of narrow high-ionization UV lines is 12.5(+23.7/−10.4)% in LRDs and 2.2(+1.7/−1.0)% in UV-selected galaxies at z>4, implying hard radiation fields in a small subset and that dense H I may not fully cover some LRD nuclei. The line ratios and non-detections argue for extending searches down to the NV doublet, though statistics remain limited by the number of deep rest-UV spectra.

2025-05-09 · 2505.05942v1

Green Flash: Residual Emissions Enshrouded in Low-mass Balmer-break Galaxies at $z\sim5$

Kosuke Takahashi, Takahiro Morishita, Tadayuki Kodama, et al.

JWST/NIRCam+NIRSpec data are used to isolate four low-mass Balmer-break galaxies in Abell 2744 at z=5.10–5.78 and fit their SEDs, showing they have been largely quiescent for ~100 Myr despite residual strong lines. All four require higher nebular than continuum attenuation, pointing to dusty star-forming pockets or obscured AGN as a lingering signature of quenching. For one galaxy with medium-band leverage, an Hβ+[O III] map shows centrally concentrated emission (Re≈0.7 kpc) that is more compact than the stellar body (Re≈0.9 kpc), favoring an outside-in quenching picture. Notably, one object (ID52153) sits on the z~5 main sequence even with a Balmer break, underscoring obscuration/bursty residual activity.

2025-05-08 · 2505.05556v1

Super-Eddington accretion in high-redshift quasar hosts: Black-hole driven outflows, galaxy quenching, and the nature of little red dots

Giada Quadri, Alessandro Trinca, Alessandro Lupi, et al.

Zoom-in cosmological simulations of a quasar host including super-Eddington accretion track how MBH feedback shapes gas, star formation, and emergent spectra. Outflows usually vent perpendicular to the disc and only moderately suppress the SFR, but after rapid super-Eddington growth the galaxy spends ≈10% of its lifetime in a distinct quenched state. This phase culminates in a powerful jet+disc-wind event that couples to the disc and excavates a central cavity. Across its history the system’s spectra can look like little red dots or quenched galaxies, implying both are transient stages in early quasar hosts.

2025-05-07 · 2505.04826v1

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) XXII. Chandra observations of narrow-line quasar candidates at z>6

K. Iwasawa, R. Gilli, F. Vito, et al.

Chandra followed up four z>6 SHELLQs narrow-line quasar candidates chosen for luminous Lyα and faint UV continua, and found no X-ray detections, placing L2–10 keV < 2×10^44 erg/s (2σ; Γ=2). JWST/NIRSpec reveals weak broad Balmer bases beneath narrow cores, while strong [O III] would predict Lx ≈ 10^45 erg/s from low‑z scaling, in stark tension with the Chandra limits. The authors argue for heavily buried nuclei—either Compton-thick columns in dense ISM or an inclined, inflated inner disc in supercritical accretion—making these sources higher-luminosity analogs of JWST-selected broad-line AGN at reionization. The work clarifies how extreme Lyα–bright, UV-faint quasars can hide powerful engines early on.

2025-05-07 · 2505.04825v1

SHELLQs. Bridging the Gap: JWST Unveils Obscured Quasars in the Most Luminous Galaxies at z > 6

Yoshiki Matsuoka, Masafusa Onoue, Kazushi Iwasawa, et al.

From the SHELLQs wide-field UV survey, the team followed 13 z>6, Lyα-luminous galaxies with JWST/NIRSpec and uncovered obscured quasars. Seven of eleven narrow‑Lyα systems show broad H I Balmer and He I components—but not in [O III]—with Balmer decrements indicating mild obscuration (0<Av<3), identifying them as UV‑obscured counterparts of luminous EoR quasars. Virial lines imply MBH≈10^(7.8–9.1) Msun with sub‑Eddington to Eddington accretion; most BL sources are unresolved and display LRD‑like blue‑UV/red‑optical colors. The AGN incidence among similarly bright Lyα emitters (≥2×10^−8 Mpc^−3) is comparable to classical quasar densities, implying a substantial obscured SMBH population previously missed by UV‑bright surveys.

2025-05-07 · 2505.04609v1

CAPERS-LRD-z9: A Gas Enshrouded Little Red Dot Hosting a Broad-line AGN at z=9.288

Anthony J. Taylor, Vasily Kokorev, Dale D. Kocevski, et al.

CAPERS-LRD-z9 is a PRIMER-selected little red dot spectroscopically confirmed with NIRSpec/PRISM as a z=9.288 broad-line AGN via a ~3500 km s−1 Hβ plus narrow [O III] λλ4959,5007. The broad Hβ implies a canonical black-hole mass log(MBH/M⊙)=7.58±0.15 (allowing 6.65–8.50 with systematics). A pronounced Balmer break requires a dense (~10^10 cm−3) neutral-gas cocoon around the nucleus; SED modeling (CLOUDY+bagpipes) limits the host to M*<10^9 M⊙, hinting at MBH/M* possibly >5% and a UV continuum that may be AGN-dominated. Together, these properties push early BH growth scenarios toward massive seeds or super‑Eddington episodes within ≲500 Myr of cosmic time.

2025-05-05 · 2505.02895v1

Abundant Population of Broad H$α$ Emitters in the GOODS-N Field Revealed by CONGRESS, FRESCO, and JADES

Junyu Zhang, Eiichi Egami, Fengwu Sun, et al.

Using JWST/NIRCam WFSS from FRESCO and CONGRESS plus JADES imaging, the authors conduct a GOODS‑N search for broad Hα at z≈3.7–6.5 and confirm 19 emitters at z≈4–5.5, including nine new ones. Their broad Hα LF aligns with other JWST BLAGN results, and virial BH masses with bolometric corrections imply ≈0.1 Eddington accretion and elevated MBH/M* relative to local relations. Color comparisons show LRD cuts miss 42% of these spectroscopic AGN—many lack the steep rest‑optical red slope—and average SEDs indicate some LRD red slopes are line‑boosted. Notably, 68% of color‑selected LRDs with Hα detections lack broad lines in the grism data, potentially due to sensitivity limits, underscoring the LRD population’s mixed nature.

2025-05-02 · 2505.01499v1

An extremely metal-poor Lyman $α$ emitter candidate at $z=6$ revealed through absorption spectroscopy

Dominika Ďurovčíková, Anna-Christina Eilers, Robert A. Simcoe, et al.

Archival VLT/MUSE data reveal a Lyα emitter at z=6.0323 just 29 pkpc in front of the quasar PSO J158-14 (z=6.0685), previously missed because it leaves no metal absorption in the quasar spectrum. The Lyα line sits at the edge of the quasar proximity zone, and a proximate sub-DLA with log N_HI≈19.7 reproduces the observed damping wing. Deep (>10 hr) FIRE+X-shooter spectroscopy yields [Z/H] < −3 after ionization-correction modeling, marking this source as an extremely metal-poor galaxy candidate. This system offers a rare window on near-pristine gas and potential Population III signatures during reionization.

2025-04-25 · 2504.18616v1

Insights on Metal Enrichment and Environmental Effect at $z\approx5-7$ with JWST ASPIRE/EIGER and Chemical Evolution Model

Zihao Li, Koki Kakiichi, Lise Christensen, et al.

Using JWST/NIRCam WFSS across 26 quasar fields (ASPIRE+EIGER), the authors build a [O III]-selected sample of 604 galaxies at z=5.34–6.94 and flag 204 protocluster members via a friends-of-friends search. Stacked spectra detect Hγ and [O III] λ4363, giving Te=2.0(+0.3,-0.4)×10^4 K and a metal-poor median 12+log(O/H)=7.65(+0.26,-0.15). With NIRSpec-anchored strong-line calibrations, the MZR shows ≈0.2 dex higher metallicity at the high-mass end in overdense regions, while the full z>5 sample sits ≈0.2 dex below the local FMR. A simple chemical-evolution model points to dilution from intense gas accretion, with protocluster galaxies closer to gas equilibrium—evidence for accelerated early enrichment during protocluster assembly at z≈5–7.

2025-04-23 · 2504.17007v1

The First Photometric Evidence of a Transient/Variable Source at z>5 with JWST

Christa DeCoursey, Eiichi Egami, Fengwu Sun, et al.

Reports AT 2023adya, a transient/variable source in a z_spec=5.274 GOODS-N galaxy, detected via a 0.19 mag fade in F356W over ~2 rest-frame months with a significant difference-image residual (SN_var≈6). No contemporaneous variability is seen in the rest-UV (F090W/F115W), and the rest-frame V-band absolute magnitude is MV≈−18.48. NIRCam/Grism data show no broad Hα (FWHM=130±26 km s−1), disfavoring an AGN origin; Ia is possible but unlikely given low high‑z rates, with CCSN remaining plausible while TDEs are disfavored by low event rates. The result establishes practical JWST sensitivity to transient/variable phenomena beyond z>5, nudging discovery space toward the reionization era.

2025-04-15 · 2504.11566v1

Tracking the assembly of supermassive black holes: a comparison of diverse models across cosmic time

Antonio J. Porras-Valverde, Angelo Ricarte, Priyamvada Natarajan, et al.

The authors cross-compare SMBH assembly across semi-analytic, empirical, and hydro frameworks (Dark Sage, Santa Cruz SAM, RN18, TRINITY, TNG300) over MBH ≈ 10^6–10^10 Msun. Physics-based models diverge from observationally inferred local BHMFs due to stellar-mass-function and scaling-relation systematics, but converge at z ~ 1–4 and broadly match JWST broad-line AGN BHMFs at z = 4–5. Dark Sage uniquely produces a strong knee in the bolometric AGN luminosity function near Lbol ~ 10^46 erg s^-1 that overlaps the inferred luminosities of JWST “Little Red Dots” at z = 5–6 if the emission is AGN-dominated. Within Dark Sage, SMBHs grow mainly via secular disk instabilities and merger-driven cold gas accretion, while BH–BH mergers contribute ~60% of the mass only for the most massive systems by z = 0; super-Eddington accretion is allowed.

2025-04-14 · 2504.10731v1

Unveiling faint X-ray AGN populations in the NewAthena era: Insights from cosmological simulations

Nuno Covas, Israel Matute, Stergios Amarantidis, et al.

From a TNG300-based 10 deg^2 SMBH light cone with post-processed X-ray properties, the authors run end-to-end NewAthena/WFI simulations via SIXTE to stress-test faint and high‑z AGN performance. The mock predicts a 5× excess of faint AGN versus current X‑ray constraints, plausibly reconciled by a higher Compton‑thick fraction and intrinsic X‑ray weakness hinted by recent JWST work. The simulated survey yields ~250,000 AGN (≈20,000 at z>3) and ~35 at z>6, with only log L_X ≳ 43.5 detectable in the EoR and a significant CTK component out to z>4. These results argue NewAthena can directly probe early SMBH growth while informing instrument trades and survey tiling.