Weekly issue

Week 6, 2026

Feb 2–8, 2026

Week 6, 2026 includes 8 curated papers, centered on QSO, high-z, LRD.

2602.06954v1

Spectral Appearance of Self-gravitating AGN Disks Powered by Stellar Objects: Universal Effective Temperature in the Optical Continuum and Application to Little Red Dots

Yi-Xian Chen, Hanpu Liu, Ruancun Li, Bingjie Wang, Yilun Ma, Yan-Fei Jiang, Jenny E. Greene, Eliot Quataert, Jeremy Goodman

Theme match 5/5

Digest

The authors build dust-poor, self-gravitating AGN disk models and show that all optically thick solutions converge to an outer “disk Hayashi limit” with Teff ≈ 4000–4500 K, naturally reproducing the red optical continua of Little Red Dots without fine-tuning in Mdot, MBH, or α. Global models with radially varying accretion show that burning of embedded stellar objects powers the outer disk and hollows the inner disk, suppressing the standard variable UV/X-ray while leaving a luminous thermal optical bump plus a separate, largely non-variable UV from nuclear-to-galaxy-scale stars. They map the viable parameter space and find LRD-like appearances whenever Mdot/α ≳ 0.1 Msol/yr, largely insensitive to MBH, with a transition to classical AGN disks at lower values that should coincide with rising metallicity/dust and emerging FIR emission. Results hinge on dust-poor opacities setting the thermalization boundary that fixes the optical continuum temperature.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Use the RUBIES-40579 example to see the proposed spectral decomposition—thermal red/optical from the self-gravitating disk plus a separate stellar UV—and how the hollowed inner disk explains weak UV/X-ray variability.
Figure 2: Inspect the dust-free Rosseland opacities and the Teff versus density curves to verify the universal transition at Teff ≈ 4–4.5 kK (gray point) and contrast it with the dusty, solar-metallicity case that would shift power to the FIR.
Figure 3: Check how midplane temperature and Teff vary with radius for different outer accretion rates and mass-loss slopes; note where the solution transitions (vertical dotted lines) toward an inner viscous disk and how embedded-star mass loss regulates the outer profile.
Figure 4: Compare luminosity budgets—AGN versus the optically thick self-gravitating region—and see that increasing mass-loss slope suppresses L_AGN while the thermal disk component remains nearly unchanged and can dominate even at modest Mdot; relate to the Eddington reference line.

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2602.06024v1

Water absorption confirms cool atmospheres in two little red dots

Bingjie Wang, Joel Leja, Ivo Labbe, Jenny E. Greene, Hanpu Liu, Anna de Graaff, Raphael E. Hviding, Jorryt Matthee, Eliot Quataert, Rachel Bezanson, Leindert A. Boogaard, Gabriel Brammer, Adam J. Burgasser, Yi-Xian Chen, Nikko J. Cleri, Sam E. Cutler, Pratika Dayal, Lukas J. Furtak, Seiji Fujimoto, Karl Glazebrook, Andy D. Goulding, Jakob M. Helton, Michaela Hirschmann, Yan-Fei Jiang, Vasily Kokorev, Yilun Ma, Tim B. Miller, Rohan P. Naidu, Pascal Oesch, Richard Pan, Casey Papovich, Sedona H. Price, Hans-Walter Rix, David J. Setton, Wendy Q. Sun, John R. Weaver, Katherine E. Whitaker, Adi Zitrin

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Digest

JWST/NIRSpec Prism spectra of four little red dots at z ~ 2 are searched for temperature-sensitive molecular features. Two sources—WIDE-EGS-2974 and UNCOVER-A2744-20698—show a broad 1.4 micron H2O absorption trough whose shape matches cool-star bands, requiring T <= 3000 K and indicating a cool, dense component contributing ~20–30% of the near-IR continuum. A two-temperature composite (~2000–4000 K) reproduces both the absorption and the optical–IR continuum better than a single blackbody. The result argues that at least some LRD red continua are intrinsic rather than dust-reddened, implying order-of-magnitude lower Lbol and black-hole masses and providing a practical molecular diagnostic.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1a: Compare the LRD spectra around 1.3–1.5 micron to M-dwarf templates; verify the trough’s centroid and breadth align with the classic H2O band and inspect the continuum windows used to define the absorption index.
Figure 1b: Water-absorption index versus atmosphere models across densities; note that models with T > 3000 K fail while a wide density range is allowed—use this to gauge the temperature constraint’s robustness to density/metallicity.
Figure 2: Continuum fits—single blackbody versus two-temperature stellar-atmosphere composite; examine residuals and the fractional flux from the cool component near ~1.6 micron (≈20–30%).
Per-object panels: WIDE-EGS-2974 vs UNCOVER-A2744-20698 side-by-side spectra; check that similar continua produce different water depths and that the feature is not driven by emission-line contamination or reduction artifacts.

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2602.05135v1

Growth of High-Redshift Quasars from Fermion Dark Matter Seeds

Yu Wang, Remo Ruffini

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Digest

Minimal, cosmology-tied growth tracks are built for z>6 quasars by taking the accretion rate as the minimum of Bondi supply from overdense primordial gas and the Eddington limit, with LRDs motivating a pre-galactic setting. Bayesian fits to J0313−1806 (z=7.64) and J0100+2802 (z=6.30) favor massive seeds, M0≈10^6 Msun, forming at z≈20–30 in regions with baryonic overdensity factors fρ≳50 relative to the mean. The histories include a long supply-limited (Bondi) stage and still reproduce the observed SMBH masses without sustained Eddington or any super‑Eddington episodes. The inferred seed scale is naturally consistent with collapse of quantum‑degenerate fermion–DM cores, offering a concrete LRD‑era pathway to early SMBHs.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 2 (J0100+2802 posteriors): Read off the MCMC contours showing the seed‑mass–overdensity degeneracy; quantify the favored log M0≈6 and that significant fρ (≳50) is required unless seeds are heavier.
Figure 3 (J0313−1806 history): Track when the model switches between Bondi‑limited and Eddington‑limited growth, how the Eddington ratio dips below unity and later resurges, and compare the final mass/luminosity to the z=7.64 data point; note the yellow line marking disfavored very‑early seed times.
Figure 4 (J0100+2802 history): Examine the mass build‑up and the duration of the Bondi‑limited plateau versus near‑Eddington phases, and confirm the model reaches the observed mass at z=6.30 without super‑Eddington demands; check the preferred seed‑redshift window relative to the yellow marker.
Figure 1 (cosmic densities vs z): Use the baryon‑density decline with expansion to understand why Bondi supply weakens with time and why overdensity fρ is pivotal for early growth in an LRD‑like environment.

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2602.06793v1

The X-ray properties of the most luminous quasars with strong emission-line outflows

Anastasia Shlentsova, Bartolomeo Trefoloni, Matilde Signorini, Guido Risaliti, Elisabeta Lusso, Emanuele Nardini, Franz E. Bauer, Matthew J. Temple, Amy L. Rankine, Gordon T. Richards

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Digest

Chandra spectroscopy of 10 extremely luminous, radio‑quiet SDSS DR16 quasars preselected for strong UV emission‑line outflows (C IV centroid blueshift ≥1400 km/s) finds largely normal coronal emission. Seven of ten show photon indices Γ>1.7, and only two qualify as X‑ray “weak,” with one of those likely an intrinsically normal but heavily obscured quasar. A tentative (~2σ) trend links unusually low X‑ray flux to very fast winds only at v_out ≳3000 km/s. Bottom line: powerful emission‑line winds in the brightest quasars do not generally require suppressed X‑rays, motivating larger unbiased X‑ray samples.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Use L2500 vs. C IV centroid shift to see how strong blueshifts become ubiquitous at the highest UV luminosities and how the 10‑object main sample was carved out of the 45 preselected targets.
Figure 2: Inspect the multi‑component fit to the C IV region; verify the outflow component’s blueshift relative to the BLR component (v_out) after masking tellurics/absorbers, confirming the ≥1400 km/s selection and how velocities were measured.
Figure 3: Locate the sample in the C IV emission‑space map colored by He II EW (MFICA reconstructions for 66,810 DR16 quasars) to gauge whether weak He II—hence softer SEDs—coincide with large C IV blueshifts in this extreme‑luminosity regime.
Figure 4: Examine the example Chandra fit to read off Γ and any absorption signatures; identify which spectra look flattened/absorbed, consistent with the obscured X‑ray‑‘weak’ outlier versus the Γ>1.7 majority.

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2602.05921v1

Early growth of massive black holes in dynamical dark energy models with negative cosmological constant

N. Menci, M. Castellano, P. Mukherjee, D. Roberts, P. Santini, A. A. Sen, F. Shankar

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Digest

Explores whether dynamical dark-energy models with a negative cosmological constant can drive early black-hole assembly seen by JWST. Using Monte Carlo–selected w0–wa histories consistent with CMB+DESI+DES, they link halo growth to maximal, continuous Eddington accretion from ~10^2 Msun Pop III seeds and predict BH mass tracks and UV luminosity functions. Models with ΩΛ ≈ −1 reproduce ≥10^7 Msun BHs at z ≳ 8 and boost bright-galaxy and AGN counts over ΛCDM without invoking heavy seeds or super‑Eddington episodes. Caveat: results are upper limits from a simplified, maximal-growth framework rather than a full BH-galaxy coevolution model.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the w0–wa confidence contours and the ‘phantom line’ to see which DE histories are allowed by CMB+DESI+DES and where negative ΩΛ solutions live (non‑phantom vs early‑phantom regions).
Figure 2: Track how the Monte Carlo draws map (w0, wa) to Ωm, ΩDE, and the implied ΩΛ; the ΩΛ probability distribution shows whether values near −1 dominate while still yielding ΩDE ≈ 0.7.
Figure 3: Compare the predicted high‑z UV luminosity functions to ΛCDM and to the cited surveys across the reported redshift bins to quantify the bright‑end enhancement that underpins the galaxy‑count boost in negative‑ΩΛ cosmologies.
Figure 4: Follow the maximal BH growth curves (Eddington‑limited from ~10^2 Msun seeds) for different ΩΛ and check which tracks reach the observed JWST/X‑ray BH masses by z ≳ 8; this tests whether ΩΛ ≈ −1 suffices without heavy seeds or super‑Eddington phases.

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2602.02702v1

Connecting the Dots: UV-Bright Companions of Little Red Dots as Lyman-Werner Sources Enabling Direct Collapse Black Hole Formation

Josephine F. W. Baggen, Matthew T. Scoggins, Pieter van Dokkum, Zoltán Haiman, Alberto Torralba, Jorryt Matthee

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Digest

Across 83 spectroscopic LRDs with JWST imaging, the authors decompose red/blue components and show that ~43% host UV-bright companions at 0.5–5 kpc (median 1.0 kpc), rising to ≳85% for the most luminous systems; in the lensed A383-LRD and newly found A68-LRD, the separations tighten to d≈0.3 kpc. These companions are modest galaxies (M* ~10^8–10^9 Msun) whose UV output yields intense local Lyman–Werner fields at the red components, J21,LW ~10^{2.5}–10^{5}. The inferred fluxes meet or exceed direct-collapse thresholds that suppress H2 cooling, naturally explaining the extreme compactness and distinctive SEDs of LRDs. This links the ubiquitous red/blue pairs to a synchronized-pair pathway for heavy-seed formation in the early universe.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Scan the RGB cutouts for the recurrent red/blue morphology and note which systems are strongly lensed (magnifications labeled), setting expectations for sub-kpc separations that may be unresolved in unlensed fields.
Figure 2: Inspect GALFIT residuals after subtracting the red component; the checkmark vs question-mark flags show where faint UV companions are securely isolated, revealing how often blue light survives model subtraction near the red core.
Figure 3: For A68-LRD1, compare the NIRCam cutouts to the SED decomposition; verify the Cliff-like red SED and the flat blue SED, and use the stacked intrinsic SEDs (right panel) to see how typical the red/blue split is across the companion-hosting subsample.
Figure 4: Read the companion LW magnitude vs effective separation plane; identify which systems lie above the J21,crit line and how lensing-driven small separations push A383-LRD/A68-LRD into the high-J21 regime supporting direct collapse.

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2602.04974v1

Clustering of z~6.6 Quasars and [O III] Emitters Constrains Host Halo Masses and Duty Cycles in 25 ASPIRE Fields

Jiamu Huang, Joseph Hennawi, Elia Pizzati, Feige Wang, Jinyi Yang, Jaclyn B. Champagne, Xiaohui Fan, Eduardo Bañados, Xiangyu Jin, Koki Kakiichi, Romain A. Meyer, Fengwu Sun, Yunjing Wu, Haowen Zhang, Chiara Mazzucchelli, Anna-Christina Eilers, Maria Pudoka, Huanian Zhang, Jan-Torge Schindler, Matthieu Schaller, Joop Schaye, Ben Snyder, Yi Kang, Silvia Onorato

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Digest

Measures clustering of [O III] emitters (5.3<z<7.0) and their cross-correlation with 25 z~6.6 quasars in JWST/ASPIRE WFSS, calibrating completeness via synthetic source injection and interpreting with FLAMINGO-10k mocks that include nonlinear bias and cosmic variance. The [O III] auto-correlation yields r0GG=4.7 h^-1 cMpc (gamma=1.8) and the quasar–[O III] cross-correlation r0QG=8.7 h^-1 cMpc (gamma=2.0). A step-function HOD fit implies minimum halo masses log Mh,min≈10.5 for [O III] emitters and 12.1 for quasars. Number-density matching gives duty cycles of 2.5% and 0.3%, i.e., UV-bright lifetimes tQ≈2.6 Myr (<10% of a Salpeter e-folding), indicating the luminous phase contributes little to total SMBH growth.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

2PCF of [O III] emitters with best-fit power law (gamma=1.8): inspect r0GG≈4.7 h^-1 cMpc, small-scale deviations from the fit, and comparison to FLAMINGO-10k mocks for scale-dependent bias.
Quasar–[O III] cross-correlation: check amplitude r0QG≈8.7 h^-1 cMpc, any excess on sub-Mpc scales, and field-to-field scatter that informs covariance.
WFSS selection function from synthetic source injection: recovery fraction versus line flux and wavelength; verify contaminants and how the completeness model feeds the mocks.
HOD/halo-mass posteriors: joint constraints showing log Mh,min≈10.5 ([O III]) and ≈12.1 (QSOs), with covariance-aware contours and degeneracies.
Duty cycle and lifetime inference: plot converting halo abundances to f_duty and tQ, highlighting tQ≈2.6 Myr and the <10% Salpeter e-folding fraction.

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2602.03030v1

From Grism to IFU: Revising the Redshift and Nature of the Massive Dusty Galaxy S1 with JWST and ALMA

Mengyuan Xiao, Longji Bing, Gabriel Brammer, Pascal A. Oesch, David Elbaz, Rui Marques-Chaves, Miroslava Dessauges-Zavadsky, Benjamin Magnelli, Rychard Bouwens, Emanuele Daddi, Maximilien Franco, Qiusheng Gu, Thomas Herard-Demanche, Garth Illingworth, Ivo Labbe, Danilo Marchesini, Jorryt Matthee, Romain A. Meyer, Rohan P. Naidu, Irene Shivaei, Pieter van Dokkum, Andrea Weibel, Christina C. Williams, Stijn Wuyts

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Digest

NIRSpec IFU spectroscopy revises the dusty GOODS source S1 from a grism-based z=5.58 to a secure z_spec=3.2439±0.0002 via multiple rest-optical/NIR lines ([S III], He I 1.083 μm, Paγ). The team demonstrates that the original single-line slitless identification was contaminated by a neighboring galaxy whose dispersed Brγ trace overlapped S1, highlighting the risk of single-PA grism redshifts. New ALMA 1 mm imaging detects S_1mm=0.99±0.03 mJy and finds compact dust (Re_1mm=0.73±0.10 kpc) slightly smaller than the F444W stellar size (Re=0.97±0.01 kpc). With the revised redshift, S1 is a very massive (log M*≈10.6), heavily obscured, dust- and gas-rich main-sequence galaxy with a moderate SFR and a long gas depletion time (τ_dep≈1.4 Gyr).

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Use the IFU 1D spectrum and model overlay to see the multi-line redshift solution at z=3.2439, confirming [S III], He I 1.083 μm, and Paγ in the G395H window and the continuum level that anchors the fit.
Figure 2: Inspect zoomed line profiles to check centroids and S/N of [S III], He I 1.083 μm, and Paγ that set z_spec, and verify mutual consistency among lines without relying on a single feature.
Figure 3: Compare the ALMA 1 mm map and contours with the JWST RGB to gauge dust–starlight co-spatiality; note the compact dust size (Re_1mm=0.73±0.10 kpc) versus the F444W stellar Re=0.97±0.01 kpc and the integrated 1 mm flux (0.99±0.03 mJy).
Figure 4: Trace the slitless contamination geometry—identify the neighboring source (CDFS_00336) and its Brγ feature whose dispersed path overlaps S1—showing how this led to the earlier Hα misassignment at a single dispersion angle.