Weekly issue

Week 38, 2026

Sep 14–20, 2026

Week 38, 2026 includes 10 curated papers, centered on LRD, high-z, QSO.

2609.20021v1

Little Red Dots as a Transient Phase of Self-Interacting Dark Matter Assisted Black Hole Growth

Yu Rong, Shuang-Nan Zhang, Jian-Min Wang, Junxian Wang, Zhicheng He

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Rong et al. propose that little red dots are a short-lived, obscured stage of black-hole assembly triggered when a gas-rich nuclear compaction compresses self-interacting dark matter (SIDM) around a pre-existing seed. In their semi-analytic picture, a compact, optically thick thick disk both ignites rapid SIDM-fed mass growth and supplies the high-column, Balmer-active reprocessing material that produces X-ray weakness and a red, V-shaped continuum. Calibrated mock spectra reproduce the broad spectral shape and Balmer-break-like curvature of RUBIES-EGS-55604 and are also compared with RUBIES-UDS-40579, linking overmassive black holes, obscuration, and a finite LRD duty cycle to one local inflow event. The model predicts that LRDs preferentially mark galaxies in strong nuclear-inflow phases before evolving into more ordinary AGN.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1. This schematic is the clearest overview of the proposed causal sequence: gas inflow creates a compact thick disk, the disk compresses SIDM and triggers black-hole growth, and edge-on high-column sight lines appear as red, X-ray-weak LRDs. It usefully distinguishes the paper's coupled SIDM-plus-obscuration scenario from models in which dark-matter growth or reddening is treated separately.
Figure 2. The fiducial RUBIES-EGS-55604 spectral comparison is the paper's central empirical demonstration. It shows how the obscured AGN, Balmer-active reprocessing photosphere, leaked young stellar light, and weak host contribution combine to reproduce the observed V-shaped continuum while masking strong emission-line regions from the continuum fit.
Figure 3. The comparison to RUBIES-UDS-40579 tests whether the same disk-atmosphere framework extends beyond the fiducial source. Its component decomposition highlights the claimed physical origin of the red continuum: an obscured AGN plus a cooler absorbed-and-reprocessed photosphere, with only a modest leaked young-star contribution.

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2609.16992v1

Lyman-$α$ forest 1D flux power spectrum constraints on QSO-assisted reionization models

Vid Iršič, Avery Meiksin

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Iršič and Meiksin use Sherwood-Relics Lyα-forest simulations post-processed with QSO-driven He III regions to test whether JWST’s faint AGN populations overheat the z=4.2–5.0 intergalactic medium. The added, patchy He II-reionization temperature boosts improve agreement with precision 1D flux-power measurements, whose small-scale suppression is sensitive to QSO abundance and EUV spectral hardness. Little Red Dots remain consistent with either a 10,000 K boost from soft-spectrum QSOs or a 20,000 K boost from hard-spectrum QSOs, but the much larger JWST faint-QSO population with MUV > -21.6 is excluded at 2σ when hard spectra produce boosts of at least 20,000 K. The result turns the Lyα forest into a statistical constraint on whether the newly identified faint AGN population can substantially drive early He II reionization.

Open paper page arXiv abstract arXiv PDF

Key figures to inspect

Figure 1. This figure establishes the physical lever arm of the analysis: hotter QSO-generated He III regions suppress small-scale Lyα flux power, with the effect strengthening as the luminosity function is integrated to fainter QSOs. Its comparison of the two QSO luminosity-function models and 10,000 versus 20,000 K temperature boosts directly motivates the paper’s LRD-versus-larger-faint-QSO constraint.
Figure 3. The posterior contours show how the Lyα forest data constrain the maximum UV magnitude of the QSO population jointly with thermal, transmission, and cosmological parameters. This is the core statistical diagnostic behind the conclusion that LRD-like number densities are allowed while a numerous hard-spectrum faint-QSO population is disfavored.
Figure 4. This synthesis figure translates the power-spectrum inference into an ionizing-emissivity history and compares it with bright-end and faint-end QSO luminosity-function expectations, as well as an optical-depth-distribution-motivated QSO-assisted model. It clarifies the population-level implications of the Lyα constraint beyond the fitted temperature parameters.

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2609.16122v1

A Dark-matter Origin of Little Red Dots: Early Seeding and Super-Bondi Accretion

Hua-Peng Gu, Fangzhou Jiang, Xian Chen, Ran Li, Zi-Xiang Jia

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Gu et al. model little red dots as the descendants of self-interacting dark-matter halos whose gravothermal collapse forms stellar-mass black-hole seeds before reionization. In their fully relativistic, non-equilibrium calculations, the post-collapse SIDM core feeds the seed through near-free-fall and heat-conduction-supported super-Bondi inflow, allowing growth to supermassive scales without baryonic accretion. Combining the required halo concentrations with halo abundances and merger survival probabilities, they find an SMBH population consistent with the observed LRD abundance and redshift distribution. The work offers a dark-sector explanation for LRDs with weak stellar hosts, while making their demographics a potential probe of SIDM microphysics and of merger disruption in early halos.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1. Use this overview schematic to establish the paper's central causal chain: SIDM thermalization, gravothermal collapse, horizon formation, and conductive super-Bondi growth into an SMBH. It makes clear that the authors treat seed formation and subsequent dark accretion as one continuous halo-evolution problem.
Figure 3. This is the key physical diagnostic for the paper's distinctive claim. The comparison with the Bondi prediction isolates the near-free-fall and heat-conduction-driven phases that keep dark-matter accretion super-Bondi for most of the relevant growth period.
Figure 4. This figure connects the modeled black-hole growth tracks directly to spectroscopically measured LRD black-hole masses and shows how varying initial halo mass and concentration spans the observed distribution. It also visualizes the merger-interruption boundary and the possible extra growth enabled by smooth cosmological halo accretion.
Figure 5. Use this parameter-space synthesis to show which pre-reionization halos can seed and grow SMBHs on time, and why the viable population occupies a preferred halo-mass range. The lower panel links the timing requirement to both merger survival and the halo mass function, which underpins the demographic argument.
Figure 7. This figure provides the merger-history caveat behind the population calculation: low-mass halos are frequently disrupted by major mergers before completing gravothermal evolution. It explains why the mechanism does not simply operate in every early SIDM halo.

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2609.13444v1

Host Galaxy UV Emission and Dust Reddening in Little Red Dots

Emmanuel Durodola, Ryan C. Hickox, Jonathan Cohn, David M. Alexander

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Using JWST/NIRSpec PRISM plus medium-resolution G235M/G395M spectra for 13 LRDs, Durodola et al. separate narrow Balmer-line emission from the nuclear components to test the origin of the faint rest-UV continuum. Their narrow-line Balmer decrements are generally above case-B expectations and correlate with both UV slope and Balmer-break strength, while the rest-optical slope shows no comparable trend, pointing to dust-reddened UV light on host-galaxy scales. SED fits likewise favor dust-attenuated stellar UV continua, and the broader 89-object PRISM sample separates into break-strength classes in which the canonical strong-break, flat-UV LRDs are an extreme sub-population rather than the whole population. The result supports young, dusty host galaxies as the dominant UV source in most LRDs, alongside intrinsically red accretion-related optical emission.

Open paper page arXiv abstract arXiv PDF

Key figures to inspect

Figure 3. This is the central empirical diagnostic: narrow-line Balmer decrement tracks both the observed UV slope and Balmer-break strength across the 13-object medium-resolution sample, but not the rest-optical slope. It directly motivates the interpretation of host-scale dust reddening for the UV component and physically distinct UV and optical SED origins.
Figure 7. The SED-fitting synthesis shows that redder modeled UV slopes correspond tightly to higher stellar attenuation and that LRD hosts occupy a dustier, generally more massive regime than the comparison star-forming galaxies. It provides the stellar-continuum counterpart to the nebular attenuation evidence from the Balmer decrements.
Figure 8. This population-level UV-slope versus Balmer-break diagram extends the interpretation from 13 medium-resolution targets to 89 PRISM-selected LRDs. Its dust-attenuation direction and break-strength split make clear that strong-break, flat-UV objects are the most extreme spectral subset.
Figure 9. The break-strength-binned composite spectra provide the clearest visual summary of LRD spectral diversity, contrasting power-law, intermediate-break, and extreme-break populations on a common normalization. This figure supports the paper's conclusion that LRDs are not monolithic and that the canonical extreme-break shape is not representative of every object.

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2609.12049v1

Little Red Dots are Direct-Collapse Black Hole-Forming Galaxies

Daniel J. Whalen, Muhammad A. Latif, Konstantinos Topalakis, Fergus Cullen, Devesh Nandal, Sadegh Khochfar

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Whalen et al. argue that little red dots are direct-collapse black hole galaxies observed while the newly formed black hole remains embedded in the dense accretion disk that created it. Their radiation-hydrodynamic disk calculations and composite Cloudy+BPASS spectra reproduce the V-shaped SEDs, Balmer absorption, weak escaping X-rays, and compact stellar components of LRDs, including RUBIES-EGS-42046, MoM-BH*-1, and CAPERS-LRD-z9. The proposed mechanism links the characteristic LRD continuum directly to X-ray trapping in gas reaching roughly 10^10 cm^-3 near the BH, while a predominantly Pop II cluster concentrated within about 150 pc supplies the observed compact host light.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1. This establishes the proposed physical engine: an ultradense DCBH accretion disk with a trapped central H II region. It is the clearest visual basis for the paper's claim that X-rays are absorbed and reprocessed rather than breaking out.
Figure 2. This shows the second essential component of the model, a predominantly Pop II stellar cluster concentrated around the DCBH within roughly 150 pc. It connects the simulated host to the compact stellar populations inferred for LRDs.
Figure 3. This is the core observational comparison, showing spectral fits across several LRDs spanning typical objects and an extreme Balmer-break source. It demonstrates that the same embedded-DCBH framework can accommodate diversity in the observed V-shaped SEDs.
Figure 4. The fit to CAPERS-LRD-z9 extends the model comparison to z=9.29, making it the strongest single illustration of the proposed channel at the highest-redshift end of the current LRD sample.

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2609.20022v1

Rapid Dark Growth of Seed Black Holes in Self-Interacting Dark Matter

Yu Rong, Shuang-Nan Zhang, Jian-Min Wang, Junxian Wang

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This paper models a distinct early-black-hole growth channel in which merger- or compaction-driven gas inflow contracts a self-interacting dark-matter halo and builds a dense SIDM reservoir around a pre-existing seed. Solving time-dependent spherical SIDM fluid equations with self-gravity, conductive heat transport, and an absorbing black-hole sink, the authors find a brief collisional dark-accretion burst that can add several orders of magnitude in mass in under 1 Myr before the flow loses efficient collisional coupling. Halo mass is the dominant control on the effective saturation mass, whereas gas fraction, nuclear size, and seed mass have weaker effects, making baryon-compressed SIDM a potentially efficient route to the massive seeds implicated by little red dots.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1. This is the paper’s central result figure: it follows the numerical black-hole mass growth during gaseous-nucleus assembly, identifies the effective collisional endpoint where the SIDM flow becomes less efficiently coupled, and contrasts the finite-reservoir calculation with the ideal unlimited-supply model. It makes clear that the rapid burst is substantial but terminates well below the formal ideal-growth outcome, while showing that halo mass drives the strongest variation across the parameter grid.

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2609.16951v1

An ALMA Band 7 survey of SDSS/Herschel quasars in Stripe 82: II. The nature of FIR-bright quasars

Evanthia Hatziminaoglou, Hugo Messias, Duncan Farrah, Anna Feltre, Dennis Koopmans, Ismael Perez-Fournon, Rhimon Souza, Lingyu Wang

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Using 0.8-arcsec ALMA Band 7 imaging to deconfuse 142 Herschel-selected SDSS quasars at 1 < z < 4 in Stripe 82, this paper revises the host-galaxy star-formation budget of FIR-bright quasars. ALMA lowers inferred SFRs by about 20% for single-counterpart systems and by more than a factor of two for SPIRE-blended systems, yet leaves a population of extreme starbursts with SFRs of 500-3000 solar masses per year and a median of 1080. Their weak starburst-accretion luminosity relation, enhanced 1.4-GHz detection rate consistent mainly with the FIR-radio correlation, and selectively weaker Lyα and C IV emission support a short transitional phase in which vigorous bulge growth and SMBH accretion coexist with AGN-driven winds. The result sharpens the case that these optically visible, FIR-bright quasars bridge obscured blowout systems and ordinary blue quasars rather than simply reflecting Herschel beam confusion.

Open paper page arXiv abstract arXiv PDF

Key figures to inspect

Figure 3. This distribution directly quantifies why ALMA resolution changes the physical interpretation: single-counterpart quasars receive modest SFR revisions, whereas systems with multiple submillimeter counterparts can have strongly inflated Herschel-based SFRs. It is the clearest visual statement of the deblending correction underlying the paper's revised starburst census.
Figure 4. The starburst-luminosity versus 1.4-GHz comparison tests whether the FIR emission is predominantly powered by star formation after ALMA deconfusion. Its placement relative to the Bell and redshift-dependent FIR-radio relations supports the conclusion that most radio-detected FIR-bright quasars remain consistent with star-forming hosts rather than being dominated by radio AGN.
Figure 5. This is the key population-level diagnostic for the claimed weak coupling between host star formation and instantaneous SMBH accretion. The maximum-likelihood regression and intrinsic scatter show that even among exceptionally star-forming quasar hosts, starburst and accretion luminosities rise only very shallowly together.
Figure 7. The equivalent-width distributions provide the concise spectral evidence for a distinct FIR-bright quasar phase: Lyα and C IV are reduced relative to the matched FIR-faint control, while Mg II is comparatively unchanged. That line-dependent difference is central to the proposed interpretation involving AGN-driven winds that affect high-ionization UV emission without comparably altering Mg II.

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2609.19459v1

Extreme Enrichment at Cosmic Dawn: Three FeII-Strong Quasars at z > 6 from the JWST Aether survey

Anniek J. Gloudemans, Emanuele Paolo Farina, Roberto Decarli, Klaudia Protušová, Fabrizio Arrigoni Battaia, Eduardo Bañados, Aaron J. Barth, Silvia Belladitta, Manuela Bischetti, Hyunseop Choi, Dominika Ďurovčíková, Anna-Christina Eilers, Simona Gallerani, Thales A. Gutcke, Luca Ighina, Brian C. Lemaux, Federica Loiacono, Yoshiki Matsuoka, Chiara Mazzucchelli, Silvia Onorato, Hyewon Suh, Fabian Walter, Feige Wang, Julien Wolf, Jinyi Yang

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Using JWST/NIRSpec IFU spectroscopy from the roughly 200-quasar Aether survey, this paper identifies J0216-5226, J0320-3521, and J1429+5447 as extreme z>6 outliers with very strong optical Fe II and weak Hβ and [O III]. Their R_FeII,λ4570≈2.5–3.6 places them in the top ∼3% of low-redshift SDSS quasars and makes them the most Fe II-strong high-redshift quasars yet observed, supporting rapid broad-line-region enrichment within the first Gyr. Hα-based estimates indicate otherwise typical massive, moderately accreting black holes in J0216-5226 and J1429+5447, while J0320-3521 may host a lower-mass, potentially super-Eddington accretor; resolved line-emitting structures around the latter two radio-loud quasars additionally expose diverse companion-galaxy or ionized-gas environments. The interpretation of the virial masses warrants caution because strong Fe II emitters may have systematically overestimated single-epoch mass estimates.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1. The NIRSpec IFU spectral fits directly establish the paper's defining evidence: unusually prominent Fe II emission together with weak Hβ and [O III] in all three z>6 quasars.
Figure 3. This is the key population-context figure, placing the three Aether objects on the Hβ-width versus Fe II-strength Eigenvector 1 plane and showing that they occupy the extreme high-R_FeII tail relative to SDSS, other high-redshift quasars, and the full Aether sample.
Figure 4. The quasar-subtracted Hβ, [O III], and Hα maps provide the central resolved-environment result, revealing the eastern emission-line region near J0320-3521 and the multiple structures around J1429+5447.
Figure 8. The broad-band radio SED of J1429+5447 anchors the radio-loudness aspect of the interpretation and tests physically motivated spectral models for this Fe II-strong quasar with a complex environment.
Figure 9. The alternative Fe II-template fits make the principal spectral-modeling systematic visible: the inferred Fe II equivalent widths and R_FeII values depend on whether the Mrk 493 or I Zw 1 template is adopted.

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2609.17680v1

A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$

Qinyue Fei, Seiji Fujimoto, Gabriel Brammer, Lise Christensen, Marianne Vestergaard, Rohan P. Naidu, Robert A. Simcoe, Norman Murray, Luis C. Ho, Ruancun Li, Volker Bromm, Javier Álvarez-Márquez, Hollis B. Akins, Yoshihisa Asada, Simona Di Stefano, Kohei Inayoshi, Vasily Kokorev, Jorryt Matthee, Romain A. Meyer, Ava Polzin, Francesco Valentino, Fabian Walter, Marcel Neeleman, Yunjing Wu, Mengyuan Xiao

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Fei et al. identify an exceptionally strong, dense metal absorber at z=7.03 along the sightline to the red quasar GNz7q and associate it with ND1, a vigorously star-forming, NIR-dark galaxy only about 16 pkpc away. JWST/NIRSpec detections of [O III] and Hα, together with NOEMA [C II], fix ND1’s systemic redshift and show the absorber is coherently blueshifted by about 50 km s⁻¹, supporting a chemically enriched outflow with an inferred mass-loss rate of 64 M⊙ yr⁻¹ and mass loading η=3. The system offers direct evidence that a dust-obscured starburst can enrich its CGM during reionization, while the absorber’s elevated [C/O] may preserve a signature of Population III enrichment. Its NIR-dark host also warns that rest-UV-selected galaxy samples can miss dusty sources responsible for early CGM and IGM metal pollution.

Open paper page arXiv abstract arXiv PDF

Key figures to inspect

Figure 1. This establishes the observational foundation: the GNz7q spectrum contains the unusually rich, multiphase metal absorption system whose extreme equivalent widths and column densities motivate the absorber-host analysis.
Figure 5. This is the key host-identification figure, combining ND1’s long-wavelength-only imaging detection, dust continuum context, and NIRSpec emission lines that anchor the galaxy at the absorber redshift.
Figure 13. This directly tests the paper’s feedback interpretation by placing the absorption components against ND1’s emission-line systemic frame and visualizing the coherent blueshift attributed to an outflowing halo.
Figure 14. This carries the chemical-enrichment conclusion: ND1’s inferred [C/O] and [Si/O] are compared with other high-redshift measurements and Population II versus Population III yield tracks, motivating the primordial-enrichment interpretation.

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2609.18646v1

A homogeneous analysis of archival and new low-resolution spectra of YZ Cancri

Zhibin Dai, Lihuan Yu, Jiao Li, Xuefei Chen, Zhanwen Han

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Dai et al. homogenize three calibrated archival outburst-related spectra and seven new BFOSC quiescent exposures of the SU UMa dwarf nova YZ Cnc, applying a common continuum and line-measurement procedure across Balmer, He I, Fe II, O I, He II, and Bowen features. The central state contrast is clear: outburst-related spectra show broad Balmer absorption or composite profiles, while quiescence is characterized by strong single-peaked Balmer and He I emission, recurrent Fe II λ5169, and weak O I λ7772; He II λ4686 and the Bowen blend appear only intermittently. The line-ratio analysis finds a relatively flat quiescent Balmer decrement, variable He I ratios, and no compelling Fe II departure from optically thin expectations, yielding a useful empirical reference for future phase-resolved, higher-resolution mapping of the line-forming gas despite the present spectra's limited resolution and phase coverage.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1. This archival-spectrum overview establishes the heterogeneous outburst-related and qualitative comparison material, making the broad Balmer absorption and composite-profile states visually explicit before the homogeneous measurements are introduced.
Figure 2. The BFOSC quiescent sequence is the key observational evidence for persistent single-peaked Balmer and He I emission, recurrent Fe II and O I, and the exposure-limited appearances of He II λ4686 and the Bowen blend.
Figure 3. This is the conclusion-driving diagnostic figure: it directly compares quiescent Balmer, He I, and Fe II ratios, showing the flat Balmer decrement, substantial He I scatter, and Fe II ratios without a clear systematic offset from optically thin reference values.