Weekly archive
LRDigestWeekly digests of little red dots and JWST-selected AGN papers, with curated reading notes and archive pages.
654 indexed papers · 430 research notes
BRAHMA mock observations suggest that overmassive, dense-gas-enshrouded AGN can yield AGN-dominated LRD colors and an LRD density of (2.04 ± 0.32) × 10^-4 Mpc^-3 at z=5–8; this is a model-dependent explanation, not a direct detection of the proposed environments.
A 184-object COSMOS sample selected through [Ne V] or C IV combines X-ray–radio SED fitting with Simba analogues. The authors infer obscured, high-accretion transitional populations, with [Ne V] hosts pre-quenching and C IV hosts more often quenched.
In an L-GalaxiesBH synthetic NIRCam lightcone, photometric LRDs are modeled as a mixed galaxy–AGN population: older low-mass stellar systems and higher-mass systems whose relatively faint AGN preserve a Balmer-break-driven V-shaped SED; torus obscuration is secondary.
A semi-analytic test of GRMHD-motivated magnetic suppression finds that limiting suppression to low-Eddington accretion and rescaling AGN feedback can retain local galaxy and black-hole demographics while allowing rapid early black-hole growth.
This paper proposes that feedback-free cluster formation, dry cluster migration, and later wet compaction can jointly make compact, black-hole-hosting LRDs at z=4–8. The central prediction remains a partly untested synthesis because no simulation yet follows all processes together.
SALSA publicly releases synthetic absorption-line spectra from cosmological simulations, using Voronoi-mesh ray tracing to connect ISM, CGM, and IGM gas to survey-like observables. Its principal value is controlled mock-survey and galaxy–absorber analyses, bounded by ionization, yield, and dust-model assumptions.
This two-component SIDM model identifies parameter space that authors argue meets relic-density, velocity-dependent scattering, linear-power, and representative direct-detection constraints; a subpercent ultra-interacting component is proposed to seed early black holes relevant to little red dots.
MESA quasi-star models predict a long-lived, cool late stage whose continuum broadly resembles two JWST Little Red Dots, including one measured Balmer break, but mismatched extreme breaks and simplified atmospheres prevent identification of LRDs as quasi-stars.
THESAN-ZOOM simulations link z=5–8 O I absorbers to evolving ionisation around faint galaxies: although CGM O I covering fractions fall by about 0.2, most observable systems are predicted beyond halo virial radii.
BRAHMA constrained simulations find that heavy-seed abundance and merger dynamics govern black-hole assembly above z≈9, whereas permissive late gas accretion is needed to reach z≈6 quasar masses; extreme z≈9–10 BH-to-stellar ratios remain difficult under subgrid dynamical friction.
The authors update the SIDES framework with revised star-forming, starburst, quiescent, and AGN SED templates plus a probabilistic assignment of the AGN contribution to the IR, applying it within pySIDES and the SC SAM lightcone. The model reproduces JWST/MIRI number counts, redshift distributions, and AGN fractions across the filters, finding AGN dominate at bright fluxes (Sν ≳ 20 μJy) while main-sequence galaxies set the faint-end counts. They quantify field-to-field variance, showing ≈30% uncertainty in bright AGN counts for survey areas <25 arcmin², and provide MIRI color–color and joint NIRCam+MIRI flux diagnostics for selecting obscured AGN. This delivers a practical forward model for interpreting MIRI-selected dusty AGN and for designing future mid/far-IR surveys.
A radiation–GRMHD suite with angle-discretized transport follows super‑Eddington inflow across accretion rates, spins a*≈0.3–0.94, and single/double‑loop fields, finding robust, radiation‑pressure supported thick disks. Inner‑disk radiation drives powerful outflows that carve conical funnels, trap photons, and keep radiative efficiencies low while thermal transport is dominated by advection. Angular momentum is carried mainly by Maxwell stress; jets occur in weak and strong modes, with strong jets (net vertical flux + high spin) evacuating the funnel and enabling geometrically beamed escape, whereas weak jets leave the funnel clogged and dimmer—implications for ULXs and little red dots. Spiral density waves appear in the plunging region, adding structure to the inner flow.
First IR spectra from a fully self-consistent, cosmological-to-sub-sublimation quasar simulation (post-processed with SKIRT) show that the emission is dominated by a torus-like structure built from a highly magnetized, turbulence-supported outer accretion disk plus dusty gas tidally stripped from the ISM. In this early phase the nucleus is buried and Compton-thick, and the escaping near–mid-IR luminosity varies by nearly an order of magnitude with sightline, driven largely by extinction in an inflowing cold dusty stream. Self-absorption within the torus cools the SED and suppresses silicate emission, while reprocessing by the surrounding ISM imprints prominent silicate absorption; sublimation zones stratified by grain size/composition yield intrinsically varied extinction curves that emerge grayed after multiple scatterings. Clearing biconical cavities in later stages preserves MIR anisotropy and silicate features, implying a buried, IR-bright phase early in dusty starburst quasar evolution.
Simulated light curves for little red dots are generated under two variability prescriptions: an empirical sub‑Eddington DRW tuned to low‑z AGN and a radiation‑MHD–motivated super‑Eddington disk model. With today’s 2–4‑epoch JWST sampling, the DRW case would have produced far more rest‑UV/optical variability than is seen, while the super‑Eddington model naturally matches the near‑steady continua. The high‑cadence nexus imaging should yield Δm>1 mag if DRW holds, but only the lowest‑mass LRDs vary appreciably in the super‑Eddington scenario; meanwhile, twinkle spectroscopy is still expected to detect broad‑line variability if soft X‑rays can reach the BLR. Net result: super‑Eddington accretion neatly explains the missing continuum variability while allowing line changes.
Builds a seed-to-SMBH pathway inside a two-phase (fast/slow halo growth) framework: Pop III remnants are bred in mini-halos at the H2- (or delayed atomic-) cooling thresholds, then grow via nuclear-burst super-Eddington episodes, SGC sub-cloud capture, and finally mergers. Implemented on subhalo merger trees, the model produces a broad seed spectrum (10–10^5 Msun at z≈20–30) and a multi-piece, redshift-dependent M_BH–M_* relation set by the dominant channel. A key result is that early nuclear bursts enable rapid mass gain, naturally yielding compact accretors reminiscent of JWST little red dots before merger-dominated quiescence. The framework links LW background and halo assembly rate to BH demographics and matches current constraints.
Assuming the star-only interpretation of compact, red z∼5 Little Red Dots, the authors model ultradense cores where dynamical friction for 10 M⊙ stars in the inner 0.1 pc is <0.1 Myr, triggering rapid mass segregation. A Fokker–Planck core-evolution calculation, an analytic collisional-growth model, and direct N-body simulations all converge on runaway mergers that build a very massive star of 9×10^3–5×10^4 M⊙ within <1 Myr. The VMS then contracts on a ∼8000 yr Kelvin–Helmholtz timescale and collapses to an ∼10^4 M⊙ black hole. This route yields seed number densities above direct-collapse expectations and, with a dense residual core, can power elevated tidal disruption event rates.
Applies the CHAR (corona-heated disk reprocessing) model to the Tee et al. (2025) 22-object LRD sample to interpret their multi-epoch photometry. Finds that the measured |Δm| is dominated by photometric uncertainties; within CHAR the non-detections are consistent with either AGN light fractions ≲30% or intrinsically luminous AGN whose fractional variability is small. Simulations specify what it would take to break this degeneracy: ≈200 LRDs, two epochs separated by ≥2 years (observed frame), and σ_phot ≤0.07 mag. If variability still fails to appear, it would point to accretion modes unlike those of low‑z quasars, offering independent constraints on what powers LRDs.
Preliminary MELIORA cosmological simulations implement a direct-collapse BH formation model that tracks Lyman–Werner irradiation and halo inflow rates to test whether newborn heavy seeds can resemble Little Red Dots. The simulated population of newly formed DCBHs drops sharply at z<6 as inflows wane, mirroring the observed emergence-and-decline trend of LRDs. DCBH birth coincides with a strong gas-compaction event and a short, bright AGN phase lasting ~200 Myr, after which the first Pop III stars appear and the AGN fades. If LRDs trace this nursery phase, their weak X-ray and hot-dust signatures follow naturally from the scenario.
Using the A-SLOTH semi-analytic framework, the authors generate a DCBH-seeded SMBH population and benchmark it against Little Red Dot (LRD) demographics and spectra. Heavy (DCBH) seeds reproduce the observed LRD BH mass functions, number densities, and host-halo trends better than stellar-remnant seeds. For the most extreme early LRDs (e.g., MoM-BH*-1), DCBH scenarios with either strong dust attenuation or dense, dust-free gas can match the distinctive V-shaped, Balmer-break–dominated SEDs, whereas even super-Eddington growth on light seeds cannot. The work points to gas metallicity as a crucial observable, beyond BH-to-stellar mass ratios, to pin down LRD progenitors.
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.
The authors run 3D Monte Carlo radiative transfer to test how resonance, Raman, and Thomson scattering sculpt Balmer lines in Little Red Dots. Resonance scattering in an n=2–populated H I medium drives strong departures from Case B and distinct Hα vs Hβ shapes, but Hβ is funneled into Paα, preventing broad Hβ wings. Raman scattering of higher Lyman-series emission can explain Hα/Hβ wing-width ratios ≳1.28, whereas Ramanization of a UV continuum is disfavored by the near-constant FWHM across transitions. Thomson scattering with Te≈10^4 K and electron column ≈10^24 cm−2 reproduces the ≳1000 km s−1 wings and implies virial BH masses can be overestimated by ≳10 if widths are taken at face value.
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.
Models little red dots as supermassive stars fed by massive self‑gravitating discs assembled in gas‑rich major mergers, reproducing the V‑shaped SED as two blackbodies and attributing Balmer broadening to disc rotation—without invoking extra AGN, stellar, or dust components. MCMC fits to two representative LRDs (J0647‑1045 and COS‑756434) yield sub‑Eddington disc accretion and SMS masses of a few ×10^6 Msun with physically motivated parameters. The framework predicts a luminosity cut‑off of order few ×10^44 erg/s and ties the observed redshift distribution of LRDs to merger rates, matching current trends. Acknowledged caveat: reproducing the absolute abundance of LRDs remains challenging, though the fits are robust to observed diversity.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Exascale AthenaK GRRMHD simulations solve full radiation transport to survey stellar-mass black hole accretion from sub- to highly super-Eddington, spanning spins and initial magnetic topologies. Super-Eddington runs build geometrically thick, radiation-supported disks with a narrow inner funnel, drive powerful equatorial outflows, and remain radiatively inefficient; near/sub-Eddington structure hinges on net vertical flux—forming a thin dense midplane plus magnetically dominated corona when present, versus magnetically dominated throughout without it. Even short of MAD, net-flux high-spin cases launch relativistic jets, connecting to ULXs (Cyg X-3, SS433) and offering a framework for interpreting JWST little red dots. Caveat: results use simplified opacities tailored to stellar-mass systems.
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.
Builds a multi-wavelength photoionization grid that co-models IMBH accretion and ULX populations in metal-poor, highly star-forming dwarfs, with BH mass tied to seeding channel and metallicity and ULXs evolving with post-starburst age and Z. Finds broadband X-rays and common UV lines carry little leverage on MBH and cannot reliably separate ULXs from IMBHs, while many optical diagrams also fail. Redefines optical cuts using He II λ4686 and [O I] λ6300, and highlights mid-IR ratios (e.g., [Ar II] 6.98μm, [Ne V] 14.3μm, [O IV] 25.9μm) as the cleanest discriminants with sensitivity to MBH and fAGN. Implication: relying on strong-line diagrams alone biases dwarf AGN demographics and may inflate claims of over-massive BHs in some JWST-selected high-z samples.
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.
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.
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.
Semi-analytic merger-tree modeling with observationally calibrated X-ray irradiation (guided by HERA’s 21 cm non-detections) shows that strong X-ray backgrounds boost H2 formation, steering most overdense halos off the classic direct-collapse path. Including baryonic streaming motion preserves an atomic-cooling route in a subset of cases, still yielding massive seeds. The model predicts seeds with M_BH ≳ 10^4 Msun by z ≃ 15 and an abundance ≈10^-4 Mpc^-3, sufficient to account for SMBHs verified by JWST spectroscopy at 3<z<6. X-ray ionization prevents formation of extremely overmassive BHs comparable to their hosts, while establishing BH-to-stellar mass ratios ≃0.01–0.1 at seeding.
Develops a CDM halo-model framework for the quasar proximity effect that explicitly includes overdense quasar environments and fits individual Lyα spectra for the radiation-equality radius r_eq and large-scale quasar bias b_q, validated on the ASTRID hydrodynamic simulation. Demonstrates that r_eq can be recovered without bias from a single spectrum with 25–50% statistical uncertainty. Scaling to DESI-sized samples enables precise measurements of the UV background intensity and its redshift evolution. Using the Uchuu simulation, shows that proximity-effect measurements could map spatial UV radiation fluctuations and measure their power spectrum on 100–1000 h−1 Mpc scales, making the radiation field a cosmological observable alongside density.
Using Monte Carlo merger trees, the authors model black hole seeding via gravothermal core-collapse in self-interacting dark matter halos and their subsequent growth at early times. Collapse occurs in rare, high-concentration halos at a characteristic mass scale set by the velocity-dependent cross section, naturally producing seeds early enough to explain compact, galaxy-poor little red dots. With simple growth assumptions and a 100% duty cycle, the model reproduces the observed LRD black hole mass function for σ0m ~ 30 cm^2 g^-1 and ω ~ 80 km s^-1, consistent with independent local constraints. If σ0m or ω are higher, the resulting overproduction at one end of the mass function can be mitigated by a reduced duty cycle or lower Eddington ratios, suggesting high‑z BH demographics as a probe of SIDM physics.
Simulation-driven forecast of a full obscured-AGN census using the far-IR PRIMA plus X-ray NewAthena, built on X-ray background synthesis models and Deep/Wide survey layouts. PRIMA dominates for heavily obscured and Compton-thick accretors, yielding an expected 7500 CT-AGN detections per square degree, while NewAthena preferentially recovers the most luminous, unobscured, and moderately obscured sources. Together they out-perform past IR efforts—PRIMA alone delivers ~60× Herschel source counts over the same area—and enable a precise BHAD history to z≈8. The alliance is pitched as the cleanest route to reveal the true CT-AGN contribution to cosmic BH growth.
Cosmological RHD zoom-ins of a dwarf progenitor with a variable, cloud-scale SFE (calibrated on AU-scale RMHD) produce burstier star formation, a richer massive cluster population, and higher total stellar mass than constant-SFE runs. Dense clouds reach up to ~80% SFE, yielding bound star clusters (Σ~10^2–10^4 M_sun pc^-2, r<=3 pc) with a flat mass function (dN/dlogM ∝ M^Γ, Γ≈−0.4); the most massive (10^4–10^5 M_sun) assemble via mergers and show 0.05–0.1 dex metallicity spreads. A nuclear star cluster is seeded by z≈8.7 and grows to ~2.4×10^5 M_sun, with 83% of its mass built through cluster mergers, reaching ~20% of the galaxy’s stellar mass. This early, merger-driven NSC pathway provides a natural route to SMBH seeding and links to the compact “little red dots” population at z≳5.
ASPIRE cross-correlates [O III] emitters from NIRCam/F356W grism with Lyα-forest pixels in five z>6.5 QSO fields (5.4<z<6.5). It finds 2σ excess Lyα transmission at ~20–40 cMpc around [O III] emitters (z=5.86) with small-scale absorption, implying highly ionized bubbles around galaxies embedded in overdense environments. Comparing to THESAN, the signal points to >50 cMpc ionized regions and a stronger UV background supplied by unseen faint galaxies; the observed [O III] sources near individual transmission spikes cannot by themselves maintain the ionization even if all hosted AGN with 100% LyC escape. Simulations underpredict the excess transmission, hinting at larger bubbles or stronger UV/temperature fluctuations, with current uncertainties dominated by cosmic variance.
A semi-analytic growth model tied to dark-matter halo assembly follows M_BH/M_star for both heavy and light seeds under feedback-limited, episodic super-Eddington accretion. Despite mass loss in winds, the ratio first increases and then converges to a universal ~0.1–0.3 set by the balance between nuclear gas feeding and star-formation efficiency, forming an attractor in the M_BH–M_star plane. On this attractor, overmassive BHs grow more slowly than their hosts while undermassive seeds catch up rapidly, erasing seed-memory by z~4–6. The model predicts that 10^5–10^6 Msun BHs at higher redshift that deviate from this trend would reveal their birth conditions.
Radially resolved disk-evolution modeling links gas inflow, star formation, outflows, enrichment, and dust to reproduce z>5 galaxy sizes, stellar masses, SFRs, metallicities, and dust-to-stellar mass ratios. The model finds SFE f_* governed by inflow–SF–outflow equilibrium with f_* ≲ 20% for M_h ~10^11–10^12 Msun down to z=5, enabling intrinsic M_UV ≲ −22 and a dust-free z≈12 UV LF consistent with observations. Yet the same galaxies are predicted to be extremely opaque (τ_1500 ≳ 10), which would depress the UV LF below the observed counts. The tension motivates mechanisms that lower effective attenuation, such as dust evacuation from star-forming regions or preferentially large grains.
Uses local BASS analogs with well-characterized 0.5–195 keV spectra, forward-modeled into the CCLS redshift–luminosity–exposure space and re-fit with the CCLS pipeline to quantify obscuration biases. Finds Chandra would miss 53.3% (563/1056) of simulated obscured (NH>10^22 cm^-2) sources, and even detected ≥30-count spectra have NH systematically overestimated. The strongest failure mode is for CT best-fits (NH≥10^24 cm^-2), where 66.7% (18/27) are actually unobscured (NH<10^22 cm^-2). Results imply deep <10 keV surveys overstate the rise of the obscured fraction and the fraction of luminous obscured AGN, motivating forward modeling, multi-wavelength obscuration tracers, and higher-sensitivity missions like AXIS.
Simulating JWST/NIRCam narrow- and medium-band [O III] maps at z≈2–3 using MUSE datacubes of nine nearby AGN, the authors show NIRCam can recover classic ionization-cone morphologies. They then apply this to 27 known AGN in GOODS-S (z=2.4–3.4), identifying six systems with [O III]+Hβ morphologies consistent with cones and characteristic NLR sizes of 1–2.5 kpc. The simulations quantify how cosmological dimming and instrument noise bias high‑z NLR size measurements low, depressing the local NLR size–AGN luminosity relation by about a factor of two. This establishes a practical medium-band imaging path to select cone candidates and calibrate NLR size trends at cosmic noon.
This paper develops a redshift-space EFT for Lyα forest cross-correlations with biased tracers and delivers one-loop full-shape power-spectrum predictions. Tested on Sherwood hydrodynamic simulations at z=2.8 with massive and light halo catalogs, the model jointly fits the Lyα auto, halo auto, and Lyα–halo cross spectra. Adding the cross term significantly tightens constraints on Lyα and halo EFT parameters relative to auto-only fits. The combined model attains percent-level accuracy for the cross-spectrum up to k_max=1 h Mpc^{-1}, improving over prior analytic approaches and enabling precision DESI-era Lyα–quasar analyses.