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
Rest-frame Chandra stacking of 38 JWST Type-2 AGN yields a ≳3σ 10–30 keV signal but softer-band limits, a spectral pattern the authors interpret as population-average, high-covering-factor Compton-thick obscuration rather than an unobscured continuum.
Broadband X-ray fits to 26 nearby mid-IR/X-ray-selected Swift-BAT AGN find few securely Compton-thick objects; line-of-sight columns are broadly model-consistent, but torus geometry and statistical intervals materially affect threshold classifications and proxy calibration.
A 255 ks Chandra study resolves NGC 5005’s soft, extended gas from a faint hard nucleus. The authors infer a lightly absorbed, intrinsically weak AGN whose reported broad Hα line persists at an exceptionally low inferred Eddington ratio.
Proposes that both the Milky Way’s Sgr A*+CMZ and JWST-selected little red dots are “electromagnetically tranquil” nuclei: million-solar-mass black holes embedded in dense, cold, molecule-rich cores that are infrared-bright yet X‑ray faint. By aligning scales, gas content, and low-Eddington accretion, the paper argues these environments shield fragile molecules and permit complex organic chemistry near the nucleus. The CMZ example (e.g., nitrile-bearing cloud G+0.693−0.027) motivates the idea that similar chemistry could arise in compact LRD cores. If common, such tranquil nuclei could link early black-hole growth to the formation and delivery of prebiotic molecules in the early universe.
XRISM/Resolve’s 2024-02-25 spectrum of the neutron-star binary GX 13+1 reveals a stratified, highly ionised, Compton-thick wind via dozens of narrow, slightly blueshifted lines from Si–Ni, including high-order Fe XXV/XXVI features above 7 keV. Photoionisation fits require a slow, very dense absorber plus a faster (~700 km/s), more ionised layer to reproduce the Fe XXVI Ly blue wing and residual core flux from wind reprocessing. After correcting for electron-scattering attenuation, the intrinsic luminosity is at or above Eddington, yet the outflow is extremely slow, favouring a thermal‑radiative outer-disc origin over an inner-disc radiation‑pressure (Eddington) wind. The contrast with ultrafast (~0.3c) SMBH winds at similar Eddington ratios points to fundamentally different launch mechanisms across mass scales.
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.
This Letter median-stacks NIRCam, MIRI, and ALMA imaging for 302 photometrically selected little red dots across CEERS, JADES(+SMILES), and PRIMER (z≈2–11; median z≈6.2). The stacked SED rises to ≈3 µm in the rest frame, and CIGALE fits require a dusty AGN component in most (≳50%) LRDs; combined with ALMA non-detections and deep Chandra stack null results, this points to Compton-thick gas (NH>3×10^24 cm^-2) likely confined within Rsub≈0.1 pc. The inferred geometry leaves optical/UV and broad-line emission largely unobscured, matching blue UV slopes and strong Balmer features. While LRDs are heterogeneous, the prevalence of AGN-heated dust implies obscured black-hole growth is common in this population.
Empirically integrating X-ray–to–far-IR SEDs for two of the most luminous Little Red Dots (A2744-45924 and RUBIES-BLAGN-1), the authors directly measure bolometric luminosities rather than adopting standard AGN corrections. They find that over half of Lbol emerges in the rest-frame optical with Lbol/L5100≈5, while X-ray, UV, and reprocessed mid/far-IR components are sub-dominant, and deep ALMA/MIRI limits rule out a standard dust-reddened AGN SED. New bolometric corrections lower previously inferred luminosities by ~10×, implying BH masses of ~10^5–10^7 Msun (and ~10^8 Msun hosts) if radiating near Eddington and easing tensions with clustering and BH mass density. A key assumption is that far-IR luminosities lie well below current observational limits.
The authors revisit the X-ray weakness of JWST-selected AGN by mapping dusty gas dynamics onto the N_H–λ plane using the effective Eddington limit for dust. Varying metallicity, grain size, and composition shifts the critical boundary: low-Z, dust-poor gas resists radiation pressure, enabling long-lived nuclear absorption and heavy X-ray obscuration consistent with early JWST-AGN and LRDs. The blowout vs. stalling analysis shows that higher metallicity is needed to expel larger columns, whereas substantial columns stall at low Z, making metallicity a key regulator of obscuration. The framework also naturally links Balmer absorption features and weak radio emission to the same radiative dusty feedback physics.
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.
The authors stack NIRCam+MIRI photometry for 326 “V-shape” LRDs (from Akins24 and Kokorev24) and compare their UV–NIR SEDs to median-stacked Blue-excess Hot DOGs (BHDs) to test the analog hypothesis. Despite superficially similar “V-shapes,” LRDs turn over at shorter wavelengths, have much bluer rest-IR continua, show F1800W non-detections in stacks, and require far lower dust attenuation in SED fits—indicating little or no AGN-heated hot dust. They also argue the UV excess in LRDs is unlikely to be scattered AGN light, and note compact morphologies plus lower X-ray detection frequencies. Bottom line: LRDs are not simply high‑z siblings of BHDs, pointing to a distinct early SMBH growth pathway from the super‑Eddington, merger-driven Hot DOG phase.
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.
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.
A nearby LRD analog is uncovered: the broad-line AGN SDSS J102530.29+140207.3 at z=0.1 shows the hallmark V-shaped SED, broad Balmer emission (FWHM 1000–2000 km/s), and deep Balmer absorption. New GTC optical spectra reveal a G–K-giant-like continuum with a clear CH G-band and unusually deep low-ionization absorption, plus a series of [Fe II] emission lines; similar [Fe II] features are identified in a JWST-selected LRD at z=2.26. Multi-epoch data show small but significant Hα variability, and NuSTAR confirms extreme X-ray weakness consistent with Compton-thick obscuration (NH>10^24 cm^-2). Together these point to a dense, complex nuclear environment that reproduces LRD hallmarks locally and informs early black-hole growth, though the strength of the ionic/atomic/molecular absorptions remains challenging for standard stellar/AGN models.
Targets seven high-λEdd DOGs and combines new, deeper Chandra exposures with archival X-ray data to measure line-of-sight obscuration. Finds these systems are typically buried: 6/7 have N_H ≳ 10^23 cm^-2 and 3/7 are Compton-thick (N_H ≳ 10^24 cm^-2), with observed X-rays strongly suppressed relative to the mid-IR relation. Placing the sources on the λEdd–N_H plane shows they overlap the regime occupied by Hot DOGs. Authors argue both populations trace a post-merger phase where rapidly accreting SMBHs are enshrouded by dust-rich gas.
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.
A BAT-selected local analog set of 21 highly luminous, obscured Seyfert 1.9–2 AGN at z<0.6 (log L_X,2–10keV>44.6) is modeled with NuSTAR, XMM-Newton, Suzaku, and Chandra to recover N_H, Γ, intrinsic L_X, covering factor, Fe Kα, and [NeV] λ3426. The sample is highly variable: 82% vary overall (73% in 2–10 keV flux; 33% in line-of-sight N_H), and 6/12 with M_BH estimates fall in the N_H–λ_Edd “forbidden region,” where they also show enhanced N_H variability/outflow signatures—consistent with a clearing phase. [NeV] λ3426 is detected in 85% and, when renormalized to the same [OIII] peak, is significantly stronger than in JWST-selected z=2–9 narrow-line AGN. These local benchmarks calibrate [NeV]-based obscured AGN searches and frame expectations for future high‑z X-ray follow-up.
Begelman and Dexter propose that JWST “Little Red Dots” are late-stage quasi-stars: black holes embedded in massive envelopes accreting at super‑Eddington rates once the BH exceeds ~10% of the total mass. In this regime the models predict mass‑insensitive global properties, yielding reddish continua with a pronounced Balmer break and Balmer lines broadened primarily by electron scattering rather than Doppler motions. The enormous electron columns naturally quench X‑rays, while BHs grow roughly linearly in time; late-stage objects with MBH ≳10^6 Msun should dominate the quasi-star population. Given lifetimes of only tens of Myr yet high observed LRD number densities, the authors argue most SMBHs likely pass through this quasi‑star/LRD phase.
X-ray selected AGNs from zCOSMOS (0.5<z<0.9) are split by obscuration (NH) and excitation (log[OIII]/Hβ>0.5) to compare host properties. Unobscured sources show a clearer rise of the ionization index O32=[OIII]/[OII] with L2–10 keV than obscured ones, while high-excitation obscured AGNs reach higher X-ray luminosities on average. High-excitation systems also have elevated R23, implying lower gas metallicities reminiscent of z~4–6 galaxies. λsBHAR positively correlates with NH, O32, and R23, linking high specific accretion to harder radiation fields in less enriched environments.
This paper presents dense optical/UV monitoring plus X-ray and radio follow-up of the ZTF nuclear transient AT2019cmw (z=0.519), which reached an extraordinary peak bolometric luminosity of ~10^45.6 erg s^-1. Spectra remained featureless while the continuum cooled steadily from ~30 kK to ~10 kK over the first ~300 days, supporting a classification as a luminous, “featureless” TDE in an early-type host. Deep non-detections in X-ray and radio constrain on-axis jets and any visible inner accretion disk. Light-curve modeling (cooling-envelope, with a reprocessing-outflow alternative) favors the disruption of a tens-of-solar-masses star by an SMBH, hinting at localized nuclear star formation despite the quiescent host.
Using JWST/MIRI MRS, the authors detect ro‑vibrational H2 in the z≈2.2 X‑ray AGN cid_346, measuring 1‑0 S(1) (and S(0)) and inferring a hot H2 mass of ≈8×10^5 M⊙. They map hot molecular emission and CO(3‑2) to >10 kpc, and NIRCam imaging reveals two nearby satellites at ≈3.3 and 7.4 kpc, pointing to an interacting environment. The hot phase is 10^5–10^6× less massive than the cold reservoir, but the authors argue H2 ro‑vibrational lines effectively trace locally heated/shocked gas where CO may be faint. Ionized gas shows [O III] extension and a blue wing toward the SE, consistent with outflow activity shaping the multiphase medium.
First optical–UV spectral analysis of 30 faint (mB=19.6–21.8) Type 1 AGN from the Lockman‑SpReSO survey spanning 0.33<z<4.97, using Quasar Main Sequence–based deblending of the principal UV/optical broad‑line regions. Derived ranges are 44.85<log Lbol<47.87, 7.59<log MBH<9.80, and −1.70<log REdd<0.56; 18 high‑z sources fall in Population B, with a few A/B1/B1+ at low z, and none are extreme accretors. CIV c(1/2) indicates modest winds (941 to −1587 km s−1) and the Baldwin effect shows a slope of −0.23±0.03, consistent with comparable samples. Twelve spectra overlap with SDSS DR17 and show no variability, providing a stable benchmark for FIR/X‑ray–selected quasar demographics.
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.
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.
Builds the obscured black hole accretion history from CEERS MIRI sources whose AGN components are identified via CIGALE SED fitting, then converts accretion power and MIR luminosity functions into BHAD across 0<z<4.25. By summing BHARs for composites+AGNs and by integrating LFs (modified Schechter and double power law) down to 1e7 L_sun—two orders fainter than pre-JWST—the authors find BHAD peaking at z≈1–2 (ρ_Ldisk, DPL) or z≈2–3 (modified Schechter). At z≈3 their MIR-inferred BHAD lies above X-ray estimates, hinting at obscured growth missed in X-rays. The new depth strengthens the census of faint, dusty accretion, though the z≈3 excess is within current uncertainties and awaits larger samples.
Chandra and XMM-Newton data are used to map hot atmospheres around seven local compact ellipticals selected as red‑nugget analogs, probing BH–bulge–halo coupling. Only MRK 1216 and PGC 32873 show luminous, spatially extended halos enabling radial thermodynamic profiles, with MRK 1216’s RGS spectrum hinting at super‑solar α/Fe. The others have faint or undetected halos, several instead showing AGN‑like power‑law emission. On galaxy scaling planes, cEGs follow a slightly steeper M⋆–LX and sit on the lower edge of M⋆–Mvir, implying red nuggets—and possibly their LRD progenitors—host a diverse range of halo atmospheres.
Pang et al. build a slitless-spectrum QSO selector on 3D-HST/G141 by first flagging >6,000 sources with apparently broad lines and then using forward modeling to test whether the “broad” features require a point-like QSO component rather than size-broadened ELG lines. Calibrated on known QSOs, ELGs, and simulations, the criterion recovers ~90% of point-like QSOs with Hα/Hβ while keeping ELG contamination at ~5%. Applied to clean emission-line sources, it yields 19 QSO candidates at z=0.12–1.56 (12 X-ray detections) with broader UV colors and redder optical slopes than SDSS QSOs and MBH≈10^6.9–10^8.3 M⊙, consistent with normal QSOs rather than little red dots. The method boosts QSO completeness at z≈0.8–1.6 in 3D-HST and is directly portable to Euclid and CSST slitless surveys.
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.
Deep XMM-Newton monitoring of the Green Pea SDSS J082247.66+224144.0 (z=0.216) tests for an elusive low-luminosity AGN long hinted by its Γ≈2, L2–10 keV≈10^42 erg s^-1 spectrum. Across 6.2 years (rest-frame), the hard 2–10 keV luminosity remains stable while the soft 0.5–2 keV flux drops by ~60%, yielding a markedly harder second epoch. Swapped-epoch spectral posterior checks and SDSS line decomposition (requiring a broad Hα despite BPT star-forming narrow lines) point to transient, low-column obscuration as the only viable explanation. This work delivers the first conclusive X-ray AGN identification in a Green Pea, strengthening the case that faint AGN could have contributed to reionisation and clarifying local analogs of JWST Little Red Dots.
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.
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.
SRGA J230631.0+155633 is a z=0.4389, type 2, radio‑loud quasar uncovered by SRG/ART‑XC (4–12 keV) and followed up near‑simultaneously with ART‑XC and Swift/XRT in June 2023, revealing heavy absorption with N_H ≈ 2×10^23 cm^-2. Its intrinsic 2–10 keV luminosity declined from (6^{+6}_{−3})×10^45 erg s^-1 during the 2020–2021 all‑sky scans to (1.0^{+0.8}_{−0.3})×10^45 erg s^-1 in 2023, indicating strong rest‑frame ~1 yr variability while remaining quasar‑luminous. Radio imaging shows a core plus two extended lobes consistent with a giant FR II radio galaxy. Multi‑wavelength constraints imply L_bol ~6×10^46 erg s^-1 and M_BH ~1.4×10^9 M_⊙ (λ_Edd ~0.3), making this one of the most luminous obscured quasars out to z ≈ 0.5 and a nearby laboratory for buried SMBH growth.
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.
Cross-matching RACS-low (888 MHz) with DES and Pan-STARRS, the authors selected 45 bright radio/optical-dropout candidates (S_888MHz>1 mJy, z_mag<21.3) over 16,000 deg^2 and spectroscopically confirmed 24 new quasars, 13 at 4.5<z<5 and 11 at z>5. Including comparable literature objects, the z>5 RACS set reaches 33 powerful radio quasars with νL_1.4GHz≈10^41.5–10^44.4 erg s^-1 and is ~90% complete at the stated flux and magnitude limits. Multi-band radio plus new X-ray coverage (Chandra, uGMRT, MeerKAT, ATCA) reveal predominantly flat spectra (22 with −0.5<α_r<0.5) and X-ray luminosities exceeding coronal expectations. The combined evidence points to many blazar-like, jet-aligned systems, delivering a bright, homogeneous anchor sample for population studies of early SMBH growth.
Stacks of VLASS images for eROSITA-selected, unobscured AGN in a single mass bin (log M/M☉=8–8.5) track radio behavior across the spectral transition identified from optical/UV–X-ray SEDs. After subtracting matched host-galaxy star-formation radio, the residual core radio stays roughly constant through the transition while the mean accretion rate rises by ~6× and the UV disk brightens by ~100×; the X-rays change by only ~2×, yielding an approximately constant radio/X-ray ratio consistent with the Fundamental Plane. The result favors a persistent, compact jet coupled to the X-ray hot flow (not the thin disk), explaining why radio-loudness flips mainly reflect optical/UV changes rather than jet quenching. Compared to binaries, AGN retain strong coronal X-rays in the disk-dominated state, accounting for the continued radio–X coupling.
Using 82 X-ray AGN within 4 r500 of 164 XXL clusters (z ≲ 1) and deep HSC imaging, the authors classify host morphologies (Statmorph + visual) and assess obscuration and SFR via X-ray hardness ratios, optical spectra, and SEDs. They find a moderately significant excess of cluster AGN hosted by merging/disturbed galaxies relative to non-active cluster members and field AGN, with the signal concentrated in the outskirts (≈1–2 r500). Clusters also show a higher share of X-ray-hard (likely obscured) AGN than the field, especially in the outskirts. Together, the results point to mergers/interactions in cluster outskirts as key drivers of both AGN triggering and obscuration.
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.
Using Euclid Q1 Deep Fields, the team builds a stellar‑mass–complete (M*>10^9.8 Msun) sample at 0.5<z<2, identifies major mergers with CNNs trained on simulations, and selects AGN via X‑ray, optical spectroscopy, MIR colours, and I_E‑band PSF decompositions. Across all AGN selections, mergers host an AGN excess by factors of 2–6, and the AGN merger fraction rises with point‑source contribution f_PSF up to ~0.55 before declining. In luminosity terms, f_merg increases with L_PSF, exceeding 50% for L_PSF>2×10^43 erg/s at z<0.9 and becoming dominant only above ~10^45 erg/s at z>0.9; for X‑ray AGN, f_merg also increases with L_bol, with AGN mostly in mergers at L_bol>10^45 erg/s. This ties major mergers to the most powerful, dust‑obscured SMBH growth phases, with spectroscopic trends weaker due to small samples.
NuSTAR timing of the eclipsing IP V902 Mon reveals a clear X‑ray eclipse in energy‑resolved lightcurves, phase‑coincident with AAVSO/CV optical minima. Joint NuSTAR+XMM‑Newton spectroscopy requires heavy local absorption (N_H ~1e23 cm^-2) and a strong 6.4 keV Fe Kα line with EW ≈0.7 keV. The authors favor an accretion‑disk‑corona–like, very high‑inclination geometry in which the direct accretion‑column emission is blocked at all phases and we see only scattered/reprocessed X‑rays. This positions V902 Mon as a reflection‑dominated IP where eclipse timing can localize the extended pre‑shock region a few WD radii above the plane.
Using the black-hole fundamental plane alongside star-formation radio scaling, the authors predict continuum fluxes for little red dots (LRDs) across BH mass, X-ray luminosity, SFR, and redshift (≈3–7). They find AGN radio fluxes are typically 10–100× the host stellar contribution at 3–8 GHz, and that a ≥500 nJy detection above 2 GHz at z ≥ 5 or ≥2000 nJy at z = 3–4 would be a clear AGN signature if SFR < 30 M⊙/yr. The analysis implies most LRDs are radio-quiet AGN, consistent with current survey non-detections. Forecasts show ngVLA and SKA could confirm typical LRD AGN in ~10–100 hr integrations, providing a dust-robust discriminator between starbursts and accretion.
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.
Tests a proxy-based black hole mass estimator for obscured AGN that infers FWHM_bHα from the narrow-line ratio L[O III]/L_nHβ and λL5100 from either intrinsic 2–10 keV X-rays or narrow lines, using 99 local Swift-BAT/BASS AGN. The two λL5100 proxies differ by a mean −0.32 ± 0.68 dex (narrow-line estimate lower than X-ray), implying ≈2× MBH uncertainty from the luminosity choice. Compared to virial masses from broad Paschen lines (14 Paα, 12 Paβ), the proxy MBH is higher by 0.39 ± 0.44 dex and 0.48 ± 0.51 dex, respectively, though still within the scatter. σ*-based MBH for 151 BASS AGN agrees on average within 0.08 dex but with large ≈0.74 dex scatter, so the method scales to large samples with overall ≈3–5× uncertainty and a possible mild high bias needing more data.
The authors re-monitor the z=6.025 QSO CFHQS J164121+375520 (J1641) with Chandra and rest‑UV imaging in 2022–2024 after a dramatic X-ray dimming seen between 2018 and 2021. J1641 is now detected only in the hard 2–7 keV band, while its soft 0.5–2 keV flux has faded by >20× relative to 2018, establishing it as an X‑ray changing‑look quasar at z>6. They attribute the transition to intervening, ongoing Compton‑thick obscuration along our line of sight—potentially a thickened inner disk/failed wind or an occultation by dust‑free sub‑pc clouds—with the near‑constant rest‑UV light curve supporting obscuration over intrinsic fading. Catching such events in the reionization era offers a new handle on how rapidly growing SMBHs are fueled and shrouded.
Using MIDIS MIRI 5.6 μm imaging in the HUDF cross-matched to the CDF-S 7 Ms catalog, the authors morphologically decompose 31 X-ray sources (24 AGN; z≈0.5–3) with visual, Sérsic+PSF, and non-parametric classifiers to isolate unresolved nuclear emission at rest-frame ~2 μm. They find ≥70% show an unresolved MIRI component with unresolved-to-total 2 μm flux fractions spanning ~0.2–0.9, and at Lx>10^43 erg s^-1 the 2 μm point-source luminosities align with local AGN relations. At lower X-ray luminosities, they report an excess 2 μm nuclear component relative to pre-JWST expectations, plausibly linked to Compton-thick AGN and/or compact nuclear starburst/merger activity. The work demonstrates that MIRI can robustly quantify nuclear IR emission in faint X-ray sources and clarifies the AGN/host balance across Cosmic Noon.
NuSTAR multi-epoch X-ray spectra of five CLAGNs (ESO 362-G18, NGC 1365, NGC 4151, NGC 5548, NGC 7582) are fit with phenomenological and clumpy-torus models to track Γ, L2–10 keV/LEdd, and NH,los. The authors find a positive Γ–(L2–10 keV/LEdd) correlation and, for four objects, a strong anti-correlation between NH,los and L2–10 keV/LEdd, with ESO 362-G18 standing out as an exception. They argue this links changing-obscuration to accretion-driven evolution: a disc wind that strengthens with accretion rate pushes line-of-sight clouds outward, lowering NH at moderate inclinations. The trends persist across model choices, tying CLAGN absorption changes to the same engine that drives changing-state behavior.
Deep 0.144–3 GHz maps across COSMOS, GOODS-N, and GOODS-S are mined for radio counterparts to ~700 JWST-selected AGN candidates (including LRDs). Only PRIMER-COS 3866 at z=4.66 is individually detected; its spectrum (α=−0.76+0.11−0.09), modest radio-loudness (R≈0.5), and Tb≳10^3 K remain consistent with either AGN or star-formation power. Stacks of spectroscopic and photometric subsamples yield non-detections with 3σ limits L1.4GHz<8.6×10^39 erg s−1 and L1.3GHz<1.3×10^39 erg s−1, still compatible with local L_X–L_Hα and L_X–L_R relations. The authors argue present radio depths are insufficient to label the population radio-weak and forecast SKA/ngVLA detections within hours to enable brightness-temperature tests that separate AGN from starbursts.