654 indexed papers · 430 research notes

Research archive

2025-04-01 · 2504.01103v1

JWST reveals the diversity of nuclear obscuring dust in nearby AGN: nuclear isolation of MIRI/MRS datacubes and continuum spectral fitting

Omaira González-Martín, Daniel J. Díaz-González, Mariela Martínez-Paredes, et al.

Download highlighted PDF arXiv abstract

The authors PSF-isolate nuclear mid-IR emission in 21 nearby (z<0.05) AGN with a new tool (MRSPSFisol) and fit the continuum using multiple dust libraries. Twelve nuclei achieve good fits (chi2/dof<2), typically with a flared-disk model combining clumpy and smooth dust and allowing grain size to vary; two prefer disk+wind and one the classical clumpy torus. About 40% resist all models because of extreme silicate profiles plus pervasive water-ice and aliphatic hydrocarbon absorption, pointing to missing chemistry. This establishes JWST/MRS as a clean nuclear isolator and shows that next-generation dust models must capture more complex compositions.

JWST AGN obscured AGN spectroscopy low-z

2025-04-01 · 2504.01079v1

HI 21-cm Absorption Associated with Foreground Galaxies on Top of Quasars

Labanya Kumar Guha, Raghunathan Srianand, Rajeshwari Dutta

Pilot uGMRT 21-cm searches toward three SDSS-identified Galaxies On Top Of Quasars (J0758+1136, J1159+5820, J1451+0857) yield a 100% detection rate of HI absorption at extremely small impact parameters. Combining with literature, the authors argue GOTOQs form a distinct absorber population with much higher detection rates than DLA- or metal-selected samples. They find a Milky Way–like reddening relation, ∫τ dv (km s⁻¹) = 13.58(+2.75/−2.35) E(B−V) + 0.68(+1.06/−1.27), and show both detection rate and optical depth drop rapidly with impact parameter. This demonstrates that fiber-selected GOTOQs efficiently trace cold HI close to star-forming galaxies and set the stage for a large, intervening 21-cm absorber sample with upcoming wide-field spectroscopy.

radio spectroscopy QSO

2025-03-31 · 2504.00172v1

Evidence for evolutionary pathway-dependent black hole scaling relations

Jonathan H. Cohn, Emmanuel Durodola, Quinn O. Casey, et al.

Download highlighted PDF arXiv abstract

This letter benchmarks secure dynamical black hole masses in a z~2 lensed quiescent galaxy and six local red‑nugget relics against recent 4<z<11 AGN, quasar, and Little Red Dot samples on the M_BH-M_star and M_BH-sigma_* planes. The relics and the z~2 quiescent system land on both the local bulge M_BH-M_star relation and the 4<z<7 Pacucci et al. relation, while luminous QSOs and broad-line AGN follow Pacucci et al. more closely and LRDs scatter across all three; on M_BH-sigma_* most sources sit above the local median except the lensed system. The authors argue the bulge relation was already in place at high z and that differing evolutionary pathways—compact-core assembly by z~2 followed by dry-merger stellar-mass growth versus ongoing BH and star formation in AGN—govern positions on scaling planes. Given large systematics in single‑epoch high‑z masses, they emphasize dynamical detections in relics and strongly lensed galaxies as a complementary, less biased probe of early scaling relations.

LRD overmassive BH demographics high-z low-z

2025-03-31 · 2503.23710v1

Formation of the Little Red Dots from the Core-collapse of Self-interacting Dark Matter Halos

Fangzhou Jiang, Zixiang Jiang, Haonan Zheng, et al.

Download highlighted PDF arXiv abstract

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.

LRD BH seeds simulation demographics high-z

2025-03-25 · 2503.19915v1

A New Hope for Obscured AGN: The PRIMA-NewAthena Alliance

Luigi Barchiesi, F. J. Carrera, C. Vignali, et al.

Download highlighted PDF arXiv abstract

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.

obscured AGN simulation X-ray demographics high-z

2025-03-24 · 2503.19078v1

MEGA Mass Assembly with JWST: The MIRI EGS Galaxy and AGN Survey

Bren E. Backhaus, Allison Kirkpatrick, Guang Yang, et al.

Download highlighted PDF arXiv abstract

MEGA is a 67 hr, four-band MIRI imaging program in the EGS (25 pointings; 70 arcmin^2) that adds F770W–F2100W coverage over 68.9% of CEERS NIRCam, targeting obscured galaxy and SMBH growth near Cosmic Noon. The team augments the JWST pipeline with warm‑pixel masking and iterative super–background subtraction, delivering mosaics with 5σ depths of ≈0.18, 0.41, 1.26, and 4.10 µJy in F770W, F1000W, F1500W, and F2100W. They release a photometric catalog and new galaxy number counts in all four bands, extending the faint mid‑IR regime over wider area than prior JWST fields. This fills the mid‑IR gap in EGS, enabling PAH‑based SFRs and dusty AGN selection to sharpen constraints on coupled galaxy–black hole growth.

obscured AGN demographics

2025-03-21 · 2503.17183v1

Halfway to the Peak: ice absorption bands at $z\approx0.5$ with JWST MIRI/MRS

Anna Sajina, Alexandra Pope, Henrik Spoon, et al.

Download highlighted PDF arXiv abstract

JWST/MIRI–MRS spectroscopy of the dusty starburst–AGN composite SSTXFLS J172458.3+591545 (z=0.494) yields the first combined extragalactic detections of CO2, CO, XCN, and H2O ices, with gas‑phase CO alongside solid CO. Ice-band profiles match Galactic/local templates, and their decomposition (polar‑dominated XCN and CO complexes) plus the silicate depth imply a compact, dense, cold nucleus with n>10^5 cm^-3, T≈20–90 K, and A_V≈6–7; [NeV]/[NeVI] confirm a deeply buried AGN. The authors introduce τ_Si versus τ_CO2/τ_Si as a diagnostic that jointly traces total dustiness and dust clumpiness along the line of sight. Together, these results showcase MIRI’s power to map dust composition and geometry well beyond the local Universe.

obscured AGN spectroscopy low-z

2025-03-20 · 2503.16600v1

A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at $z=3.5$

Anna de Graaff, Hans-Walter Rix, Rohan P. Naidu, et al.

Download highlighted PDF arXiv abstract

JWST/NIRSpec+NIRCam+MIRI data on The Cliff, a luminous Little Red Dot at z=3.55, reveal an extreme Balmer break—about twice stronger than any previously seen at high-z—alongside broad Hα (FWHM∼1500 km s⁻¹) and He I emission but no significant metal lines. Stellar-population solutions (even with steep dust or IMF tweaks) fail, and their formal M*∼10^10.5 M⊙ with re∼40 pc would imply implausibly high stellar-collision rates. The spectra and continuum are instead best matched by a “black hole star” configuration: a powerful central ionizing source embedded in dense, absorbing gas that imprints the Balmer edge and Hα absorption while favoring an intrinsically red continuum over heavy dust. This makes The Cliff compelling evidence that at least some LRDs are not ultra-dense galaxies but compact, accretion-powered nuclei shrouded by dense gas.

LRD broad Balmer stellar envelope super-Eddington spectroscopy high-z

2025-03-20 · 2503.16596v1

A "Black Hole Star" Reveals the Remarkable Gas-Enshrouded Hearts of the Little Red Dots

Rohan P. Naidu, Jorryt Matthee, Harley Katz, et al.

Download highlighted PDF arXiv abstract

JWST/NIRSpec spectroscopy of the point-like source MoM-BH*-1, observed ~660 Myr after the Big Bang, reveals an enormous Balmer break, broad multi-peaked Hβ, and deep Balmer-line absorption. The authors model it as a “black hole star”: a supermassive black hole enshrouded by extremely dense, turbulent, dust-free gas whose atmosphere imprints the break and absorption while dominating the observed light; narrow [OIII] and residual UV are attributed to a faint host. The data are well matched by a simple Cloudy setup that reproduces the break strength, Balmer EWs, UV faintness, and MIRI continuum, with line ratios consistent with high densities that can collisionally suppress [OIII] and a hint of variability reinforcing the SMBH interpretation. They further argue that Little Red Dots can be explained as BH*s embedded in comparably bright hosts, implying current LRD black hole masses—derived with steep dust corrections and standard scaling relations—may be overestimated by orders of magnitude.

LRD BH seeds super-Eddington stellar envelope broad Balmer high-z

2025-03-20 · 2503.16595v1

Little red dots as young supermassive black holes in dense ionized cocoons

V. Rusakov, D. Watson, G. P. Nikopoulos, et al.

Download highlighted PDF arXiv abstract

Using the highest-S/N JWST/NIRSpec spectra of LRD-like broad-line sources, the authors show that Balmer-line wings are exponential and symmetric, as expected from electron scattering in a compact, Compton-thick ionized cocoon. Convolving a narrow Doppler core with this scattering kernel yields intrinsic widths of only a few hundred km/s, implying black holes of ~10^5–10^7 M⊙ accreting near the Eddington limit within light‑day–scale gas with mild outflows. Accounting for scattering lowers previous mass estimates by ~2 dex and naturally explains LRD traits, including very weak X-ray/radio via nebular reprocessing. This reframes LRDs as young, rapidly growing SMBHs rather than overmassive quasars for their hosts.

LRD broad Balmer nebular continuum super-Eddington high-z

2025-03-19 · 2503.15323v1

Euclid Quick Data Release (Q1). Extending the quest for little red dots to z<4

Euclid Collaboration, L. Bisigello, G. Rodighiero, et al.

Download highlighted PDF arXiv abstract

Using 63 deg² from Euclid’s Quick Data Release (Q1) plus IRAC and ground-based griz, the team fits two power laws to photometry to isolate little red dots with blue UV and red optical slopes while removing extended sources, strong line emitters, and artifacts. They assemble 3341 LRD candidates at z=0.33–3.6 (29 with IRAC), and derive a rest‑frame UV luminosity function that rises from high z down to z≈1.5–2.5 before declining toward lower redshift. Comparing to quasar UV LFs shows LRDs are not the dominant AGN population at z<4 for M_UV<-21. A noted caveat is that evolution inferred from the IRAC‑detected subsample is limited by small numbers and IRAC’s resolution, motivating follow‑up.

LRD v-shaped SED demographics low-z

2025-03-19 · 2503.15317v1

Euclid Quick Data Release (Q1). First Euclid statistical study of galaxy mergers and their connection to active galactic nuclei

Euclid Collaboration, A. La Marca, L. Wang, et al.

Download highlighted PDF arXiv abstract

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.

demographics obscured AGN X-ray spectroscopy

2025-03-18 · 2503.14739v1

DESI DR2 Results I: Baryon Acoustic Oscillations from the Lyman Alpha Forest

DESI Collaboration, M. Abdul-Karim, J. Aguilar, et al.

Download highlighted PDF arXiv abstract

DESI DR2 doubles the Lyα-forest dataset over DR1, analyzing both the Lyα auto-correlation and the Lyα–QSO cross-correlation from >820k quasar spectra and >1.2M quasar positions. It delivers sub‑percent BAO distances at zeff=2.33: 1.1% radial and 1.3% transverse, for 0.65% isotropic precision, measuring DH/rd=8.632±0.098(stat)±0.026(sys) and DM/rd=38.99±0.52(stat)±0.12(sys). The team details analysis upgrades, validation on improved synthetic data, and refined DLA identification. Motivated by nonlinear BAO shift studies, they include—for the first time in Lyα BAO—a dedicated systematic error term, strengthening high‑z expansion constraints.

QSO high-z spectroscopy

2025-03-14 · 2503.11752v1

BlackTHUNDER strikes twice: rest-frame Balmer-line absorption and high Eddington accretion rate in a Little Red Dot at $z=7.04$

Francesco D'Eugenio, Roberto Maiolino, Michele Perna, et al.

Download highlighted PDF arXiv abstract

BlackTHUNDER re-analyzes JWST/NIRSpec-IFS G395H data for the Little Red Dot Abell2744-QSO1 at z=7.04, focusing on the Hα region. The Hα profile is distinctly non-Gaussian, requiring at least two broad Gaussians plus a narrow component, and shows strong rest-frame Balmer-line absorption (EW ≈22 Å) centered at the systemic velocity of the broad line; the absorber’s dispersion (σ_abs ≈110 km s⁻¹) matches that inferred from the Balmer break, arguing for a long‑lived, non-flowing structure. An Hα-based virial mass of log(MBH/M⊙) ≈7.2 and a deconvolved narrow-line width σ_n ≈22 km s⁻¹ yield MBH/Mdyn = 0.15–1.2, confirming an overmassive black hole with limited room for a host galaxy. The revised mass implies high accretion, λ_Edd ≈0.7–1.6 (potentially super‑Eddington at the low‑mass end), tying Balmer-break strength directly to Balmer-line absorption in LRDs.

LRD broad Balmer stellar envelope overmassive BH super-Eddington spectroscopy

2025-03-14 · 2503.11611v1

A Census of the Most Obscured Galaxy Nuclei over Cosmic Time to be revealed by PRIMA

Fergus R. Donnan, Dimitra Rigopoulou, Ismael García-Bernete, et al.

Download highlighted PDF arXiv abstract

Concept study for the 1.8 m far‑IR PRIMA mission shows how to census the most buried galaxy nuclei across cosmic time. PRIMAger (25–235 um) photometry captures rest‑frame 9.8 um silicate absorption from z=2–7, enabling color selections that recover local CONs and scale to high z. FIRESS low‑resolution (R~100) spectroscopy to z~7 would detect PAHs, ice bands, and warm‑gas diagnostics even when high‑ionization lines are quenched, yielding redshifts and column densities. Simulations plus local (U)LIRG templates (NGC 4418 vs NGC 7714) suggest large, confusion‑mitigated yields in 1500 h/deg^2 surveys, making PRIMA pivotal for the obscured phase of SMBH growth.

obscured AGN demographics high-z

2025-03-13 · 2503.10958v1

Dot to dot: high-$z$ little red dots in $M_{\rm bh}$-$M_{\rm \star}$ diagrams with galaxy-morphology-specific scaling relations

Alister W. Graham, Igor V. Chilingarian, Dieu D. Nguyen, et al.

Download highlighted PDF arXiv abstract

Places high‑z little red dots onto morphology‑aware Mbh–M★ diagrams alongside compact stellar systems and local galaxy sequences. With 2023–2024 masses, LRDs are not NSCs (NSCs have higher Mbh/M★); the least‑massive LRDs overlap UCD‑like Mbh and M★, and the full LRD set spans from UCDs to primaeval S0s, while spirals and merger‑built ETGs sit at higher M★. Low‑z AGN align with the quasi‑quadratic/steeper relations defined by local disc galaxies with direct black‑hole masses, emphasizing morphology in coevolution. As 2025 mass updates arrive, placements may shift, potentially bringing LRDs closer to NSCs/UCDs/green‑peas.

LRD overmassive BH demographics high-z

2025-03-11 · 2503.08779v1

Seeding Cores: A Pathway for Nuclear Star Clusters from Bound Star Clusters in the First Billion Years

Fred Angelo Batan Garcia, Massimo Ricotti, Kazuyuki Sugimura

Download highlighted PDF arXiv abstract

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.

simulation BH seeds high-z

2025-03-10 · 2503.07074v1

JWST ASPIRE: How Did Galaxies Complete Reionization? Evidence for Excess IGM Transmission around ${\rm [O\,{\scriptstyle III}]}$ Emitters during Reionization

Koki Kakiichi, Xiangyu Jin, Feige Wang, et al.

Download highlighted PDF arXiv abstract

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.

reionization high-z spectroscopy simulation

2025-03-07 · 2503.05537v1

Little Red Dots as the Very First Activity of Black Hole Growth

Kohei Inayoshi

Download highlighted PDF arXiv abstract

Using 341 Little Red Dots (39 with spectroscopic redshifts) compiled from JWST surveys, this paper models their occurrence across cosmic time. The counts peak at z ~ 6–8 and fall steeply by z < 4, well described by a log‑normal distribution interpreted as the first one or two accretion episodes of newborn seed black holes. Dense circumnuclear gas naturally explains broad Balmer-line absorption, X‑ray weakness, and brief super‑Eddington bursts that yield overmassive BHs relative to local relations. Summing recurrent episodes reproduces the global AGN abundance evolution ∝ (1+z)^(−5/2) and provides an analytic form for the LRD redshift dependence for future tests.

LRD BH seeds super-Eddington overmassive BH demographics high-z

2025-03-05 · 2503.03870v1

The Convergence of Heavy and Light Seeds to Overmassive Black Holes at Cosmic Dawn

Haojie Hu, Kohei Inayoshi, Zoltan Haiman, et al.

Download highlighted PDF arXiv abstract

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.

overmassive BH BH seeds super-Eddington simulation high-z

2025-03-05 · 2503.03547v1

Exploring the physical properties of Type II Quasar candidates at intermediate redshifts with CIGALE

P. A. C. Cunha, A. Humphrey, J. Brinchmann, et al.

Download highlighted PDF arXiv abstract

CIGALE SED fits are used to derive SFR, M*, AGN luminosity, and AGN fraction for 366 machine‑learned Type II quasar candidates in the redshift desert (median z≈1.1), then benchmarked against SPRITZ populations and literature samples. On the SFR–M* plane many candidates sit above the main sequence at their redshift, while a tail appears quenched, pointing to episodes of enhanced star formation alongside possible feedback or obscured SF. The inferred properties align with SPRITZ composite systems and AGN2, supporting their obscured‑AGN nature and validating machine‑learning selection beyond simple colour–colour cuts.

obscured AGN QSO demographics

2025-03-05 · 2503.03431v1

Self-Consistent JWST Census of Star Formation and AGN activity at z=5.5-13.5

Jordan C. J. D'Silva, Simon P. Driver, Claudia D. P. Lagos, et al.

Download highlighted PDF arXiv abstract

Combining ≈400 arcmin^2 of JWST imaging from PEARLS, CEERS, NGDEEP, JADES, and PRIMER, this work jointly fits galaxy and AGN components with EAZY+ProSpect for ≈3.9k galaxies at z=5.5–13.5 to build SMF, SFRF, and AGNLF in four bins. Integrating these functions shows a ~1 dex rise in the CSFH from z≈13.5→5.5, while the CAGNH also increases and tentatively does so more rapidly, implying early SMBH accretion can outpace stellar mass growth. The results are stitched to z<5 measurements to provide a continuous, self-consistent census spanning >13 Gyr. This anchors the early coevolution picture and constrains the AGN contribution around reionization.

JWST AGN demographics high-z reionization

2025-03-04 · 2503.02942v1

Spectroscopic AGN survey at $z$ $\sim$ 2 with NTT/SOFI for GRAVITY+ observations

D. J. D. Santos, T. Shimizu, R. Davies, et al.

Download highlighted PDF arXiv abstract

NTT/SOFI K-band spectroscopy vets 29 z≈2 type 1 quasars for GRAVITY+, measuring Hα fluxes and Balmer-line shapes to preview BLR kinematics. The Balmer profiles are strongly non-Gaussian with narrow cores plus broad wings, consistent with rotation plus turbulence or a two-zone BLR; two objects show tentative radial-motion dominance. Low FWHM/σ ratios yield small Hα virial factors, cautioning that single-epoch mass scalings can under-estimate MBH for these profiles. Predicted differential-phase signals guide VLTI/GRAVITY+ strategies to secure dynamical BLR masses at cosmic noon.

broad-line AGN QSO broad Balmer spectroscopy

2025-03-03 · 2503.02059v1

A confirmed deficit of hot and cold dust emission in the most luminous Little Red Dots

David J. Setton, Jenny E. Greene, Justin S. Spilker, et al.

Download highlighted PDF arXiv abstract

Deep MIRI imaging plus new ALMA continuum and [C II] spectroscopy on two luminous LRDs at z=3.1 (A2744-45924) and z=4.47 (RUBIES-BLAGN-1) set the tightest IR constraints yet. Rest-frame 1–4 μm detections show a flat IR slope, excluding hot (T≳500 K) dust, while far-IR non-detections exclude a cold (T≲75 K) component and typical [C II]-bright dusty starbursts. Empirical maximal SEDs require log(L_IR/L_sun) ≲ 12.2 (3σ), in strong tension with energy-balance predictions from reddened galaxy, AGN, or composite fits. The authors favor intrinsically red LRD SEDs over heavily dust-reddened blue engines, reshaping how these compact sources are interpreted.

LRD ALMA/mm v-shaped SED broad Balmer spectroscopy

2025-03-03 · 2503.01945v1

No [CII] or dust detection in two Little Red Dots at z$_{\rm spec}$ > 7

Mengyuan Xiao, Pascal A. Oesch, Longji Bing, et al.

Download highlighted PDF arXiv abstract

Two z_spec > 7 Little Red Dots in FRESCO GOODS-N (ID9094, ID2756) show v‑shape colors, compact morphologies, and broad Hβ (FWHM 2280±490 and 1070±240 km/s), marking them as Type‑I AGN candidates. Deep NOEMA follow-up finds no [CII] 158 μm or 1.3 mm continuum; a DSFG interpretation would have yielded strong detections (>16σ [CII] and >3σ 1.3 mm for ID9094; >5σ [CII] for ID2756). Using the 3σ FIR limits in UV–FIR SED fitting (with/without AGN) and comparison to the L_[CII]–SFR_tot relation, the data favor an AGN contribution, as a dust‑only model would require unusually high dust temperatures. The work shows FIR non‑detections can discriminate AGN‑dominated LRDs from DSFG impostors at z > 7, though a purely dusty origin cannot be fully excluded.

LRD v-shaped SED broad Balmer ALMA/mm spectroscopy high-z

2025-03-02 · 2503.00998v1

Tentative detection of neutral gas in a Little Red Dot at $z=4.46$

Hollis B. Akins, Caitlin M. Casey, John Chisholm, et al.

Download highlighted PDF arXiv abstract

ALMA Band 3/4/5 spectroscopy targets CO(7–6) and [CI](2–1) in three Little Red Dots at z=3.10, 4.46, and 7.04, finding no CO and no far-IR continuum, implying conservative molecular gas limits ≲1–5×10^10 Msun. A2744-45924 (z=4.4655) shows a tentative 4.9σ [CI](2–1) line with a narrow FWHM ~80 km s−1. The [CI]-inferred dynamical mass is ≲10^10 Msun for conservative size assumptions, well below the local MBH–Mdyn relation and an order of magnitude under SED-based stellar mass. If confirmed, this points to LRD hosts unlike massive, gas-rich quasar hosts and lends weight to a non-stellar origin for the Balmer break.

LRD ALMA/mm spectroscopy high-z

2025-02-27 · 2502.20550v1

JWST's PEARLS: A z=6 quasar in a train-wreck galaxy merger system

Madeline A. Marshall, Rogier A. Windhorst, Giovanni Ferrami, et al.

Download highlighted PDF arXiv abstract

JWST/NIRSpec IFU prism data (0.6–5.3 μm, R≈100) on the z=5.89 quasar NDWFS J1425+3254 capture rest-UV/optical lines and spatially resolve its host environment. Broad Hα and Hβ yield MBH≈1.4×10^9 M⊙ and Lbol/LEdd≈0.3, while [O III] exposes a quasar-driven outflow with v≈6050 km s−1 and an ionized outflow rate ≈1650 M⊙ yr−1. The cube maps a “train-wreck” triple merger: an older, massive NE companion (M⋆≈3.6×10^11 M⊙, age≈65 Myr) linked to the host by a gas bridge, plus a very young SE companion (age≈6.7 Myr, M⋆≈1.9×10^10 M⊙) with ongoing star formation. These results argue for merger-triggered early SMBH growth; a likely foreground z=1.135 galaxy may modestly lens the quasar (1<μ<2; <0.75 mag).

luminous quasar QSO high-z broad Balmer outflows spectroscopy

2025-02-25 · 2502.18310v1

High-velocity outflows in [OIII] emitters at z=2.5-9 from JWST NIRSpec medium-resolution spectroscopy

Ryan A. Cooper, Karina I. Caputi, Edoardo Iani, et al.

Download highlighted PDF arXiv abstract

From the full JADES NIRSpec R~1000 sample of 1087 [O III] 5007 emitters at z=2.5–9, the authors flag 40 galaxies with clear blue-side line broadening, of which 34 are robust ionized outflow candidates and 6 may reflect rotating clumps. The outflows occur mostly in star-forming systems (~65% starbursts) spanning log10(M*/Msun)=7.5–11, and include two type-2 AGN candidates plus one little red dot. They measure a median outflow velocity of 531(+146/−159) km/s and a global incidence of 3.4%, higher velocities and lower incidence than prior work, attributed to R1000 resolution and stricter selection. No v_out–M* or SFR correlations are found; v_out/v_esc has a median 0.77 (generally bound), while mass loading anti-correlates with M* up to ~10^10 Msun, exceeding unity in many M*<10^9 Msun galaxies.

outflows spectroscopy high-z demographics

2025-02-18 · 2502.12664v1

Where to search for supermassive binary black holes

Paola Marziani, Edi Bon, Natasa Bon, et al.

Download highlighted PDF arXiv abstract

This note argues that the best hunting ground for supermassive binary black holes is a specific, evolved segment of the quasar main sequence—Population B/B1 sources with weak Fe II and broad Balmer lines—where BLR kinematics most clearly betray companions. On a flux-limited sample, the authors decompose Hβ and Mg II with broad/very-broad components and measure centroids at multiple fractional intensities, finding characteristic offsets and asymmetries suggestive of perturbed BLR dynamics. In the M•–L plane, these targets cluster at low Eddington ratios (Population B), reinforcing a focused search strategy. They advocate time-domain spectroscopy to confirm periodic profile changes, cautioning that photometric periodicities alone are vulnerable to red-noise false positives.

broad Balmer QSO variability spectroscopy

2025-02-18 · 2502.12538v1

Bridging Theory and Observations: Insights into Star Formation Efficiency and Dust Attenuation in $z > 5$ Galaxies

Daisuke Toyouchi, Hidenobu Yajima, Andrea Ferrara, et al.

Download highlighted PDF arXiv abstract

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.

high-z simulation

2025-02-14 · 2502.10501v1

An X-ray view of the Cataclysmic Variable V902 Mon: Discovery of an X-ray eclipse

Nazma Islam, Koji Mukai

Download highlighted PDF arXiv abstract

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.

X-ray spectroscopy low-z

2025-02-14 · 2502.10271v1

The Rich JWST Spectrum of the Western Nucleus of Arp 220: Shocked Hot Core Chemistry Dominates the Inner Disk

Victorine Buiten, Paul van der Werf, Serena Viti, et al.

Download highlighted PDF arXiv abstract

JWST MIRI/MRS and NIRSpec/IFU 3–28 μm spectroscopy isolates the western nucleus of Arp 220 and reveals a forest of rovibrational absorptions, enabling column densities and rotational temperatures for 10 species, with optically thick C2H2, HCN, and HNC and columns ≈10× higher than Spitzer. A warm HCN component with Trot ≈ 330 K points to radiative excitation by a hot, ~20 pc inner core veiled by cooler dust. The chemistry resembles hot cores with added shocks, placing the absorbing gas in the inner starburst disk directly encasing the core. No X-ray–driven chemistry or extreme excitation is found, arguing against an energetically dominant buried AGN in this band.

spectroscopy low-z

2025-02-11 · 2502.07875v1

Investigating photometric and spectroscopic variability in the multiply-imaged Little Red Dot A2744-QSO1

Lukas J. Furtak, Amy R. Secunda, Jenny E. Greene, et al.

Download highlighted PDF arXiv abstract

Exploiting the three lensed images of the z=7.045 LRD A2744-QSO1 with 22 yr (observer; 2.7 yr rest) delays, the authors test variability using two NIRSpec epochs and multi-epoch NIRCam. Magnification-insensitive EWs of broad Hα and Hβ vary by up to 18±3% and 22±8%, respectively, over 875 d (2.4 yr) in the rest frame, coherently across images. No significant broadband photometric variability is detected beyond ≈0.3 mag systematics, so the EW changes cannot yet be tied to line- versus continuum-driven variability. A DRW model for MBH≈4×10^7 M⊙ matches the sparse sampling, bolstering the AGN interpretation and motivating continued monitoring.

LRD variability broad Balmer broad-line AGN spectroscopy high-z

2025-02-07 · 2502.05048v1

A prevalent population of normal-mass central black holes in high-redshift massive galaxies

Junyao Li, Yue Shen, Ming-Yang Zhuang

Download highlighted PDF arXiv abstract

From a galaxy-selected parent sample of 52 massive systems at z≈3–5, the authors use JWST/NIRSpec medium–high resolution spectra to search the Hα+[N II]+[S II] region for broad components (FWHM>1000 km/s), identifying 13 moderate-luminosity BLAGNs. Virial Hα masses and AGN luminosities place these sources on the local M_BH–M_* relation with an average M_BH/M_*≈0.1%, contrasting with previously JWST-selected overmassive LDs and quasars. Back-tracing indicates limited evolution in this mean ratio to z≈6, implying that a prevalent population of “normal” SMBHs was already in place within the first Gyr. Host SEDs show prominent Balmer/4000 Å breaks and red continua, suggesting many of these massive galaxies are already quenching, so assembling massive quiescents need not require overmassive black holes.

broad-line AGN high-z spectroscopy

2025-02-06 · 2502.03742v1

Radio emission from little red dots may reveal their true nature

Muhammad A. Latif, Ammara Aftab, Daniel J. Whalen, et al.

Download highlighted PDF arXiv abstract

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.

LRD radio high-z X-ray

2025-02-06 · 2502.03684v1

Iron-corrected Single-epoch Black Hole Masses of DESI Quasars at low redshift

Zhiwei Pan, Linhua Jiang, Wei-Jian Guo, et al.

Download highlighted PDF arXiv abstract

Using >55,000 type 1 DESI quasars at 0.25<z<0.8, the authors show that Fe emission strength (R_Fe) tracks Eddington ratio and derive iron-corrected R–L relations for Hβ, then calibrate Mg II masses against the Hβ-based results. Relative to canonical single-epoch scalings, black hole masses are overestimated by ~1.5× on average and up to ~5× for super-Eddington objects, which raises the super-Eddington fraction to ~5% (vs. 0.4%). The Mg II relation adds a −0.34 R_Fe term and is applied to build a ~0.5M-quasar DESI catalog at 0.6<z<1.6. If these iron-corrected relations hold at high z, z≥6 quasar masses would drop by a mean factor of ~2.3, easing early SMBH growth tension.

QSO broad-line AGN spectroscopy super-Eddington low-z

2025-02-06 · 2502.03683v1

AGN ruled out as the dominant source of cosmic reionization

Danyang Jiang, Linhua Jiang, Shengxiu Sun, et al.

Download highlighted PDF arXiv abstract

JWST GOODS-S/N imaging is used to build a highly complete z=7.15–7.75 sample and decompose each source into a point-source (AGN) and extended component in F115W and F150W, yielding 93 faint AGNs down to M_UV ≈ −15. From the PSF-only UV magnitudes they measure the faint-end AGN UV luminosity function and integrate a 1–4 Ryd SED with f_esc=1 to set an absolute upper bound on AGN ionizing emissivity. The cumulative result is that AGNs provide at most one third of the LyC photon budget at z≈7.5, with the contribution dominated by the lowest-luminosity bins. This effectively rules out AGNs as the dominant drivers of reionization, implying galaxies supply most ionizing photons during the EoR.

reionization JWST AGN high-z demographics

2025-01-29 · 2501.17925v1

Possible environmental quenching in an interacting little red dot pair at $z\sim7$

Rosa M. Mérida, Gaia Gaspar, Marcin Sawicki, et al.

Download highlighted PDF arXiv abstract

CANUCS NIRCam imaging behind Abell 370 reveals a compact z∼7 group with two little red dots only 3.3 kpc apart plus three satellites. SEDs show strong Balmer breaks implying recent (~100 Myr) quenching in the LRDs, while the satellites are consistent with a recent-onset (~100 Myr), ongoing burst. Modeling suggests a dust-free AGN produces the UV excess in LRD1 (with the optical dominated by an obscured post‑starburst and a subdominant AGN), and LRD2 is more ambiguous; in this picture the LRDs are massive (~10^10 M⊙, AV>1 mag) and the satellites are lower-mass (10^8–10^9 M⊙) with low attenuation. The tight configuration points to interaction-driven environmental bursting and quenching during reionization.

LRD high-z JWST AGN

2025-01-28 · 2501.16708v1

BASS XLV: Quantifying AGN Selection Effects in the Chandra COSMOS-Legacy Survey with BASS

Yarone M. Tokayer, Michael J. Koss, C. Megan Urry, et al.

Download highlighted PDF arXiv abstract

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.

X-ray obscured AGN simulation demographics low-z

2025-01-28 · 2501.16648v1

Three Brown Dwarfs Masquerading as High-Redshift Galaxies in JWST Observations

Zhijun Tu, Shu Wang, Xiaodian Chen, et al.

Download highlighted PDF arXiv abstract

From RUBIES NIRSpec PRISM/CLEAR (0.6–5.3 μm) spectra, the authors confirm three compact RUBIES sources (o005_s41280, o006_s00089, o006_s35616) are brown dwarfs rather than distant galaxies. Sonora Elf Owl fits yield Teff ≈2100–2300 K and 1800–2000 K for the two L-dwarf candidates and <1000 K for the late‑T object, with distances around 2 kpc; adding an extinction term notably improves Y/J/H residuals, especially for o006_s35616. NIRCam color–color planes place the cool T dwarf within the little red dot locus while the hotter L dwarfs sit among high‑z galaxy selections, implying ≈0.1% brown‑dwarf contamination in deep extragalactic surveys dominated by L dwarfs. The work pins down how specific substellar SED shapes infiltrate LRD/high‑z samples and shows that low‑resolution prism spectra efficiently weed them out.

LRD spectroscopy

2025-01-23 · 2501.14072v1

Estimating Black Hole Masses in Obscured AGN from X-ray and Optical Emission Line Luminosities

S. LaMassa, I. Farrow, C. M. Urry, et al.

Download highlighted PDF arXiv abstract

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.

obscured AGN X-ray spectroscopy low-z

2025-01-23 · 2501.14026v1

Luminous Mid-IR Selected Type-2 Quasars at Cosmic Noon in SDSS Stripe82 I: Selection, Composite Photometry, and Spectral Energy Distributions

Ben Wang, Joseph F. Hennawi, Zheng Cai, et al.

Download highlighted PDF arXiv abstract

WISE W4>5 mJy selection in SDSS Stripe 82 yielded 24 candidates, with GNIRS (all) plus LRIS (18/24) confirming 23 luminous Type‑2 QSOs at 0.88<z<2.99, including 12 at z>2. Multi‑band photometry (DESI Legacy, PS1, UKIDSS, Spitzer, WISE) enables rest‑frame 0.1–10 μm composite photometry and AGNfitter SEDs. The IR is torus‑dominated with average L_torus ≈10^46.84 erg s−1; inferred L_bol spans 10^46.28–10^47.49 erg s−1 and Eddington masses ~10^8.18–10^9.39 M⊙, and the sample is redder with brighter tori than earlier Type‑2 SEDs. Their SED shapes closely resemble JWST “little red dots,” highlighting mid‑IR selection as an efficient path to luminous z>2 Type‑2s; a key open point is the origin of the rest‑UV/optical light (scattered, stellar, or a reddened disk).

obscured AGN QSO luminous quasar spectroscopy high-z

2025-01-22 · 2501.13082v1

BlackTHUNDER -- A non-stellar Balmer break in a black hole-dominated little red dot at $z=7.04$

Xihan Ji, Roberto Maiolino, Hannah Übler, et al.

Download highlighted PDF arXiv abstract

BlackTHUNDER analyzes JWST NIRSpec-IFU plus archival MSA data of the triply imaged lensed LRD Abell2744-QSO1 at z=7.04, confirming a smooth Balmer break and a broad Hβ from the BLR. The narrow Hβ dispersion gives M_dyn < 4×10^8 Msun, capping the stellar contribution to <10% of the optical continuum and favoring a non-stellar Balmer break produced by an AGN continuum filtered by very dense (n_H ~ 10^10 cm^-3), nearly dust-free gas likely in/around the BLR; a tentative 3σ Hβ absorption appears in the R2700 spectrum. The black hole is overmassive relative to both stellar and dynamical masses, with hints of variability and an initial reverberation-mapping attempt. This picture alleviates the extreme stellar-density problem for LRDs and may generalize to similar V-shaped continua.

LRD v-shaped SED broad Balmer overmassive BH spectroscopy high-z

2025-01-22 · 2501.12567v1

Exploring quasar evolution with proximate molecular absorbers: Insights from the kinematics of highly ionized nitrogen

R. Cuellar, P. Noterdaeme, S. Balashev, et al.

Download highlighted PDF arXiv abstract

X-shooter spectroscopy of 13 z≈2.5–3.3 quasars with proximate H2+HI absorbers finds NV in 9/13 (70%), far exceeding intervening DLA (~10%) and generic proximate (~30%) rates. High-ionization lines show blue-extended, broader kinematics decoupled from the neutral/low-ionized profiles, and NV/SiIV varies with velocity such that blueshifted components require higher ionization parameters. Redshifted systems lack NV and are interpreted as infall pre-feedback, while blueshifted proximate H2 systems trace outflow phases that can reach neutral/molecular gas. The authors argue that ionization state—not a fixed velocity threshold—should define “associated” versus “intervening” classifications.

QSO outflows spectroscopy high-z

2025-01-21 · 2501.12449v1

Intervening nuclear obscuration changing the X-ray look of the $z\approx6$ QSO CFHQS J164121+375520

Fabio Vito, William Nielsen Brandt, Andrea Comastri, et al.

Download highlighted PDF arXiv abstract

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.

QSO high-z X-ray obscured AGN variability

2025-01-20 · 2501.11491v1

MIDIS: Quantifying the AGN component of X-ray-detected galaxies

Steven Gillman, John P. Pye, Almudena Alonso-Herrero, et al.

Download highlighted PDF arXiv abstract

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.

X-ray JWST AGN obscured AGN

2025-01-17 · 2501.10574v1

A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes -- IV. Ultraviolet spectroscopy

Jessie C. Runnoe, Michael Eracleous, Tamara Bogdanović, et al.

Download highlighted PDF arXiv abstract

HST UV spectra (COS/STIS) for 13 z<0.7 quasars with large H-beta velocity offsets are compared to contemporaneous optical Balmer profiles to test supermassive black hole binary (SBHB) versus single-BH disk-like BLR scenarios. The authors isolate broad components and ask whether UV resonance lines (e.g., Lyα, C IV) share the same velocity offset as Balmer lines set by [O III]. They find three objects with strong SBHB support, five tentative, one disfavored, and four inconclusive due to severely absorbed UV profiles. This cross-wavelength line-profile test tightens SBHB vetting by demanding consistent Doppler shifts across independent broad lines.

QSO broad-line AGN broad Balmer spectroscopy low-z

2025-01-16 · 2501.09602v1

The NuSTAR view of five changing-look active galactic nuclei

Bing Lyu, Zhen Yan, Xue-bing Wu, et al.

Download highlighted PDF arXiv abstract

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.

obscured AGN X-ray variability low-z

2025-01-16 · 2501.09585v1

New Methods of Identifying AGN in the Early Universe using Spectroscopy and Photometry in the JWST Era

Flor Arevalo Gonzalez, Titanilla Braun, James Trussler, et al.

Download highlighted PDF arXiv abstract

This paper stress-tests UV-line diagnostics and NIRCam SED selection to find early AGN, showing that classic optical BPT/VO87 fail in low-metallicity regimes. Using photoionization grids, the most effective discriminants emerge as (CIII]+CIV)/HeII λ1640, CIII]/HeII λ1640, and the EW of HeII λ1640, with HeII λ1640/Hβ also separating AGN from star-formers when dust is low. Applied to three JADES/NIRSpec sources (IDs 9422, 18846, 10058975), the diagnostics are promising but current spectra blend HeII λ1640 with OIII] λλ1661,1666 and optical lines are unreliable, limiting firm AGN claims. An EAZY-based NIRCam SED search flags one strong candidate with strong UV emission, and the authors argue longer integrations—especially at z>6—are needed to cleanly deblend key lines.

JWST AGN spectroscopy high-z demographics

2025-01-09 · 2501.05512v1

JWST NIRCam simulations and observations of AGN ionization cones in cosmic noon galaxies

Sophie Lebowitz, Kevin Hainline, Stéphanie Juneau, et al.

Download highlighted PDF arXiv abstract

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.

JWST AGN high-z simulation low-z

2025-01-09 · 2501.04912v1

Another piece to the puzzle: radio detection of a JWST detected AGN candidate

Anniek J. Gloudemans, Kenneth J. Duncan, Anna-Christina Eilers, et al.

Download highlighted PDF arXiv abstract

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.

JWST AGN radio X-ray demographics high-z

2025-01-08 · 2501.04770v1

Lyman Alpha Forest - Halo Cross-Correlations in Effective Field Theory

Anton Chudaykin, Mikhail M. Ivanov

Download highlighted PDF arXiv abstract

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.

QSO simulation high-z

2025-01-07 · 2501.04085v1

The Cosmic Evolution Early Release Science Survey (CEERS)

Steven L. Finkelstein, Micaela B. Bagley, Pablo Arrabal Haro, et al.

Download highlighted PDF arXiv abstract

CEERS is a 77.2 hr ERS survey in the EGS that uses coordinated, overlapping NIRCam/MIRI imaging, NIRSpec low–medium resolution spectroscopy, and NIRCam slitless grism data to validate efficient extragalactic mapping. From ~90 arcmin^2 of NIRCam imaging it uncovered large samples of z ≳ 10 galaxies and secured >1000 spectra, including dozens at 6<z<10, enabling redshifts and rest‑optical line diagnostics that probe star formation and supermassive black hole growth. The program also quantifies the first bulge, bar, and disk structures at z>3 and leverages MIRI mid‑IR emission to trace dust‑obscured star formation and black‑hole accretion at z~1–3. As a legacy, CEERS releases processed data with detailed reduction notes and reproducible notebooks.

spectroscopy high-z demographics

2025-01-06 · 2501.03309v1

Little Red Dots are Tidal Disruption Events in Runaway-Collapsing Clusters

Jillian Bellovary

Download highlighted PDF arXiv abstract

Proposes that Little Red Dots are recurrent tidal disruption events triggered during runaway collapse of the first dense star clusters, forming intermediate-mass black hole seeds. Matching JWST LRD number densities to seed-formation predictions implies a required TDE rate of ~10^-4 yr^-1; analytic (loss-cone) and simulation-based scalings show this rate is feasible in dense clusters. The scenario naturally explains compact, UV-bright emission with broad H-alpha and links LRDs to early black-hole growth. A top-heavy IMF may be needed to satisfy ΛCDM mass-function limits, and the hypothesis is testable via TDE-like variability in JWST follow-up.

LRD BH seeds broad Balmer variability