Weekly issue

Week 44, 2025

Oct 27 – Nov 2, 2025

Week 44, 2025 includes 6 curated papers, centered on high-z, LRD, QSO.

2510.26990v1

Faint active galactic nuclei supplied 31-75% of hydrogen-ionizing photons at z>5

Mainak Singha, Sangeeta Malhotra, James Ely Rhoads

Theme match 5/5

Digest

Using 4.5≤z≤6.5 samples from JWST and ground-based surveys, the authors build a unified rest-UV AGN luminosity function with two physical populations—Type I fit by a Schechter form and Type II by a double power law—showing that little red dots and X-ray–selected sources are magnitude-filtered Type I with η=0.10±0.02. They tie the Lyman-continuum escape fraction to outflow-driven geometric clearing, yielding luminosity-averaged fesc≈0.64 for faint Type I, 0.25 for Type II, and ≈0.91 for bright quasars. Integrating −27<MUV<−17 gives Ndot_ion,AGN=(3.77+1.08/−0.95)×10^51 s^−1 Mpc^−3, so AGN provide 31–75% of the ionizing photons at z≈5–6 when combined with ξion=25.7 and galaxy fesc=0.03–0.20. The implied ΓHI≈(0.5–2)×10^−12 s^−1 matches Lyα-forest constraints, pointing to AGN as a major—but not sole—driver of the late reionization background.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Rest-UV AGN luminosity function decomposed into Type I (Schechter) and Type II (double power law), with LRD/XRB overplotted as η=0.10±0.02 scaled subsets—inspect residuals and ΔAIC/ΔBIC to see why only two populations are required.
Class-dependent LyC escape fraction vs MUV from the outflow-clearing model (Rout/Rreq, Φgeom): read off fesc≈0.64 (faint Type I), 0.25 (Type II), 0.91 (bright quasars), 0.08 (X-ray weak) and how fesc increases with luminosity.
Ionizing photon production integrated over −27<MUV<−17: Ndot_ion,AGN with uncertainty band; compare to earlier estimates and to the Lyα-inferred requirement at z∼6.
Predicted ΓHI at z≈5–6 with bands for different galaxy fesc assumptions, plotted against Lyα-forest measurements after mean free path and IGM clumpiness corrections—check where models remain consistent.
Link between Lbol/MBH/λEdd and outflow incidence (Pwind) showing where Rout>Rreq; see how this threshold sets Φgeom and the fraction of cleared vs screened sightlines across classes.

Tags

2510.26884v1

Constraining the AGN tori at cosmic noon using high-resolution JWST imaging and simultaneous SED fitting

Devang H. Liya, David J. Rosario, Matthaios Charidis

Theme match 4/5

Digest

Using CEERS near- and mid-IR imaging, the authors isolate nuclear emission and perform simultaneous SED fits that combine new high-resolution JWST photometry with archival UV–FIR data for 88 X-ray selected z≈2 AGN. Their Bayesian framework tightens constraints on accretion-disc luminosity and torus geometry, finding a covering-fraction distribution peaking near 0.25 with a long high-CF tail. At the population level, the CF distribution shows no strong statistical difference from local or intermediate-redshift AGN of similar luminosity, despite major ISM evolution at cosmic noon. This argues that torus geometry may be governed primarily by nuclear-scale processes rather than evolving host conditions.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 (L2–10 keV vs. z with NH coding): Verify the luminosity and obscuration spread of the 88 CEERS/AEGIS-X AGN and how the dashed selection cuts define the final sample around z~2.
Figure 2 (sky footprint with HST F160W): Check which sources have NIRCam, MIRI, or both; note how MIRI coverage anchors hot-dust constraints and how full HELP/AEGIS-X overlap supports multiwavelength SEDs.
Figure 3 (workflow diagram): Follow the dual-SED pathway—central (nuclear) plus integrated photometry—into the Bayesian fit, noting where torus priors enter and how simultaneous fitting mitigates galaxy–torus degeneracies.
Figure 4 (postage stamps for XID471): Examine the fixed F277W 80% EE nuclear aperture versus the CANDELS Kron radius to see host dilution control, and compare the AEGIS-X optical position to the JWST-recentered nucleus to gauge astrometric and contamination impacts.

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2510.25830v1

Unveiling Extended Components of 'Little Red Dots' in Rest-Frame Optical

Yiyang Zhang, Xuheng Ding, Lilan Yang, Erini Lambrides, Hollis Akins, Andrew J. Battisti, Caitlin M. Casey, Chang-hao Chen, Isa Cox, Andreas Faisst, Maximilien Franco, Aryana Haghjoo, Luis C. Ho, Kohei Inayoshi, Shuowen Jin, Mitchell Karmen, Anton M. Koekemoer, Jeyhan S. Kartaltepe, Kai Liao, Ghassem Gozaliasl, Masafusa Onoue, Vasily Kokorev, Namrata Roy, R. Michael Rich, John D. Silverman, Takumi S. Tanaka, Bei You, Hassen M. Yesuf, Jorge A. Zavala

Theme match 4/5

Digest

Stacking 217 Little Red Dots from COSMOS-Web across F115W–F444W and decomposing with PS+Sérsic, the authors unambiguously recover faint rest‑optical host emission, including a ring-like residual in F444W with total SNR ~72. The mean extended component has Re ≈ 200 pc and m_F444W ≈ 27.7 AB at z ≈ 6.5; four-band host photometry fit with Bagpipes yields log10(M*) = 8.91 ± 0.1. The extended-to-total flux fraction declines from ~60% (F115W) to ~12% (F444W), underscoring the dominance of the compact nucleus. Hosts are ≈2.5× smaller than SFGs at similar mass, and implied MBH are ~1.5 dex above the local MBH–M* relation, pointing to overmassive early black holes and compact stellar hosts.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the stacked residual “ring” after PS-only subtraction and its SNR map (~72), and compare with the star-control stack to verify the extended component is not a PSF artifact.
Figure 2: Check the PS+Sérsic fits per NIRCam band and the azimuthal profiles versus the PSF to read off the mean effective radius (~200 pc) and any wavelength-dependent morphology of the host light.
Figure 3: From the Bagpipes SED fit to the isolated host fluxes, verify the inferred m_F444W ≈ 27.7 AB and log10(M*) ≈ 8.91, and gauge the uncertainty envelope on the stellar component.
Figure 4: Use the size–mass panel to see that LRD hosts are ~2.5× smaller than SFGs at the same M*, and the MBH–M* panel to appreciate the ~1.5 dex MBH excess relative to local relations and to quasars plotted for context.

Tags

2510.27214v1

AGN--Host Galaxy Image Decomposition with JWST

Callum Dewsnap, Pauline Barmby, Sarah C. Gallagher

Theme match 3/5

Digest

Tests JWST/CEERS F115W AGN–host decompositions for 87 X-ray AGNs (0.1<z<4) using Sérsic+PSF models with PSFs from photutils vs PSFEx and fits from Galfit vs AstroPhot. PSFEx PSFs systematically mis-reproduce point-source radial profiles, while Galfit and AstroPhot converge to different regions of parameter space, yielding inconsistent host properties. AGN and host magnitudes are robust, but host morphology is poorly constrained: Sérsic n and Re are strongly covariant and large parameter shifts barely affect χ² or radial profiles. Conclusion: single-Sérsic models do not uniquely represent typical AGN hosts in JWST extragalactic fields, and the authors offer practical recommendations.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Fig. 3 — Compare PSF FWHM distributions for photutils (red) vs PSFEx (blue) across JWST and HST; note systematic offsets and where PSFEx broadens/narrows relative to the point-source ensemble and external benchmarks (green stars).
Fig. 4 — Inspect the 2D PSF stamps and 1D radial profiles: quantify where PSFEx departs from the empirical point-source profile (core/wings) and how photutils better tracks the gray point-source stack.
Fig. 1 — Check the Lx–z plane and flux-limit line to see the dynamic range of rest-frame 2–10 keV luminosities and redshifts feeding the 87-object sample; verify spectroscopic vs photometric-z coverage.
Fig. 2 — Evaluate point-source vetting: artifacts in the HST/ACS F814W core that contaminate PSF training, motivating strict selection for reliable JWST/HST PSFs.
(If available in the main text) Decomposition residual/radial-profile comparison — verify that markedly different n and Re solutions produce nearly indistinguishable residuals/profiles, illustrating the covariance-driven non-uniqueness.

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2510.26554v1

The $N_H$ Distribution of Hard X-ray Selected AGN in the NEP Field

Samantha Creech, Francesca Civano, Daniel R. Wik, Ross Silver, Xiurui Zhao, Rafael Ortiz, Tonima Ananna, Normal A. Grogin, Rolf Jansen, Anton M. Koekemoer, Christopher N. A. Willmer, Rogier A. Windhorst

Theme match 2/5

Digest

NuSTAR Cycles 5+6+8+9 plus simultaneous XMM-Newton enable the first full spectral analysis of all 60 hard X-ray sources in the JWST–NEP TDF, yielding the sample’s N_H distribution. The team finds an observed Compton-thick fraction of 0.13_{-0.04}^{+0.15} to an 8–24 keV flux limit of 6.0×10^-14 erg s^-1 cm^-2, which rises to 0.32_{-0.08}^{+0.23} after correcting for absorption bias. These results, derived from the deepest NuSTAR survey to date, align with AGN population-synthesis expectations and prior surveys, sharpening constraints on obscured growth contributing to the CXB. The work provides a clean, hard-band-selected benchmark for CT demographics in the NEP field.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 — Redshift and 3–24 keV luminosity distributions: verify the z–L_X range of the NEP sample and how quasars/galaxies/unclassified sources populate it, setting context for where CT candidates sit in parameter space.
Figure 2 — Net counts histogram (NuSTAR vs XMM-Newton): assess spectral leverage per source and which subset (high-count vs low-count) dominates the N_H constraints and CT identification.
Figure 3 — Baseline spectral model schematic: track how absorbed and scattered components plus Galactic emission map onto XMM (soft) and NuSTAR (hard) bands, clarifying where CT sensitivity originates.
Figure 4 — N_H from baseline vs clumpy models: check robustness of CT classifications and identify sources that shift across the CT threshold; note red-square points lacking redshifts as a potential systematic.

Tags

2510.25089v1

XRISM Spectroscopy of the Stellar-mass Black Hole GRS 1915+105

Jon M. Miller, Liyi Gu, John Raymond, Laura Brenneman, Elena Gallo, Poshak Gandhi, Timothy Kallman, Shogo Kobayashi, Junjie Mao, Megumi Shidatsu, Yoshihiro Ueda, Xin Xiang, Abderahmen Zoghbi

Theme match 2/5

Digest

First XRISM/Resolve spectroscopy of GRS 1915+105 catches the source in a micro–Type 2/CTAGN-like state, where a sub‑Eddington engine is veiled by warm, Compton‑thick gas that turns the 1.6–11.6 keV band into a forest of narrow H‑/He‑like lines with clear RRCs. Modeling requires three photoionized emission zones; bulk redshifts and modest line broadening indicate an origin in the outer disk atmosphere or a slow wind at r ≃ 10^6 GM/c^2, with a broad base under Fe XXV–XXVI hinting at emission from r ~ 3×10^3 GM/c^2. A weak 6.4 keV Fe Kα plus strong RRCs point to photoionized reprocessing, the heavy warm cover acting as a coronagraph that reveals the line-emitting gas. The authors favor obscuration by an irradiated, warped, precessing outer disk as the driver of the current state.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Use the full-band Resolve spectrum to see how narrow H-/He-like lines dominate over the continuum and to spot RRCs; note the weak, narrow 6.4 keV Fe Kα that flags some cold gas at intermediate radii.
Figure 2: In the 2 keV slices, compare line centroids to the marked lab energies to gauge the systematic redshift of the bulk emitter and to trace RRC features across the band.
Figure 3: Inspect the Fe-peak complex (Cr–Ni) where lines tower 8–10× above the local continuum; check the Fe RRCs near 8.8 and 9.3 keV that verify photoionization.
Figure 4: Examine the decomposition of Fe XXV He-α and Fe XXVI Ly-α into three pion components to see why multiple photoionized zones are required, and to assess the redshift and the broad base hinting at r ~ 3×10^3 GM/c^2 emission.