Weekly issue

Week 14, 2025

Mar 31 – Apr 6, 2025

Week 14, 2025 includes 9 curated papers, centered on spectroscopy, high-z, QSO.

2504.01852v1

Deciphering the Nature of Virgil: An Obscured AGN Lurking Within an Apparently Normal Lyman-α Emitter During Cosmic Reionization

Pierluigi Rinaldi, Pablo G. Pérez-González, George H. Rieke, Jianwei Lyu, Francesco D'Eugenio, Zihao Wu, Stefano Carniani, Tobias J. Looser, Irene Shivaei, Leindert A. Boogaard, Tanio Diaz-Santos, Luis Colina, Göran Östlin, Stacey Alberts, Javier Álvarez-Márquez, Marianna Annuziatella, Manuel Aravena, Rachana Bhatawdekar, Andrew J. Bunker, Karina I. Caputi, Stéphane Charlot, Alejandro Crespo Gómez, Mirko Curti, Andreas Eckart, Steven Gillman, Kevin Hainline, Nimisha Kumari, Jens Hjorth, Edoardo Iani, Hanae Inami, Zhiyuan Ji, Benjamin D. Johnson, Gareth C. Jones, Álvaro Labiano, Roberto Maiolino, Jens Melinder, Thibaud Moutard, Florian Peißker, Marcia Rieke, Brant Robertson, Jan Scholtz, Sandro Tacchella, Paul P. van der Werf, Fabian Walter, Christina C. Williams, Chris Willott, Joris Witstok, Hannah Übler, Yongda Zhu

Theme match 5/5

Digest

JWST/MIRI imaging plus deep NIRSpec/PRISM place the LAE “Virgil” at z=6.6379 and reveal Little Red Dot–like photometry with an extreme color F444W−F1500W=2.84±0.04, and a strongly rising mid-IR SED. SED fits across multiple codes favor an obscured AGN whose IR slope and UV excess resemble blue-excess HotDOGs. The host shows subsolar metallicity, low–moderate dust, and high ionization/electron temperature; UV and Hα SFRs suggest Virgil is entering or fading a burst. High‑z line‑ratio diagnostics (e.g., O32–R23, Ne3O2) nominally flag AGN, though this is ambiguous after accounting for redshift evolution; a tentative broad Hα improves residuals only marginally, while the new 15 μm data strengthen the AGN case and highlight MIRI’s leverage on early black‑hole growth.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 (2D PRISM + NIRCam RGB/slits): Verify the secure z=6.6379 via the stacked emission-line pattern and check for any slit contamination from the nearby foreground LAE; the slit overlays also show how Virgil was targeted relative to neighbors.
Figure 2 (mass–metallicity): See where Virgil’s subsolar metallicity lands against JADES/CEERS and simulation tracks (Astraeus/FirstLight/FLARES/TNG50), clarifying that the host is chemically typical for z~6–7 SF galaxies despite its extreme mid‑IR color.
Figure 3 (O32–R23 and Ne3O2 grids): Inspect Virgil’s position with and without dust correction relative to CLOUDY model grids, SDSS, local analogs, and z>6 samples to understand why classical cuts imply AGN yet become ambiguous once redshift evolution is considered.
Figure 4 (Hα+[NII] fits): Compare fits with/without a broad Hα component; note the improved residuals but only marginal BIC gain, framing how weak BLR evidence contrasts with the strong mid‑IR AGN signal.

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2504.00172v1

Evidence for evolutionary pathway-dependent black hole scaling relations

Jonathan H. Cohn, Emmanuel Durodola, Quinn O. Casey, Erini Lambrides, Ryan C. Hickox

Theme match 5/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 (M_BH vs M_star): Verify that cyan/magenta diamond relics and the z~2 lensed quiescent point sit on both the Reines & Volonteri bulge line and the Pacucci et al. (4<z<7) relation; contrast with squares/Xs (QSOs/AGN) that hug Pacucci et al. and note the broad LRD scatter, plus the placement of GN‑z11.
Figure 2 (M_BH vs sigma_*): Check that most AGN and relics lie above the median Saglia et al. relation, with the lensed quiescent galaxy near the median; note that only the Maiolino et al. sample has sigma_* estimates, highlighting how central potential may evolve less than total mass.
Figure 3 (pathways schematic): Read vectors showing dry mergers moving systems rightward in M_star at near-constant M_BH (relic/ETG track) versus AGN accretion driving upward movement in M_BH (AGN/LRD track), clarifying why bulge-based scaling appears stable while total-mass scaling depends on assembly history.

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2504.03551v1

JADES: comprehensive census of broad-line AGN from Reionization to Cosmic Noon revealed by JWST

Ignas Juodžbalis, Roberto Maiolino, William M. Baker, Emma Curtis Lake, Jan Scholtz, Francesco D'Eugenio, Bartolomeo Trefoloni, Yuki Isobe, Sandro Tacchella, Andrew J. Bunker, Stefano Carniani, Stéphane Charlot, Gareth C. Jones, Eleonora Parlanti, Michele Perna, Pierluigi Rinaldi, Brant Robertson, Hannah Übler, Giacomo Venturi, Chris Willott

Theme match 4/5

Digest

Using JADES spectroscopy, the authors assemble a uniform census of 34 broad-line (Type 1) AGN spanning 1.5<z<9 with virial black-hole masses of 10^6–10^9 M⊙ and bolometric luminosities down to 10^43 erg s^-1, generally at sub-Eddington rates (<0.5 L_Edd). These AGN are typically in low-mass (M⋆≈10^8 M⊙) hosts whose black holes are overmassive relative to the local M_BH–M⋆ relation yet consistent with the local M_BH–σ⋆ relation, enabling a view of how these scalings emerge across cosmic time. The team shows that standard narrow-line diagnostics would miss many counterparts—especially at low metallicity or with attenuated/soft ionizing continua—complicating Type 2 selection. They also find strong cosmic-variance sensitivity in the UV luminosity function and rule out electron/Balmer scattering as the origin of broad Balmer components, arguing BH masses are not severely overestimated.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the prism+R1000 fits across redshift to see how BLR H-line widths and profiles are identified in diverse hosts, including a low-z case flagged as tentative due to [O III] outflows and a high-z, low-luminosity AGN; note the NIRCam stamps and slit placement for host context.
Figure 2: Examine where the JADES broad-line sources lie in the M_BH–L_bol plane relative to prior samples and constant L/L_Edd tracks; verify the predominantly sub-Eddington regime and the caution that the apparent trend may be inflated by H-based scalings on both axes.
Figure 3: Compare velocity-dispersion inferences from medium/high-resolution data versus R1000; learn that R1000 overestimates σ by ~80% after LSF correction, impacting dynamical interpretations and tests of the M_BH–σ⋆ relation.
Figure 4: Check host stellar-mass systematics by contrasting ForcePho-based masses with prism-spectrum and photometry-only fits; assess offsets/uncertainties that set the placement of these low-mass hosts on the M_BH–M⋆ plane.

Tags

2503.23710v1

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

Fangzhou Jiang, Zixiang Jiang, Haonan Zheng, Luis C. Ho, Kohei Inayoshi, Xuejian Shen, Mark Vogelsberger, Wei-Xiang Feng

Theme match 4/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Read the c–M maps to see where halos lie above the collapse-time contour by the LRD epoch; this shows the need for very high concentrations and reveals the cross‑section–dependent characteristic mass that collapses fastest (aligned with rare 2–3σ peaks).
Figure 2: Track the blue collapse-time curves against the EPS look‑back distributions; the red highlighted early-forming tail pinpoints which halo masses and redshifts actually seed BHs, emphasizing that seeding only operates at high z and within a narrow mass window.
Figure 3: Inspect the VVV‑L1 concentration distribution and its high‑c tail (84–99th percentiles) to judge whether the concentrations required in Fig. 1 are plausible and how often such progenitors appear in merger trees.
Figure 4: Compare the modeled BH mass function (median/mean and scatter) with the LRD-inferred points from Kokorev et al.; check how the chosen σ0m and ω reproduce the normalization and shape, and where deviations hint at duty cycle or Eddington-ratio adjustments.

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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, Almudena Alonso-Herrero, Enrique López-Rodríguez, Begoña García-Lorenzo, Cristina Ramos Almeida, Ismael García-Bernete, Donaji Esparza-Arredondo, Sebastian F. Hoenig, Santiago García-Burillo, Chris Packham, Nancy A. Levenson, Alvaro Labiano, Miguel Pereira-Santaella, Francoise Combes, Anelise Audibert, Erin K. S. Hicks, Lulu Zhang, Enrica Bellocchi, Richard I. Davies, Laura Hermosa Muñoz, Masatoshi Imanishi, Claudio Ricci, Marko Stalevski

Theme match 3/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

MRSPSFisol demonstration: nuclear vs extended spectra/maps across the four MRS channels, showing removal of PAH-dominated host emission and the recovered nuclear flux fraction at 0.3–0.8″ scales.
Representative continuum fits for type-1 and type-2 nuclei: compare silicate 9.7/18 µm profiles and continuum slopes, and see how the flared-disk (clumpy+smooth, variable grain size) reproduces them versus alternatives.
Fit-quality and model-preference summary: histogram/scatter of chi2/dof and best-fit families across the 21 targets, confirming 12/21 successes, two disk+wind, one clumpy torus, and the 40% failures.
Stacked residuals in the 5–8 µm region: highlight systematic deficits at ~6.0 µm (H2O ice) and 6.85/7.25 µm (aliphatic hydrocarbons) that current models miss.
Posterior constraints on dust grain size in successful flared-disk fits: inspect whether large grains are favored and any trend with optical type (1 vs 2).

Tags

2504.03848v1

Large-scale surveys of the quasar proximity effect

Rupert A. C. Croft, Patrick Shaw, Ann-Marsha Alexis, Nianyi Chen, Yihao Zhou, Tiziana Di Matteo, Simeon Bird, Patrick Lachance, Yueying Ni

Theme match 2/5

Digest

Develops a CDM halo-model framework for the quasar proximity effect that explicitly includes overdense quasar environments and fits individual Lyα spectra for the radiation-equality radius r_eq and large-scale quasar bias b_q, validated on the ASTRID hydrodynamic simulation. Demonstrates that r_eq can be recovered without bias from a single spectrum with 25–50% statistical uncertainty. Scaling to DESI-sized samples enables precise measurements of the UV background intensity and its redshift evolution. Using the Uchuu simulation, shows that proximity-effect measurements could map spatial UV radiation fluctuations and measure their power spectrum on 100–1000 h−1 Mpc scales, making the radiation field a cosmological observable alongside density.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Compare real- vs redshift-space model curves with and without local quasar radiation and with the one-halo term removed to see how environment biases the transmitted-flux profile and where r_eq imprints a scale break.
Figure 2: Slice through the Astrid volume centered on the brightest quasar (uniform UVBG only) to visualize the overdense IGM structure and neutral-fraction gradients before adding quasar radiation—use the slice thickness to gauge how these structures compare to expected r_eq scales.
Figure 3: For the top-luminosity quasars, examine how r_eq scales with black-hole mass and how M_BH tracks halo mass; use the bottom panel’s trend versus halo mass to connect fitted b_q (or related clustering proxy) to host mass and identify scatter/outliers relevant for single-sightline fits.
Figure 4: With a halo-mass–selected sample, check how r_eq and quasar properties populate the most massive halos and how the clustering/bias metric varies with M_h—highlighting selection effects that matter when aggregating proximity-effect measurements for large surveys.

Tags

2504.03422v1

XXL-HSC: Host properties of X-ray detected AGNs in XXL clusters

E. Drigga, E. Koulouridis, E. Pouliasis, Y. Toba, M. Akiyama, C. Vignali, A. Ruiz, I. Georgantopoulos, T. Nagao, S. Paltani, M. Plionis, M. Pierre, B. Vijarnwannaluk

Theme match 2/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Radial distribution of AGN incidence vs r/r500, split by host morphology (disturbed/merger vs undisturbed): verify the peak between 1–2 r500 and quantify the excess in cluster outskirts.
Hardness-ratio comparisons (cluster vs field and as a function of radius): check where the X-ray-hard/obscured fraction rises and how strongly it differs from the field.
HSC cutouts with Statmorph outputs (e.g., segmentation maps, Gini–M20/Asymmetry): assess the visual and quantitative disturbance signatures used to flag mergers.
Host SFR (from SEDs) versus morphology or cluster-centric radius: look for interaction-linked SFR enhancements that accompany the disturbed AGN hosts.

Tags

2504.02683v1

Probing patchy reionisation with JWST: IGM opacity constraints from the Lyman-$α$ forest of galaxies in legacy extragalactic fields

Romain A. Meyer, Guido Roberts-Borsani, Pascal Oesch, Richard S. Ellis

Theme match 2/5

Digest

Using public JWST/NIRSpec PRISM spectra of z≈4–7 galaxies, the authors detect the Gunn–Peterson trough in stacked galaxy spectra and derive the first galaxy-based IGM Lyα opacity measurements, plus intrinsic Lyβ opacity at 5<z<6. The galaxy-based opacities agree with state-of-the-art quasar Lyman-α forest constraints and will sharpen as JWST samples grow. In GOODS-South, a z=5.8–5.9 overdensity of galaxies and Lyα emitters coincides with an anomalously low Lyα IGM opacity, directly linking local large-scale structure to an over-ionised IGM patch. The required photo-ionisation rate can be produced by galaxies down to M_UV≲−10 if log10⟨ξion fesc⟩≈25 (e.g., log10 ξion=25.4 with fesc=0.4).

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the stacked, normalised spectra to see the onset of the Gunn–Peterson trough blueward of Lyα and any damping-wing signature; check the systemic Lyα/Lyβ markers (from rest-optical lines) and the stack errors to gauge the robustness of the trough detection across redshift bins.
Figure 2: Compare the galaxy-derived Lyα transmission/opacity versus redshift to the colored quasar measurements; note the continuous 4≲z≲7 coverage and how single-field (gray) points scatter around the stacked (black) values, highlighting emerging field-to-field variance.
Figure 3: Use the cumulative distribution of τeff(Lyα) to place each field (GOODS-S, GOODS-N, EGS, Abell 2744) within the Bosman+2022 distributions; GOODS-S should sit at unusually low τeff, quantifying the over-ionised patch relative to typical sightlines.
Figure 4: Top panel shows observed τeff in Lyβ including foreground Lyα contamination—verify how GOODS-S dominates the stack; bottom panel applies the foreground-galaxy correction to recover intrinsic Lyβ opacity and compare it to Lyα-based expectations and IGM parameter bands.

Tags

2504.01079v1

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

Labanya Kumar Guha, Raghunathan Srianand, Rajeshwari Dutta

Theme match 2/5

Digest

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.

Open paper page arXiv abstract arXiv PDF

Key figures to inspect

Figure 1: Use the SDSS/eBOSS emission-line fits ([O II] doublet, others) to confirm the foreground galaxy redshifts captured in the quasar fibers and compare DESI-LIS images; note that only J1451+0857 shows the galaxy directly, enabling a measured impact parameter, while the others provide fiber-size upper limits.
Figure 2: Inspect the multi-Gaussian 21-cm absorption profiles for J0758+1136, J1159+5820, and J1451+0857; read component velocities relative to the galaxy emission redshift and sum components to reproduce the reported integrated optical depths.
Figure 3: Examine the trend of integrated 21-cm optical depth versus impact parameter; locate the new uGMRT GOTOQs (boxed squares) against earlier QGP compilations to see the sharp decline in τ with increasing D and where detections cluster.
Figure 4: Compare covering fraction versus impact parameter for GOTOQs/QGPs to the red points from Gupta et al. (2021); note the assumed ∫τ dv sensitivity (~0.3 km s⁻¹) and how f_c rises at the smallest D, highlighting why GOTOQs are effective low-D probes.