Weekly issue

Week 16, 2025

Apr 14–20, 2025

Week 16, 2025 includes 7 curated papers, centered on QSO, spectroscopy, high-z.

2504.11566v1

Tracking the assembly of supermassive black holes: a comparison of diverse models across cosmic time

Antonio J. Porras-Valverde, Angelo Ricarte, Priyamvada Natarajan, Rachel S. Somerville, Austen Gabrielpillai, L. Y. Aaron Yung

Theme match 5/5

Digest

The authors cross-compare SMBH assembly across semi-analytic, empirical, and hydro frameworks (Dark Sage, Santa Cruz SAM, RN18, TRINITY, TNG300) over MBH ≈ 10^6–10^10 Msun. Physics-based models diverge from observationally inferred local BHMFs due to stellar-mass-function and scaling-relation systematics, but converge at z ~ 1–4 and broadly match JWST broad-line AGN BHMFs at z = 4–5. Dark Sage uniquely produces a strong knee in the bolometric AGN luminosity function near Lbol ~ 10^46 erg s^-1 that overlaps the inferred luminosities of JWST “Little Red Dots” at z = 5–6 if the emission is AGN-dominated. Within Dark Sage, SMBHs grow mainly via secular disk instabilities and merger-driven cold gas accretion, while BH–BH mergers contribute ~60% of the mass only for the most massive systems by z = 0; super-Eddington accretion is allowed.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 3: Examine the bolometric AGN luminosity function—locate Dark Sage’s knee at Lbol ~ 10^46 erg s^-1 and compare it directly to the shaded LRD luminosity band; note that RN18 and TNG300 track the Shen et al. fits, while Santa Cruz departs at the low‑z bright end.
Figure 2: Track the BHMF evolution versus redshift, focusing on model convergence by z ~ 1–4 and the distinct Dark Sage bump; compare to JWST broad-line AGN BHMF points at z = 4–5 (Taylor+2024) and NIRCam WFSS constraints (Matthee+2024), keeping the flagged low-mass incompleteness in mind.
Figure 1: Contrast the local SMF, MBH–M* relation, and local BHMF across models; check how different SMF calibrations and scaling relations propagate into BHMF discrepancies, and note the Dark Sage dashed curve for halos with <200 particles.
Figure 4: Inspect median MBH growth histories at fixed halo mass—observe order‑of‑magnitude convergence at z = 0 for most bins but larger spread in the most massive halos; use Sgr A* and M87* markers as anchors and relate differences to model seeding and accretion prescriptions.

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2504.13658v1

SRGAJ230631.0+155633: an extremely X-ray luminous, heavily obscured, radio-loud quasar at z=0.44 discovered by SRG/ART-XC

Grigory Uskov, Sergey Sazonov, Igor Lapshov, Alexander Mikhailov, Ekaterina Filippova, Alexander Lutovinov, Ilya Mereminskiy, Maria Mochalina, Andrey Semena, Alexey Tkachenko

Theme match 3/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Check the ART‑XC survey vs pointed and Swift/XRT images to verify the association with SDSS J230630.38+155620.4, the 98% localization (23.2″ radius), the ~6.5″ offset between X‑ray and optical, and the source/background extraction regions used for spectroscopy.
Figure 2: Inspect the joint ART‑XC+XRT spectrum and absorbed power‑law fit to see the heavy obscuration and continuum slope; use the data‑to‑model ratio to judge residual structure and the adequacy of a single absorbed power‑law across 0.3–20 keV.
Figure 3: Study the 68/90/99% joint confidence contours for the key tbabs*ztbabs*cflux*zpowerlaw parameters to gauge degeneracies between obscuration and intrinsic continuum/flux and how tightly N_H is constrained.
Figure 4: Examine the 1‑hour binned light curves in multiple energy bands to look for intra‑observation variability or hardness changes, complementing the year‑scale luminosity drop between the survey and June 2023 pointed data.

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2504.11531v1

Oxyster: A Circumgalactic Low-ionization Oxygen Nebula next to a Starburst Galaxy at $z\sim1$

Pengjun Lu, Mingyu Li, Dalya Baron, Minghao Yue, Song Huang, Zheng Cai

Theme match 3/5

Digest

Subaru/HSC narrow-band NB718/NB973 imaging plus Magellan LDSS3 follow-up reveal “Oxyster,” a CGM oxygen nebula next to a disturbed, interacting starburst at z=0.924, extending ~30 kpc in [O II] and ~20 kpc in [O III]. On the luminosity–size plane it outscales low‑z ENLRs and evokes a high‑z Voorwerp analog, but shows uniformly low O32 and no Hβ. HST/JWST imaging and SED fitting place the 2–6×10^10 Msun host above the main sequence with <5% AGN contribution and no X-ray/radio AGN, while standard photoionization/shock models cannot reproduce the luminosities, low O32, and Hβ non‑detection. The authors favor a recent (<10^8 yr) starburst plus a low‑luminosity AGN (~10^42 erg s^-1), underscoring narrow-band searches as a route to CGM mapping around non‑AGN systems near z~1.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Fig. 1: Compare [O II] (green) and [O III] (white) contours to the JWST/NIRCam morphology to gauge the nebula–galaxy offset, anisotropy, and whether the blue spiral arm aligns with the brightest oxygen emission.
Fig. 2: Inspect Prospector SED fits for the whole galaxy vs. “core” and “arm” to quantify the bursty SF episode, stellar mass range (2–6×10^10 Msun), and the <5% AGN light fraction that matches the multiwavelength non-detections.
Fig. 3: Use the LDSS3 long‑slit spectra to verify redshifted [O II] and [O III] detections, measure their spatial extent along the slit, and read off the stringent Hβ upper limit that drives the low O32/Hβ tension.
Fig. 4: Examine the smoothed O32 map for its uniform, low ionization state and the radial surface‑brightness profiles showing [O II] more extended than [O III], constraining the hardness and reach of the ionizing source(s).

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2504.10596v1

An obscured quasar census with the 4MOST IR AGN survey: design, predicted properties, and scientific goals

Carolina Andonie, David M. Alexander, Claire Greenwell, Sotiria Fotopoulou, Ryan Hickox, David J Rosario, Carolin Villforth, Johannes Buchner, Jens-Kristian Krogager, Brivael Laloux, Andrea Merloni, Mara Salvato, Ole Streicher, Wei Yan

Theme match 3/5

Digest

Introduces the 4MOST IR AGN survey, a ~10,000 deg^2, rAB≤22.8 program targeting ≈212k mid-IR–selected obscured AGN via unWISE colors plus an r−W2≥5.9 mag cut. Using X-ray spectral constraints and UV–far-IR SEDs in four deep fields, they forecast 80–87% AGN purity with ≈70% obscured (NH>10^22 cm−2) and that ≈80% of targets will evade even the deepest eROSITA exposures. About 55% will be quasar-luminous (LAGN,IR>10^45 erg s−1) at z≈0.5–3.5 in massive (10^10–10^12 M⊙) hosts, with ≈33% in starbursts. This 100× expansion over prior spectroscopic obscured-IR samples will deliver a uniform census of heavily absorbed, X-ray–faint quasars complementing the 4MOST X-ray AGN survey.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 — Selection workflow: confirms the unWISE color preselection, the r−W2≥5.9 obscuration cut, LS10 matching radius, and deep (r≤22.8) vs wide (r≤22.1) components; use it to reproduce the final target list logic.
Figure 2 — Sky footprint and ancillary overlap: shows wide/deep tiling within the eROSITA-covered 4MOST area and where Herschel/Spitzer/Chandra/XMM/DESI add leverage; gauge environmental and SED follow-up potential.
Figure 3 — r−W2 vs redshift with NH coding (COSMOS): visually verifies that r−W2≥5.9 tracks higher NH and illustrates any redshift-dependent leakage using both IRAC2 and unWISE W2.
Figure 4 — NH distributions by color bin: quantifies the median NH shift and the obscured fraction gained by the r−W2 cut, providing the most direct evidence that the color criterion selects NH>10^22 cm−2 sources.

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2504.10731v1

Unveiling faint X-ray AGN populations in the NewAthena era: Insights from cosmological simulations

Nuno Covas, Israel Matute, Stergios Amarantidis, José Afonso, Giorgio Lanzuisi, Andrea Comastri, Stefano Marchesi, Ciro Pappalardo, Rodrigo Carvajal, Polychronis Papaderos

Theme match 2/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

LogN–logS (or number counts) from the mock versus current X-ray constraints to visualize the reported 5× overabundance at the faint end and where discrepancies emerge.
Redshift–luminosity plane with NewAthena/WFI detection limits, highlighting the z>6 locus showing the log L_X ≳ 43.5 threshold and the predicted ~35 EoR detections.
Obscuration (N_H) distribution versus redshift from the catalogue, isolating the CTK fraction evolution and the subset remaining detectable beyond z>4.
Survey design and yield figure from the SIXTE runs (area–depth tiling), showing how total detections (~2.5×10^5) and z>3 counts (~2×10^4) change with exposure strategy.
Sky-coverage/sensitivity curve for the WFI setup used, clarifying the impact of the broader PSF and effective area changes in NewAthena on completeness at the faint end.

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2504.10581v1

Massive Black Hole Seed Formation in Strong X-ray Environments at High Redshift

Kazutaka Kimura, Kohei Inayoshi, Kazuyuki Omukai

Theme match 2/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Follow the temperature–density tracks across J_X and v_bc to see when gas flips from atomic to H2-cooling; compare the annotated seed masses to quantify how strong X-rays trigger early H2 formation while streaming delays collapse and preserves the atomic track.
Figure 2: Read the halo counts in the H2, H–H2, and H–H channels versus J_X and v_bc to measure how X-rays shift systems away from direct collapse, and how streaming partially restores the atomic-cooling pathways.
Figure 3: Inspect the stacked seed-mass distributions by track for each J_X and v_bc; identify where M_BH ≳ 10^4 Msun seeds arise and how their incidence declines as J_X increases, with streaming pushing the distribution to higher masses.
Figure 4: Compare seed BH mass functions at the seeding epoch across the J_X–v_bc grid; check whether the amplitude approaches ≈10^-4 Mpc^-3 and how suppressing atomic-cooling tracks reshapes the BHMF.

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2504.10573v1

High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties

L. Ighina, A. Caccianiga, A. Moretti, J. W. Broderick, J. K. Leung, F. Rigamonti, N. Seymour, J. Afonso, T. Connor, C. Vignali, Z. Wang, T. An, B. Arsioli, S. Bisogni, D. Dallacasa, R. Della Ceca, Y. Liu, A. López-Sánchez, I. Matute, C. Reynolds, A. Rossi, C. Spingola, P. Severgnini, F. Tavecchio

Theme match 2/5

Digest

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.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Fig. 1 — Map the 16,000 deg^2 footprint and locate which new sources lie at z>5 (squares) versus previously known objects (darker stars) to gauge sky coverage and selection uniformity.
Fig. 2 — Inspect the DES color/magnitude cuts, especially how the tiered criteria isolate specific redshift windows; note where dropout thresholds sit relative to the radio-prior from RACS.
Fig. 3 — Use the color–color panels to see contamination control: region (2) shows many interlopers (likely stars with spurious radio matches), and the role of Y-band visual checks in pruning candidates.
Fig. 4 — Compare the Pan-STARRS selection branches for different redshift bins and how ‘mean’ magnitudes are applied; this sets expectations for completeness versus contamination outside DES coverage.
Radio/X-ray SED panels (if included in the full text) — Look for single vs. broken power-law radio fits and instances of X-ray excess over coronal predictions that flag likely blazars.