Weekly issue

Week 27, 2025

Jun 30 – Jul 6, 2025

Week 27, 2025 includes 7 curated papers, centered on high-z, QSO, spectroscopy.

2507.04011v1

Investigating the Growth of Little Red Dot Descendants at z<4 with the JWST

Jean-Baptiste Billand, David Elbaz, Fabrizio Gentile, Maxime Tarrasse, Maximilien Franco, Benjamin Magnelli, Emanuele Daddi, Yipeng Lyu, Avishai Dekel, Fabio Pacucci, Valentina Sangalli, Mark Dickinson, Mauro Giavalisco, Benne W. Holwerda, Dale D. Kocevski, Anton M. Koekemoer, Vasily Kokorev, Ray A. Lucas, Pablo G. Pérez-González

Theme match 5/5

Digest

Using CEERS imaging, the authors select z<4 “post-LRD” candidates by requiring a compact, very red core plus a blue star-forming envelope, then model inner/outskirts with stellar-only SED fits and single-Sérsic morphologies. The sample shows LRD-like cores with M* ~1e10 Msun, Σ* ~1e11 Msun kpc^-2, and compact sizes about 1 kpc below the size–mass relation, while adding an extended young component; their number density at z=3±0.5 (~10^-4.15 Mpc^-3) matches that of LRDs at 5<z<7, indicating an evolutionary link. Outskirts mass fraction and size increase toward lower redshift (≈250 pc at z=5 to ≈600 pc at z=3), as the core stays red/compact and the hallmark V-shaped SED fades, consistent with growth by cold accretion. This offers an explanation for the apparent decline of LRD counts at lower z, with the caveat that it assumes a single evolutionary path and stellar-only modeling.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect where the color–magnitude–selected post-LRDs fall relative to the CEERS locus and the F277W–F444W > 1.5 LRD red-core cut; verify that selected sources are LRD-red in the core while permitting blue outskirts.
Figure 2: Check the segmentation/ellipse defining inner vs outskirts and compare to the F444W PSF circle to confirm the red core is resolved and the blue envelope extends beyond the beam.
Figure 3: Examine the redshift distribution and the six objects overlapping the Kocevski et al. (2025) LRD sample; use this to contextualize the z=3±0.5 bin used for the number-density comparison.
Figure 4: Use the mock-injection errors vs half-light radius and Sérsic n, along with the F444W HWHM and adopted resolution limit, to gauge the robustness of compactness claims and any size floor biases.

Tags

2507.03230v1

Little Red Dots from Ultra-Strongly Self-Interacting Dark Matter

M. Grant Roberts, Lila Braff, Aarna Garg, Stefano Profumo, Tesla Jeltema

Theme match 4/5

Digest

Proposes ultra-strongly self-interacting dark matter (uSIDM) as a route to rapid gravothermal core collapse in early halos, yielding massive black hole seeds (≳10^5 Msun) by z≳5 that can power Little Red Dots. Builds a semi-analytic framework tracking halo evolution, collapse redshifts z_coll, and the SMBH mass function with stochastic growth via a log-normal Eddington ratio and finite duty cycle. Finds that uSIDM reproduces LRD abundance, compactness, and characteristic BH masses, with a z≈5 SMBH mass function matching LRD data and SIDM merger-tree results, especially at m_BH≳10^7 Msun. Implies LRDs could be incisive tracers of non-gravitational dark sector physics and that early SMBH assembly may depart from CDM expectations.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

SMBH mass function at z≈5 overlaid with LRD-inferred number densities and a SIDM merger-tree comparison—inspect agreement at the high-mass end (m_BH≳10^7 Msun) and any residuals at lower masses.
Redshift of gravothermal collapse (z_coll) versus halo mass and uSIDM cross-section—use this to see what parameter space yields seeds ≳10^5 Msun by z≳5 and the sensitivity to cross-section strength.
LRD abundance/compactness predictions versus redshift—compare model number densities and effective sizes to JWST LRD counts to verify the claimed match in prevalence and compactness.
Growth prescription diagnostics: distribution of Eddington ratios and duty cycle and their impact on luminosity functions—check how sub-Eddington, intermittent growth reproduces LRD luminosities while remaining X-ray faint.
Parameter variation panel: how changing the uSIDM cross-section or duty cycle shifts the predicted BH mass function—identify degeneracies and ranges still consistent with LRD observables.

Tags

2507.02058v1

On the rapid growth of SMBHs in high-z galaxies: the aftermath of Population III.1 stars

Mahsa Sanati, Julien Devriendt, SergioMartin-Alvarez, Adrianne Slyz, Jonathan C. Tan

Theme match 4/5

Digest

High-resolution zoom-in simulations with Pop III.1 progenitor preheating follow 10^5 Msun seeds through a suite of AGN feedback modes (Eddington-limited thermal; non-Eddington thermal, kinetic, and radiative). Across all models the seeds grow efficiently to ~10^7 Msun by z≈8, with growth largely unimpeded by feedback; the radiative case shows brief super-Eddington bursts that launch fast, mass-loaded outflows (>2500 km s^-1) to ~50 kpc and slightly suppress stellar mass. The simulated systems resemble JWST moderate-luminosity quasars, yielding overmassive BHs, dynamical masses ~10^9.5 Msun, and short-lived high Eddington fractions. This argues that early AGN feedback coexists with rapid SMBH build-up while exporting energy and metals deep into the CGM/IGM.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Follow the multi-panel timelines to see how each feedback prescription changes BH mass growth, f_Edd spikes, gas inflow→outflow transitions, and the modest reduction in stellar mass; note the strong outflow signature in the ThermKinRad run coincident with super-Eddington peaks.
Figure 2: Compare the PDFs of f_Edd across models to verify that most growth is near/below Eddington with only a small super-Edd tail, and assess how adding radiation shifts the high-f_Edd incidence.
Figure 3: Examine the tracks in f_Edd–MBH space against the JDEEP points and the Eddington-limited reference to distinguish early burst-dominated growth (weak thermal-only) from self-regulated, gradual buildup (kinetic/radiative).
Figure 4: Inspect the BH’s displacement from the galaxy center to gauge how orbital wandering modulates encounters with dense central gas and correlates with the most efficient accretion phases in each model.

Tags

2507.01952v1

The Lockman-SpReSO project. Spectroscopic analysis of Type 1 AGN

Castalia Alenka Negrete, Hector J. Ibarra-Medel, Erika Benitez, Irene Cruz-Gonzalez, Yair Krongold, J. Jesus Gonzalez, Jordi Cepa, Carmen Padilla-Torres, Miguel Cervino, Mirjana Povic, Martin Herrera-Endoqui, Nancy Jenaro-Ballesteros, Takamitsu Miyaji, Mauricio Elias-Chavez, Miguel Sanchez-Portal, Bernabe Cedres, Jacub Nadolny, Mauro Gonzalez-Otero, Bereket Assefa, Hector Hernandez-Toledo, J. Antonio de Diego, J. Ignacio Gonzalez-Serrano, A. M. Perez Garcia

Theme match 2/5

Digest

First optical–UV spectral analysis of 30 faint (mB=19.6–21.8) Type 1 AGN from the Lockman‑SpReSO survey spanning 0.33<z<4.97, using Quasar Main Sequence–based deblending of the principal UV/optical broad‑line regions. Derived ranges are 44.85<log Lbol<47.87, 7.59<log MBH<9.80, and −1.70<log REdd<0.56; 18 high‑z sources fall in Population B, with a few A/B1/B1+ at low z, and none are extreme accretors. CIV c(1/2) indicates modest winds (941 to −1587 km s−1) and the Baldwin effect shows a slope of −0.23±0.03, consistent with comparable samples. Twelve spectra overlap with SDSS DR17 and show no variability, providing a stable benchmark for FIR/X‑ray–selected quasar demographics.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Inspect the redshift–magnitude plane by selection class (FIR, FIR+X‑ray, X‑ray) to see where the z≈5 sources sit relative to the survey faint limit and how the selection mix populates high‑z.
Figure 2: Study the multi‑component fits (Lorentzian vs Gaussian) across Lyα, CIV, the 1900 Å blend, Mg II, and Hβ to see how Pop A vs B profiles are separated, how Fe II/Fe III templates are applied, and where CIV blueshifted and VBC components drive the c(1/2) wind metric.
Figure 3: Use the log MBH–log Lbol and REdd–FWHM(BC) distributions to verify the lack of extreme accretors, identify the REdd spread versus line width, and gauge where the sample sits relative to REdd=1 and the expected trends.
Figure 4: Read the optical/UV QMS planes and the RMgII–REdd relation against SDSS DR17 background to confirm that most high‑z objects land in Pop B and to assess whether RMgII tracks the inferred accretion state in this faint FIR/X‑ray–selected set.

Tags

2507.01355v1

The birth of young radio jets in changing-look AGN: a population study

Sufia Birmingham, Charlotte Ward, Kristina Nyland, Dougal Dobie, Matthew J. Graham, David L. Kaplan, Tara Murphy

Theme match 2/5

Digest

A population study of 474 spectroscopically confirmed changing-look AGN tracks their radio behavior with ASKAP VAST and VLASS to test whether optical state changes spawn newborn radio jets. Across 20 VAST-detected CLAGN, the authors see no Mrk 590– or 1ES 1927+654–like radio fading within ~10 years of the changing-look epoch, and for six low‑z, high‑mass objects they rule out a Mrk 590–like flare. Population-wide, CLAGN show higher VAST/VLASS detection and 1 GHz variability rates but lower radio‑loud fractions than a control AGN sample, and VLA SEDs plus Magellan spectra do not support a link to VLASS sources that transitioned from radio‑quiet to radio‑loud. The results imply enhanced accretion episodes often stir compact radio activity but rarely mirror the decadal jet turn‑on channel seen in RL-transition systems, constraining when and how young radio jets are born.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Compare CLAGN and control redshift and black-hole mass distributions to assess matching; this frames whether radio detection/variability differences are intrinsic rather than selection-driven.
Figure 2: Inspect Mrk 590 and NGC 1566 radio light curves relative to the gray changing-look windows to gauge post‑event trends and the paper’s constraints on Mrk 590–like fading timescales.
Figure 3: Examine VLASS radio contours over optical images for the nine CLAGN with extended structure to distinguish jet morphologies from circumnuclear stellar emission and read off physical scales.
Figure 4: Read the distribution of radio luminosities for VLASS- vs VAST-detected CLAGN to see where the sample sits relative to common radio‑loudness cuts and how frequency/epoch selection impacts detections.

Tags

2507.00129v1

Lya2pcf: an efficient pipeline to estimate two- and three-point correlation functions of the Lyman-$α$ forest

Josue De-Santiago, Rafael Gutiérrez-Balboa, Gustavo Niz, Alma X. González-Morales

Theme match 2/5

Digest

Lya2pcf introduces a GPU-optimized pipeline for three-dimensional two- and three-point correlation measurements of the Lyman-α forest, including the standard distortion matrix and covariance estimation. Applied to SDSS DR16 and a DESI Year-5 mock, it achieves substantial computational speedups over PICCA, most notably for the 2PCF and its distortion matrix. The code delivers the first large-sample anisotropic 3PCF measurement for all triangle configurations out to 80 Mpc/h, with signal-to-noise above one for many bins. This demonstrates that higher-order Lyα statistics are ready for inclusion in Stage IV cosmological inference.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Geometry and binning of the 2PCF estimator: inspect the sky-patch visualization and the (r⊥, r∥) histogram grid (50×50 up to 80 Mpc/h) to see how inter-forest pairs are accumulated and why same-forest pairs are omitted.
Timing benchmarks versus PICCA: look for CPU/GPU wall-clock comparisons for the 2PCF and the distortion matrix, and scaling trends with number of quasars and deltas per skewer, to quantify the reported speedups.
Distortion matrix M_ij: examine its structure and comparison to the PICCA-based model to understand continuum-fitting–induced mixing and its impact on the recovered 2PCF.
Anisotropic 3PCF maps: check triangle-bin or wedge plots up to 80 Mpc/h and the corresponding S/N heatmaps to identify which triangle shapes drive S/N > 1.
Validation on SDSS DR16 and DESI Y5 mock: compare measured 2PCF/3PCF and covariances against expectations to assess robustness before applying to Stage IV data.

Tags

2506.24128v1

Beneath the Surface: >85% of z>5.9 QSOs in Massive Host Galaxies are UV-Faint

R. J. Bouwens, E. Banados, R. Decarli, J. Hennawi, D. Yang, H. Algera, M. Aravena, E. Farina, A. Gloudemans, J. Hodge, H. Inami, J. Matthee, R. Meyer, R. P. Naidu, P. Oesch, H. J. A. Rottgering, S. Schouws, R. Smit, M. Stefanon, P. van der Werf, B. Venemans, F. Walter, Y. Fudamoto

Theme match 2/5

Digest

Ranks 190 z>5.9 QSOs by host mass using ALMA [CII] luminosity as a gas/host-mass proxy, boosted by CISTERN cycle-10 coverage of UV-faint sources, and defines “massive hosts” at L[CII]>1.8x10^9 Lsun. From the resulting UV-luminosity distribution and [CII] luminosity functions, only ~3% of massive-host QSOs are UV-bright (Muv<-26) while >85% are UV-faint (Muv>-24.5). At Muv≈-23 the median extrapolated log10(MBH/Msun)=8.1±0.4, implying UV-bright QSOs host SMBHs ~15x more massive than typical massive-host systems at z~6. This points to most SMBH growth in massive galaxies being missed by UV-bright QSO selections; spectroscopy is still needed to confirm the MBH interpretation.

Open paper page arXiv abstract arXiv PDF

Key figures to inspect

Figure 1: Inspect the [CII]–UV plane to see which faint QSOs are [CII]-luminous and thus in massive hosts; note the stated 21% fraction among UV-faint and how CISTERN dramatically improves coverage in the faint regime.
Figure 2: Compare median L[CII], L_IR, and [CII] FWHM versus Muv for [CII]-bright QSOs; look for the similarity of far-IR and kinematic properties between UV-faint and UV-bright systems that supports comparable host masses.
Figure 3: Read the cumulative fraction of massive-host QSOs versus UV magnitude to verify that only ~15% are brighter than Muv=-24.5 and ~3% brighter than Muv=-26; use the lower panel to contrast the derived number densities with the Schindler et al. (2023) UV LF.
Figure 4: Examine the [CII] luminosity functions split by UV class; confirm that [CII]-luminous UV-faint QSOs dominate the volume density by ~29x and use the top-axis gas-mass scale to interpret what L[CII] implies for host reservoirs.