@article{20974,
  abstract     = {Thus far, Lyman-α damping wings towards quasars have been used to probe the global ionization state of the foreground intergalactic medium (IGM). A new parametrization has demonstrated that the damping wing signature also carries local information about the distribution of neutral hydrogen (H I) in front of the quasar before it started shining. Leveraging a recently introduced Bayesian JAX-based Hamiltonian Monte Carlo inference framework, we derive constraints on the Lorentzian-weighted H I column density NDW H I , the quasar’s distance rpatch to the first neutral patch, and its lifetime tQ based on James Webb Space
Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra of the two z ∼ 7.5 quasars J1007+2115 and J1342+0928. After folding in model-dependent topology information, we find that J1007+2115 (and J1342+0928) is most likely to reside in a (xH1)= 0.32+0.22 −0.20 (0.58+0.23 −0.23) neutral IGM while shining for a remarkably short lifetime of log10 tQ/yr = 4.14+0.74 −0.18 (an intermediate lifetime of 5.64+0.25 −0.43) along a sightline with log10 NDW
H I /cm−2 = 19.70+0.35 −0.86 (20.24+0.25 −0.22) and rpatch = 28.9+54.0 −14.4 cMpc
(10.9+5.6−5.9 cMpc). In light of the potential presence of local absorbers in the foreground of J1342+0928 as has been recently suggested, we also demonstrate how the Lorentzian-weighted column density NDW H I provides a natural means for quantifying their contribution to the observed damping wing signal.},
  author       = {Kist, Timo and Hennawi, Joseph F. and Davies, Frederick B. and Bañados, Eduardo and Bosman, Sarah E.I. and Cai, Zheng and Eilers, Anna Christina and Fan, Xiaohui and Haiman, Zoltán and Jun, Hyunsung D. and Liu, Yichen and Yang, Jinyi and Wang, Feige},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {3},
  publisher    = {Oxford University Press},
  title        = {{First constraints on the local ionization topology in front of two quasars at z ∼ 7.5}},
  doi          = {10.1093/mnras/staf2219},
  volume       = {545},
  year         = {2026},
}

@article{21712,
  abstract     = {Supermassive black hole binary (SMBHB) systems are expected to form as a consequence of galaxy mergers. At subparsec separations, SMBHBs can be identified as quasars with periodic variability, with previous periodicity searches uncovering significant candidates. However, these searches focused primarily on sinusoidal signals, while theoretical models and hydrodynamical simulations predict that binaries produce more complex non-sinusoidal pulse shapes. Here we examine the efficacy of the Lomb–Scargle periodogram (LSP; one of the most popular tools for periodicity searches in unevenly sampled lightcurves) to detect periodicities with a sawtooth shape mimicking results of hydrodynamical simulations. We simulate idealized well-sampled lightcurves, lightcurves that mimic the data in the Palomar Transient Factory (PTF) analyzed in M. Charisi et al. (2016), and lightcurves that resemble our expectations for single-band data in the upcoming Legacy Survey of Space and Time (LSST) of the Rubin Observatory. We approximate quasar variability with a damped random walk (DRW) model, inject sinusoidal and sawtooth pulse shapes, and assess their statistical significance. We find that in the presence of red noise, the LSP detects a relatively low fraction of the sinusoidal signals (∼45%, ∼24%, and ∼23%, in the PTF-like, idealized, and LSST-like lightcurves, respectively). The fraction is significantly reduced for sawtooth periodicity (with only ∼9% in PTF-like and ∼1% in idealized and LSST-like lightcurves). These low recovery rates imply that previous searches have missed the large majority of binaries. They also have significant implications for the detection of SMBHBs in upcoming LSST necessitating the development of advanced tools that go beyond the simple LSP.},
  author       = {Lin, Allison and Charisi, Maria and Haiman, Zoltán},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Lomb-scargle periodogram struggles with non-sinusoidal supermassive Black Hole binary signatures in quasar lightcurves}},
  doi          = {10.3847/1538-4357/ae29a7},
  volume       = {997},
  year         = {2026},
}

@article{21713,
  abstract     = {GW231123 represents the most massive binary–black hole merger detected to date, lying firmly within, or even above, the pair-instability mass gap. The component spins are both exceptionally high (a1 = 0.90 +0.10/-0.19, a2 = 0.80 +0.20/-0.51), which is difficult to explain with repeated mergers. Here we show that the black hole spin vectors are closely aligned with each other while significantly tilted relative to the binary’s orbital angular momentum, pointing to a common accretion-driven origin. We examine astrophysical formation channels capable of producing near-equal, high-mass, and mutually aligned spins consistent with GW231123—particularly binaries embedded in AGN disks and Population III remnants, which grew via coherent misaligned gas accretion. We further argue that other high-mass, high-spin events, e.g., GW190521, may share a similar evolutionary pathway. These findings underscore the critical role of sustained, coherent accretion in shaping the most extreme black hole binaries.},
  author       = {Bartos, Imre and Haiman, Zoltán},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Accretion is all you need: Black Hole spin alignment in merger GW231123 indicates accretion pathway}},
  doi          = {10.3847/2041-8213/ae2bff},
  volume       = {996},
  year         = {2026},
}

@article{21844,
  abstract     = {Little red dots (LRDs) are a newly identified class of broad-line active galactic nuclei (AGNs) with a distinctive V-shaped spectrum characterized by red optical and blue UV continuum emission. Their high abundance at redshifts of z ∼ 6–8 and decline at lower redshifts suggest a transient origin. We propose that the spectral shape of LRDs originates from compact binary black hole systems, in which each black hole is surrounded by a mini-disk and embedded within a larger circumbinary disk. With a binary separation of ≲103 Schwarzschild radii, the Wien tail of a T ≃ 5000 K blackbody spectrum at the inner edge of the circumbinary disk produces the red optical emission, while the mini-disks power the UV continuum. Binary torques carve out a gap between the circumbinary disk and the mini-disks, setting the turnover wavelength of the V-shaped spectrum around the Balmer limit. This scenario naturally reproduces LRD spectra requiring only modest dust attenuation (AV ≲ 1 mag), resolving overestimated luminosities for LRDs in previous studies and alleviating a tension with the so-called Sołtan argument. This model predicts distinct spectral evolution as the binary orbit decays through binary disk interactions and gravitational-wave (GW) emission, linking early-stage “proto-LRD” binaries to the broader AGN population and late-stage “LRD descendants” to coalescing binaries detectable in GW experiments.},
  author       = {Inayoshi, Kohei and Shangguan, Jinyi and Chen, Xian and Ho, Luis C. and Haiman, Zoltán},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{The emergence of Little Red Dots from binary massive black holes}},
  doi          = {10.3847/1538-4357/ae548d},
  volume       = {1002},
  year         = {2026},
}

@article{21846,
  abstract     = {We compile a sample of 83 little red dots (LRDs) with JWST imaging and find that a substantial fraction (∼43%, rising to ≳80% for the most luminous LRDs) host one or more spatially offset, UV-bright companions at projected separations of 0.5 kpc ≲ d ≲ 5 kpc, with median 〈d〉 = 1.0 kpc. This fraction is even higher when smaller spatial scales are probed at high signal-to-noise ratio: the two most strongly lensed LRDs, A383-LRD1 and the newly discovered A68-LRD1, both have UV-bright companions at separations of only d ∼ 0.3 kpc, below the resolution limit of most unlensed JWST samples. We explore whether these ubiquitous red/blue configurations may be physically linked to the formation of LRDs, in analogy with the “synchronized pair” scenario originally proposed for direct-collapse black hole formation. In this picture, UV radiation from the companions, with typically modest stellar masses (M∗ ∼ 108−109 M⊙), suppresses molecular hydrogen cooling in nearby gas, allowing nearly isothermal collapse and the formation of extremely compact objects, such as massive black holes, supermassive stars, or quasi-stars. Using component-resolved photometry and spectral energy distribution modeling, we infer Lyman–Werner radiation fields of J21,LW ∼ 102.5–105 at the locations of the red components, comparable to those required in direct-collapse models, suggesting that the necessary photodissociation conditions are realized in many LRD systems. This framework provides a simple and self-consistent explanation for the extreme compactness and distinctive spectral properties of LRDs and links long-standing theoretical models for early compact object formation directly to a population now observed with JWST in the early Universe.},
  author       = {Baggen, Josephine F.W. and Scoggins, Matthew T. and Van Dokkum, Pieter and Haiman, Zoltán and Torralba Torregrosa, Alberto and Matthee, Jorryt J},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation}},
  doi          = {10.3847/2041-8213/ae58a5},
  volume       = {1002},
  year         = {2026},
}

@article{22362,
  abstract     = {We present a systematic study of the environments of 25 luminous quasars at z > 6.5 from the ASPIRE program.
Using JWST/NIRCam wide-field slitless spectroscopy data, we identified 487 galaxies at 5.3 ≲ z ≲ 7.0 exhibiting
[O III] emission. Among these, 122 [O III] emitters lie within |Δvlos| < 1000 km s
−1 of the quasars, corresponding
to a ∼9.4-fold enhancement relative to the average galaxy density at other redshifts. Furthermore, we identified 16
[C II]-emitting galaxies at the quasar redshifts from Atacama Large Millimeter/submillimeter Array (ALMA) mosaic observations. A cross-correlation function analysis between quasars and [O III]+[C II] emitters yields a
cross-correlation length of r 8.68 h cMpc 0
QG
0.55 = +0.51 1
and an autocorrelation of r 15.76 h cMpc 0
QQ
2.70 = +2.48 1 ,
indicating that z ∼ 7 quasars reside in dark matter halos with
Mhalo 1012.27 0.26 M 0.21
= +
and have a quasar lifetime of
tQ 10 yr 7.05 1.01
0.95
= +
. Notably, the number of [O III]-emitting galaxies at quasar redshifts varies significantly from
field to field, ranging from 0 to 20, highlighting a diverse quasar environment. Remarkably, seven quasars trace
significant galaxy overdensities (i.e., protoclusters), with δgal > 5 within a volume of V ∼ 500 cMpc3
. We also
find that |Δvlos| increases rapidly toward smaller galaxy–quasar separations in protocluster fields, consistent with
galaxy kinematics around extremely massive halos in cosmological simulations. By combining JWST and ALMA
data, we reveal the complex and diverse environments of these early quasars, providing robust evidence that the
earliest luminous quasars are effective tracers of galaxy overdensities, albeit with substantial field-to-field
variation.},
  author       = {Wang, Feige and Champagne, Jaclyn B. and Huang, Jiamu and Yang, Jinyi and Hennawi, Joseph F. and Fan, Xiaohui and Zhang, Haowen and Costa, Tiago and Decarli, Roberto and Habouzit, Melanie and Sun, Fengwu and Bañados, Eduardo and Jin, Xiangyu and Kakiichi, Koki and Meyer, Romain A. and Wu, Yunjing and Belladitta, Silvia and Blecha, Laura and Bosman, Sarah E.I. and Cai, Zheng and Connor, Thomas and Davies, Frederick B. and Eilers, Anna Christina and Haiman, Zoltán and Jun, Hyunsung D. and Li, Mingyu and Li, Zihao and Liu, Weizhe and Lupi, Alessandro and Lyu, Jianwei and Mazzucchelli, Chiara and Onoue, Masafusa and Pizzati, Elia and Pudoka, Maria and Rojas-Ruiz, Sofía and Schindler, Jan Torge and Shen, Yue and Tee, Wei Leong and Trakhtenbrot, Benny and Trebitsch, Maxime and Vestergaard, Marianne and Volonteri, Marta and Walter, Fabian and Zhang, Huanian and Zou, Siwei},
  issn         = {15384357},
  journal      = {Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{ASPIRE: The environments and dark matter halos of luminous quasars in the epoch of reionization}},
  doi          = {10.3847/1538-4357/ae7bfa},
  volume       = {1006},
  year         = {2026},
}

@article{22616,
  abstract     = {Accretion disks in active galactic nuclei (AGN) are promising sites for mergers of stellar-mass black holes (BHs) detectable via gravitational waves (GWs). These environments facilitate both in situ formation and dynamical capture of compact objects and their subsequent mergers. The uncertain origin of GW events detected by LIGO, Virgo, and KAGRA motivates searching for accompanying electromagnetic (EM) signatures. Here, we investigate postmerger EM flares associated with jets launched from merger remnants, as well as from the shocked ambient gas as the jet breaks out of the disk. We find that jet breakout produces luminous gamma-ray emission, detectable with MeV-band telescopes. Cooling emission from a shocked circum-BH minidisk, winds, and background AGN disk peaks in the UV and optical, with durations ranging from about an hour to a month, and can be identified through year-long monitoring of ∼103 AGNs with luminosities ranging from ∼1044 to ∼1045 erg s−1. With a single set of parameters, this postmerger jet model produces gamma-ray, hard X-ray, and optical flares similar to those claimed to be associated with GW events. Furthermore, by incorporating a transition from a high- to low-angular-momentum accretion state after the merger, the model avoids excessive BH growth, alleviating tensions with hyper-Eddington accretion scenarios.},
  author       = {Tagawa, Hiromichi and Haiman, Zoltán and Kimura, Shigeo S. and Yesuf, Hassen M. and Guo, Hengxiao},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Electromagnetic flares from compact-object mergers in active galactic nucleus disks: Signatures and predictions}},
  doi          = {10.3847/1538-4357/ae7d29},
  volume       = {1006},
  year         = {2026},
}

@article{22676,
  abstract     = {We search for a population-level signature of gravitational-wave recoiling supermassive black holes: a positive correlation between dust obscuration and the magnitude of the line-of-sight velocity offset of broad emission lines relative to the host. Using the SDSS DR16 quasar catalogue, we estimate the velocity offset, $\Delta v$, as the difference between the broad H$\beta$ redshift and a noise-weighted redshift from narrow lines ([O iii] 5007, [O ii] 3728, and Ca ii 3934). We adopt the redshift-relative colour excess $\Delta (g-i)$ as a proxy for dust column density. Analysing $\sim 10^{5}$ quasars that meet basic spectral quality requirements, we find a modest but highly significant positive correlation between $|\Delta v|$ and $\Delta (g-i)$ (Spearman $r\simeq 0.12$ and Pearson $r\simeq 0.13$, with $p\ll 10^{-10}$ in both cases). The fraction of highly obscured quasars increases with $|\Delta v|$, indicating that the correlation is driven by a dust-reddened subpopulation. The result is robust to the choice of minimum $|\Delta v|$ threshold and to the line redshift estimator (peak vs. centroid). As expected, the correlation is largely absent when velocity offsets are computed between narrow emission lines. We find systematic differences between redshifted and blueshifted subsamples, which may point to residual velocity biases or additional physical effects (e.g. winds, inflows, orientation-dependent obscuration, or asymmetric broad-line regions). Recoiling massive black holes provide a natural explanation for the observed correlation, but alternative scenarios should be explored. If confirmed, this would enable population-level constraints on massive black hole merger rates, recoil dynamics, and active galactic nuclei disc properties.},
  author       = {Bécsy, Bence and Raffai, Peter and Haiman, Zoltán and Budai, Andor and Frei, Zsolt},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {4},
  publisher    = {Oxford University Press},
  title        = {{Statistical evidence for massive black hole recoils in active galactic nuclei}},
  doi          = {10.1093/mnras/stag1367},
  volume       = {550},
  year         = {2026},
}

@article{22713,
  abstract     = {Ground-based gravitational-wave (GW) observatories have detected approximately 200 binary black hole (BH) mergers. The astrophysical origin of these events is debated, with evidence suggesting that at least a subset originated from dynamic environments characterized by frequent close encounters. Accretion disks in active galactic nuclei (AGNs) are of particular interest, as certain observed features could be more readily produced within such environments. In this paper, we investigate the expected properties of mergers in these environments, and their dependence on various parameters, using 1D N-body simulations combined with a comprehensive semianalytical model. In our fiducial model, the distributions of masses (m1 and m2) and mass ratios (q ≡ m2/m1 ≤ 1) are similar to those observed. However, they depend strongly on the lifetime and density of the AGN disk and on the number and accretion efficiency of BHs, with higher masses predicted as these quantities increase. The most massive mergers, such as GW231123, can be produced either by efficient gas accretion or by hierarchical mergers among ≥3 generations of BHs. The observed negative correlation between q and the average effective spin (χeff), along with the positive correlation between χeff and the chirp mass (Mchirp), can be explained by a combination of efficient gas accretion, which promotes spin alignment, and hierarchical mergers, which produce high-∣χeff∣ and low-q binaries. Hierarchical mergers can also explain the negative correlation between q and the dispersion of χeff, as well as the positive correlation between ∣χeff∣and Mchirp. We present a comprehensive study on how the expected distribution of each of these quantities depends on model parameters and assumptions, which will aid the interpretation of observed GW population properties.},
  author       = {Tagawa, Hiromichi and Haiman, Zoltán and Kocsis, Bence},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Properties of black hole mergers in disks of active galactic nuclei}},
  doi          = {10.3847/1538-4357/ae8760},
  volume       = {1007},
  year         = {2026},
}

@article{22964,
  abstract     = {We investigate whether the nonaccreting phases found in thin, locally isothermal circumbinary disks survive when the disk thermodynamics are evolved self-consistently. We present grid-based hydrodynamics simulations of circumbinary accretion with an energy equation that includes viscous and hydrodynamic heating coupled to radiative blackbody cooling in the high-Mach number regime. We find that, although gas accumulates and heats at the far edge of the circumbinary cavity, the regions that launch accretion streams remain comparatively cold, leading to potentially long-lived suppression of the binary accretion rate as the large-scale feeding rate is reduced towards the Eddington limit. This runaway nonaccretion problem, however, is weakened relative to locally isothermal solutions. Despite their low accretion rates, binaries interacting with disks in a nonaccreting phase can remain sufficiently luminous and variable at optical and near-infrared frequencies to be detectable in upcoming wide-field surveys such as LSST and the Roman Space Telescope. Because of the effective truncation of the surrounding disk, though, such systems are comparatively faint in high energy, photoionizing emission, and may therefore appear as intrinsically X-ray–weak active galactic nuclei with weak or absent emission line features. We additionally suggest an update to grid-based sink prescriptions for approximating mass loss across an unresolved horizon when including an energy conservation equation.},
  author       = {Tiede, Christopher and O'Neill, David W and D’Orazio, Daniel J.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Dynamics and detectability of long-lived nonaccretion phases for massive Black Hole binaries in cold thermally regulating disks}},
  doi          = {10.3847/1538-4357/ae914e},
  volume       = {1008},
  year         = {2026},
}

@article{23054,
  abstract     = {We investigate the cosmological information in higher-order statistics of the cosmic microwave background (CMB) lensing convergence field for a near-term experiment with noise properties similar to the Simons Observatory (SO). Using a fully field-level forward-modeling pipeline based on ray-traced simulations from the massivenus suite and realistic SO-like CMB lensing reconstruction, we naturally include nonlinear structure formation, post-Born effects, and higher-order reconstruction noise. We measure several non-Gaussian statistics, including Minkowski functionals, peak and minima counts, moments, and wavelet-scattering coefficients. We train Gaussian-process emulators to model each statistic’s dependence on the matter density fraction Ω𝑚, the scalar power spectrum amplitude 𝐴𝑠, and the neutrino mass sum 𝑀𝜈. We quantify the relative information gain these statistics provide beyond the lensing power spectrum and identify which are most robust to reconstruction noise. We find that morphology-based statistics, particularly Minkowski functionals and peak/minima counts, offer significant complementary constraining power: combining all non-Gaussian statistics with the power spectrum yields reductions of 40% and 38% in the marginalized uncertainties on Ω𝑚 and 𝐴𝑠, respectively, and a 70% reduction in the one-sided uncertainty on 𝑀𝜈. These gains remain non-negligible even when the power spectrum is extended to larger scales and combined with primary CMB and BAO data, with Minkowski functionals providing an additional 11% improvement in 𝜎⁡(𝑀𝜈) and 35% in 𝜎⁡(Ω𝑚) beyond the extended power spectrum. By contrast, moments and wavelet-scattering coefficients provide more limited gains at SO noise levels. Our results highlight the potential of non-Gaussian statistics to enhance cosmological constraints from SO and future CMB surveys.},
  author       = {Chen, Shu Fan and Hill, J. Colin and Haiman, Zoltán},
  issn         = {2470-0029},
  journal      = {Physical Review D},
  number       = {2},
  publisher    = {American Physical Society},
  title        = {{Probing cosmology through higher-order CMB lensing statistics}},
  doi          = {10.1103/CLVJ-GL8P},
  volume       = {114},
  year         = {2026},
}

@article{23116,
  abstract     = {The Legacy Survey of Space and Time (LSST) is expected to observe up to ∼100 million quasars in the next decade. In this work, we show that it is possible to use such data to measure the characteristic frequency evolution of a “chirp” induced by gravitational waves, which can serve as robust evidence for the presence of a compact supermassive black hole binary. Following the LSST specifications, we generate mock lightcurves consisting of (i) a post-Newtonian chirp produced by orbital motion through, e.g., relativistic Doppler boosting, (ii) a damped random walk representing intrinsic quasar variability, and (iii) Gaussian photometric errors, while assuming nonuniform observations with extended gaps over a period of 10 yr. Through a fully Bayesian analysis, we show that we can simultaneously measure the chirp and noise parameters with little degeneracy between the two. For chirp signals with an amplitude of A = 0.5 mag and a range of times to merger (tm = 15–104 yr), we can typically measure a nonzero amplitude and positive frequency derivative with over 5σ credibility. For binaries with tm = 50 yr, we achieve 3σ (5σ) confidence that the signal is chirping for A ≳ 0.1 (A  >  0.2). The median runtime of our analysis is 5.6 minutes, with a minimum as low as 35 s, making it scalable to a large number of lightcurves. This implies that LSST could, on its own, establish the presence of a compact supermassive black hole binary, and thus discover gravitational wave sources detectable by LISA and by Pulsar Timing Arrays.},
  author       = {Xin, Chengcheng and Isi, Maximiliano and Farr, Will M. and Haiman, Zoltán},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Identifying compact chirping SMBHBs in LSST using Bayesian analysis}},
  doi          = {10.3847/1538-4357/ae40b3},
  volume       = {999},
  year         = {2026},
}

@article{23150,
  abstract     = {High-redshift supermassive black holes (SMBHs) have challenged our understanding of black hole formation and growth. The ‘heavy-seed’ pathway eases the problem with the progenitors of these SMBHs having birth masses up to∼105 M. Here, we investigate the possibility that a local dwarf galaxy, Leo I, harbours a heavy-seed descendant. Using Monte Carlo merger trees to generate the merger histories of 1000 dark matter haloes similar to the Milky Way (MW), we search for Leo- like satellite haloes and investigate the probability that the progenitors of these satellites formed a heavy seed. We derive the likelihood of such ‘heavy-seed survivors’ (HSSs) across various formation and survival criteria as well as Leo-similarity criteria. We find that the virial temperature for the onset of atomic cooling and rapid gas infall that yields heavy seeds, Tact , has the largest impact on HSS frequency. We find HSSs in a fraction 0.7 per cent, 18.1 per cent, and 96.5 per cent of MW-like haloes when Tact is set to 9000, 7000, and 5000 K, respectively. For the canonical atomic-cooling threshold ( Tact  8000 K), the HSS fraction is 1per cent , indicating that Leo I hosting a heavy-seed descendant is unlikely under well-motivated physical assumptions. Higher HSS fractions occur only under optimistic and currently unsubstantiated assumptions on Tact . Nevertheless, these results motivate future work that clarifies the possibility of heavy-seed BH formation in pristine haloes with nominal virial temperatures below 8000 K. This may motivate Leo I as a target for disentangling heavy seeds from other SMBH formation mechanisms.},
  author       = {Scoggins, Matthew T. and Haiman, Zoltán and Pacucci, Fabio},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {3},
  publisher    = {Oxford University Press},
  title        = {{Heavy black hole seed survivors in dwarf galaxies: A case study of Leo I}},
  doi          = {10.1093/mnras/stag1839},
  volume       = {552},
  year         = {2026},
}

@article{23159,
  abstract     = {The Vera C. Rubin Observatory has now seen first light, and over a 10 year duration, Legacy Survey of Space and Time (LSST) is projected to catalog tens of millions of quasars, many of which are expected to be associated with subparsec supermassive black hole binaries (SMBHBs). Out of these SMBHBs, up to thousands of relatively massive binary-quasars are expected to exhibit gravitational self-lensing flares (SLFs) that last for at least 20–30 days. We assess the effectiveness of the Lomb-Scargle (LS) periodogram and matched filters (MFs) as methods for systematic searches for these binaries, using toy-models of hydrodynamical, Doppler, and self-lensing variability from equal-mass, eccentric SMBHBs. We inject SLFs into random realizations of damped random walk (DRW) lightcurves, representing stochastic quasar variability, and compute the LS periodogram with and without the SLF. We find that periodograms of SLF+DRW light-curves do not have maximum peak heights that could not arise from DRW-only periodograms. On the other hand, the matched filter signal-to-noise ratio (SNR) can distinguish SLFs from noise even with LSST-like cadences and DRW noise. Furthermore, we develop a three-step procedure with matched filters, which can also recover injected binary parameters from these light-curves. We expect this method to be computationally efficient enough to be applicable to millions of quasar light-curves in LSST.},
  author       = {Park, Kevin S and Haiman, Zoltán and Xin, Chengcheng and Shen, Tzuken and Villar, Ashley and Davelaar, Jordy},
  issn         = {2470-0029},
  journal      = {Physical Review D},
  number       = {4},
  publisher    = {American Physical Society},
  title        = {{Self-lensing flares from black hole binaries. V. Systematic searches in LSST}},
  doi          = {10.1103/p328-62sl},
  volume       = {113},
  year         = {2026},
}

@article{22381,
  abstract     = {Context. X-ray binaries exhibit complex variability patterns studied in the power spectrum. These include the broadband noise (BBN)
components and various types of narrow components called quasi-periodic oscillations (QPOs). There is currently no consensus about
what determines the presence or absence of the BBN or what generates the QPOs. Many believe that QPO generation is due to framedragging effects caused by Lense–Thirring torques.
Aims. We investigated the potential impact of frame-dragging effects on the accretion disk itself. In particular, we focused on its
impact on the observed variability and on the presence (and types) of associated QPOs.
Methods. We made analytical estimates to assess the potential presence of a geometric warp in the inner accretion disk during state
transitions.
Results. We show that the presence of a warp can modify the spectral-timing properties in a way that matches the observed transition
between QPO types during outbursts. We also discuss the peculiar case of Cyg X-1, as well as how the hard-to-soft transition could
be driven by the warp itself.
Conclusions. The (expected) emergence of a warp provides a consistent explanation for the evolution of both the BBN and the QPO
properties during state transitions. This offers a first path toward unifying the variability of black hole X-ray binaries.},
  author       = {Marcel, G. and Turner, S. G. D. and Ricketts, B. J. and López-Barquero, V. and Buisson, D. J. K. and Vincentelli, F. and Middleton, M. and Reynolds, C.S. and Avara, Mark},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{Disk warping and black hole X-ray binaries: I. Tentative unification of low-frequency quasi-periodic oscillations}},
  doi          = {10.1051/0004-6361/202558103},
  volume       = {710},
  year         = {2026},
}

@article{23199,
  abstract     = {The physics governing the morphology of radio-loud active galactic nucleus (AGN) jets is not fully understood. We investigate how magnetization, flickering jet power and the interplay between them affects the morphology of radio galaxies. We present a grid of relativistic magnetohydrodynamic simulations using the pluto code covering constant and variable jets with two levels of magnetization. We find that the constant high-magnetization jets can lead to highly asymmetrical cocoon morphologies, while the variable high-magnetization jet can exhibit a broken morphology, caused by a discontinuous jet beam. Our work highlights the importance of magnetization and variability on the stability and resulting morphology of radio-loud AGN jets, suggesting both are significant factors in addition to jet power or environment. Furthermore, we show that the interaction between magnetization and variability can lead to the development of localized kink instabilities along the jet beam. Finally, we discuss the effects of hydrodynamic mixing in low-magnetization jets and the role of viewing-angle dependence in comparisons between our simulations and observed sources. To facilitate this comparison we present a library of simulated radio images at different times in the simulations and from various viewing angles, which highlight a diverse set of complex morphologies.},
  author       = {Elley, Emma L and Matthews, James H and Whitehead, Henry William and Cooper, Alex J},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {4},
  publisher    = {Oxford University Press},
  title        = {{The impact of flickering variability and magnetization on the dynamics, stability, and morphology of radio-loud AGN jets}},
  doi          = {10.1093/mnras/stag1798},
  volume       = {552},
  year         = {2026},
}

@article{21121,
  abstract     = {The relation between the masses of supermassive black holes (SMBHs) and their host galaxies encodes information on their mode of growth, especially at the earliest epochs. The James Webb Space Telescope (JWST) has opened such investigations by detecting the host galaxies of active galactic nuclei (AGN) and more luminous quasars within the first billion years of the Universe (z ≳ 6). Here, we evaluate the relation between the mass of SMBHs and the total stellar mass of their host galaxies using a sample of nine quasars at 6.18 ≤ z ≤ 6.4 from the Subaru High-z Exploration of Low-luminosity Quasars survey with NIRCam and NIRSpec observations. We find that the observed location of these quasars in the SMBH–galaxy mass plane (logMBH/M 8–9; logM*/M 9.5–11) is consistent with a nonevolving intrinsic mass relation with dispersion (0.80 +0.23 -0.28 dex) higher than the local value (∼0.3–0.4 dex) of their more massive descendants. Our analysis is based on a forward model of systematics and includes a consideration of the impact of selection effects and measurement uncertainties with an assumption on the slope of the mass relation. While degeneracies between parameters persist, the best-fit solution has a reasonable AGN fraction (2.3%) of galaxies at z ∼ 6 with an actively growing UV-unobscured black hole. In particular, models with a substantially higher normalisation in MBH would require an unrealistically low intrinsic dispersion (∼0.22 dex). Consequently, our results predict a large population of AGN at lower black hole masses, as are now just starting to be discovered in focused efforts with JWST.},
  author       = {Silverman, John David and Li, Junyao and Ding, Xuheng and Onoue, Masafusa and Strauss, Michael A. and Matsuoka, Yoshiki and Izumi, Takuma and Jahnke, Knud and Treu, Tommaso and Volonteri, Marta and Phillips, Camryn L. and Andika, Irham T. and Aoki, Kentaro and Arita, Junya and Baba, Shunsuke and Bosman, Sarah E. I. and Eilers, Anna-Christina and Fan, Xiaohui and Fujimoto, Seiji and Habouzit, Melanie and Haiman, Zoltán and Imanishi, Masatoshi and Inayoshi, Kohei and Iwasawa, Kazushi and Kashikawa, Nobunari and Kawaguchi, Toshihiro and Lee, Chien-Hsiu and Lupi, Alessandro and Nagao, Tohru and Schindler, Jan-Torge and Schramm, Malte and Shimasaku, Kazuhiro and Toba, Yoshiki and Trakhtenbrot, Benny and Umehata, Hideki and Vestergaard, Marianne and Walter, Fabian and Wang, Feige and Yang, Jinyi},
  issn         = {2041-8213},
  journal      = {The Astrophysical Journal Letters},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{SHELLQs–JWST perspective on the intrinsic mass relation between supermassive black holes and their host galaxies at z > 6}},
  doi          = {10.3847/2041-8213/ae279c},
  volume       = {995},
  year         = {2025},
}

@article{21122,
  abstract     = {The multimessenger combination of gravitational waves (GWs) from merging massive black hole binaries (MBHBs) and the electromagnetic (EM) counterpart from the surrounding circumbinary disc (CBD) will open avenues to new scientific pursuits. In order to realize this science, we need to correctly localize the host galaxy of the merging MBHB. Multiwavelength, time-dependent EM signatures can greatly facilitate the identification of the unique EM counterpart among many sources in LISA’s localization volume. To this end, we studied merging unequal-mass MBHBs embedded in a CBD using high-resolution 2D simulations, with a $\Gamma$-law equation of state, incorporating viscous heating, shock heating, and radiative cooling. We simulate each binary starting from before it decouples from the CBD until just after the merger. We compute EM signatures and identify distinct features before, during, and after the merger. We corroborate previous findings of a several orders of magnitude drop in the thermal X-ray luminosity near the time of merger, but with delayed timing compared to an equal-mass system. The source remains X-ray dark for hours post-merger. Our main results are a potential new signature of a sharp spike in the thermal X-ray emission just before the tell-tale steep drop occurs. This feature may further help to identify EM counterparts of LISA’s unequal MBHBs before merger without the need for extensive pre-merger monitoring. Additionally, we find a role-reversal in which the primary out-accretes the secondary during late inspiral, which may diminish signatures originating from Doppler modulation.},
  author       = {Krauth, Luke Major and Davelaar, Jordy and Haiman, Zoltán and Westernacher-Schneider, John Ryan and Zrake, Jonathan and MacFadyen, Andrew},
  issn         = {1365-2966},
  journal      = {Monthly Notices of the Royal Astronomical Society},
  number       = {3},
  pages        = {2670--2685},
  publisher    = {Oxford University Press},
  title        = {{Thermal X-ray signatures in late-stage unequal-mass massive black hole binary mergers}},
  doi          = {10.1093/mnras/staf1583},
  volume       = {543},
  year         = {2025},
}

@article{21123,
  abstract     = {We present a study of the late-time interaction between supermassive black hole binaries and retrograde circumbinary disks during the period of gravitational wave-driven inspiral. While mergers in prograde disks have received extensive study, retrograde disks offer distinct dynamics that could promote mergers and produce unique observational signatures. Through 2D numerical hydrodynamical simulations, we explore the process of binary-disk decoupling, where the binary’s orbital decay rate is faster than the disk’s viscous response rate. We find the point of decoupling to be comparable in prograde and retrograde disks, suggesting that any associated electromagnetic (EM) signatures will be produced at comparable times preceding the merger. However, we find smaller central cavities for retrograde disks, likely leading to higher-frequency EM emissions and shorter postmerger rebrightening timescales compared to their prograde counterparts. Retrograde disks form intrabinary bridges, which are prone to instabilities when the viscosity is low. These instabilities manifest as quasiperiodic flares in the accretion rate, which may produce distinctive EM signatures for retrograde disks.},
  author       = {O’Neill, David and Tiede, Christopher and D’Orazio, Daniel J. and Haiman, Zoltán and MacFadyen, Andrew},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{Gravitational wave decoupling in retrograde circumbinary disks}},
  doi          = {10.3847/1538-4357/ae0ca8},
  volume       = {993},
  year         = {2025},
}

@article{21124,
  abstract     = {The advent of the James Webb Space Telescope (JWST) has opened new horizons in the study of quasar host galaxies during the reionization epoch (z > 6). Building upon our previous initial measurements of stellar light from two quasar host galaxies at these redshifts, we now report the detection of the stellar light from the full Cycle 1 sample of 12 distant moderate-luminosity quasar (M1450 > −24 mag) host galaxies at z > 6 from the Hyper Suprime-Cam Subaru Strategic Program. Using JWST/NIRCam observations at 1.5 and 3.6 μm combined with 2D image decomposition analysis, we successfully detect the host galaxies in 11 of the 12 targets, underscoring the high detection rates achievable with moderate-luminosity quasars. Based on two-band photometry and spectral energy distribution fitting, we find that our host galaxies are massive, with log M*/M⊙ = 9.5–11.0. The effective radii range from 0.6 to 3.2 kpc, comparable to the sizes of inactive galaxies with similar masses at z ∼ 6 as measured with imaging from COSMOS-Web. Intriguingly, the two quasar hosts with post-starburst features, which reside at the high-mass end of our sample and exhibit relatively compact morphologies, have similar size and stellar mass surface densities to quiescent galaxies at z ∼ 4–5. These findings suggest that the so-called galaxy compaction scenario is already in place at the reionization epoch, in which gas inflows during starburst phases drive centrally concentrated star formation followed by rapid quenching, bridging the structural transition of massive galaxies from relatively extended star-forming disks to compact quiescent systems.},
  author       = {Ding, Xuheng and Onoue, Masafusa and Silverman, John D. and Matsuoka, Yoshiki and Izumi, Takuma and Strauss, Michael A. and Yang, Lilan and Jahnke, Knud and Phillips, Camryn L. and Treu, Tommaso and Andika, Irham T. and Aoki, Kentaro and Arita, Junya and Baba, Shunsuke and Bosman, Sarah E. I. and Eilers, Anna-Christina and Fujimoto, Seiji and Haiman, Zoltán and Imanishi, Masatoshi and Inayoshi, Kohei and Iwasawa, Kazushi and Kartaltepe, Jeyhan and Kashikawa, Nobunari and Kawaguchi, Toshihiro and Li, Junyao and Lee, Chien-Hsiu and Lupi, Alessandro and Schindler, Jan-Torge and Schramm, Malte and Shimasaku, Kazuhiro and Shuntov, Marko and Tanaka, Takumi S. and Toba, Yoshiki and Trakhtenbrot, Benny and Umehata, Hideki and Vestergaard, Marianne and Wang, Feige and Yang, Jinyi},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{SHELLQs-JWST unveils the host galaxies of 12 quasars at z > 6}},
  doi          = {10.3847/1538-4357/ae045b},
  volume       = {993},
  year         = {2025},
}