@article{21724, abstract = {The next generation of weak-gravitational-lensing surveys has the potential to place stringent constraints on cosmological parameters. However, their analysis is limited by systematics such as the intrinsic alignments of galaxies, which alter weak-lensing convergence and can lead to biases in cosmological parameter estimations. For the first time, in this work, we investigate the impact of intrinsic alignments on non-Gaussian statistics of the weak-lensing field using galaxy shapes derived from the IllustrisTNG hydrodynamical simulation. We create two catalogs of ray-traced convergence maps: one that includes the measured intrinsic shape of each galaxy and another where all galaxies are randomly rotated to eliminate intrinsic alignments. We compare a range of weak-lensing statistics between the two catalogs, including the shear–shear correlation function, the map-level angular power spectrum, one-point, peak count, and minimum distribution functions, and Minkowski functionals. For each statistic, we assess the level of statistical distinguishability between catalogs for a set of future survey angular areas. Our results reveal strong small-scale correlation in the alignment of galaxies and statistically significant boosts in weak-lensing convergence in both positive and negative directions for high-significance peaks and minima, respectively. We note that our analysis is at a fixed number density of ˜ 5 arcmin^-2, drawn from a single realization of initial conditions, and does not include observational uncertainties or supersample covariance contributions. Weak-lensing analyses utilizing non-Gaussian statistics must account for intrinsic alignments to avoid significantly compromised cosmological inferences.}, author = {Lee, Max E. and Haiman, Zoltán and Pandey, Shivam and Genel, Shy}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The effect of intrinsic alignments on weak-lensing statistics in hydrodynamical simulations}}, doi = {10.3847/1538-4357/ae1ca7}, volume = {996}, year = {2025}, } @article{19497, abstract = {The stochastic gravitational wave (GW) background recently discovered by several pulsar timing array experiments is consistent with arising from a population of coalescing super-massive black hole binaries. The amplitude of the background is somewhat higher than expected in most previous population models or from the local mass density observations. Such binaries are expected to be produced in galaxy mergers, which are also thought to trigger bright quasar activity. Under the assumptions that (i) a fraction fbin∼1 of all quasars are associated with mergers, (ii) the typical quasar lifetime is tQ∼108 yr, and (iii) adopting Eddington ratios fEdd∼0.25 for the luminosity of quasars, we compute the GW background associated directly with the empirically measured quasar luminosity function. This approach bypasses the need to model the cosmological evolution of black holes or galaxy mergers from simulations or semi-analytical models. We find the amplitude matching the value measured by NANOGrav. Our results are consistent with most quasars being associated with black hole binaries and being the sources of the GW background, and imply a joint constraint on tQ, fEdd and the typical mass ratio q≡M2/M1. The signal in this case would be dominated by relatively distant ∼109M⊙ sources at z≈2−3, at the peak of quasar activity. Similarly to other models, our results remain in tension with the local super-massive black hole mass density.}, author = {Kis-Tóth, Ágnes and Haiman, Zoltán and Frei, Zsolt}, issn = {1361-6382}, journal = {Classical and Quantum Gravity}, number = {7}, publisher = {IOP Publishing}, title = {{Can quasars, triggered by mergers, account for NANOGrav’s stochastic gravitational wave background?}}, doi = {10.1088/1361-6382/adbda6}, volume = {42}, year = {2025}, } @article{19638, abstract = {The James Webb Space Telescope has revealed low-luminosity active galactic nuclei at redshifts of z ≳ 4–7, many of which host accreting massive black holes (BHs) with BH-to-galaxy mass (MBH/M⋆) ratios exceeding the local values by more than an order of magnitude. The origin of these overmassive BHs remains unclear but requires potential contributions from heavy seeds and/or episodes of super-Eddington accretion. We present a growth model coupled with dark matter halo assembly to explore the evolution of the MBH/M⋆ ratio under different seeding and feedback scenarios. Given the gas inflow rates in protogalaxies, BHs grow episodically at moderate super-Eddington rates, and the mass ratio increases early on, despite significant mass loss through feedback. Regardless of seeding mechanisms, the mass ratio converges to a universal value ∼0.1–0.3, set by the balance between gas feeding and star formation efficiency in the nucleus. This behavior defines an attractor in the MBH–M⋆ diagram, where overmassive BHs grow more slowly than their hosts, while undermassive seeds experience rapid growth before aligning with the attractor. We derive an analytical expression for the universal mass ratio, linking it to feedback strength and halo growth. The convergence of evolutionary tracks erases seeding information from the mass ratio by z ∼ 4–6. Detecting BHs with ∼105−6 M⊙ at higher redshifts that deviate from the convergence trend would provide key diagnostics of their birth conditions.}, author = {Hu, Haojie and Inayoshi, Kohei and Haiman, Zoltán and Ho, Luis C. and Ohsuga, Ken}, issn = {2041-8213}, journal = {The Astrophysical Journal Letters}, number = {2}, publisher = {IOP Publishing}, title = {{The convergence of heavy and light seeds to overmassive black holes at cosmic dawn}}, doi = {10.3847/2041-8213/adc680}, volume = {983}, year = {2025}, } @article{19699, abstract = {We demonstrate that gas disks around binary systems might deliver gas to the binary components only when the circumbinary disk is relatively warm. We present new grid-based hydrodynamics simulations, performed with the binary on the grid and a locally isothermal equation of state, in which the binary is seen to functionally "stop accreting" if the orbital Mach number in the disk exceeds a threshold value of about 40. Above this threshold, the disk continues to extract angular momentum from the binary orbit, but it delivers very little mass to the black holes and instead piles up mass in a ring surrounding the binary. This ring will eventually become viscously relaxed and deliver mass to the binary at the large-scale inflow rate. However, we show that the timescale for such relaxation can far exceed the implied binary lifetime. We demonstrate that the ability of a binary–disk system to equilibrate is dependent on the efficiency at which accretion streams deposit mass onto the binary, which, in turn is highly sensitive to the thermodynamic conditions of the inner disk. If disks around massive black hole binaries do operate in such nonaccreting regimes, it suggests these systems may be dimmer than their single black hole counterparts but could exhibit dramatic rebrightening after the black holes inspiral and merge. This dimming begins in the UV/optical and could completely choke high-energy emission, such that these systems would likely be intrinsically X-ray weak with reddened continua, potentially resembling the spectra of "little red dots" recently identified in JWST observations.}, author = {Tiede, Christopher and Zrake, Jonathan and Macfadyen, Andrew and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Suppressed accretion onto massive black hole binaries surrounded by thin disks}}, doi = {10.3847/1538-4357/adc727}, volume = {984}, year = {2025}, } @article{20193, abstract = {Understanding the rapid formation of supermassive black holes in the early Universe requires insights into stellar mass growth in host galaxies. Here we present NIRSpec rest-frame optical spectra and NIRCam imaging from JWST of two galaxies at z > 6, both hosting moderate-luminosity quasars. These galaxies exhibit Balmer absorption lines, like low-redshift post-starburst galaxies. Our analyses of the medium-resolution spectra and multiband photometry show that the bulk of the stellar mass (log(M*/M☉) ≥ 10.6) formed in starburst episodes at redshift 9 and 7. One of the galaxies shows a clear Balmer break and lacks spatially resolved Hα emission. It falls well below the star-formation main sequence at z = 6, indicating quiescence. The other is transitioning to quiescence; together, these massive galaxies are among the most distant post-starburst systems known. The blueshifted wings of the quasar [O iii] emission lines indicate quasar-driven outflow, which possibly influences star formation. Direct stellar velocity dispersion measurements reveal that one galaxy follows the local black hole mass versus σ* relation whereas the other is overmassive. The existence of massive post-starburst galaxies hosting billion-solar-mass black holes in short-lived quasar phases indicates that supermassive black holes and host galaxies played a principal role in each other’s rapid early formation.}, author = {Onoue, Masafusa and Ding, Xuheng and Silverman, John D. and Matsuoka, Yoshiki and Izumi, Takuma and Strauss, Michael A. and Ward, Charlotte and Phillips, Camryn L. and Ito, Kei and Andika, Irham T. and Aoki, Kentaro and Arita, Junya and Baba, Shunsuke and Bieri, Rebekka and Bosman, Sarah E.I. and Eilers, Anna Christina and Fujimoto, Seiji and Habouzit, Melanie and Haiman, Zoltán and Imanishi, Masatoshi and Inayoshi, Kohei and Iwasawa, Kazushi and Jahnke, Knud and Kashikawa, Nobunari and Kawaguchi, Toshihiro and Kohno, Kotaro and Lee, Chien Hsiu and Li, Junyao and Lupi, Alessandro and Lyu, Jianwei and Nagao, Tohru and Overzier, Roderik and Schindler, Jan Torge and Schramm, Malte and Scoggins, Matthew T. and Shimasaku, Kazuhiro and Toba, Yoshiki and Trakhtenbrot, Benny and Trebitsch, Maxime and Treu, Tommaso and Umehata, Hideki and Venemans, Bram and Vestergaard, Marianne and Volonteri, Marta and Walter, Fabian and Wang, Feige and Yang, Jinyi and Zhang, Haowen}, issn = {2397-3366}, journal = {Nature Astronomy}, pages = {1541--1552}, publisher = {Springer Nature}, title = {{A post-starburst pathway for the formation of massive galaxies and black holes at z > 6}}, doi = {10.1038/s41550-025-02628-1}, volume = {9}, year = {2025}, } @article{20250, abstract = {Population III stars are possible precursors to early supermassive black holes (BHs). The presence of soft UV Lyman–Werner (LW) background radiation can suppress Population III star formation in minihaloes and allow them to form in pristine atomic-cooling haloes. In the absence of molecular hydrogen (⁠H2⁠) cooling, atomic-cooling haloes enable rapid collapse with suppressed fragmentation. High background LW fluxes from preceding star-formation have been proposed to dissociate H2⁠. This flux can be supplemented by LW radiation from one or more Population III star(s) in the same halo, reducing the necessary background level. Here, we consider atomic-cooling haloes in which multiple protostellar cores form close to one another nearly simultaneously. We assess whether the first star’s LW radiation can dissociate nearby ⁠, enabling rapid accretion on to a nearby protostellar core, and the prompt formation of a second, supermassive star (SMS) from warm, atomically-cooled gas. We use a set of hydrodynamical simulations with the code enzo, with identical LW backgrounds centred on a halo with two adjacent collapsing gas clumps. When an additional large local LW flux is introduced, we observe immediate reductions in both the accretion rates and the stellar masses that form within these clumps. While the LW flux reduces the H2 fraction and increases the gas temperature, the halo core’s potential well is too shallow to promptly heat the gas to >1000 K and increase the second protostar’s accretion rate. We conclude that this internal LW feedback scenario is unlikely to facilitate SMS or massive BH seed formation.}, author = {Sullivan, James and Haiman, Zoltán and Kulkarni, Mihir and Visbal, Eli}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {822--838}, publisher = {Oxford University Press}, title = {{Can supermassive stars form in protogalaxies due to internal Lyman-Werner feedback?}}, doi = {10.1093/mnras/staf1269}, volume = {542}, year = {2025}, } @article{20493, abstract = {We propose a formation pathway linking black holes (BHs) observed in gravitational-wave (GW) mergers, wide BH–stellar systems uncovered by Gaia, and accreting low-mass X-ray binaries (LMXBs). In this scenario, a stellar-mass BH binary undergoes isolated binary evolution and merges while hosting a distant, dynamically unimportant tertiary stellar companion. The tertiary becomes relevant only after the merger, when the remnant BH receives a GW recoil kick. Depending on the kick velocity and system configuration, the outcome can be: (1) a bright electromagnetic (EM) counterpart to the GW merger; (2) an LMXB; (3) a wide BH–stellar companion system resembling the Gaia BH population; or (4) an unbound isolated BH. Modeling the three-body dynamics, we find that ∼0.02% of LIGO–Virgo–KAGRA (LVK) mergers may be followed by an EM counterpart within ∼10 days, produced by tidal disruption of the star by the BH. The flare is likely brightest in the optical–UV and lasts for days to weeks; in some cases, partial disruption causes recurring flares with a period of ∼2 months. We further estimate that this channel can produce ∼1%–10% of Gaia BH systems in the Milky Way. This scenario provides the first physically motivated link between GW sources, Gaia BHs, and some X-ray binaries, and predicts a rare but robust pathway for EM counterparts to binary BH mergers, potentially detectable in LVK’s O5 run.}, author = {Naoz, Smadar and Haiman, Zoltán and Quataert, Eliot and Holzknecht, Liz}, issn = {2041-8213}, journal = {The Astrophysical Journal Letters}, number = {1}, publisher = {IOP Publishing}, title = {{Triples as links between binary Black Hole mergers, their electromagnetic counterparts, and galactic Black Holes}}, doi = {10.3847/2041-8213/ae0a20}, volume = {992}, year = {2025}, } @article{20651, abstract = {The origin of merging binary black holes detected through gravitational waves remains a fundamental question in astrophysics. While stellar evolution imposes an upper mass limit of ∼50⁢𝑀⊙ for black holes, some observed mergers—most notably GW190521—involve significantly more massive components, suggesting alternative formation channels. Here we investigate the maximum masses attainable by black hole mergers within active galactic nucleus (AGN) disks. Using a comprehensive semianalytic model incorporating 27 binary and environmental parameters, we explore the role of AGN disk conditions in shaping the upper end of the black hole mass spectrum. We find that an AGN disk lifetime is the dominant factor, with high-mass mergers (≳200⁢𝑀⊙) only possible if disks persist for ≳40  Myr. The joint electromagnetic observation of an AGN-assisted merger could therefore lead to a direct measurement of the age of an AGN disk.}, author = {Xue, Ling Qin and Tagawa, Hiromichi and Haiman, Zoltán and Bartos, Imre}, issn = {2470-0029}, journal = {Physical Review D}, number = {6}, publisher = {American Physical Society}, title = {{What determines the maximum mass of AGN-assisted black hole mergers?}}, doi = {10.1103/5m1n-qh9v}, volume = {112}, year = {2025}, } @article{20686, abstract = {Emission from two massive black holes (MBHs) bound in a close binary is expected to be modulated by different processes, such as the Doppler boost due to the orbital motion, accretion rate variability generated by the interaction with a circumbinary disc, and binary gravitational self-lensing. When the binary is compact enough, the two black holes are thought to be surrounded by a common broad-line region that reprocesses the impinging periodically varying ionising flux, creating broad emission lines with variable line shapes. Therefore, the study of broad emission line variability through multi-epoch spectroscopic campaigns is of paramount importance for the unambiguous identification of a binary. In this work, we study the response of a disc-like broad-line region to the Doppler-boosted ionising flux emitted by sub-milliparsec MBH binaries on a circular orbit and compare it with the response of a broad-line region illuminated by a single MBH with a periodically but isotropically varying intrinsic luminosity. We show that in the binary case, the time lags of the blue and red wings of the broad emission lines, arising from diametrically opposite sides of the circumbinary disc, are out of phase by half of the binary’s orbital period, as they each respond to the periodic ‘lighthouse’ modulation from the binary’s continuum emission. This asymmetric time lag represents a new binary signature that cannot be mimicked by a single MBH.}, author = {Bertassi, Lorenzo and Sottocorno, Erika and Rigamonti, Fabio and D’Orazio, Daniel and Eracleous, Michael and Haiman, Zoltán and Dotti, Massimo}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, publisher = {EDP Sciences}, title = {{Testing compact massive black hole binary candidates through multi-epoch spectroscopy}}, doi = {10.1051/0004-6361/202554574}, volume = {702}, year = {2025}, }