High Energy Astrophysical Phenomena
The long quest for vacuum birefringence in magnetars: 1E 1547.0-5408 and the elusive smoking gun
Roberto Taverna, Roberto Turolla, Lorenzo Marra et al. (+7 more)
Magnetars are now known to be among the most strongly polarized celestial sources in X-rays. Here we report on the $500\,\mathrm{ks}$ observation of the magnetar 1E 1547.0-5408 performed by the Imaging X-ray Polarimetry Explorer (IXPE) in March 2025. The IXPE spectrum is well reproduced by a single thermal component with blackbody temperature $kT_\mathrm{BB}\sim 0.67\,\mathrm{keV}$ and emission radius $R_\mathrm{BB}\sim 1.2\,\mathrm{km}$. The source exhibits a high linear polarization degree in the $2$–$6\,\mathrm{keV}$ band ($\mathrm{PD}=47.7\pm2.9\%$) with polarization angle $\mathrm{PA}=75^\circ.8 \pm 1.^\circ8$, measured West of celestial North. While $\mathrm{PA}$ does not appear to vary with energy, there is some evidence (at the $1\sigma$ confidence level) of a minimum in $\mathrm{PD}$ between $3$ and $4\,\mathrm{keV}$, compatible with what is expected by partial mode conversion at the
vacuum resonance in a magnetized atmosphere. Phase-resolved spectral and polarimetric analyses reveal that X-ray thermal radiation likely originates from a single, fairly small hot spot with a non-uniform temperature distribution. Fitting the phase-dependent $\mathrm{PA}$ measured by IXPE with a rotating vector model (RVM) constrains the source geometry and indicates that both the dipole axis and line-of-sight are misaligned with respect to the
spin axis. Under these conditions, the high polarization of the source cannot be regarded as compelling evidence for the presence of
vacuum birefringence in the
star magnetosphere. Nevertheless, the fact that the RVM successfully reproduces the modulation of the X-ray polarization angle and the behavior of $\mathrm{PD}$ with the energy hint once more to the presence of QED effects in magnetars.
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All authors Roberto Taverna, Roberto Turolla, Lorenzo Marra, Ruth M. E. Kelly, Alice Borghese, Gian Luca Israel, Sandro Mereghetti, Andrea Possenti, Silvia Zane, Michela Rigoselli
Earth and Planetary Astrophysics
Perihelion Asymmetry in the Water Production Rate of the Interstellar Object 3I/ATLAS
Hanjie Tan, Xiaoran Yan and Jian-Yang Li
3I/ATLAS is an interstellar object whose activity provides critical insights into its composition and origin. However, due to its orbital geometry, the object is too close to the Sun near perihelion to be observed from the ground, and space-based measurements are therefore required. Here we characterize the water production rate of 3I/ATLAS using SOHO/SWAN Lyman-$\alpha$ observations from 2025 November to December (heliocentric distances 1.4 to 2.2 au) with 3D Monte Carlo modeling. We report a peak post-perihelion water production rate of $Q_{\mathrm{H_2O}} \approx 4 \times 10^{28}$ molecules~s$^{-1}$, corresponding to a minimum active fraction of $\sim$30% (assuming a maximum
nucleus radius of 2.8 km). Comparison of our post-perihelion measurements with published pre-perihelion results reveals a heliocentric asymmetry, with an $r^{-5.9 \pm 0.8}$ scaling for the inbound rise, followed by a shallower $r^{-3.3 \pm 0.3}$ scaling during the outbound decline, where $r$ is heliocentric distance. The post-perihelion behavior indicates that the water production of 3I/ATLAS was driven primarily by the varying
solar insolation acting on a stable active area. Combined with other evidence, including comparison with the hyperactive comet 103P/Hartley 2, our findings suggest that its water production is likely dominated by a distributed source of icy grains. Furthermore, it displayed remarkable stability in the activity with no signs of outbursts or rapid depletion of water production.
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Astrophysics of Galaxies
The role of gas stripping in the quenching of satellite galaxies using SHARK v2.0
Megan K. Oxland, Matías Bravo, Laura C. Parker et al. (+1 more)
Observational studies have made substantial progress in characterizing quenching as a function of
stellar mass and environment, but they are often limited in their ability to constrain quenching timescales and to determine the dominant environmental process responsible for the shutting down of
star formation. To address this, we combine recent Sloan Digital Sky Survey (SDSS) observations with the SHARK v2.0 semi-analytic model to study the quenching of satellite
galaxies in groups and clusters. We generate mock SDSS-like observations to calibrate the hot
halo and cold interstellar medium (ISM) gas stripping prescriptions against observed satellite quenched fractions, finding that the previously adopted stripping prescriptions in SHARK v2.0 are too aggressive and overestimate the quenched fraction of satellite
galaxies. Reducing the efficiency of both hot and cold gas stripping yields excellent agreement with observations for low- and intermediate-mass satellite
galaxies. We use the calibrated model to investigate quenching timescales and find that satellites quench more quickly in clusters compared to groups, with timescales that generally decrease with increasing
stellar mass. The long (>2 Gyr) timescales we measure favour hot
halo gas removal as the dominant driver of satellite quenching.
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All authors Megan K. Oxland, Matías Bravo, Laura C. Parker, Claudia del P. Lagos
Solar and Stellar Astrophysics
Supernova interactions with aspherical circumstellar material I: calculations of light curves, AB magnitudes, spectra, and polarisation
Petr Kurfürst, Georgi Bless, Jakub Fišák et al. (+5 more)
We present an upgraded detailed numerical calculations of
supernova (SN) interactions with significantly aspherical circumstellar matter (CSM), primarily formed as a disc or bipolar lobes. The circumstellar disc can arise as a result of, for example, mass transfer in a binary, while bipolar lobes can be the result of a violent pre-explosive ejection of matter, similar to the iconic cases of luminous blue variable
stars (LBVs). We numerically simulate the radiation-hydrodynamic (RHD) behaviour of interaction processes using a 2D cylindrical version of the RHD code CASTRO. We then calculate light curves, spectral patterns, and polarisation profiles, all up to a relatively long time of two years after an SN shock breakout and from different directions, using the multidimensional Monte Carlo radiation transfer (MC-RT) codes SEDONA and SIROCCO. We calculated a total of five models for the two aforementioned configurations of the surrounding CSM, for stratified density levels, comparing the simulated hydrodynamic behaviour and differences in their observable properties. RHD models exhibit similar behaviour to previous adiabatic models, but with a significantly slower expansion velocity. The calculated light curves show a relatively smooth
evolution in SN-disc interaction, and declines and brightening in SN-lobes interaction. Comparing models with real events with a presumed similar physical process provides guidance for selecting a more accurate CSM configuration when simulating real situations.
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All authors Petr Kurfürst, Georgi Bless, Jakub Fišák, Filip Holoubek, Jiří Krtička, Brankica Kubátová, Jiří Kubát, Michal Zajaček
High Energy Astrophysical Phenomena
Spin-down changes in PSR B0540-69 induced by a drift of the magnetic axis
Lucas G. Barão and J. E. Horvath
The dynamics of the solid crust +
magnetic field lines of
pulsars is a much debated issue, and remains unsettled after 50 years. Some pieces of evidence have emerged to complete and confirm theoretical calculations and expectations. We discuss in the present work an interpretation of the behavior of the ”Crab Twin”
pulsar PSR B0540-69 in terms of the
evolution of the
magnetic field/quakes, connecting the behavior of the braking index with the underlying platelet drift and sudden discontinuous rearrangement (fast-slip) and long-term ones (slow-slip events), suggested by analogy with existing theoretical picture observed in the Earth's crust. The relationship of this scenario with permanent torque-changing glitches seen in the Crab and other young
pulsars, and a set of similar events in the same object and others is addressed. We conclude that this physical approach is in principle consistent with all these sudden events, and point out future work to clarify the whole picture.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Compact Stars Sourced by Dark Matter Halos and Their Frozen States
Yuan Yue and Yong-Qiang Wang
Inspired by regular black holes (RBHs) sourced by dark matter
halos, we generalize the anisotropic energy-momentum tensor by relaxing the $P_r = -\rho$ condition between radial pressure and density. We demonstrate that while RBHs are a unique special case, a broader class of relations yields horizonless compact
stars. Under specific parameter limits, these objects approach a “frozen state," mimicking black hole features without an event horizon. These compact
star solutions could satisfy weak energy conditions and provide a robust mechanism for dark matter-sourced black hole mimickers.
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Solar and Stellar Astrophysics
The age sequence of young clusters in Perseus: Estimating ages from mass distributions
Tatiana Pavlidou, Aleks Scholz and Koraljka Muzic
Establishing ages for young clusters is key for properly tracking the
star formation history of a region. In this paper we investigate a new approach to estimating ages for young populations, based on the well-founded assumption that the initial mass function is the same throughout a
star forming cloud. We trial this method for six young clusters in the Perseus
star forming region. For all six clusters, we construct new member samples in a homogeneous way using
Gaia DR3. We estimate masses by comparing 2MASS photometry to theoretical isochrones, including Monte Carlo simulations to propagate the errors. We compare the mass distributions of the clusters for a range of plausible ages, looking for a combination of ages that results in indistinguishable mass distributions across the region. We find the best fit for ages of 1 Myr for NGC1333+Autochthe, 2 Myr for IC348, 2-3 Myr for Heleus, 3-4 Myr for Mestor, 4-5 Myr for Electryon+Cynurus, and 5-8 Myr for Alcaeus. All other combinations of ages are ruled out by this criterion. The established age sequence is consistent with the relative ages inferred from disc fractions, and broadly aligns with the age sequence determined in previous studies using isochrone fitting. We suggest that this approach can be a useful complement and cross-check to established methods to estimate ages in young populations.
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High Energy Astrophysical Phenomena
Dynamic shocks powered by a wide, relativistic, super-Eddington outflow launched by an accreting neutron star in the mid-20th century
F. J. Cowie, R. P. Fender, I. Heywood et al. (+11 more)
Accreting systems can launch powerful
outflows which interact with the surrounding medium. We combine new
radio observations of the accreting
neutron star X-ray binary (XRB) Circinus X-1 (Cir X-1) with archival
radio observations going back 24 years. The $\sim3$ pc scale wide-angle
radio and X-ray emitting caps found around Cir X-1 are identified as synchrotron emitting shocks with significant proper motion and morphological
evolution on decade timescales. Proper motion measurements of the shocks reveal they are mildly relativistic and decelerating, with apparent velocity of $0.14c\pm0.03c$ at a propagation distance of 2 pc. We demonstrate that these shocks are likely powered by a hidden relativistic ($\gtrsim0.3c$) wide-angle conical
outflow launched in $1972\pm3$, in stark contrast to known structures around other XRBs formed by collimated jets over 1000s of years. The minimum time-averaged power of the
outflow required to produce the observed synchrotron emission is $\sim0.1L_\text{Edd}$, while the time-averaged power required for the kinetic energy of the shocks is $\sim40 \left(\frac{n}{10^{-2} \text{cm}^{-3}}\right)L_\text{Edd}$, where $n$ is the average ambient medium number density. This reveals the
outflow powering the shocks is likely significantly super-Eddington. We measure significant linear polarisation up to $52\pm6\%$ in the shocks demonstrating the presence of an ordered
magnetic field of strength $\sim200~\mu\text{G}$. We show that the shocks are potential PeVatrons, capable of accelerating electrons to $\sim0.7~\text{PeV}$ and
protons to $\sim20~\text{PeV}$, and we estimate the injection and energetic efficiencies of electron acceleration in the shocks. Finally, we predict that next generation gamma-ray facilities may be able to detect hadronic signatures from the shocks.
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All authors F. J. Cowie, R. P. Fender, I. Heywood, F. Carotenuto, J. H. Matthews, B. Reville, L. Olivera-Nieto, A. J. Cooper, A. K. Hughes, K. Savard, P. A. Woudt, J. van den Eijnden, N. Grollimund, P.Saikia
Solar and Stellar Astrophysics
Solar twins in Gaia DR3 GSP-Spec I. Building a large catalog of Solar twins with ages
Daisuke Taniguchi, Patrick de Laverny, Alejandra Recio-Blanco et al. (+2 more)
[Abbreviated] Context.
Solar twins,
stars whose
stellar parameters (Teff, log g, and [M/H]) are very close to the
Solar ones, offer a unique opportunity to investigate
Galactic archaeology with very high accuracy and precision. However, most previous catalogs of
Solar twins contain only a small number of objects (typically a few tens), and their selection functions are poorly characterized. Aims. We aim at building a large catalog of
Solar twins from
Gaia DR3 GSP-Spec, providing model-driven, rather than data-driven,
stellar parameters including ages, together with a well-characterized selection function. Methods. Using
stellar parameters from the
Gaia DR3 GSP-Spec catalog, we selected
Solar-twin candidates whose parameters lie within +- 200 K in Teff, +- 0.2 in log g, and +- 0.1 dex in [M/H] of the
Solar values. Candidates unlikely to be genuine
Solar twins were removed using
Gaia flags and photometric constraints. We determined accurate ages for individual twins with a
Bayesian isochrone-projection method, considering three combinations of parameters: Teff, [M/H], and either log g, M_G, or M_Ks. We also constructed a mock catalog to characterize the selection function. Results. Our final GSP-Spec
Solar-twin catalog contains 6,594
stars. The mock catalog consisting of 75,588 artificial twins well reproduces the main characteristics of the observed catalog, especially for ages determined with M_G or M_Ks. To demonstrate the usefulness of our catalog, we compared chemical abundances [X/Fe] with age. We statistically confirmed the age–[X/Fe] relations for several species (e.g., Al, Si, Ca, and Y), demonstrating that trends previously identified in small but very high-precision samples persist in a much larger, independent sample. Conclusions. Our study bridges small high-precision
Solar-twin samples and large data-driven ones, enabling demographic studies of
Solar twins.
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All authors Daisuke Taniguchi, Patrick de Laverny, Alejandra Recio-Blanco, Takuji Tsujimoto, Pedro A. Palicio
Astrophysics of Galaxies
An Analysis of AGN Feedback in the Compact Galaxy Group Stephan's Quintet
Maura Kathleen Shea, D. Michael Crenshaw, Travis C. Fischer et al. (+7 more)
Compact
galaxy groups are ideal laboratories for studying the effects of interactions between AGN and multiple nearby
galaxies. Recent JWST observations of the nearby compact group Stephan's Quintet highlight
tidal flows between the interacting
galaxies as well as
outflows from the active
galaxy NGC 7319. To study the kinematics on a large scale throughout the group, we obtained spatially-resolved long-slit spectra of Stephan's Quintet at multiple slit positions with Apache Point Observatory's Kitt Peak Ohio State Multi-Object Spectrograph. We fit multiple Gaussians to the H$\alpha$ $\lambda$6563 Å and [N II] $\lambda\lambda$6548, 6583 Å emission lines to isolate the different kinematic components. We used the kinematics to develop the first biconical
outflow model of the narrow-line region of NGC 7319. Using a combination of
galactic rotation models, biconical
outflow models, and kinematic maps of the ionized gas, we disentangled the
outflows, rotation, and
tidal flows in the group. We found
outflow radial velocities up to 550 km s$^{-1}$ peaking at 2.6 kpc from the central supermassive black hole, and a transition from AGN-powered
outflows to gravitationally-powered
tidal flows at a projected distance between 2.4 – 6.3 kpc. We performed a line ratio analysis and determined the gas shows Seyfert-like ionization out to 6.3 kpc (projected), which supports our finding that gas outside this radius is predominantly powered by
tidal flows. Our separation of kinematic components in Stephan's Quintet will enable future studies of the physical conditions and dynamical forces in the ionized gas to better quantify the feeding and feedback processes of AGN in compact groups.
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All authors Maura Kathleen Shea, D. Michael Crenshaw, Travis C. Fischer, Mitchell Revalski, Julia Falcone, Beena Meena, Zo Chapman, Jacob Tutterow, Madeline Davis, Kesha Patel
Astrophysics of Galaxies
An Investigation of 5-year Simultaneous X-ray and Radio Light Curves of the Dwarf Seyfert Galaxy UGC 6728
Krista Lynne Smith, Macon Magno and Michael Koss
We present serendipitous simultaneous
radio and X-ray light curves of the
dwarf Seyfert
galaxy UGC 6728 spanning 5 years. The X-ray light curve exhibits a flaring period, followed by a gradual rise and decline. Throughout these events, the X-ray hardness ratio and spectrum do not change significantly. The
radio flux is constant, as far as can be determined from its sparse sampling, until the end of the X-ray
flare, then decreases by a factor of two by the midpoint of the gradual X-ray rise before returning to baseline at the end of the X-ray decline. We interpret this behavior in light of a similar event recently reported in NGC 2992, in which there is a temporary obscuration of the
radio source by a blob of
plasma ejected by a
magnetic reconnection in the
accretion disk. The energetics of the X-ray
flare are consistent with those expected from
magnetic disk activity. As in NGC 2992, the X-ray spectrum does not evolve during the obscuration event. We also discuss the possibility that the observed phenomena are due to normal AGN coronal flaring and variability, which is plausible but unlikely given the lack of spectral variation.
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Astrophysics of Galaxies
A Stratification in Magnetic Field Structures: The Radio Outflow in NGC 4151
Salmoli Ghosh, P. Kharb, E. Costantini et al. (+3 more)
The nature of
radio outflows in
radio-quiet AGN remains poorly understood. In this study, we present kpc-scale polarization observations of the Seyfert
galaxy NGC\,4151 using the Karl G. Jansky Very Large Array (VLA) in B-array at 3 and 10 GHz. We find that the inferred
magnetic (B-) field structures show a stratification: a `spine-sheath'-like structure, with fields perpendicular to the jet direction in the `spine' and parallel in the `sheath', is observed in the higher resolution (0.5 arcsec) image at 10 GHz. In addition, a `wind'-like component with B-fields perpendicular to the
radio outflow is observed in the 3 GHz image (resolution 2 arcsec); this feature is prominent along the `receding' (eastern) jet direction. Rotation measure (RM) ranges from $-230$ to 250 rad m$^{-2}$ over the polarized regions, indicating a low-electron-density ($10^{-2}-10^{-3}$ cm$^{-3}$) tenuous medium surrounding the source causing Faraday rotation. A {tentative} RM gradient of $+75$ to $-25$ rad m$^{-2}$ is observed transverse to the northern `wind' component, while a similar gradient with opposite sign is seen across the southern `wind' component, suggestive of a helical
magnetic field threading the
outflow. Based on an analysis of the available
radio and X-ray data, we conclude that the stratified
radio outflow in NGC 4151 is magnetically-driven. The bi-conical
radio `wind' is found to be massive ($1050-3200 M_\odot$) with a high mass
outflow rate ($0.01-0.03$ M$_\odot$ yr$^{-1}$) but low in kinetic power ($<0.01$% of L$_{\rm{bol}}$), making it less impactful for
galactic-scale feedback. Our study suggests that
radio-quiet AGN may also host magnetically dominant jets and winds, even while their jets are smaller and weaker compared to
radio-loud AGN.
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All authors Salmoli Ghosh, P. Kharb, E. Costantini, J. Gallimore, D. Williams-Baldwin, M. Mehdipour
Astrophysics of Galaxies
Blazars define a stable celestial reference frame
Nathan Secrest and Sebastien Lambert
Recent work has shown that optical-
radio position offsets and
radio position variability are inversely correlated with the photometric variability of active
galactic nuclei (AGN). A key prediction of these findings is that a reference frame constructed using highly photometrically variable AGN should be more stable than a frame that does not account for variability and that variability can be used to optimally weight all sources in order to maximize frame stability. Using ICRF3 matched to
Gaia DR3, we employed a bootstrap method to estimate the multi-epoch stability of frames constructed using AGN selected at varying levels of photometric variability. We fit vector spherical harmonics to the coordinate differences between the three ICRF3 frames (S/X, K, and X/Ka) and
Gaia and quantified the statistical dispersion as a function of blazar-like (high variability),
quasar-like (low variability), and intermediate-variability class. An S/X reference frame constructed using blazars exceeds the stability of a frame constructed with
quasars by a factor of 6 and is twice as stable as the ICRF3 defining sources. At K and X/Ka, a blazar-based frame matches or exceeds the stability of the defining sources by a factor of 1.4 in the case of X/Ka and exceeds the stability of a frame based on
quasars by over a factor of 2 in both cases. The smaller improvement at K and X/Ka is likely because sources selected at higher frequency are more likely to be blazars. We derived a variability-based astrometric covariance scaling method that results in factor of 2 reduction in frame distortions and instabilities between S/X and
Gaia, with a mild improvement for K but no difference for X/Ka, which is dominated by known distortions. Our results confirm the prediction that an optimal weighting of the link between the optical and
radio celestial reference frames is enabled by accounting for photometric variability.
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Astrophysics of Galaxies
Optimizing Optical Searches for Supermassive Black Hole Binaries in AGN Light Curves: Fourier versus Bayesian Periodicity Detection
Sebastian Banaszak, Caitlin Witt and Adam Miller
Simulations predict that supermassive black hole binaries (SMBHBs) will exhibit periodic brightness variations that may exceed the
stochastic variability intrinsic to active
galactic nuclei (AGN). In this paper, we simulate SMBHBs with damped random walk (DRW) AGN variability and an added sinusoidal signal from the orbital motion, and test three methods – the Generalized Lomb Scargle Periodogram (GLSP), the nested
Bayesian sampler (NBS), and the Weighted Wavelet Z-Transform (WWZ) – to determine which is best at recovering the periodicity. Our simulated light curves follow the properties of the Catalina Real-Time Transient Survey (CRTS), Legacy Survey of Space and Time (LSST), and Zwicky Transient Facility (ZTF) to best inform current and future SMBHB searches. We map a broad range of parameter space and identify which DRW-only light curves best mimic periodicity and pass each method's model selection. The NBS performs best at detecting periodicity and filtering out DRW-only light curves. Combined candidate selection with both the NBS and GLSP significantly reduces false positive rates with marginal impact to true positive rates. With this joint model selection pipeline, we find the lowest false positive rates in ZTF-like simulations and the highest detection rates in LSST-like simulations. Using a modified computation of the False Alarm Probability (FAP) with GLSP, we efficiently triage LSST AGN light curves (~10^7 light curves in ~10-30 hours) and achieve true- and false- positive rates of ~40% and ~0.5%, respectively.
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Cosmology and Nongalactic Astrophysics
The Back-in-time Void Finder: dynamical identification of cosmic voids through optimal transport reconstruction
Simone Sartori, Sofia Contarini, Elena Sarpa et al. (+4 more)
Cosmic voids have increasingly emerged as a powerful cosmological probe. However, their large spatial extent and intrinsically underdense environments make their identification highly sensitive to shot noise,
redshift-space distortions (RSD), and observational systematics, particularly for topological and density-based void definitions. We introduce the Back-In-Time Void Finder (BitVF), a novel dynamical and physically motivated
algorithm that identifies
cosmic voids as regions of negative divergence of the Lagrangian displacement field reconstructed from the present-day tracer distribution. The reconstruction relies on an optimized discrete optimal transport
algorithm that recovers the backward-in-time dynamics of tracers, naturally accounting for tracer bias without relying on cosmological assumptions. We validate BitVF against the widely used topological void finder REVOLVER using high-resolution N-body simulations, showing that it produces void catalogs with smoother and more physically motivated density profiles, as well as abundances that are more stable under tracer subsampling and shot noise. We further apply it to realistic DESI-like mock light-cone
galaxy catalogs, demonstrating that it intrinsically mitigates
redshift-space systematic effects, preserving real-space void size functions more faithfully than topological methods. Modeling RSD, the reconstruction can be combined with a fiducial cosmology and an assumed tracer bias within a bias-corrected Kaiser framework, yielding reconstructed-space void catalogs consistent with real-space statistics across
redshift. Its performance is characterized as a function of the main internal parameters, showing an optimal balance between accuracy, computational efficiency, and applicability to stage IV
galaxy surveys. BitVF will be publicly released within the CosmoBolognaLib.
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All authors Simone Sartori, Sofia Contarini, Elena Sarpa, Giulia Degni, Federico Marulli, Stephanie Escoffier, Lauro Moscardini
Astrophysics of Galaxies
What factors shape the radio luminosity of star-forming galaxies? A new calibration from LoTSS-DR2
Shravya Shenoy, Daniel J. B. Smith, Sarah K. Biddle et al. (+8 more)
Radio observations offer a
dust-unobscured view of
galaxy star formation via the
radio continuum-
star formation rate (RC–SFR) relation. Emerging evidence of a
stellar mass dependence in the RC–SFR relation raises the broader question of how other
galaxy properties may influence this relation. In this work, we study the dependence of the global RC–SFR relation on
galaxy properties in local ($z\,\leq$\,0.3)
star-forming
galaxies (SFGs) using the second data release of the LOFAR Two-Metre Sky Survey (LoTSS-DR2). Employing a non-parametric decision-tree regression
algorithm, we identify the most important
galaxy properties for estimating the
radio luminosity using a sample of 18,828 emission-line-classified SFGs based on spectroscopic data from the SDSS-DR8. Along with the spectroscopically obtained SFRs and
stellar mass values, we also use SFRs and
stellar masses derived using photometric SED-fitting from the GALEX–SDSS–WISE Legacy Catalogue (GSWLC) for the same sample. We find that a
galaxy's SFR is most important for predicting the
radio luminosity, followed by the
stellar mass, at $>5\sigma$ significance. Complementing the LoTSS catalogue 150\,MHz flux densities with aperture photometry for the rest of the emission-line classified sample (35,099
galaxies in total), we obtain a new calibration of the RC–SFR relation, which does not change significantly whether we use spectroscopic or photometrically derived SFRs and
stellar masses, despite the fact that the methods probe
star formation on different characteristic timescales. Our results highlight the utility of decision-tree
algorithms for handling censored
radio-selected
galaxy samples, which will be useful for future spectroscopic surveys of
radio sources.
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All authors Shravya Shenoy, Daniel J. B. Smith, Sarah K. Biddle, Gülay Gürkan, Martin J. Hardcastle, Marina I. Arnaudova, Soumyadeep Das, Luke R. Holden, Gaoxiang Jin, Leah K. Morabito, Huub J. A. Röttgering
Astrophysics of Galaxies
Constraining the population of dark matter halo shapes using hierarchical inference with extragalactic stellar streams
David Chemaly, Elisabeth Sola, Vasily Belokurov et al. (+4 more)
Stellar streams, the debris of tidally disrupted satellites, trace their host's gravitational potential and thus probe dark matter
halo structure. While six-dimensional phase-space data of
Galactic streams enable precise dark matter
halo modelling in the Milky Way, streams around external
galaxies are typically available only as low surface brightness features without kinematics (i.e. two-dimensional photometric data), providing only weak constraints when considered individually. We present a hierarchical
Bayesian framework that infers the population distribution of
halo flattening using only projected stream tracks. Streams are forward-modelled in StreaMAX, a new JAX-accelerated particle-spray package that achieves orders of magnitude faster stream generation when compared to traditional methods. For each stream we fit an axisymmetric dark matter
halo model and obtain a posterior on the flattening. These posteriors are then combined through hierarchical reweighting to constrain the population distribution. Using mock data, we show that individual fits recover the correct flattening with modest precision and exhibit projection-induced multi-modalities. Nevertheless, aggregating these fits yields accurate and confident constraints on the underlying population distribution of dark matter
halo morphologies, clearly distinguishing between oblate, spherical, and prolate populations. The total computational cost scales linearly with sample size. Our results demonstrate that ensembles of purely photometric streams carry sufficient information to constrain dark matter
halo shapes in external
galaxies at the population level. With the forthcoming samples from Euclid and Rubin/LSST, this approach offers a practical path to population-level inferences of
halo morphology without any kinematic measurements.
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All authors David Chemaly, Elisabeth Sola, Vasily Belokurov, Sergey Koposov, GyuChul Meyong, HanYuan Zhang, Denis Erkal
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Single-wave solutions of the neutrino fast flavor system. Part I. Mechanical properties
Damiano F. G. Fiorillo and Georg G. Raffelt
A dense
neutrino plasma can exhibit collective
flavor evolution caused by
neutrino–
neutrino refraction. Recently, a new class of exact nonlinear inhomogeneous solutions was discovered: single-wave (SW) solutions of the fast
flavor system. The key property is that the
flavor occupation numbers remain homogeneous, whereas the field of
flavor coherence varies spatially with a single wave vector. The equations of motion for this structure resemble those of a collection of classical
spins, in analogy with the homogeneous slow and fast
flavor cases. In contrast, the SW system is not integrable (it does not possess Gaudin invariants) so that, while two-beam pendulum solutions are inevitable, they do not extend to a multi-angle system. We develop a taxonomy of all known nonlinear collective
flavor solutions, explaining the overlap between categories and their differences.
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Solar and Stellar Astrophysics
Digging into the Interior of Hot Cores with ALMA (DIHCA). VII. Disk candidates around high-mass stars and evidence of anisotropic infall
Fernando A. Olguin, Patricio Sanhueza, Yoko Oya et al. (+19 more)
We study the kinematics of condensations in 30 fields forming high-mass
stars with ALMA at a high-resolution of ~0.08” on average (~230 au). The presence of disks is important for feeding high-mass
stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH$_3$OH, CH$_3$CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred au scales in the high-mass regime. Their position-velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position-velocity maps of the disk candidates and find indices between -0.5 (Keplerian rotation) and -1 (rotation under specific angular momentum conservation) with a median of -0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 to 45 M$_\odot$. Excluding outliers, the disk candidates are relatively more compact (<200 au) and less massive (<5 M$_\odot$) than previous results at coarser angular resolution. We calculate an average Toomre-$Q$ parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays an role in feeding high-mass (proto)
stars.
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All authors Fernando A. Olguin, Patricio Sanhueza, Yoko Oya, Adam Ginsburg, Maria T. Beltrán, Kaho Morii, Roberto Galván-Madrid, Huei-Ru Vivien Chen, Qiuyi Luo, Kei E. I. Tanaka, Suinan Zhang, Yu Cheng, Fumitaka Nakamura, Shanghuo Li, Kotomi Taniguchi, Guido Garay, Qizhou Zhang, Masao Saito, Takeshi Sakai, Xing Lu, Jixiang Weng, Andrés E. Guzmán
Instrumentation and Methods for Astrophysics
Non-uniform Antenna Loading Effect on Embedded Element Patterns and Application to Fault Detection
Georgios Kyriakou
An iterative technique is presented to calculate the Embedded Element Pattern (EEP) transformation from a set of patterns computed for a uniform
antenna port loading (scaled identity
matrix) to a set of those computed for a non-uniform one (arbitrary diagonal
matrix). Inverting this transformation to derive the non-uniform impedances of the arbitrary load leads to a new, efficient
algorithm which disposes of the redundancy of the trivial use of all \( N \) EEPs at the faulty array condition, requiring only one such EEP for numerically stable impedance fault calculation. As the EEPs are envisioned to be obtained primarily through measurement, our method is also tested with the inclusion of various noise components and its convergence is evaluated, leading to suggested measurement apparatus SNR and fading levels, as well as the optimal choice of reference
antenna to minimize the estimation error.
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Instrumentation and Methods for Astrophysics
LISA and the LISA Science Team
Anna Heffernan, Chiara Caprini, Neil Cornish et al. (+19 more)
LISA, the
Laser Interferometer Space
Antenna, due to launch mid-2035, is a large class space mission by the European Space Agency (ESA). In partnership with NASA and ESA-member states, ESA is on track to launch what is expected to be the first space-based gravitational wave detector. By hosting detectors in space, one gains access to a lower frequency band of gravitational wave sources and, with them, a plethora of new science. To maximise this scientific gain, ESA and NASA selected 20 scientists for the LISA Science Team to carry out and/or lead the necessary actions leading up to LISA's launch. We give a short overview and update of the LISA mission, its science objectives and related waveforms, as well as the work of the LISA Science Team as of April 2026.
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All authors Anna Heffernan, Chiara Caprini, Neil Cornish, Jonathan Gair, Catia Grimani, Zoltan Haiman, Erin Kara, Nikos Karnesis, Valeriya Korol, Astrid Lamberts, Nora Lützgendorf, Guido Müller, Gijs Nelemans, Antoine Petiteau, Elena Maria Rossi, Alberto Sesana, Joey Shapiro Key, Deirdre Shoemaker, Krista Lynne Smith, Stephen R. Taylor, Alberto Vecchio, William Joseph Weber
Instrumentation and Methods for Astrophysics
OmniSpectra: A Unified Foundation Model for Universal Spectra Representation Learning
Md Khairul Islam, Zeyu Xia, Adam S. Bolton et al. (+1 more)
Standard sequence models encode position by
token rank rather than physical coordinate, typically forcing practitioners to destructively resample continuous physical signals such as spectra observed across heterogeneous instruments. We identify this coordinate mismatch as a structural limitation in cross-instrument representation learning, and propose OmniSpectra, a wavelength-native foundation model for spectral representation learning: a continuous-coordinate masked autoencoder that discards the integer pixel indexing of sequence modeling. Mapping physical coordinates to a logarithmic basis turns the multiplicative scaling induced by cosmological
redshift into a uniform additive shift. In continuous rotary position
embeddings, this shared shift cancels from relative
token distances rather than producing grid-dependent positional distortion. We further counter the spectral bias inherent to implicit neural decoders with a physics-grounded, resolution-gated
Fourier decoder that provides anti-aliasing. Pretrained on eight surveys and benchmarked against seven baselines, our model reaches state-of-the-art performance with only 12.2M parameters while outperforming substantially larger models, indicating that encoding physical structure can substitute for parameter scale.
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All authors Md Khairul Islam, Zeyu Xia, Adam S. Bolton, Judy Fox
Astrophysics of Galaxies
Tracing the Galactic Disk with Gaia DR3: A Deep Study of Berkeley 17, 18, and 39 Open Star Clusters
A. Ahmed, W. H. Elsanhoury, D. C. Ç{\i}nar et al. (+4 more)
We report a detailed investigation of three intermediate-to-old age open clusters, Berkeley 17, Berkeley 18, and Berkeley 39, utilizing precise astrometric and photometric data from
Gaia DR3. Cluster membership was robustly determined through a probabilistic proper-motion analysis, yielding statistically significant samples of 600, 1042, and 907
stars, respectively. From the mean parallaxes of these members, we determine astrometric distances ranging from approximately 3.40 kpc for Berkeley 17 to 5.80 kpc for Berkeley 18. Isochrone fitting applied to the decontaminated color-magnitude diagrams constrains the cluster ages to 9.12 +/- 1.00 Gyr, 3.36 +/- 0.50 Gyr, and 5.10 +/- 0.50 Gyr, respectively. Interstellar reddening spans a wide range, from E(B-V) = 0.17 mag in Berkeley 39 to 0.58 mag in Berkeley 17. Structural parameters derived from King model fits to the radial density profiles, combined with mass function analyses, indicate that the clusters are dynamically relaxed systems with mass distributions broadly consistent with the canonical Salpeter slope. Our kinematic analysis reveals that Berkeley 17, Berkeley 18, and Berkeley 39 are part of the outer disk population.
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All authors A. Ahmed, W. H. Elsanhoury, D. C. Ç{\i}nar, S. Taşdemir, R. Canbay, A. A. Haroon, M. S. Alenazi
Earth and Planetary Astrophysics
A radially broad collisional cascade in the debris disk of $\gamma$ Ophiuchi observed by JWST
Yinuo Han, Mark Wyatt, Kate Y. L. Su et al. (+13 more)
The A1V
star $\gamma$ Oph, at a distance of 29.7 pc, is known from Spitzer imaging to host a debris disk with a large radial extent and from its spectral energy distribution to host inner warm
dust. We imaged $\gamma$ Oph with JWST/MIRI at 15 and 25.5 $\mu$m, revealing smooth and radially broad emission that extends to a radius of at least 250 au at 25.5 $\mu$m. In contrast to JWST findings of an inner small-grain component with distinct ringed structures in Fomalhaut and Vega, the mid-infrared radial profile combined with prior ALMA imaging suggests a radially broad steady-state collisional cascade with the same grain size distribution throughout the disk. This further suggests that the system is populated by a radially broad planetesimal belt from tens of au or less to well over 200 au, rather than a narrow planetesimal belt from which the observed
dust is displaced to appear broad. The disk is also found to be asymmetric, which could be modelled by a stellocentric offset corresponding to a small eccentricity of $\sim$0.03. Such a disk eccentricity could be induced by a mildly eccentric $<10\,M_\mathrm{Jup}$
giant planet outside 10 au, or a more eccentric companion up to
stellar mass at a few au, without producing a resolvable radial gap in the disk.
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All authors Yinuo Han, Mark Wyatt, Kate Y. L. Su, Antranik A. Sefilian, Joshua B. Lovell, Carlos del Burgo, Jonathan P. Marshall, Sebastian Marino, David J. Wilner, Brenda C. Matthews, Max Sommer, A. Meredith Hughes, John M. Carpenter, Meredith A. MacGregor, Nicole Pawellek, Thomas Henning
Astrophysics of Galaxies
The baryonic mass-size relation of galaxies. II. Implications for the evolutionary paths between star-forming and passive galaxies
Zichen Hua, Lelli Federico, Enrico Di Teodoro et al. (+2 more)
The baryonic mass-size relation of
galaxies links the total baryonic mass (
stars plus gas) to the baryonic half-mass radius. In the first paper of this series, we showed that
star-forming
galaxies from the SPARC sample follow two distinct relations in the baryonic mass-size plane: one defined by high-surface-density (HSD),
star-dominated, Sa-to-Sc
galaxies, and one defined by low-surface-density (LSD), gas-dominated, Sd-to-dI
galaxies. In this second paper, we study the structural relations between baryonic mass, half-mass radius, and mean surface density to constrain possible morphological transformations between
star-forming and passive
galaxies. We complemented the SPARC sample with $\sim$1200 passive
galaxies that are nearly devoid of gas: ellipticals (Es), lenticulars (S0s),
dwarf ellipticals (dEs) or
dwarf spheroidals (dSphs), and the so-called `ultra-diffuse
galaxies' (UDGs). Our results can be summarised as follows: (1) passive
stellar components follow four distinct relations at high statistical significance, namely (i) ellipticals plus bulges, (ii) S0 disks, (iii) non-nucleated
dwarfs (dEs, dSphs, UDGs), and (iv) nucleated dEs; (2)
star-forming HSD disks (mostly Sa to Sc) overlap with S0 disks within 2$\sigma$ in the baryonic relations and within 1$\sigma$ in the
stellar ones, so present-day spirals may simply evolve into lenticulars as they run out of gas; (3)
star-forming LSD disks (mostly Sd to dI) are offset from non-nucleated passive
dwarfs at more than 3$\sigma$ in the baryonic relations, but the two
galaxy populations overlap within 1$\sigma$ in the
stellar relations, suggesting that non-nucleated passive
dwarfs may form from
star-forming
dwarfs only after gas removal; (4) UDGs extend the sequence of non-nucleated dEs/dSphs and may originate from the most diffuse
star-forming LSD
galaxies with no need for a substantial expansion of the
stellar component.
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All authors Zichen Hua, Lelli Federico, Enrico Di Teodoro, Stacy McGaugh, James Schombert
Earth and Planetary Astrophysics
The Circumbinary Disk of HD 34700A: I. CO gas kinematics indicate spirals, infall, and vortex motions
J. Stadler, M. Benisty, F. Zagaria et al. (+9 more)
We present the first high-resolution ($\sim$ 0.14") Atacama Large Millimeter/submillimeter Array (ALMA) Band 6
dust continuum and CO molecular line emission observations of the quadruple system HD 34700. In particular, HD 34700AaAb is a spectroscopic binary ($M_{\rm{bin}}=4\,M_\odot$) surrounded by two low-mass companions at large separations. Its circumbinary disk is highly substructured, featuring numerous spiral arms and a large cavity observed in infrared (IR) scattered light. We analyzed the CO line channel and intensity moment maps. By fitting a Keplerian model to the line channel emission, we identified the residual motions and conducted a line spectra analysis. We resolved an asymmetric continuum crescent on top of a
dust ring at 0.39" (138 au), colocated with the IR ring. The CO molecule line emissions trace a smaller cavity in gas, whose edge aligns with the inner rim of the ring detected in H$\alpha$ emission at 0.20" (65 au). The $^{12}$CO line emission and kinematics trace highly non-Keplerian motions ($\sim0.1\Delta\upsilon_{\rm kep}$), and these CO spiral features align well with the spiral structures in scattered light. The $^{12}$CO line spectra analysis reveals a streamer above the southeastern disk plane, likely falling onto the disk. The $^{13}$CO and C$^{18}$O kinematics largely follow the disk's underlying Keplerian rotation, while $^{13}$CO exhibits tentative signs of anticyclonic
vortex flows at the continuum crescent location. Our multimolecular line study suggests that the circumbinary disk of HD 34700A is highly perturbed in its upper layers, possibly warped and influenced by infalling material. While late-stage infall may account for the IR spirals and the formation of the
vortex through Rossby wave instability, an embedded massive companion within the cavity may also contribute to these features.
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All authors J. Stadler, M. Benisty, F. Zagaria, A. F. Izquierdo, J. Speedie, A. J. Winter, L. Wölfer, J. Bae, S. Facchini, D. Fasano, N. Kurtovic, R. Teague
Cosmology and Nongalactic Astrophysics
Cosmic strings, domain walls and environment-dependent clustering
Øyvind Christiansen, Julian Adamek and Martin Kunz
Recent cosmological data favour phantom-crossing dark energy, motivating models with non-minimal couplings that induce a fifth force on structure formation. Reconciling these models with local tests often requires strong screening, leading to environment-dependent clustering. We investigate such effects via a late-time structure-induced phase transition driven by a non-minimally coupled scalar field. For this purpose, we introduce norns, a fully relativistic cosmological particle-mesh code that self-consistently evolves a complex scalar field - a generalisation of the symmetron producing global U(1) strings rather than domain walls. Using simulations, we compare string and wall-forming models, quantifying impacts on the matter power spectrum,
halo mass function, and defect dynamics. Strong environment-dependent effects can generate significant departures from LCDM in underdense regions while keeping the overall power spectrum changes modest (~ 4-15% at k~0.3-0.5 h Mpc^-1, sub-percent for z > 0.2). We find that an attractive fifth force can locally suppress structure growth in voids while enhancing it in surrounding overdense regions by driving
outflows from the voids. These effects leave distinctive signatures in the matter density probability density function and in marked
halo power spectra, which are likely detectable in low-
redshift data.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Exact general solutions for cosmological scalar field evolution in a vacuum-energy dominated expansion
Patrick Hu and Robert J. Scherrer
We derive exact general solutions (as opposed to attractor particular solutions) for the
evolution of a scalar field $\phi$ in a universe dominated by a background fluid with equation of state parameter $w_B = -1$, extending earlier work on exact solutions with $w_B > -1$. Straightfoward exact solutions exist when the
evolution is described by a linear differential equation, corresponding to constant, linear, and quadratic potentials. In the nonlinear case, exact solutions are derived for $V = V_0\ln \phi$, $V = V_0 \phi^{1/2}$ and $V = V_0/\phi$, and the logarithmic potential also yields an exact first integral. These complicated parametric solutions are considerably less useful than those derived previously for a universe dominated by a barotropic fluid such as matter or radiation with $w_B > -1$. However, we generalize the slow-roll approximation and show that it applies to all sufficiently flat potentials in the case of a
vacuum-dominated expansion, while it never applies when the universe is dominated by a background fluid with $w_B > -1$.
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Earth and Planetary Astrophysics
Transit distances and composition of low-velocity exocomets in the $\beta$ Pic system
Théo Vrignaud and Alain Lecavelier des Etangs
$\beta$ Pictoris is a young nearby A5V
star, about 20 Myr old, embedded in a prominent debris disc. For the past 40 years, variable absorption features have been observed in the
stellar spectrum, produced by the gaseous tails of exocomets transiting the
star. Yet, despite the large number of observations available, the origin and dynamical
evolution of the exocomets remain poorly understood. Here we present new spectroscopic observations of $\beta$ Pic, obtained on April 29, 2025, with the Hubble Space
Telescope and the HARPS spectrograph. We report the detection of three strong exocomet signatures at low radial velocities (-7.5, +2.5 and +10 km/s), in a large set of lines from various species and excitation levels. We show that the three exocometary tails have different excitation states, indicating that they are located at different distances from the
star. Using a detailed modelling of the excitation state of the transiting gas, which includes both radiative and collisional excitation, we derive the transit distance of the three exocometary gaseous tails to be $0.88 \pm 0.08$, $4.7 \pm 0.3$, and $1.52 \pm 0.15$ au. These values are much larger than previous estimates, which generally placed the transient features within 0.2 au. This reveals that gaseous tails produced by exocomets sublimating close to the
star can expand and migrate over large distances, while still remaining detectable in absorption spectroscopy. Our study provides a new method to measure the transit distance of exocomets, based on excitation modelling, complementing the acceleration method only applicable for high-velocity objects.
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Astrophysics of Galaxies
The importance of super-Eddington black hole accretion for the emergence of massive quiescent galaxies at high redshift
Evgenii Chaikin, Joop Schaye, Filip Huško et al. (+3 more)
Recent JWST observations indicate that massive quiescent
galaxies (
stellar mass $M_{*}\gtrsim 10^{10}~\mathrm{M_\odot}$) at high
redshift ($z\gtrsim 6$) are more abundant than predicted by most existing
galaxy formation simulations and semi-analytic models. Notably, the new COLIBRE simulations have succeeded in reconciling this tension, though the precise reason for their improved agreement with JWST data remains unclear. We demonstrate that the improved agreement is largely due to super-Eddington growth of supermassive black holes (BHs) at high
redshift. We run a series of $(100~\mathrm{cMpc})^{3}$ simulations with the COLIBRE subgrid physics at m7 COLIBRE resolution (gas and dark matter particle masses $m_{\rm gas}\approx m_{\rm dm}\sim 10^7~\mathrm{M_\odot}$), varying the maximum allowed BH
accretion rate in units of the Eddington rate. We show that only the fiducial COLIBRE model, which permits super-Eddington
accretion, is consistent with the JWST constraints at $z \gtrsim 6$. Moreover, we find that in COLIBRE about $50$ per cent of BH mass growth at high
redshift occurs in the super-Eddington regime, even though such events are extremely rare in time. Our work highlights the important role of super-Eddington
accretion in simulations of
galaxy formation for reproducing the observed early emergence of quenching of massive
galaxies.
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All authors Evgenii Chaikin, Joop Schaye, Filip Huško, Cedric G. Lacey, Sylvia Ploeckinger, Matthieu Schaller