Astrophysics of Galaxies
HII-CHI-mistry for active galactic nuclei: optical sulphur abundances without empirical ionisation correction factors
E. Pérez-Montero, O.L. Dors Jr., I.A. Zinchenko et al. (+2 more)
> The determination of sulphur abundances in active galactic
nuclei (AGN) is uncertain because ionisation correction factors (ICFs) are commonly calibrated for HII regions. We extend the HII-CHI-mistry methodology to derive total S/H in AGN from optical emission lines through comparison with photoionisation models. Tests against Seyfert
galaxies with direct-method ionic abundances favour models with alpha_ox=-1.2 and a 98% free-electron stopping criterion. While O/H agrees with previous determinations, HCm yields systematically larger S/H than direct-method analyses using classical ICFs, suggesting that these prescriptions underestimate higher sulphur ionisation stages in AGN. Applied to MaNGA Seyfert and LINER-like regions, the method reveals a common positive S/O-
metallicity relation. Seyferts show slightly larger median S/O than
star-forming regions at high O/H, while LINERs occupy an intermediate position. These differences become weaker when S/H rather than O/H is used as the
metallicity tracer, although Seyferts still tend to populate the upper envelope. Sulphur may therefore provide a robust tracer of gas-phase
metallicity, while the differences between Seyferts and LINERs may reflect differences in their ionisation conditions and ionising SEDs.
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All authors E. Pérez-Montero, O.L. Dors Jr., I.A. Zinchenko, B. Pérez-Díaz, J.M. Vílchez
Cosmology and Nongalactic Astrophysics
An Inverse Lyth Bound for Non-Attractor Inflation
William H. Kinney
I present a novel physics result generated entirely autonomously by ChatGPT 5.6 Sol. The Lyth bound relates an observable primordial tensor amplitude to a lower limit on the field excursion during single-field slow-roll inflation. We show that non-attractor
evolution obeys a complementary upper bound. For a canonically normalized scalar field, the nonconstant superhorizon
curvature mode is anti-damped whenever the second Hubble-flow parameter satisfies $\epsilon_2\equiv d\ln\epsilon/dN<-3$. The same condition requires the inflaton kinetic energy to decrease sufficiently rapidly that the field-space distance traversed during a non-attractor interval obeys $\Delta\phi_{\rm NA} / M_{\text{P}} < \left(2\sqrt{2\epsilon_{\rm in}}/3\right) \left(1-e^{-3\Delta N/2}\right) < \left(2\sqrt{2\epsilon_{\rm in}}/3\right)$.The result is independent of the potential and does not require the slow-roll approximation. If $\epsilon_2=-p<-3$ is constant, the stronger bound $\Delta\phi/M_{\text{P}}<2\sqrt{2\epsilon_{\rm in}}/p$ is saturated asymptotically. In ultra-slow-roll inflation, $p=6$, giving $\Delta\phi<\sqrt{2\epsilon_{\rm in}}M_{\text{P}}/3$. We derive an exact relation between field excursion and amplification of the velocity of the nonconstant
curvature mode, and give the corresponding scalar-power relation in the quasi-de Sitter limit. In contrast with the usual Lyth relation, arbitrarily large non-attractor amplification approaches a finite field distance. This provides a model-independent field-range constraint on canonical single-field mechanisms for amplifying primordial fluctuations.
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Instrumentation and Methods for Astrophysics
RISTRETTO: Assembly and Testing of the Seven-spaxel, High-resolution, Diffraction-limited Spectrograph
Leonie Hoerner, Bruno Chazelas, Nathanaël Restori et al. (+24 more)
The RISTRETTO project aims at the direct detection of the reflected light of extra-solar
planets to measure albedos and detect possible biosignatures, using the high-contrast / high-resolution method. We report on the assembly, lab-testing and on-sky testing of the seven-spaxel high-resolution single-mode spectrograph which was built ahead of the rest of the instrument. The spectrograph is a high resolution echelle spectrograph build for high spectral fidelity being uder
vacuum and thermally controlled. Once the assembly has been completed we had the chance to test it on sky using OHP 1.52 m
telescope using the PAPYRUS AO system for injection in our spectrograph.
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All authors Leonie Hoerner, Bruno Chazelas, Nathanaël Restori, Christophe Lovis, Nicolas Blind, Ludovic Genolet, Ian Hughes, Michael Sordet, Robin Schnell, Anthony Carvalho, Maddalena Bugatti, Adrien Crausaz, Samuel Rihs, Gilles Simond, Isaac Bernardino Dinis, David Ehrenreich, Emeline Bolmont, Christoph Mordasini, Martin Turbet, Angelie Alagao, Vincent Chambouleyron, Mathieu Motte, Arnaud Striffling, Francissco Oyarzun, Benoit Neichel, Jean-François Sauvage, Thierry Fusco
Instrumentation and Methods for Astrophysics
LP-Infinity: overcoming limits to the number of lifetime positions in the COS FUV channel
David J. Sahnow and Christian I. Johnson
Since the
Cosmic Origins Spectrograph (COS) was installed on the Hubble Space
Telescope (HST) in 2009, thousands of spectra have been collected with the Far Ultraviolet (FUV) channel. Due to the gain sag inherent in the cross delay line detector, regular adjustments to the positions of the spectra have been made, with the seventh and eighth becoming available to Guest Observers in October 2025. Recent improvements to models of the FUV channel, including more extensive optical modeling and better prediction and accommodation of detector gain sag, have allowed us to identify previously excluded locations on the detector for future use, thus requiring additional Lifetime Positions (LPs) to be defined. Since the onboard flight software limited the number of Lifetime Positions to eight, we developed a new method for implementing additional LPs to avoid dealing with the complications of reassigning previously used LPs. This novel strategy, dubbed LP-Infinity, allows an effectively unlimited number of LPs that is now constrained only by the available detector real estate, allowing COS to continue obtaining high-quality FUV spectra well into the 2030s. We discuss the conception, development and implementation of LP-Infinity, its initial use in Cycle 33, and the plans for future LPs starting in 2027.
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Astrophysics of Galaxies
Formation of Accretion Disks around Intermediate-Mass Black Holes in Ultra Compact Dwarf Galaxies and Nuclear Stellar Clusters
Sebastian Darr and Kenji Bekki
Recent observations have found many ultra-compact dwarf
galaxies (UCDs) that contain massive black holes (MBHs) typically consisting of $10\%-15\%$ of their total mass, with some as high as $40\%$. However, whether UCDs initially started with MBHs or grew from intermediate-mass black holes (IMBHs) is unclear. We propose a mechanism in which AGB
stars have their gas ejected which forms an
accretion disk around an IMBH to fuel BH growth. We used smooth particle hydrodynamical simulations to (i) model the creation and
evolution of gas disks that can finally evolve into
accretion disks and to investigate (ii) how the properties of the gas disk depend on the model. We find that the amount of mass in the disk increases more with UCD mass than with IMBH mass. For lower-mass IMBHs of $100 \text{ M}_\odot$, a majority of the gas mass present can be trapped in a disk, leading to the idea that lower-mass BHs can utilise the proposed mechanism. The main mechanism working against
accretion disk formation is the creation of new
stars within the disk, not just through the removal of gas but through gravitational disruption as well. Finally, an estimation of the total BH growth provides a list of observed UCDs which could have formed MBHs using the proposed mechanism which can be useful for verifying the proposed mechanism. Future simulations aimed at modelling the formation of such UCDs can be employed to provide a full picture of the results presented in this paper.
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Cosmology and Nongalactic Astrophysics
Filaments within filaments: unraveling the hierarchy of the cosmic web
Saee Dhawalikar, Aseem Paranjape and Shadab Alam
Cosmic filaments are the most striking feature of the hierarchical
cosmic web. Yet, their own sub-structure remains unexplored, unlike the well-known, universal
halo/sub-
halo hierarchy. We use a hierarchical reconstruction scheme to identify sub-filaments within larger filaments. Examining differences in the radial phase-space profiles of parent and sub-filaments, we argue that the latter constitute a statistically distinct class of structures. Establishing the existence of a universal filament hierarchy must then account for these differences, with implications for cosmology and dark matter.
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Cosmology and Nongalactic Astrophysics
Constraining primordial non-Gaussianity and energy injection with the thermal Sunyaev-Zeldovich effect and integrated Sachs-Wolfe effect cross-correlation
Ayodeji Ibitoye, Yin-Zhe Ma and Prabhakar Tiwari
Constraining primordial non-Gaussianity (PNG) provides key insights into the physics of
cosmic inflation and the initial conditions of the Universe, which remain central topics in cosmology. In this study, we use the cross-correlation between the integrated Sachs-Wolfe (ISW) effect and the thermal Sunyaev-Zeldovich (tSZ) effect derived from Ibitoye et al. (2024) to jointly constrain PNG and early-Universe energy injection, including the standard intergalactic medium contribution. For scale-independent PNG we obtain $f_{\rm NL} = -358^{+140}_{-114}$ ($68\%$~C.L.). For a scale-dependent model ($f_{\rm NL}=f_{\rm NL}^{0}(\ell/\ell_{0})^{n_{\rm NL}}$, with $\ell_{0}=200$), we find $f^{0}_{\rm NL} = -296^{+173}_{-157}$ and $n_{\rm NL} = 0.62^{+1.02}_{-0.64}$, both consistent with Gaussian initial conditions. We also constrain the early-Universe energy injection amplitude to be $\alpha_{\rm inj} = -3.93^{+1.34}_{-0.99}$, with uncertainty reduced by a factor of $\sim\!2.6$ if Planck 2018 $f_{\rm NL}$ constraint is applied as a prior. Future surveys such as Simons Observatory and Euclid will tighten these constraints further. Complementary to conventional probes, this work provides the first ISW-tSZ constraint on exotic energy injection and enables precision tests of early-Universe physics while probing late-time gravitational potential and thermal energy perturbations.
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Earth and Planetary Astrophysics
STXM-XANES and TEM analysis of UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs)
B. Guérin, C. Engrand, C. Le Guillou et al. (+7 more)
The Concordia micrometeorite collection contains UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs) of probable cometary origin. Eight FIB sections of UCAMMs were studied by Scanning Transmission X-ray Microscopy - X-ray Absorption Near Edge Structure and (Scanning)Transmission Electronic Microscopy. Three different phases of organic matter (OM) exist in UCAMMs and small mineral aggregates are distributed in the OM. Two OMs share spectral features with those of insoluble organic matter (IOM) of carbonaceous chondrites and of cometary grains returned by the Stardust mission. The third OM is N-rich (N/C at. ratios up to 0.22) and has only a few equivalents in extraterrestrial OM analyzed so far, such as in cometary particles collected during the Stardust mission, Interplanetary Dust Particles (IDPs) and UCAMMs collected near the Dome Fuji Station. This N-rich OM could have formed by irradiation of N-rich ices in the outer regions of the protoplanetary disk. UCAMMs contain variable amounts of minerals, consisting of crystalline Mg-rich silicates, Fe(Ni) sulfides and Fe oxides, which can be cemented in a Si-rich groundmass. Hypocrystalline mineral assemblages are also observed. Glassy phases showing morphological resemblance to GEMS are also found in some UCAMMs. This mineralogy is mainly consistent with that of previous UCAMM analyses, and is close to what is observed in Chondritic Porous IDPs, which are also considered as cometary dust particles. A mineral exhibiting a phyllosilicate texture has been observed in this work, and raises the question of the possibility of aqueous alteration on comets. Overall, UCAMMs' mineralogical and organic characterization implies a complex formation history of UCAMMs, and the presence of large-scale radial mixing in the early solar system, to transport their mineral components to the outer parts of the protoplanetary disk.
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All authors B. Guérin, C. Engrand, C. Le Guillou, H. Leroux, E. Dartois, J. Duprat, S. Bernard, K. Benzerara, L. Delauche, D. Troadec
High Energy Astrophysical Phenomena
Dynamics and Spectra-Polarimetric Signatures of GRMHD Simulations with Multiple Magnetic Loops
Raoul Kinadeter, Christian M. Fromm, Yosuke Mizuno et al. (+3 more)
Relativistic jets are a common outcome of
accretion onto black holes, yet their presence and variability depend strongly on the
magnetic and dynamical state of the
accretion flow. While some systems, such as Blazars and
Quasars, launch powerful persistent jets, others, including the Galactic Centre black hole Sgr~A$^\star$, show only weak or transient outflows. The physical conditions leading to the onset or suppression of jet activity remain poorly understood. We investigate the
accretion flow conditions that produce transient jets or inhibit jet formation, aiming to improve our understanding of black holes that accrete without strong, steady outflows. We further predict observational signatures in total and polarized emission for comparison with recent observations of Sgr~A$^\star$ in the quiescent state from the
radio to the $\gamma$-ray regime. We perform three-dimensional GRMHD simulations of an accreting black hole surrounded by a
torus threaded by a poloidal multi-loop
magnetic field of alternating polarities. We follow the
evolution of the
accretion rate,
magnetic flux, and jet power, and analyze angular momentum transport. In addition, radiative transfer calculations including Compton scattering are used to derive synthetic total and polarized emission. The simulations show strong variability in jet power while the initial
magnetic polarity loops accrete, followed by weaker activity at later times as the system approaches a semi-MAD state. The emission from the disk is relatively stable, weakly polarized and consistent with the quiet state values reported for SgrA$^\star$. The resulting jet emission is strongly suppressed, depolarized by Faraday rotation and conversion in the surrounding cold
plasma. Upscattering calculations yield near-infrared (NIR) high energy light curves that respect observational constraints of the quiescent NIR and X-ray fluxes in SgrA$^\star$
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All authors Raoul Kinadeter, Christian M. Fromm, Yosuke Mizuno, Antonios Nathanail, Matthias Kadler, Karl Mannheim
Solar and Stellar Astrophysics
Can circumbinary discs produce the eccentricities of shell-burning stripped giant binaries?
C. A. S. Moltzer, O. R. Pols and H. Van Winckel
Post-RGB and post-AGB binaries, collectively shell-burning stripped giant (SBSG) binaries, contain a primary
star recently stripped of its envelope, alongside a main-sequence companion. These systems are characterised by a stable circumbinary disc (CBD), thought to have formed from envelope material stripped via mass transfer. Their eccentricities range between $0-0.63$, contradicting canonical binary
evolution that predicts such post-mass-transfer systems should have circularised. We investigate whether CBD-binary interaction can explain the observed eccentricities of SBSG binaries using a new formalism based on hydrodynamic simulations. To compare with observations, we generated model populations for which post-mass-transfer eccentricity and amount of mass accreted from the CBD were free parameters. We found that CBD-binary interaction can reproduce the observed eccentricity distribution of SBSG binaries, provided that: (1) their post-mass-transfer eccentricities range up to at least 0.05, (2) their CBDs have initial masses of at least $0.1$ $M_\odot$, and (3)
accretion onto the SBSG
star is highly inefficient to prevent refilling of its Roche lobe. Our model requires higher post-mass-transfer eccentricities than canonically predicted and more massive CBDs than currently observed. We speculate that there is a population of post-mass-transfer progenitor systems with CBDs massive enough to facilitate significant eccentricity pumping. Mass loss via the $L_2$ point during mass transfer needs investigation, as this could form the CBD and shorten the orbital period, necessary for many SBSG binaries assuming they formed stably. We hypothesise that the observed eccentricities are related to the amount of mass lost via $L_2$. Since many other post-interaction systems exhibit similar orbital properties, we speculate that they may all have interacted with CBDs shortly after mass transfer.
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High Energy Astrophysical Phenomena
The properties of the first continuous gravitational waves: Optimizing pulsar timing observations for supermassive black hole binary detection
Blaze Houlden, Eric Thrane and Katie Auchettl
Several
pulsar timing arrays have reported evidence for a nanohertz gravitational-wave background. This background is thought to arise from the superposition of signals from a population of inspiraling supermassive black hole binaries. A key test of this interpretation is the search for individually resolvable binaries whose signals emerge above this background. Here we investigate this possibility by addressing two related questions: (1) what are the most probable properties of the first resolvable binary; and (2) how can
pulsar timing observations be optimized to maximize its prospects for electromagnetic identification? By simulating populations of supermassive black hole binaries constrained by evidence for the gravitational-wave background and studying the loudest binary in each simulation, we infer the expected properties of the first individually resolvable systems. If MeerKAT continues its current observing strategy for a total of 9 years, the probability of detecting an individual binary is $\approx10-27\%$. Improving the timing precision by a factor of two changes this probability to $\approx11-28\%$, whereas increasing the cadence by a factor of four gives $\approx12-30\%$. Combining both improvements yields a detection probability of $\approx12-33\%$. Furthermore, implementing a high-cadence observing campaign preferentially resolves higher-frequency systems ($\gtrsim\unit[10]{nHz}$), whose shorter orbital periods make them considerably easier to identify through electromagnetic observations than lower-frequency binaries that repeat infrequently. We discuss prospects of electromagnetic follow-up of gravitational-wave resolved binaries with current high-cadence all-sky optical surveys.
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Astrophysics of Galaxies
Evidence for the transformation from lenticular to spiral galaxies
Mengkui Zhou, Huiyuan Wang, Ran Li et al. (+8 more)
It is widely accepted that late-type
galaxies, such as spirals, evolve into early-type systems, including elliptical and lenticular
galaxies, through
galaxy mergers and violent disk instability processes. Throughout this morphological transformation,
star formation is typically suppressed by quenching mechanisms whose detailed nature remains the subject of active investigation. Here, we present compelling evidence for an evolutionary pathway that proceeds in the reverse direction. Using the integral field unit observations, we identify a population of spiral
galaxies hosting quenched central cores (QCCs). These
galaxies exhibit bimodal distributions in both their stellar population properties and their dynamical properties, along with sharp changes in radial gradients near the QCC boundary. These results indicate that the QCCs and the surrounding outer disks formed at distinct
cosmic epochs and through different physical processes. Remarkably, QCCs closely resemble quiescent early-type
galaxies, particularly lenticular
galaxies, in their mass-size and mass-velocity dispersion scaling relations, as well as in their stellar population demographics and internal kinematics. These findings provide strong support for a rejuvenation scenario in which spiral disks are reassembled around pre-existing quiescent lenticular or early-type systems. Moreover, we show that such rejuvenation, accompanied by a reverse morphological transformation from early- to late-type appearance, is quite common. This indicates that quenching in
galaxies is not invariably a terminal state and can be reversed under appropriate conditions.
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All authors Mengkui Zhou, Huiyuan Wang, Ran Li, Yangyao Chen, Hui Hong, Houjun Mo, Yu Rong, Enci Wang, Huiling liu, Zhicheng He, Ziwen Zhang
Astrophysics of Galaxies
Stellar mass growth in COSMOS-Web: a mass-complete main sequence to z ~ 8 and its consistency with GSMF evolution
M. P. Koprowski, K. Lisiecki, P. Sawant et al. (+1 more)
The
star-forming main sequence (MS) links the instantaneous
star-formation rate of
galaxies to their stellar-mass growth and therefore to the
evolution of the
galaxy stellar mass function (GSMF). We determine a mass-complete MS in COSMOS-Web out to z=8 and test whether its mass and
redshift dependence is consistent with the observed
evolution of the GSMF. We stacked 251,462
star-forming
galaxies in Herschel and JCMT maps and corrected the far-infrared fluxes for blending using forward-modeled maps. We combined the resulting infrared luminosities with the unobscured ultraviolet emission to derive total
star-formation rates and fitted a
redshift-dependent MS. We independently measured the quiescent fraction and evolved the observed z=8 COSMOS-Web GSMF forward within a continuity-equation framework including stellar-mass return, suppression of in-situ growth by the quiescent fraction, and mergers. The MS is well described by a power law at low masses with a
redshift-dependent turnover toward high masses. We measure a low-mass slope of gamma=1.215+/-0.028, implying a mildly increasing specific
star-formation rate with stellar mass. The GSMF evolved using this relation follows the observed progressive flattening of the low-mass end substantially better than the literature MS prescriptions considered here. Mergers change the low-mass number densities by <=0.2 dex by z~0.65 and have little effect on the slope. Small differences in MS normalization also accumulate strongly, producing large differences in the evolved GSMF after several Gyr. The observed GSMF
evolution provides an independent integral test of the MS. Our results favor a mildly super-linear low-mass MS and show that both its slope and normalization must be measured accurately to reproduce the buildup of the
galaxy stellar-mass distribution.
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All authors M. P. Koprowski, K. Lisiecki, P. Sawant, J. V. Wijesekera
Cosmology and Nongalactic Astrophysics
Distinguishing cold and self-interacting dark matter through topological analysis
Adrian Szpilfidel, Clotilde Laigle, Pierre Boldrini et al. (+2 more)
Alternative dark matter (DM) models have emerged to solve the challenges faced by the predictions of collisionless cold dark matter (CDM) on galactic scales ($\lesssim 1$ Mpc). However, disentangling alternative models from CDM is difficult on such small scales because of the degeneracy with baryonic physics. It is therefore necessary to use DM probes that are not affected by baryons, e.g. that stand on intermediate scales, larger than galactic while remaining smaller than the scale at which the models converge to CDM. For the first time, we distinguish self-interacting DM (SIDM) from CDM using the genus statistic, a metric that characterises the
topology of the density field. We carried out the analysis on the Darkium DM-only cosmological simulations, using one CDM model and four SIDM models with cross-sections of various amplitudes and velocity dependencies. We computed the genus on selected 3-virial radius wide regions centred around
halos, for few hundred
halos with masses ranging from $10^{12}$ to $10^{14}$ M$_\odot/h$ over
redshifts $z=0$ to $z=2$. We also explored a more observation-like configuration, where the DM density field is traced only from the
halo distribution in thick 2D projection since in principle
redshift errors hinder a 3D reconstruction of the density field. We find that the density field is systematically clumpier in CDM than in SIDM models up to $0.05~\mathrm{Mpc}/h$, for
halos of masses larger than $10^{12}$ M$_\odot/h$ at $z=0$. These predictions show that the genus of the density field is sensitive to DM self-interactions, suggesting that topological analysis could provide a valuable probe for distinguishing SIDM from CDM in observed
halo distributions.
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All authors Adrian Szpilfidel, Clotilde Laigle, Pierre Boldrini, Moritz S. Fischer, Dmitri Pogosyan
High Energy Astrophysical Phenomena
Ultraluminous X-ray sources in the first eROSITA survey I. Candidate catalogs
P. Weber, T. P. Roberts, S. Hämmerich et al. (+28 more)
Ultraluminous X-ray sources (ULXs) are luminous non-nuclear X-ray point sources embedded in
galaxies. Their luminosities exceeding 10^39 erg/s potentially require sub-Eddington
accretion by objects with masses from ~10^2$M_{\odot}$ to ~10^4$M_{\odot}$ or supercritical
accretion beyond the Eddington limit by stellar mass black holes or
neutron stars. We identified ULXs by searching for X-ray counterparts in the ~10^5
galaxies of the HECATE catalog in the footprint of the first eROSITA all-sky survey, while excluding nuclear regions to avoid the selection of active galactic
nuclei (AGN). We characterized the completeness of the sample and its contamination by unidentified AGN and determined the influence of source confusion. The catalog is unaffected by X-ray selection biases. We removed known contaminants such as
supernovae,
stars, and AGN, and manually vetted all candidates to further remove contaminants. We derived the X-ray selection function and fraction of unidentified AGN interlopers using a simulation with subsequent source detection. We present two samples of ULX candidates. The main sample consists of 90 sources with highly confident X-ray detections, 53 of which are identified for the first time. This sample is complete to a distance of ~7Mpc, contains at most 29% of unknown background AGN, and is mostly unaffected by source confusion. Several candidates are newly identified even though their locations have been observed by other instruments before, and some previously reported candidates we expected to identify are absent from our sample, demonstrating the transient behavior of ULXs. Based on our list of less confident detections, we also provide an extended catalog of 260 sources identified as potential candidates for further ULX identifications. Of these, 245 are identified as potential candidates for the first time. (Abridged)
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All authors P. Weber, T. P. Roberts, S. Hämmerich, E. Kyritsis, A. Zezas, M. G. F. Mayer, A. Zainab, I. Kreykenbohm, A. Merloni, M. Sasaki, A. Schwope, M. Middleton, A. Basu-Zych, A. Hornschemeier, N. Vulic, M. Salvato, N. Webb, H. Tranin, N. Schettino, C. Kirsch, S. Saeedi, F. Zangrandi, M. Lorenz, L. Dauner, T. Dauser, F. Haberl, C. Maitra, Z. Igo, A. Santangelo, L. Ducci, J. Wilms
Astrophysics of Galaxies
Revealing Galactic dust beneath the cosmic infrared background anisotropies with Wavelet Phase Harmonics
Srijita Sinha, Tuhin Ghosh, Erwan Allys et al. (+2 more)
Separating Galactic dust emission from
cosmic infrared background (CIB) anisotropies is challenging because both the emission components have similar spectral properties. The primary objective of this work is to develop a component-separation
algorithm to extract the Galactic dust emission from CIB anisotropies dominated sky regions using Wavelet Phase Harmonics statistics (WPH). We apply our
algorithm to the Planck $353\,\mathrm{GHz}$ frequency band over three sky regions spanning a range of neutral hydrogen ($\text{HI}$) column densities at high Galactic latitudes. In all three regions, we successfully recover the dust signal without significant leakage between the dust and CIB anisotropy components. We use the low signal-to-noise ($\mathrm{S/N}$) region to validate the component-separation
algorithm and compare its performance with the standard template-fit approach that uses the linear dust-$\text{HI}$ correlation relation. For intermediate and high $\mathrm{S/N}$ regions, we separate the dust signal map from the contamination while preserving the statistical correlation with $\text{HI}$ column density map. Dust maps are used to analyze the relationship between dust and $\text{HI}$ emissions. We characterize the spatial variations in dust emission relative to the hydrogen column density as a function of the angular scale.
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All authors Srijita Sinha, Tuhin Ghosh, Erwan Allys, François Boulanger, Jean-Marc Delouis
Astrophysics of Galaxies
The Nobeyama 45 m Survey of Shocked Molecular Gas in the Central Molecular Zone. I. Survey Data, Cloud Catalog, and SiO Line-Ratio Trends
Shunya Takekawa, Shiho Tsujimoto, Tomoharu Oka et al. (+1 more)
We present large-scale molecular line maps of the Central Molecular Zone (CMZ) in our
Galaxy obtained with the Nobeyama
Radio Observatory 45 m
telescope. The observations cover a 3.5 deg x 0.5 deg region with 20 arcsec resolution in eight molecular lines including SiO J=2-1, CS J=2-1, H13CN J=1-0, and HCN J=1-0. We release the calibrated data cubes and a catalog of SiO-emitting clouds identified by the SCIMES
algorithm. For each cloud, we provide cloud-integrated intensities of the observed lines and derive an H13CN-based molecular gas mass and a cloud-averaged H2 number density. We compare SiO intensity ratios with the density, dynamical time, and their product n_H2 t_dyn. We find that SiO intensity ratios relative to six other molecular lines all decrease systematically with increasing n_H2 t_dyn. The tightest correlations are found for SiO/H13CN (r_s = -0.82) and SiO/CS (r_s = -0.70). The released data cubes and cloud catalog enable systematic studies of SiO enhancement, shock chemistry, and gas dynamical
evolution across the CMZ.
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All authors Shunya Takekawa, Shiho Tsujimoto, Tomoharu Oka, Rei Enokiya
High Energy Astrophysical Phenomena
Weak gravitational lensing by a dark-matter-admixed neutron star: a self-consistent two-fluid halo and the Gauss–Bonnet deflection angle
Yashmitha Kumaran and Ilídio Lopes
We compute the weak gravitational deflection of light by a
neutron star that carries a self-consistent dark-matter component, in the regime in which the dark matter forms an "extended
halo" reaching beyond the baryonic surface. Two observations motivate this configuration. First, a dark-matter core confined within the baryonic radius leaves no distinctive
lensing signature, since by Birkhoff's
theorem the exterior is Schwarzschild with the total mass, so a ray passing outside the
star feels only that mass and the compactness it implies. Second, the signature we seek resides in the complementary case, in which the ray genuinely traverses the
halo, so that the surrounding density enters the optical geometry directly. We model the
star by integrating the coupled two-fluid Tolman–Oppenheimer–Volkoff equations, with the baryonic and dark components interacting solely through
gravity, and we obtain the deflection angle from the resulting external profile through the Gibbons–Werner construction of the Gauss–Bonnet
theorem. The defining feature of the approach is that the deflection is tied to a "self-consistent" two-fluid profile rather than to a medium inserted by hand. We show that, for impact parameters smaller than the
halo radius, the deflection departs measurably from the point-mass prediction, the deficit being governed by the dark-matter fraction and the
halo extent, and we argue that the "shape" of this deficit furnishes a
geometric,
lensing-based handle on the degeneracy between dark matter and the nuclear equation of state. The framework thereby unites the structural modelling of compact
stars with their gravitational-
lensing phenomenology.
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Astrophysics of Galaxies
Energetics of AGN Feedback
Ross J. Turner, Andrew Sullivan and William R. Q. Gaffney
Integrating realistic active galactic
nucleus (AGN) feedback into cosmological hydrodynamical simulations remains a major challenge as resolving the spatial coupling of jet energy over
cosmic timescales is computationally prohibitive. We present an analytic framework that predicts the radial and polar-angle dependence of feedback energy from lobed AGNs, enabling a physically motivated, computationally efficient prescription for jet feedback. Built upon the
Radio AGN in Semi-analytic Environments (RAiSE) dynamical model, our approach tracks the post-AGN jet phase
evolution of
radio sources through two distinct mechanisms: buoyantly rising bubbles subject to ablation, and the gravitational collapse of swept-up gas in the shocked shell. We find that these two feedback mechanisms produce strongly contrasting spatial distributions across ten representative cluster environments. Buoyant bubbles preferentially deposit energy in steep density gradients near the core radius, while the collapsing shocked gas shell drives heating within flatter cluster cores. Weak, short-lived AGN outbursts ($Q<10^{37}$ W and $t_{\rm on}<10$ Myr) confine their energy deposition to the inner 10 kpc of the cluster; longer-lived events ($t_{\rm on} \geqslant 100$ Myr) deposit less than 1% of their injected energy within 30 kpc. We find that time-averaged heating rates across multiple outbursts are sufficient to offset radiative cooling in all but the highest density cluster cores (within 100 kpc) for duty cycles of $0.08< \delta \leqslant 1$. This framework provides a scalable basis for modelling anisotropic, physically motivated jet feedback that can be incorporated into next-generation cosmological simulations.
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Solar and Stellar Astrophysics
Sequential Magnetic Reconnections in a Fishbone-like Structure Leading to Recurrent Brightenings
Bo Yang, Jiayan Yang, Junchao Hong et al. (+1 more)
The fine-scale release of
magnetic free energy in the solar atmosphere is a fundamental open question in solar physics. Multi-wavelength observations at high spatiotemporal resolution now offer a direct window into this process. Using data from NVST, SDO, IRIS, and Hinode, we reveal the energy release process in a fishbone-like
magnetic structure within active region 12297. The fishbone-like structure consists of a spine along a narrow, elongated positive-polarity field, with herringbone branches rooted in negative-polarity sunspots. Persistent photospheric
magnetic flux emergence and shearing motions are observed beneath the fishbone-like structure, which may play a key role in maintaining its
topology and producing the recurrent brightenings. During brightenings, compact bright features propagate sequentially from west to east along the spine, accompanied by bidirectional flows along the branches and
plasma blobs ejected toward the distant positive sunspot. These propagating features could be interpreted as signatures of sequential
magnetic reconnection events occurring in chronological order at nodes along the spine, predominantly in the chromosphere and transition region. Our observations may provide evidence that recurrent brightenings could arise from repeated sequential reconnection events organized by a coherent
magnetic structure, deepening our understanding of how such recurrent brightenings are generated and how
magnetic free energy is dissipated at fine scales in solar active regions.
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All authors Bo Yang, Jiayan Yang, Junchao Hong, Yi Bi
High Energy Astrophysical Phenomena
Energy Partition in AGN-driven Bubbles of NGC 4438: From Nuclear Bubbles to a Galaxy-scale Outflow
Luan Luan, Jiang-Tao Li, Jianghui Xu et al. (+4 more)
Jets launched by accreting supermassive black holes represent a major mode of active galactic
nucleus (AGN) feedback. However, how their energy is divided among bulk kinetic motion, thermal gas,
magnetic fields,
cosmic rays (CRs), and radiation - and how this distribution changes with spatial scale - remains poorly constrained. NGC 4438 provides a unique laboratory for probing this
evolution, hosting two 200-pc-scale nuclear bubbles and a lopsided ~10 kpc
galaxy-scale outflow plausibly associated with the same AGN. We present a multi-wavelength analysis to investigate the morphology, radiation mechanisms, and energetics of these structures. Joint
radio-X-ray modeling shows that the non-thermal emission in the nuclear bubbles may require two distinct populations of
cosmic-ray electrons, suggesting that in addition to shock acceleration at the bubble rim, the highest-energy particles may be linked to acceleration processes closer to the unresolved central engine. A spatially resolved energy inventory reveals that bulk kinetic energy dominates the current energy budget of the nuclear bubbles, while roughly half of the injected energy has already been transformed into thermal, CR, and
magnetic energy, as well as radiative losses. Across all bubble sizes, the thermal and
magnetic pressures are consistent within the uncertainties, implying that
magnetic fields remain dynamically significant on all examined spatial scales. Furthermore, the empirical correlation between
radio luminosity and jet power, established for kiloparsec-scale jet bubbles (MerloniHeinz2007), matches the energetics of the
galaxy-scale outflow but substantially overestimates the power of the 200-pc-scale nuclear bubbles, underscoring the scale dependence of jet energy dissipation.
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All authors Luan Luan, Jiang-Tao Li, Jianghui Xu, Yang Yang, Guilin Liu, Fulai Guo, Q. Daniel Wang
Solar and Stellar Astrophysics
Triple-induced mergers of black hole binaries: A comprehensive look at the role of stellar evolution, dynamical stability, and spin evolution
C. W. Bruenech, S. Toonen, T. Boekholt et al. (+1 more)
Mergers of black holes (BHs) have been shown to be a ubiquitous phenomenon in the Universe. However, uncertainties remain in our theoretical understanding of the
evolution of the BHs prior to their merger. Black hole progenitors are seemingly born primarily in triples or higher-order multiples, and the presence of a tertiary object can perturb a black hole binary (BHB) enough to precipitate a merger. We used population synthesis coupled with orbit-averaged descriptions of triple dynamics to evolve a population of triples with initially wide orbits and massive progenitors. Wide orbits were chosen to avoid stellar interaction prior to BH formation. Systems that remain bound and form an inner BHB were evolved using a direct n-body code with post-Newtonian terms up to an order of 2.5. We also simulated the precession of the BH
spin vectors by coupling the n-body solver with the differential equations for the
spins. For the dynamically stable triples with inner BHBs, mergers occur with an estimated rate density of $\sim 5$ Gpc$^{-3}$ yr$^{-1}$. Mergers also occur in triples that become dynamically unstable at a rate of $\sim 1.4$ Gpc$^{-3}$ yr$^{-1}$. At the point of entering the 10 Hz gravitational wave frequency band, the merging inner binaries exhibit eccentricities between $10^{-4}$ and $10^{-2}$. The final effective
spin of a BHB that merges through this channel can display a wide range of values between $-1$ and $1$, with a slight tendency towards $\chi_\text{eff} \approx 0$. This is a result of the strong three-body dynamics experienced by the merging triples before the inner binary begins to shrink due to GW emission. The inner angular momentum can explore the full phase space before the binary rapidly shrinks and decouples from the tertiary, effectively freezing out the effective
spin to its value at the time of the highest inner eccentricity.
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All authors C. W. Bruenech, S. Toonen, T. Boekholt, A. Dorozsmai
Solar and Stellar Astrophysics
BV photometry of the cataclysmic variable LY UMa
L. Dankova, D. Marchev, S. Peneva et al. (+1 more)
We performed B- and V-band photometry of the probable dwarf nova LY UMa. We find that it has apparent magnitude V=15.26+/-0.03 on 2024-04-14, V=15.43+/-0.02 on 2025-04-28, and V = 15.57+/-0.02 on 2025-06-02. Using the GAIA distance d=310pc, we find that the lower values correspond to absolute V band magnitude M_V=7.94-8.10 and indicate that the mass donor of LY UMa is a K7-K8V
star with M_V=8.0-8.5. Our B-band measurements show slightly bluer B-V index of LY UMa than that of its donor, consistent with its nature as a cataclysmic variable. Close to LY UMa is the Active
Galaxy Nucleus Mrk 153, for which we estimate V=14.81+/-0.03.
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All authors L. Dankova, D. Marchev, S. Peneva, R. Zamanov
High Energy Astrophysical Phenomena
A Population Study for Searching Supermassive Binary Black Holes in Active Galactic Nuclei: Continuum Spectral Features and Periodic Variabilities
Zekun Li, Changshuo Yan and Youjun Lu
Active sub-pc supermassive binary black holes (SMBBHs) are expected to exhibit various electromagnetic signatures due to unique dynamical and
geometric structures of their
accretion, but observational identification of them remains challenging. In this paper, we adopt semianalytic models to investigate both deficits in spectral-energy-distributions (SEDs) of these systems induced by gaps/holes in their
accretion disks and periodic variations in their light curves induced by either orbital-modulated Doppler boosting or
accretion rate variation of each SMBH component. We construct a population model to generate SMBBHs across
cosmic time by considering their orbital
evolution and associated
accretion and radiation processes. By estimating the continuum emission from each mock system and its variation, we investigate the detection of SMBBHs via either SED-deficit signature or light curve periodicity under reasonably given criteria. We find that all-sky surveys with filters similar to those of the China Space Station
Telescope or Rubin/LSST could identify up to approximately $3\times 10^2$ SMBBHs via SED-deficit features and/or $10^3$ SMBBHs via periodicity ($\lesssim5$\,yr), although both selections may suffer from a high rate of false positives. A few to a dozen SED-deficit SMBBHs may be detected by future
pulsar timing arrays with signal-to-noise ratio $\gtrsim3$, enabling multi-messenger observations. Only $\sim20\%-53\%$ of SED-deficit selected SMBBHs may also be detected via periodic variations, and $\sim7\%-9\%$ of periodic variation selected SMBBHs may be detected via SED-deficit signatures. The false positives for those SMBBHs selected jointly by both methods are negligible, highlighting the importance of searching for active SMBBH systems using joint methods.
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High Energy Astrophysical Phenomena
Energy-dependent extension of the Crab Nebula as a diagnostic of ultrahigh-energy hadronic emission
Fang-Wu Lu, Bo-Tao Zhu, Ji-Yang Ren et al. (+1 more)
The energy-dependent apparent extension of the Crab Nebula, inconsistent with leptonic expectations between X-ray and TeV bands, can be naturally accounted for in a spatially resolved lepto-hadronic scenario. A transition to hadronic dominance occurs above $\sim400~\rm{TeV}$, with nearly pure hadronic emission at PeV energies. The predicted $68\%$ containment radius at $1.1~\rm{PeV}$ is $\sim1.4'$, about six times larger than in purely leptonic scenarios. This energy-dependent extension therefore provides an observable discriminator of the origin of ultra-high-energy gamma-ray emission in
pulsar wind nebulae, offering a diagnostic of PeV hadronic acceleration in the Crab Nebula.
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All authors Fang-Wu Lu, Bo-Tao Zhu, Ji-Yang Ren, Li Zhang
Astrophysics of Galaxies
Infrared photoprocessing of porous amorphous solid water with a free electron laser
J.G.M. Schrauwen, S. Ioppolo, L. Slumstrup et al. (+3 more)
Water ice is the most abundant ice in the interstellar medium (ISM). Previous studies on porous amorphous solid water (pASW) have shown that the infrared radiation field in the ISM modeled with infrared free electron
laser (FEL) irradiation can result in changes in the ice towards a more ordered structure, characterized by a change in the OH-stretching vibration band. This paper aims to study the restructuring in more detail by varying the irradiation intensity and irradiation time for irradiations on-resonance with the OH-stretching, bending and libration modes. In addition, desorption of H2O is monitored during the irradiations. The research presented in this paper considers 42 infrared FEL irradiations on pASW samples deposited at two different rates, using the infrared FELs of the HFML-FELIX laboratory. Restructuring is studied using reflection absorption infrared (RAIR) spectroscopy, with a mass spectrometer monitoring the desorption of H2O in an ultra-high
vacuum system. Desorption and restructuring occur in parallel, with the strongest effects observed for irradiation on-resonance with the OH-stretching vibration. Both processes exhibit two distinct regimes: an initial strong restructuring and desorption, characterized by an exponential decrease in the intensity of the desorption peaks within the first 5 s of irradiation, followed by a second regime of less efficient, yet continued restructuring and constant desorption in an extended area, involving energy dissipation through the hydrogen-bonding network. The trends in restructuring and desorption, depending on the absorbed energy during irradiation, are significantly different, suggesting separate processes. The astrophysical relevance of in particular the second regime of constant desorption and restructuring is discussed.
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All authors J.G.M. Schrauwen, S. Ioppolo, L. Slumstrup, J. D. Thrower, B. Redlich, H.M. Cuppen
Earth and Planetary Astrophysics
A calibrated dust-trail model of the Leonid meteoroid stream and forecasts of the 2031-2035 encounters
Shinsuke Abe
We combine N-body dust-trail generation with a fast nodal-encounter forecast and apply the model to the Leonid returns of 2031-2035. The dominant error is neither the ejection physics nor the encounter machinery but the parent trajectory at the moment of ejection: a back-integration of 55P/Tempel-Tuttle places the pre-1700 ejection sites more than 1 au from the fitted apparition solutions. We therefore anchor the ejection sites, not the dust, to the JPL Horizons ephemeris. Anchoring removes an age-proportional bias in the modelled nodes and, for the first time in this model, reproduces the classical attribution of the 2001 and 2002 storms to the 1767 trail, with peak times accurate to 1 and 40 min. A second systematic is not a property of the parent: a forecast read from a stored
dataset holds each node where the snapshot left it, while the real node moves a median 1.2e-2 au in 0.12 revolutions. Two frozen snapshots of the same trail disagree by as much, so each year uses its own epoch-matched
dataset. A completeness audit – every encounter the model predicts, not only the nominated ones – over-predicts the 1932 trail eighteenfold. We predict two comparable maxima on 2034 November 18, zenithal hourly rate ~1.4e3 at 03:30 UT from the 1932 trail and ~1.2e3 at 23:45 UT from the 1733 trail, with ~1.4e3 in 2033 and ~650 in 2035. Which dominates is a direct observational test of the trail-density term.
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Earth and Planetary Astrophysics
Assessing the Climate and Habitability of Tidally Locked Rocky Exoplanets
Erica Bisesi, Giuseppe Murante, Jost von Hardenberg et al. (+5 more)
Tidally locked
exoplanets orbiting M dwarf
stars are
prime targets in the search for habitable worlds, yet their complex
climate dynamics challenge conventional models of habitability. We homogeneously estimated the
liquid-water habitability of
exoplanets with the highest up-to-date Earth-similarity index. We modified the
climate model PLASIM to apply it to tidally locked
exoplanets across a range of parameters. We systematically classified and compared potentially habitable
exoplanets and selected among the ones featuring the highest Earth-similarity index in the conservative sample of the Habitable Wolds Catalog, both relative to each other and as a function of atmospheric pressure. Our analysis revealed three main
climate regimes: Snowball, Hot, and Eyeball
planets-the latter having a warm and habitable substellar region with T > 273 K and a localized hydrological cycle. Although surface temperature generally increases with pressure, Eyeball
planet climates remain stable in a wide pressure range. Complex atmospheric dynamics govern the behavior of the
climate, highlighting the need for detailed
climate simulations to guide future observations.
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All authors Erica Bisesi, Giuseppe Murante, Jost von Hardenberg, José A. Caballero, Michele Maris, Daniela Billi, Nicoletta La Rocca, Laura Silva
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Impact of Nuclear Level Density on $r$-Process Rare-Earth Peak Nucleosynthesis
Hang Xu, Peng-Xiang Du, Jian Li et al. (+1 more)
The rare-earth peak ($A\sim164$) is a prominent feature of the $r$-process, and previous theoretical studies suggest that it is possibly linked to local nuclear structural effects. However, the nuclear level density (NLD), a physical quantity directly reflecting these properties, has been largely overlooked compared to other structural properties such as nuclear masses. To address this, we perform $r$-process simulations across three astrophysical scenarios using
neutron-capture rates derived from six distinct NLD models. Our results reveal that microscopic models yield systematic deviations in NLD relative to phenomenological ones, leading to critical impacts on nucleosynthesis. Specifically, systematic NLD differences in even-$A$
nuclei redirect the nuclear flow, accelerating the early formation of the rare-earth peak and temporarily enhancing its magnitude. This underlying structural shift also fundamentally alters the $r$-process sensitivity to the
neutron-capture rate, effectively eliminating its dependence on the odd-even nature of
protons. Overall, these findings demonstrate that the internal nuclear structure encoded within NLDs can collectively induce a global redirection of the nucleosynthesis pathway, highlighting the critical need for self-consistent microscopic inputs in future simulations.
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All authors Hang Xu, Peng-Xiang Du, Jian Li, Dong-Liang Fang
Solar and Stellar Astrophysics
Circular polarimetry of suspect wind-accreting pre-polars II
Pasi Hakala, Steven Parsons, Gavin Ramsay et al. (+2 more)
The origin of white dwarf
magnetic fields is an open question. Furthermore, such fields play a vital role in the
evolution of interacting binary
stars. Here we present a study of white dwarf fields in so called pre-polars (or low
accretion rate polars, LARPs , i.e.
magnetic cataclysmic variables, where the mass losing secondary
star is not in Roche lobe contact, but the systems experience
accretion via stellar wind. Such systems play a crucial role in understanding the
magnetic braking and the angular momentum
evolution of close binaries. We aim to identify a set of wind-accreting pre-polars amongst our sample of nine candidate systems. We also attempt to measure the white dwarf
magnetic fields and study the
accretion geometry associated with wind-accreting pre-polars. We have obtained optical circular imaging photopolarimetry and circular spectropolarimetry of the targets. These are used to model the cyclotron emission and to estimate the white dwarf
magnetic field strengths. We find that at least in four out of our nine candidate systems, we can confirm the
magnetic nature of the white dwarf. Out of these, One system, ZTF J1737+4013, appears to be an eclipsing polar. Furthermore, ZTF J2220+0721 and ZTF J2353+4153 appear to be very strong candidates for wind-accreting pre-polars (or LARPs), with the fourth, ZTF J0056+4926, showing strong variable $H_{\alpha}$ emission, atypical of pre-polars. However, the emission could be related to the strong activity of the donor
star, dominating the optical spectrum. One system, ZTF J0504+2145, is likely a novalike CV. The exact nature of the other systems remains unclear.
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All authors Pasi Hakala, Steven Parsons, Gavin Ramsay, Boris T. Gänsicke, Alex Brown