Astrophysics of Galaxies
Predicting CO and dust emission of star-forming galaxies
B. Vollmer, J. Braine, M. Soida et al. (+1 more)
How do
Dwarf Galaxies differ from spirals? Does
star formation produce
radio and far-infrared emission in the same way as in spiral
galaxies?
Radio, FarIR, and CO emission depend on gas density, temperature,
magnetic field strength, and
metallicity. The
radio-FarIR correlation and Schmidt-Kennicutt relation characterize the links for Milky Way-like
galaxies but do they hold for smaller objects, with different morphologies? Here we extend our previous work on the IR, line, and
radio emission of local and high-z
galaxies to local
star-forming low-mass and
dwarf galaxies. The calculation of the
cosmic ray (CR) densities were improved compared to the previous version of the model. The CR ionization rate we found for the different
galaxy samples is higher by a factor of three than for the
solar neighborhood. This means that the mean yield of low-energy CR particles three times higher in external
galaxies than was observed by Voyager I. The dependence of the N_H2/I_CO factor on the
metallicity and
stellar mass are calculated by the model. The weaker CO emission from low-
metallicity galaxies is due to the large amount of (CO-dark) H_2 surrounding the regions where CO is not photo-dissociated. Within our model framework,
star-forming low-mass and
dwarf galaxies follow the
radio-IR correlation.
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All authors B. Vollmer, J. Braine, M. Soida, P. Gratier
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Topological defect induced phase separation in a holographic system
Zi-Qiang Zhao, Zhang-Yu Nie, Jing-Fei Zhang et al. (+1 more)
We investigate the coupled dynamics of
symmetry breaking and phase separation during quenches across the critical point in a first-order phase transition. Based on the Einstein-Maxwell-scalar theory, we construct a
holographic superfluid model with $\mathbb{Z}_2$
symmetry. By introducing higher-order nonlinear terms $\lambda\Psi^4$ and $\tau\Psi^6$ into the scalar field potential, we realize a rich phase structure, which enables us to study the coupling effects between
symmetry breaking and phase separation. Furthermore, by preparing initial conditions with well-defined spatial partitions, we discover a new triggering mechanism for the invasion phenomenon, namely that kinks serve as triggering sites for the phase separation process. This study reveals a novel coupling mechanism between topological defects and phase separation, enriches our understanding of nonequilibrium structure formation in strongly coupled systems.
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All authors Zi-Qiang Zhao, Zhang-Yu Nie, Jing-Fei Zhang, Xin Zhang
Earth and Planetary Astrophysics
Arches of chaos, heteroclinic connections of first-order MMRs and the chaotic transport of small bodies in the Sun-Jupiter system
Alessia Francesca Guido and Christos Efthymiopoulos
We investigate the heteroclinic connections between stable and unstable
manifolds of unstable periodic orbits associated with the most important mean motion resonances (MMRs) in the Sun-Jupiter planar restricted three-body problem. We explicitly compute the stable and unstable
manifolds of the unstable periodic orbits associated with the first order interior MMRs 2:1, 3:2, and the exterior MMR 2:3. We also compute short-time FLI maps showing the chaotic saddle structure created by the
manifolds of several interior or exterior MMRs other than the 1:1 (co-orbital) resonance. Transits of particles from the exterior to the interior of Jupiter's orbit and vice versa are allowed for Tisserand parameter lesser than 3, and are shown to exist through a variety of heteroclinic channels. Besides the classical ones by Koon et al., we find heteroclinic connections between
manifolds of short-period orbits around L3 and periodic orbits of interior or exterior first order MMRs, as well as direct connections between interior and exterior MMR
manifolds not involving co-orbital periodic orbits. Through these
manifolds and the corresponding FLI ridges, we explain the 'arches-of-chaos' in the asteroid orbital plane (a,e). Chaotic orbits shadowing heteroclinic trajectories exhibit resonance hopping, suggesting links to quasi-Hildas and Jupiter-family comets. Results are obtained in the circular RTBP but persist in the
elliptic problem.
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Astrophysics of Galaxies
OJALÁ: Optimizing J-PAS Astronomy for Large-scale Analysis. A foundation model for the SED of galaxies, QSOs and stars
G. Martínez-Solaeche, R. M. González Delgado, R. García-Benito et al. (+37 more)
The advent of large-scale surveys requires efficient ML techniques to exploit the information of massive
datasets. We present OJALA, a
transformer-based autoregressive foundation model designed to simultaneously classify astronomical objects and infer their physical parameters using 54 narrow bands from J-PAS, combined with broad bands from the DESI Legacy Imaging Surveys and WISE. The model is trained on $\sim20$ million synthetic SEDs generated from DESI DR1 spectra. We validate OJALA using a cross-matched sample of $\sim121,000$ objects between J-PAS and DESI. The model achieves a weighted F1-score of approximately 0.9 for spectral classification (
stars,
galaxies, and QSOs) at $i < 21$. For
galaxies, we recover photo-z with a precision of $\sigma_{\rm NMAD} < 0.01$, while for QSOs, the precision improves significantly at $z > 1.5$, reaching $\sigma_{\rm NMAD} \approx 0.006$ at $z \approx 3.5$. We demonstrate robust estimation of physical properties for
galaxies, recovering
stellar masses and SFR with a scatter of approximately 0.11 dex and 0.22 dex, respectively. Furthermore, the model accurately predicts EWs for major optical emission lines, allowing for the derivation of extinction-corrected H$\alpha$ luminosities with a scatter of 0.29 dex. OJALA successfully reproduces the BPT and WHAN diagnostic diagrams, classifying SF, AGN, and passive
galaxies with F1-scores typically ranging from 70% to 90% depending on the diagnostic class. For
stars, the model reliably infers effective temperature and
metallicity, though surface
gravity remains challenging. Finally, we show the modularity of the architecture by fine-tuning the pre-trained
embeddings to predict BH masses, a property not included in the primary training, recovering spectroscopic virial estimates with a precision of approximately 0.5 dex. We release the code, model weights, and a comprehensive VAC for the J-PAS EDR.
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All authors G. Martínez-Solaeche, R. M. González Delgado, R. García-Benito, A. Hernán-Caballero, I. Pérez-Ràfols, L. A. Díaz-García, L. Raul Abramo, J. E. Rodríguez-Martín, A. M. Conrado, I. Breda, H. Domínguez Sánchez, I. Márquez, M. Pieri, D. López-Cano, V. M. Placco, L. Nakazono, A. del Pino, V. Marra, J. Alcaniz, N. Benitez, S. Bonoli, S. Carneiro, A. J. Cenarro, D. Cristóbal-Hornillos, S. Daflon, R. A. Dupke, A. Ederoclite, C. Hernández-Monteagudo, J. Liu, C. López-Sanjuan, A. Marín-Franch, C. Mendes de Oliveira, M. Moles, F. Roig, L. Sodré, K. Taylor, J. Varela, H. Vázquez Ramió, J. M. Vílchez, J. Zaragoza-Cardiel
Solar and Stellar Astrophysics
A comparison of pendulum models for large-amplitude longitudinal prominence oscillations
Iñigo Arregui
Large-amplitude prominence oscillations offer diagnostic information relevant to understanding the
magnetic and
plasma structure of
solar prominences. Accurate prominence seismology requires the use of reliable models. The so-called pendulum model for large-amplitude longitudinal prominence oscillations has demonstrated robustness against observations and numerical simulations. Recent improvements have extended the model to situations with non-uniform
gravity, thus leading to corrections that have implications for the inference of the
magnetic field strength. In this study we quantify how the different model predictions given by the original and extended pendulum models impact the inference of the minimum
magnetic field strength derived from the observed periods of large-amplitude longitudinal prominence oscillations. The analysis we conducted follows a
Bayesian approach to solve the inference problem and assess the absolute and relative plausibilities of the two considered models in explaining the observed data, with their uncertainty. We find that the
Bayesian solution to the inference problem provides well-constrained posteriors for the minimum
magnetic field strength. However, the solutions from each adopted model differ, with differences increasing with the oscillation period. A model comparison analysis results in the extended model being more plausible in the full range of observed periods. However, the magnitude of the Bayes factor is not large enough to determine whether there is positive evidence supporting any of the models. We suggest computing model-averaged posteriors as the most reasonable solution to the inference problem.
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Solar and Stellar Astrophysics
The complex dependencies of Wolf-Rayet winds – Insights from detailed radiative transfer models
Andreas A.C. Sander, Roel R. Lefever and Gemma González-Torà
With their emission-line dominated spectra, the appearance of Wolf-Rayet
stars is shaped by their strong
stellar winds. Yet, the physical mechanisms behind their high mass loss have long remained enigmatic. While we know nowadays that radiative driving is sufficient to explain WR-type
outflows, a coherent description of them is still lacking, not least to the complex physical conditions invalidating some of the approximations sufficient for other hot-
star winds. One promising instrument towards a better understanding of WR winds are comoving-frame, non-LTE
stellar atmosphere models including a consistent solution of the hydrodynamics. While so far limited to 1D, their detailed treatment of the radiative transfer and the population numbers is key to overcome the traditional problem of connecting
stellar structure models with observed spectra. By creating larger model sequences, we can identify previously unknown scalings and describe trends of WR wind quantities with fundamental
stellar parameters and abundances. This article will present a summary of recent insights on WR-type winds, revealing a complex picture with various remaining challenges. Beside covering classical, hydrogen-free WR
stars, we present new results to uncover dependencies of later-type WR
stars and the presence of hydrogen-containing envelopes. We further discuss oncoming challenges and insights from 2D and 3D RHD simulations which need to be mapped into 1D dynamical atmosphere models.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Baryogenesis in $SU(2)_{L}$ multiplet models
Kiyoto Ogawa and Masanori Tanaka
We investigate baryogenesis in Standard Model (SM) extensions with new $SU(2)_L$ multiplet fields. We focus on sphalerogenesis, in which the
baryon asymmetry of the Universe (BAU) is generated through the gradual decoupling of CP-violating electroweak sphaleron-like processes. We show that the observed BAU can be reproduced when the new fields possess CP-violating Yukawa interactions, which leave a CP-violating dimension-six operator involving the $SU(2)_L$ gauge fields at low energies. As representative examples, we study models with fermionic $SU(2)_L$ quintuplets and septuplets, and find that these field masses should be $\mathcal{O}(1)\,\mathrm{TeV}$ to explain the BAU. We also show that viable parameter regions for the BAU are consistent with current bounds on the electron electric dipole moment and thoroughly probed by future measurements such as ACME III and by mono-
lepton searches at the HL-LHC. Our results provide a concrete and phenomenologically testable ultraviolet completion of sphalerogenesis.
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Earth and Planetary Astrophysics
Misaligned rings around minor planets with moons
Barnabás Deme
Recent observations have confirmed the existence of rings around minor bodies in the outer
Solar System. These objects may possess satellites as well. Here we analytically investigate the interaction between such rings and satellites. We show that the perturbations from the moons may efficiently lead to off-equatorial rings around minor bodies like trans-neptunian objects or centaurs. In particular, we derive criteria for the orbital elements under which such misaligned rings may exist. These considerations will be easily testable with the upcoming deep sky surveys.
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Cosmology and Nongalactic Astrophysics
A Geometric Theory of Cosmological Structure via Entropic Curvature in Wasserstein Space
Tsutomu T. Takeuchi
We construct a
geometric framework for cosmological large-scale structure based on optimal transport theory and Wasserstein geometry. In this framework,
Ricci curvature on the probability measure space $\mathcal{P}_2(M)$ is characterized by the geodesic convexity of
entropy and is formulated as the response of probability distributions to optimal transport. We introduce effective
Ricci curvatures $K_{\mathrm{eff}}^{(\infty)}$ and $K_{\mathrm{eff}}^{(N)}$ associated with Kullback–Leibler-type and Rényi-type
entropies, corresponding respectively to the
curvature-dimension conditions CD$(K,\infty)$ and CD$(K,N)$. By localizing these
curvatures to finite scales using local and reference measures, we construct
curvature indicators applicable to observational data. Under a local quadratic approximation, the effective
curvature reduces to the Hessian of the log-density, showing that conventional Hessian-based structure classifications arise as a limiting case of the present framework. We further show that effective
curvature depends on observational scale and formulate this dependence as a scale flow, distinct from
Ricci flow because it describes a change of resolution rather than a time
evolution of geometry. Treating
curvature as a random field then extends the statistical description of density fields:
curvature statistics are given by higher-order weighted integrals of the power spectrum and by spatial derivatives of the correlation function, emphasizing
geometric rather than amplitude information. This framework provides a unified connection between optimal transport geometry and cosmological structure analysis, and offers a new perspective on multiscale structure and nonlinear statistics.
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High Energy Astrophysical Phenomena
A Universal 1.5 GeV Gamma-Ray Line in Active Galactic Nuclei
Shi-Ju Kang, Yue Yin, Yong-Gang Zheng et al. (+1 more)
We report the detection of a gamma-ray spectral line at approximately 1.5 GeV in three active
galactic nuclei (AGN) using 17 years of
Fermi-LAT observations. The sample includes both blazars (with relativistic jets directed toward Earth) and a
radio galaxy (with a misaligned jet, free from significant beaming effects). The line is detected with local significances of $\sim$4.1$\sigma$, $\sim$3.9$\sigma$, and $\sim$2.8$\sigma$ in the individual sources. A joint likelihood analysis yields a combined test statistic TS $\simeq$ 57.77, corresponding to a significance well above 5$\sigma$. The line flux remains stable over the full observation period, in contrast to the variable continuum emission from the AGN. The appearance of an identical spectral feature in astrophysically distinct environments is difficult to reconcile with standard jet-based emission mechanisms. While a conventional astrophysical explanation remains elusive, the signal's characteristics are consistent with predictions for dark matter annihilation. This finding motivates further investigation into the nature of this spectral feature and its possible connection to particle dark matter.
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All authors Shi-Ju Kang, Yue Yin, Yong-Gang Zheng, Qingwen Wu
Astrophysics of Galaxies
Revisiting Marked Galaxy Clustering from a Joint Point Process Perspective
Tsutomu T. Takeuchi
Marked correlation functions, in which
galaxy properties such as luminosity or
stellar mass are treated as marks, are widely used to test models of
galaxy formation. In astronomy, however, these statistics are typically implemented as summary measures that do not preserve the joint structure of mark pairs conditioned on separation. In this work, we formulate
galaxies as points $(x,m)$ on the product space $\mathbb{R}^3\times\mathcal{M}$, where $x$ denotes position and $m$ a mark, and introduce the joint pair correlation function $g(r;m_1,m_2)$ as the fundamental quantity describing mark-dependent clustering. We further define a diagnostic quantity $\Delta_{\mathrm{ind}}(r;m_1,m_2)$ that locally quantifies deviations from the independence hypothesis relative to spatial clustering alone, thereby providing a projection-free description of which mark pairs are over- or underrepresented at a given separation scale. Within this framework, commonly used diagnostics such as the inhomogeneous cross-$J$ function are naturally interpreted as summary statistics obtained through averaging over mark sets and
geometric-event-based reductions of the joint structure. This perspective clarifies that previously discussed marked effects, including assembly bias, correspond to projections of an underlying joint dependence, and that observationally accessible information is the existence of non-factorizable joint structure itself. The present formulation provides both a fundamental quantity and practical diagnostics for its characterization.
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Earth and Planetary Astrophysics
Three-Dimensional Ocean Dynamics and Detectability of Tidally Locked Lava Worlds
Yanhong Lai, Wanying Kang, Jun Yang et al. (+1 more)
Tidally locked lava
planets are hot, rocky worlds on close-in orbits with a permanent molten dayside. With JWST, their surfaces and atmospheres are beginning to be revealed. This work investigates 3D magma-ocean dynamics, derives scaling laws for the resulting ocean heat transport (OHT), and predicts its detectability. For the first time, the ocean circulation driven by the intense momentum and mass exchanges with the supersonic atmosphere is considered in addition to that by thermal forcing. The wind forcing turns out to overwhelmingly dominate the other two mechanisms, driving ocean currents reaching $\sim$100 m s$^{-1}$ and greatly expanding the latitudinal extent of the Matsuno-Gill response. Despite these extreme flow speeds, scaling analysis and 3D simulations consistently demonstrate that magma-ocean circulation alone does not produce an observable hotspot offset. This inefficiency arises because basin geometry and circulation structure fundamentally constrain zonal heat redistribution, suppressing large-scale longitudinal transport even under vigorous flow.
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All authors Yanhong Lai, Wanying Kang, Jun Yang, Xianyu Tan
Solar and Stellar Astrophysics
Twists in the flow: revisiting convective mixing in rotating stellar models. I. Effect on the stellar structure
Poojan Agrawal, Aaron Dotter, Conny Aerts et al. (+2 more)
Convection and rotation are both key processes in
stellar evolution modelling. While standard mixing-length theory (MLT) provides a widely used modelling of convection, it neglects the effects of rotation on convective transport. We investigate how rotating mixing-length theory (R-MLT), which accounts for the influence of rotation on convection, affects the internal structure, convective mixing, and angular momentum transport in
stellar models in comparison to the standard non-rotating MLT. Using the MESA
stellar structure and
evolution software, we model the main-sequence
evolution of a 5 M$_{\odot}$
star, for three cases: non-rotating, rotating with standard MLT for modelling convection, and rotating with R-MLT in convection zones, with the initial rotation rate set to 20 percent of the critical (Keplerian) value at the surface for the rotating models. We find that R-MLT reduces both the convective velocity and mixing length in the
stellar core, leading to a smaller convective
diffusion coefficient and about 20 percent reduction in the extent of the convective overshooting region. While the overall size of the convective core remains nearly unchanged, R-MLT changes the resulting chemical gradient at the core-envelope boundary, shifting the peak of the Brunt-Väisälä frequency and modifying the angular momentum transport in that region. Including the effects of rotation in the treatment of convection through R-MLT introduces measurable structural and transport differences, underscoring the importance of incorporating rotation-convection coupling in models of
stars.
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All authors Poojan Agrawal, Aaron Dotter, Conny Aerts, Leïla Bessila, Stéphane Mathis
Solar and Stellar Astrophysics
Global asteroseismology of 19,000 red giants in the TESS Continuous Viewing Zones
K. R. Sreenivas, Timothy R. Bedding, Daniel Huber et al. (+5 more)
TESS (Transiting
Exoplanet Survey Satellite) has produced long-term photometry for millions of
stars across the sky. In this work, we present an asteroseismic catalogue of 19,151 red
giants in the TESS Continuous Viewing Zones using sectors 1–87 (Years 1–7). We visually assessed the power spectra for oscillations, and then applied the computationally efficient nuSYD method to confirm reliability. We identified an increase of 80% in the number of previously known oscillating red
giants at a TESS magnitude $>$ 8. We determined the frequency of maximum power ($\rm \nu_{max}$) and the large frequency separation ($\rm \Delta \nu$) using the pySYD pipeline, achieving typical precisions of 1.5% and 1%, respectively. We classified the
stars into Red
Giant Branch (RGB) and Core Helium Burning (CHeB) classes using a Convolutional Neural Network. Using spectroscopic data for 10,298
stars with reliable asteroseismic measurements, we have been able to measure
stellar mass and radii with precisions of 7.5% and 2.8%, which is comparable to that from 4-yr $Kepler$ data. A comparison of the seismic radii with
Gaia radii shows excellent agreement. With three years of TESS data, the asteroseismic parameters are precise enough to identify the RGB bump and delineate the Zero Age Helium Burning edge. Combined with astrometric data, these parameters reveal established trends across the
Galactic plane, providing a valuable set of uniformly determined asteroseismic parameters for
Galactic Archaeology.
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All authors K. R. Sreenivas, Timothy R. Bedding, Daniel Huber, Dennis Stello, Marc Hon, Claudia Reyes, Yaguang Li, Daniel Hey
Astrophysics of Galaxies
X-ray variability of SDSS J000532.84+200717.4: from a normal state to an X-weak state
Xiaohui Yang, Yanli Ai, Liming Dou et al. (+8 more)
We present a multi-epoch study of the extreme X-ray variability of the type~1
quasar SDSS~J000532.84+200717.4 using archival observations from XMM-Newton, Swift/XRT, EP-FXT, and ROSAT, together with new optical spectroscopy and multi-wavelength photometry. The 0.2–10~keV X-ray flux exhibits a transition from a high state to a subsequent low state, declining by more than an order of magnitude and placing the source in the X-ray–weak regime ($\Delta\alpha_{\rm ox} \lesssim -0.3$). Significant variability on timescales of days to weeks persists within the low state. In contrast, the optical and mid-infrared emission remain stable over decade-long timescales, while the UV continuum varies only mildly and broadly tracks the X-ray
evolution. Multi-epoch optical spectroscopy shows no significant long-term changes in either the continuum shape or the broad emission-line profiles. The \ion{Mg}{2} emission is relatively weak compared with typical
quasars, suggesting similarities to weak-line
quasars. The pronounced wavelength-dependent variability indicates that the
accretion disk remains largely intact while the X-ray emission undergoes dramatic changes. The spectral hardening in the low state and the viability of ionized partial-covering models are consistent with variable, largely
dust-free absorbing gas, possibly associated with clumpy inner disk winds, although intrinsic coronal variations cannot be excluded. SDSS~J0005+200717.4 therefore provides evidence that extreme X-ray weakness can arise as a transient phase in otherwise normal
quasars.
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All authors Xiaohui Yang, Yanli Ai, Liming Dou, Tinggui Wang, Chichuan Jin, Wenfeng Wen, Xu Zhang, Yuming Fu, Jinhong Chen, Ning Jiang, Fukun Liu
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Gravitational wave spectrum from first-order QCD phase transitions based on a parity doublet model
Bikai Gao, Jingdong Shao and Hong Mao
We investigate the gravitational wave spectrum from first-order QCD phase transitions using the parity doublet model at finite
baryon chemical potential. The model incorporates the
chiral invariant mass $m_0$, representing the portion of nucleon mass that persists even when
chiral symmetry is restored. Within the model, we identify two first-order phase transition regions: the
nuclear liquid–gas transition and the
chiral phase transition. By solving the bounce equation and computing the Euclidean action $S_3/T$, we obtain the gravitational wave spectra from both transitions. The
liquid–gas transition yields $\alpha \sim \mathcal{O}(1)$ and $\beta/H \sim \mathcal{O}(10)$–$\mathcal{O}(100)$ near the endpoint of the first-order line, producing signals with peak frequencies from the millihertz to the nanohertz band that can fit the existing data. In contrast, the
chiral transition produces signals suppressed by approximately five orders of magnitude, well below the sensitivity of all current and planned detectors. These results connect the
chiral invariant mass to the gravitational wave spectrum, offering a novel probe of the origin of nucleon mass through gravitational wave astronomy.
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Solar and Stellar Astrophysics
FAST Observations of Wave-like Structures in the Radio Dynamic Spectrum of AD Leo
Wenjie Zou, Hui Tian, Jiale Zhang et al. (+1 more)
M-
dwarf flare stars like AD Leo are laboratories for studying intense
magnetic activities. The coherent
radio bursts they produce are powerful probes of
stellar coronal
plasma and
magnetic fields. In this study, we present high-resolution observations of AD Leo from the Five-hundred-meter Aperture Spherical
radio Telescope (FAST) that reveal wave-like structures in its
radio dynamic spectrum. The observations show trains of short-duration, narrowband sub-bursts where the central frequency, frequency drift rate, and flux density are all simultaneously modulated with a period of 1.53 s. Notably, modulation of the central frequency is approximately in-phase with that of the drift rate but roughly in anti-phase with that of the flux density. Furthermore, the amplitude of the frequency modulation grows with an e-fold timescale of 2.4 s. We interpret the observed sinusoidal frequency modulations as a possible signature of a magnetohydrodynamic (MHD) wave in the
stellar corona. Our work provides a window into
stellar coronal seismology and offers an opportunity to infer the local
plasma environment via the MHD wave model.
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All authors Wenjie Zou, Hui Tian, Jiale Zhang, Yuhang Gao
Cosmology and Nongalactic Astrophysics
Relic Magnetic Fields from Non-Adiabatic Photon Freeze-Out at Recombination
Hyeong-Chan Kim
We propose a new mechanism for generating a
primordial electromagnetic relic during the recombination–decoupling transition, based on the rate-dependent thermodynamics of the
cosmic photon gas. Treating the
photon sector as an open system coupled to the electron
plasma, we show that a finite Thomson relaxation rate generates a departure from instantaneous thermal
equilibrium, leading to non-adiabatic mode squeezing. As this relaxation rate rapidly decreases across recombination, the system quickly loses the ability to further amplify the deviation, and the squeezing freezes out at a small but finite value. This dynamics is naturally described as a narrow transition layer between an adiabatic tracking regime and a post-relaxation freeze-out regime. By a canonical transformation, the reduced
evolution equation is recast into a forced oscillator with a smooth effective potential, clarifying the origin of the squeezing and the selection of the relic scale. Projecting the resulting non-
equilibrium electromagnetic relic onto the
magnetic sector, we derive the corresponding spectrum and show that its characteristic peak is controlled not by the squeezing parameter alone but by the weighted combination \(k^3\mathscr S_k\). In representative realizations, the peak corresponds today to scales of order \(10\)–\(20\) Mpc, while the present-day field amplitude remains extremely small. The mechanism is therefore better viewed as a source of a frozen non-
equilibrium electromagnetic relic than as a complete explanation of the observed
cosmic magnetic fields.
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Cosmology and Nongalactic Astrophysics
Calibrating optical galaxy cluster projection effects with sparse spectroscopic samples: A clustering redshift approach
Lei Yang, Hao-Yi Wu, Tesla Jeltema et al. (+3 more)
Wide-field optical imaging surveys are efficient at identifying
galaxy clusters, but optically identified clusters suffer from projection effects—physically unassociated
galaxies along the line of sight are often included as cluster members due to distance uncertainties. Previous studies have used spectroscopic follow-up observations of cluster members to quantify projection effects; however, such follow-up efforts cannot keep pace with the rapidly growing cluster samples. On the other hand, spectroscopic surveys designed for large-scale structure studies collect tens of millions of spectra but tend to have sparse spectra in cluster regions. To bridge this gap, we develop a clustering
redshift approach that cross-correlates cluster members with sparse, noncluster-targeted spectroscopic
galaxy samples. We validate this approach using the Cardinal simulation, recovering the correct spectroscopic
redshift distribution and projection effect parameters of cluster members identified by the red-sequence Matched-filter Probabilistic Percolation
algorithm. Our approach is insensitive to the selection of the spectroscopic sample and paves the way for calibrating projection effects in the upcoming Legacy Survey of Space and Time clusters using DESI and Roman spectroscopic samples.
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All authors Lei Yang, Hao-Yi Wu, Tesla Jeltema, Chun-Hao To, Ross Cawthon, Shulei Cao
High Energy Astrophysical Phenomena
A large misalignment between continuous jet and discrete ejecta in microquasar GRS 1915+105 during its obscured phase
Wu Jiang, Xi Yan, Zhen Yan et al. (+3 more)
We report a large misalignment between the continuous jet and the discrete ejecta in GRS 1915+105, detected in April 2023 with the East Asian VLBI network (EAVN). Two-sided ejecta are shown at 6.7 GHz images and central continuous jets are resolved at 43 GHz by EAVN quasi-simultaneously. While the continuous jet was aligned with the long-standing jet position angle (PA) of about 147 degree, the discrete ejecta appeared at a markedly different PA about 188 degree, with the lowest intrinsic velocity about 0.35 c ever reported. A similar misalignment of PA between discrete ejecta and continuous jet was independently detected in late September of 2023 during a consecutive
flare event. The pronounced and recurrent angular deviations suggest a time-variable jet launching geometry, which, in conjunction with the observed X-ray obscuration, can be attributable to a warped
accretion disk. Our result could offer new insight into the fundamental differences between continuous jet and discrete ejecta, and broadly provides a clue to understand the phenomena for transient black hole X-Ray binaries and changing-look active
galactic nuclei during the X-ray obscured phase.
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All authors Wu Jiang, Xi Yan, Zhen Yan, Ya-Ping Li, Lang Cui, Zhi-Qiang Shen
Earth and Planetary Astrophysics
Planetary Radar at the Arecibo Observatory
Michael C Nolan, Lynn M. Carter and Edgard G. Rivera-Valentín
In the late 1990s, the Arecibo Observatory and its planetary radar system were upgraded to increase sensitivity by a factor of 20. This upgrade substantially improved the quality of the data and the ability to observe terrestrial
planets, outer
planet satellites, planetary rings, and near-Earth objects until the
telescope's collapse in 2020. The higher sensitivity allowed radar observations of 889 near-Earth asteroids and comets from 1997 to 2020, compared to the 40 achieved in the previous 30 years, and showed that the population of near-Earth asteroids is heterogeneous, suggesting a wide variety of formation and
evolution mechanisms. The planetary radar's ability to see through the atmospheres of Venus and Titan, into the shadows of Mercury and the Moon, and under the surface of the Moon and Mars provided a unique perspective on those bodies that has driven in-situ exploration. No other existing or planned facility matches the sensitivity that Arecibo had.
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