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宇宙工学・惑星科学・宇宙物理の最新プレプリント。

astro-ph.GA

Morphology classification for galaxies in the Kilo Degree Survey using a label-efficient self-supervised learning framework

Xu Huang, Rui Li, Liang Gao, Liqing Chen, Hui Li, Huijun Mu, Hao Su, Fucheng Zhong et al.

Galaxy morphology classification is fundamental to understanding galaxy formation and evolution. The advent of large-scale sky surveys has produced an unprecedented volume of galaxy images, making traditional manual classification impractical. Although supervised deep learning can achieve high accuracy, it requires large labeled datasets that are time-consuming to construct. In contrast, unsupervised methods often show limited classification performance. To address this limitation, we propose a…

astro-ph.COastro-ph.GA

Lens Modeling and Cosmological Inference from an Impure Sample of Galaxy-Galaxy Strong Lenses

Philip Holloway, Aprajita Verma, Philip J. Marshall, Padmavathi Venkatraman, Sydney Erickson, Tian Li, Simon Birrer, Steven Dillmann et al.

The start of the Legacy Survey of Space and Time marks a new era for strong lensing science, where the number of strong lenses identified is expected to increase to $\mathcal{O}(10^5)$. In this paper we use a neural network to determine the precision with which lens parameters can be determined, using realistic simulated LSST lensed systems. We find that the Einstein radius can be measured with a mean precision of $3.7\%$ with calibrated uncertainties accurately reflecting the corresponding meas…

astro-ph.IMcs.LGphysics.data-an

Bayesian classification of astronomical spectra with class uncertainties

Simon Barton, Martin Sahlén, Andreas Korn, Christian Glaser

Context: We developed a probabilistic machine learning method with the aim of performing the O(10)-way classification of low- and high-resolution spectra of stellar and extragalactic targets for the upcoming 4MOST survey. In fulfilment of the survey requirements, this method should be able to express uncertainty in the input data as well as uncertainty introduced in its prediction. Aims: Four different methods are explored: (1) convolutional neural networks (CNNs), (2) the Dirichlet distribution…

astro-ph.GA

LenNet: Direct Detection and Localization of Strong Gravitational Lenses in Wide-Field Sky Survey Images

Pufan Liu, Hui Li, Ziqi Li, Xiaoyue Cao, Rui Li, Hao Su, Ran Li, Nicola R. Napolitano et al.

Strong gravitational lenses are invaluable tools for addressing fundamental questions in astrophysics, from the nature of dark matter to the expansion of the universe. While current sky surveys have successfully identified thousands of lens candidates, the search methods employed face a critical challenge. The conventional approach relies on a "crop-and-classify" strategy, where small images are first cut out around billions of potential host galaxies before being individually classified. This p…

astro-ph.IMastro-ph.GA

Identification of gravitational lenses obscured by foreground light in the KiDS dataset using U-Nets and ResNets

S. Liu, Rui Li, J. Jia, Hui Li, Liqing Chen, Xiaoyue Cao, Zizhao He, Valerio Busillo et al.

*Context.* Many lensing images are often obscured by foreground light from the central galaxies, making them challenging to detect. *Aims.* To address the limitations of previous lens search efforts, particularly for samples with smaller $R_E$ or faint lensed images, we developed a composite convolutional neural network framework that utilizes both U-Net and ResNet architectures for feature extraction and classification. *Methods.* We propose a hybrid search method that combines U-Net and ResNet…

astro-ph.GA

KiDS J1447-0149: The first spatially resolved spectroscopy of a relic galaxy beyond the local universe. An old high-dispersion core embedded in a compact rotating stellar structure

Johanna Hartke, Chiara Spiniello, Michele Cappellari, Davide Bevacqua, Enrico Congiu, Anna Ferré-Mateu, Adriano Poci, Claudia Pulsoni et al.

Relic galaxies are the descendants of high-redshift compact quiescent systems. We present the first spatially resolved spectroscopic study of J1447-0149, a massive relic at $z=0.21$, observed with MUSE+AO. We characterize its kinematics and stellar population properties to probe its spatially resolved mass assembly history. We measured stellar kinematics with sub-kpc bin sizes, covering $\sim 1.4$ effective radii. We then used a coarser three-bin configuration informed by the kinematics to recov…

astro-ph.HE

Wave-particle acceleration during supernova explosions

Zaza N. Osmanov, S. M. Mahajan

We investigate particle acceleration during the early stages of a supernova explosion via a resonant interaction between electromagnetic waves and quantum waves associated with particles. For typical progenitor masses of $(8; 12; 20)\times M_s$, we find that this mechanism can accelerate protons to energies of up to $3\times 10^{14}$ eV. Interestingly, despite the continuously declining luminosity, the particle energy initially increases, reaches a maximum, and subsequently decreases, reflecting…

astro-ph.HEhep-ex

A method for enhanced gamma-proton discrimination with imaging atmospheric Cherenkov telescopes

Jianling Liu, Hu Liu

Purpose: Very-high-energy gamma-ray astronomy is an important window to study the extreme astrophysical processes in the universe, and how to effectively distinguish between gamma photons and background signals (mainly protons) is a key technical challenge to realize very-high-energy gamma-ray detection. Spaceborne calorimeters record secondary particle spatial distributions, achieving a background rejection power of 10000-100000 near 1 TeV. Ground-based imaging Cherenkov telescopes measure Cher…

astro-ph.IMastro-ph.COastro-ph.HEgr-qc

Combining astrometry with pulsar timing: the first joint analysis of very low frequency gravitational waves

Lorenzo Filipello, William Beordo, Volodymyr Akhmetov, Mariateresa Crosta, Mario Gilberto Lattanzi

The pHz to sub-nHz GW regime remains largely unexplored but is crucial for mapping the early inspiral stage of SMBHBs and probing early-Universe physics. Astrometry and pulsar timing offer orthogonal and deeply complementary secular observables to investigate this frequency band. We aim to present the first joint data analysis combining real astrometric proper motions with binary pulsar timing, to search for and constrain continuous gravitational waves (CWs) sourced by SMBHBs in the ultra-low-fr…

astro-ph.GA

ALMA Chemical Evolution (ACE) survey: an overview -- extending dust and gas inference to low metallicities at cosmic noon

Irene Shivaei, Gergő Popping, Leindert A. Boogaard, Alexandra Pope, Ivanna Langan, Roxana Popescu, Nikki N. Geesink, Manuel Solimano et al.

The baryon cycle governs the exchange of gas, metals, and dust between galaxies and their environments, but simultaneous constraints on these constituents remain scarce beyond z~1. The ALMA Chemical Evolution (ACE) survey is a Cycle 11 ALMA Large Program designed to address this by studying the molecular gas, dust, and metal content of sub-solar metallicity at cosmic noon. ACE consists of CO(3-2) and dust continuum observations of 25 galaxies at z=2.0-2.5 with robust gas-phase metallicity measur…

astro-ph.GA

Hierarchical Hub Formation in Mon~R2: Evidence for Cloud-to-core Gas Flows

L. K. Dewangan, O. R. Jadhav, A. K. Maity, Saurabh Sharma, Ram K. Yadav

We present a multi-scale kinematic study of the hub-filament system in Mon R2 using JCMT $^{13}$CO(3--2) and ALMA C$^{18}$O(1--0) observations to investigate how molecular gas converges toward the central hub and connects across cloud-to-core scales. The $^{13}$CO data reveal several velocity-coherent filaments with diverse position angles converging toward the central region hosting massive stars and stellar clusters, where distinct velocity components become spatially superposed. Two dominant…

astro-ph.IM

Status and performance of the Asgard/NOTT cold nulling camera

P. Chingaipe, G. Medgyesi, A. Mazzoli, E. Bouzerand, R. Laugier, P. Abraham, C. Dandumont, D. Defrère et al.

Long-baseline nulling interferometry suppresses the on-axis light of a star, enabling high-contrast observations of faint circumstellar emission and exoplanets at high angular resolution. The Nulling Observations of dusT and PlaneTs (NOTT) instrument is the L'-band nulling interferometer of the Asgard instrument suite and will be the first nuller installed at the Very Large Telescope Interferometer (VLTI). Its main scientific goals are to characterise hot/warm exozodiacal dust and young Jupiter-…

astro-ph.SR

The independence of the mid-infrared RR Lyrae Period-Luminosity relation from metallicity from a study of three globular clusters in the Large Magellanic Cloud

Steve Ardern, Vicky Scowcroft, Stijn Wuyts

RR Lyrae are pulsating variable stars tracing old ($>10$ Gyr) stellar populations, and exhibit a strong mid-infrared Period-Luminosity (PL) relation that can be calibrated with known parallaxes to infer distances. Here we present Period-Luminosity relations and distance moduli for three isolated globular clusters in the Large Magellanic Cloud: Reticulum, NGC 1841, and NGC 1466. Our analysis uses legacy \textit{Spitzer Space Telescope} images obtained by the Carnegie RR Lyrae Program, and an inte…

astro-ph.GA

An Orbital Interpretation of Decreasing Galaxy Velocity Distance Relations in Systems Dominated by Giant Elliptical Galaxies

Rabia Melati, Takia Larbaoui, Mohammed Ridha Benzidane, Mourad Lounis

The persistence of approximately flat rotation curves observed in many galaxies, is commonly interpreted as evidence for extended dark matter halos or as an indication of modified gravitational laws at low accelerations. In this work, we investigate an alternative orbital framework for the large scale kinematics of galaxy systems dominated by giant elliptical galaxies. We propose that selected non active companion galaxies form gravitationally bound orbital systems around a dominant central elli…

astro-ph.IMphysics.ins-det

Development of a Temperature-Variable Cold Blackbody Calibrator for Millimeter and Submillimeter Wave Detectors

Kazuki Watanabe, Taiki Sato, Shuhei Inoue, Shinsuke Uno, Tatsuya Takekoshi, Tai Oshima

We report the design, fabrication, and characterization of a cryogenic blackbody calibrator intended for laboratory-based detector characterization, providing multi-temperature calibration of millimeter- and submillimeter-wave detectors over a temperature range of 4 K to ~10 K. The device employs a Stycast/SiC absorber shaped for uniform array illumination and mounted on a phosphor-bronze substrate with optimized thermal links. Measured thermal conductance and heat capacity show the expected tem…

hep-phastro-ph.COastro-ph.GA

The high-velocity dark matter halo of the Milky Way in light of the LZ 248 keV event

Ciaran A. J. O'Hare

The interpretation of high-energy nuclear recoil events in direct-detection experiments can depend sensitively on the poorly understood high-speed tail of the Galactic dark matter velocity distribution. This fact has been brought into sharper focus recently by an anomalous nuclear-recoil event at $E_R\approx248~\mathrm{keV}$ observed by the LZ experiment. If interpreted as caused by a dark-matter-induced recoil, kinematic constraints on many models imply this particle would have to emerge from t…

astro-ph.HE

Gamma-ray Quasi-periodic Oscillations in the Changing Look Blazar B2 1420+326 (OQ 334)

Sunanda, Shubham Kishore, Alok C. Gupta

In the Fermi-LAT gamma-ray light curve from January 1 to August 25, 2026, of the changing look blazar B2 1420+326, we report here the detection of transient quasi-periodic oscillations (QPOs) of period ranging around 10-13 d. The source entered the flare state around May 7, 2026, and lasted till around mid-August, 2026 during which it depicted strong QPO signatures. We utilized standard techniques, including weighted wavelet Z-transform analysis, generalized Lomb-Scargle periodogram, and phase d…

astro-ph.GA

Fountain pattern of baryon cycle revealed in galaxy ecosystems

Chengyu Ma, Yangyao Chen, Enci Wang, Houjun Mo, Huiyuan Wang, Tao Wang, Qirong Yuan, Min Du et al.

Baryons in galaxy ecosystems are believed to undergo continuous cycles of inflow and outflow, forming fountain-like patterns that encode key information about how galaxies acquire matter from their environments and respond through feedback. The presence of such baryon cycles has been inferred from pieces of observational evidence, but a concrete understanding remains elusive because individual galaxy ecosystems are diverse and dynamic. Here we introduce a stacking method that combines baryonic f…

astro-ph.GAastro-ph.IM

From Observation to Ground Truth: Reconstruction Losses of Galaxy Imaging Under Heteroscedastic Noise

Renhao Ye, Shiyin Shen, Quanfeng Xu

Deep learning is widely used to analyze galaxy images, and the reconstruction loss determines which image features a model prioritizes during training. Mean squared error (MSE) and mean absolute error (MAE) correspond to homoscedastic Gaussian and Laplace likelihoods, respectively, whereas the inverse-variance-weighted $χ^2$ loss accounts for the spatially varying uncertainties of heteroscedastic astronomical noise. Comparing how closely these objectives recover the underlying signal requires a…

astro-ph.HEastro-ph.GA

A Gamma-ray Emitting Head-Tail Radio Galaxy Swimming Through the Hot Medium of the Merging Cluster Abell 3627

Vaidehi S. Paliya, M. Böttcher, Swayamtrupta Panda, Kiran Wani, D. J. Saikia, Mahadev Pandge, C. S. Stalin

Head-tail radio sources are jetted active galactic nuclei (AGN) moving through the dense intracluster medium of galaxy clusters. They are extremely rare in the gamma-ray sky, likely because they are usually observed at large viewing angles. Therefore, every new gamma-ray detection of head-tail radio galaxies allows us to probe the origin of the high-energy emission in this unique class of AGN. Here we report, for the first time, the association of ESO~0137-G007 (z=0.016), a head-tail radio galax…

astro-ph.GA

A large overdensity of LRD-like galaxies discovered by JWST in the SPT2349-56 protocluster at z=4.30

Scott C. Chapman, Kedar A. Phadke, Nikolaus Sulzenauer, Dazhi Zhou, Hollis Akins, Manuel Aravena, James R. Burgoyne, Caitlin M. Casey et al.

We present 11 newly identified ultra-red galaxies selected with JWST/NIRCam in the core of the z=4.3 protocluster SPT2349-56. Although these sources are yet spectroscopically confirmed, their extremely red colours (m200-m444 > 2.0 mag), strong spatial concentration, and number density - at least 2000x that of comparable field populations - make a chance projected association unlikely. Their colours overlap those used to select the "little red dot" (LRD) population, although most of the sources a…

astro-ph.GA

A large overdensity of LRD-like galaxies discovered by JWST in the SPT2349-56 protocluster at z=4.30

Scott C. Chapman, Kedar A. Phadke, Nikolaus Sulzenauer, Dazhi Zhou, Hollis Akins, Manuel Aravena, James R. Burgoyne, Caitlin M. Casey et al.

We present 11 newly identified ultra-red galaxies selected with JWST/NIRCam in the core of the z=4.3 protocluster SPT2349-56. Although these sources are not yet spectroscopically confirmed, their extremely red colours (m200-m444 > 2.0 mag), strong spatial concentration, and number density - at least 2000 times that of comparable field populations - make a chance projected association unlikely. Their colours overlap those used to select the widely studied ``little red dot'' (LRD) population, alth…

astro-ph.GA

Patchy Reionization Delays Quenching in Isolated Ultra-faint Dwarf Galaxies

Juyoung Kim, Myoungwon Jeon, Yumi Choi, Sangmo Tony Sohn

The spatially inhomogeneous nature of cosmic reionization is directly encoded in the quenching timescales of ultra-faint dwarf galaxies (UFDs). While most cosmological simulations employ a spatially uniform UV background (UVB) for computational efficiency, such homogeneous treatment may oversimplify the physical impact of reionization on UFDs, whose star formation histories (SFHs) are highly sensitive to local environments. Under these idealized, instantaneous UVB frameworks, star formation in U…

astro-ph.HE

Why most neutron star low-mass X-ray binaries accrete transiently: an evolutionary study of transient and persistent phases

Divyansh Tripathi, Sudip Bhattacharyya, Pulkit Ojha

A neutron star (NS) low-mass X-ray binary (LMXB), in which an NS accretes matter from a low-mass donor star, is an ideal source for probing some fundamental aspects of physics and astronomy, such as strong gravity, superdense matter, and the accretion-ejection processes. However, to reliably achieve these goals, one must adequately understand NS LMXBs, including why some accrete persistently and others transiently. Focused models, such as those based on a thermal-viscous instability in the accre…

astro-ph.HE

Neutrino Emission from Proton Photon Jet Interactions in Microquasars

Theodoros Smponias

Microquasars are candidate sites for high energy particle production within our galaxy. Because their distances and compact emission regions limit direct observational constraints, numerical simulations are useful for connecting jet dynamics with possible multi messenger signatures. This work models neutrino production from relativistic magnetohydrodynamic microquasar jets, focusing on the proton photon channel associated with interactions between accelerated protons and ambient photon fields. P…

astro-ph.IM

A report on the First Technology Demonstration mission of the Little UV Camera (LUVCam1)

Coby Silayan, Suresh Sivanandam, Aaron Tohuvavohu, Albert Lau, Marianna Dafčíková, Mark Barnet, Patrick Nkwari, Shaojie Chen et al.

Here we report on the status of the first on-orbit technology demonstration of the Little UV Camera (LUVCam1). LUVCam1 is a 0.4U payload aboard the 2U cubesat GRBBeta that was launched in July 2024. The primary objective of the mission was to qualify the GSENSE4040 CMOS sensor and its readout electronics in preparation for the Quick UltraVIolet Kilonova Surveyor (QUVIK; Werner et al. \cite{Werner22, Werner24}) satellite. LUVCam will serve as the primary scientific camera for this mission. We rep…

astro-ph.HE

CRAFT HTR2: Polarimetry of 64 non-repeating fast radio bursts from the updated CRAFT catalogue

T. Dial, A. T. Deller, Marcin Glowacki, A. Bera, R. M. Shannon, Clancy W. James, Joscha N. Jahns-Schindler, Ziteng Wang et al.

We present high-time resolution spectro-polarimetric data for 34 new fast radio bursts (FRBs) discovered by the Commensal Real-time Fast Transients (CRAFT) survey on the Australian Square Kilometer Array Pathfinder (ASKAP) during the period May 2024 to June 2026. Most of these were detected by the higher-sensitivity CRAFT COherent (CRACO) detection system that was commissioned on the telescope during this period. This new sample doubles the size of the CRAFT HTR catalogue and probes a fainter po…

astro-ph.SRastro-ph.HE

COPAS: Compact Objects and the Physics of Accretion Survey I. Accreting Binaries with P < 83 Minutes

Wendy Mendoza, Liliana Rivera Sandoval, Jan Kára, Ryan J. Oelkers, Yuri Cavecchi, Thomas J. Maccarone, Manuel Pichardo Marcano, Meryem K. Dağ et al.

We present the first results from the Compact Objects and the Physics of Accretion Survey (COPAS), a high-cadence photometric survey focused on the detection of accreting white dwarf binaries mainly through their outbursts using TESS. From an initial sample of 2,054 cataclysmic variable (CV) candidates observed during TESS Cycle 6 and 7, we identify 11 systems with periods below 83 minutes. This includes 7 AM CVns and 4 CVs. Our Gemini spectroscopic data confirm ZTF18aaxuusk and ASASSN-21eo as A…

astro-ph.HEastro-ph.SR

Effects of Physical Cooling on the Structure of Circumbinary Disks

Minjae V. Kim, Julian H. Krolik, Scott C. Noble

Radiation pressure and radiative cooling often play an important role in deciding the structure and dynamics of astrophysical objects. In this paper, we present a radiative MHD simulation of a circumbinary disk (CBD) around an equal-mass SMBBH. It employs an approximate thermodynamic model based on local thermodynamic equilibrium and diffusion cooling which captures how the internal energy evolves in an optically thick region. The disk reaches a quasi-steady state within $r=5a$ whose mass distri…

gr-qcastro-ph.GA

Granular Structure and Local de Broglie Wavelength in Fuzzy Dark Matter Halos

Flavio Rosales-Infante, Alejandro Quiñonez-Guerrero, Iván Álvarez-Rios, Francisco S. Guzmán

We study the granular structure that emerges in a Fuzzy Dark Matter (FDM) halo formed through kinetic relaxation. After the system reaches a virialized core-halo structure, we separate the density field into a smooth spherical component and a residual density that contains the interference pattern characteristic of FDM halos. The power spectrum of this residual field shows a well defined dominant scale, different from the characteristic scale of the total density and of the smooth core-halo mode…