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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 3 July

Instrumentation and Methods for Astrophysics

How Low Can We Go? Minimum Spectroscopic Requirements For Supernova Subtype Classification

Willow Fox Fortino, Federica B. Bianco, Maryam Modjaz et al. (+2 more)

Millions of supernovae will be discovered with the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). As a result, spectrographs around the world will have to make difficult decisions about which supernova candidates receive spectroscopic follow-ups. This work identifies the minimum spectral resolution, $R_{\lambda} = \frac{\lambda}{\Delta \lambda}$, as a function of signal-to-noise ratio (SNR) at which spectral classification of supernova subtypes becomes impossible. We include supernova types Ia, Ia-91T, Ia-91bg, Iax, Ib, Ic, broad-lined Ic, IIb, IIP, and Ibn in this work. We produce a definition of SNR based on specific lines for each SN subtype that allows us to generate homogeneous datasets at 16 different values of $R_{\lambda}$ and 14 different SNR's and we tested the classification performance of a recently developed deep-learning classifier, ABC-SN, on each $R_{\lambda}$ and SNR combination. We find that classification of supernova spectra into a refined taxonomy that separates, for example, between different subtypes of stripped envelope supernovae, is possible at low resolution and low SNR with no loss in model performance down to $R_{\lambda} = 50$ and $\text{SNR} = 5$. Classification performance is only minimally impacted even as low as $R_{\lambda} = 25$. We hope that astronomers using the LSST alert stream, as well as designers of future instruments and observatories, will benefit from knowing what spectral resolution is necessary to classify a supernova for arbitrary \SNR{}.
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All authors Willow Fox Fortino, Federica B. Bianco, Maryam Modjaz, Thomas Matheson, Umer Zubair

Cosmology and Nongalactic Astrophysics

Disentangling modified gravity and galaxy bias with field-level inference

Sophie Hoyland, Daniela Saadeh, Kazuya Koyama et al. (+1 more)

We present a field-level inference framework for testing gravity with large-scale structure, exploiting the full information of the galaxy distribution. Traditional analyses based on the power spectrum discard non-Gaussian and Fourier phase information, resulting in strong degeneracies between modified gravity (MG) and galaxy bias. Our approach overcomes this limitation by performing a Bayesian analysis directly on the three-dimensional galaxy number counts, jointly constraining MG and bias parameters using both amplitudes and phases. As an illustrative application, we analyse mock data in real space in the context of $f(R)$ gravity and a non-linear galaxy bias model designed to mimic the real-data 2M++ BORG analysis of Jasche&Lavaux (2019). Non-linear structure formation is modelled using COmoving Lagrangian Acceleration (COLA) under different gravity strengths, parameterised by $f_{R0}$. The resulting dark-matter fields are then mapped to mock galaxy catalogues via a non-linear bias prescription. We demonstrate that, with the initial phases assumed known, including non-Gaussian and phase information yields tighter constraints on both $f_{R0}$ and the primary bias parameter $\beta$ (corresponding to the linear galaxy bias on large scales), relative to power-spectrum-only analyses. Notably, the field-level approach breaks the degeneracies between MG and galaxy bias inherent to two-point statistics. Through a cosmic-web classification into voids, walls, filaments and clusters, we find that under-dense regions are the primary drivers in distinguishing gravity at the field level. Finally, we establish the robustness of our pipeline against variations in initial conditions, Poisson noise, and galaxy-field thresholding, providing a powerful path forward for field-level tests of gravity.
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All authors Sophie Hoyland, Daniela Saadeh, Kazuya Koyama, Harry Desmond

Earth and Planetary Astrophysics

The recent crossing of the 7:3 resonance between Ganymede and Callisto

Giacomo Lari and Mattia Rossi

Io, Europa and Ganymede are locked in the well-known Laplace resonance, while Callisto is not, even though it is very close to the 7:3 mean motion resonance with Ganymede. When considering the estimated tidal dissipation in the Jovian system and the consequent orbital migration rate of the moons, it follows that the 7:3 resonance should have been encountered around two million years ago. Through accurate numerical simulations, we investigated the dynamical effects of the 7:3 resonance crossing on the recent orbital evolution of the Galilean moons. We found that the most probable dynamical pathway is that Ganymede and Callisto were not captured into resonance, not even temporarily, while their eccentricities experienced a downward kick because of the resonance crossing, reducing their mean values of about 16% and 5%, respectively. Since this kind of evolution requires a value of the eccentricity of Ganymede before the resonant encounter slightly larger than today's, it follows that tidal dissipation within the moon must be low. In fact, a null free eccentricity of Ganymede would have led to an almost certain capture into the 7:3 resonance that would have survived until today. As a result of the resonance encounter, the amplitude of the free libration of the Laplace resonant angle increased, providing an explanation for its current value. Moreover, we found evidence that a three-body resonance crossing between the three outer moons occurred within the last few tens of thousands of years.
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Earth and Planetary Astrophysics

A Bayesian Search for Planet Engulfment Signatures in Solar Analogs

Zimo Cheng, Sharon Xuesong Wang, Fan Liu et al. (+11 more)

We present a systematic Bayesian search for chemical fingerprints of planet engulfment in 113 solar twins and analogs with high-precision abundance measurements, 45 of which host known or candidate planets or brown-dwarf companions. We constructed a Bayesian framework with three sets of abundance models: random scatter, Galactic chemical evolution, and planet engulfment with bulk Earth or CM chondrite compositions. Through model comparisons, we identified three candidates whose abundance patterns strongly favor planet engulfment over the alternatives, with inferred engulfed masses of about 7.5-33 Earth masses. Our findings correspond to a nominal detection rate of 1-3% for planet-engulfment signatures among solar analogs. This work extends abundance-based engulfment searches beyond the binary-star context and provides a framework for probing star-planet co-evolution with solar analogs, which goes beyond the commonly used abundance-condensation-temperature correlation (Tc slope).
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All authors Zimo Cheng, Sharon Xuesong Wang, Fan Liu, Haiyang Wang, Qinghui Sun, Johannes Buchner, Mia Babatsikos, Huiling Chen, Jiayue Zhang, Yuan-Sen Ting, Zhen Guo, Aaron Dotter, Serat M. Saad, Javier Osses

Astrophysics of Galaxies

Discovery of a low surface brightness galaxy in the Zone of Avoidance using VVVX Deepstack imaging

J. L. Nilo-Castellón, L. Baravalle, D. Minniti et al. (+12 more)

We report the discovery of VVVX J080705.96-273823.6, the first low-surface-brightness galaxy candidate identified in the Zone of Avoidance by the VISTA Variables in the Via Lactea eXtended Survey (VVVX). The source was detected serendipitously during a visual inspection of the new Deepstack images, reconstructed mosaics generated through an updated reprocessing and stacking procedure that significantly improves the depth and spatial uniformity of the original survey images. First-order morpho-photometric parameters were obtained using SExtractor together with PSF models derived with PSFEx, applied to star-subtracted images to minimize foreground contamination. Structural properties were derived from PSF-convolved modeling of azimuthally averaged surface-brightness profiles in the J, H, and Ks bands using exponential, Sersic, and composite models. The galaxy candidate is clearly detected in all three near-infrared bands. The profiles are consistently described by an exponential disk, with scale lengths of 32-36 arcsec and extinction-corrected central surface brightnesses of 19.82-22.35 mag arcsec^-2. The J band provides the best-constrained profile, while H and Ks show the same behavior with larger uncertainties. The projected proximity to ESO 494-25 and ESO 494-26 suggests a possible physical association. If located at the same distance (11-12 Mpc), the exponential scale length would be about 1.8-2.0 kpc, consistent with nearby LSB disk galaxies, although the lack of a spectroscopic redshift prevents confirmation. This discovery demonstrates that the new VVVX Deepstack products can reveal faint diffuse galaxies at low Galactic latitudes, opening a path toward a more complete census of the obscured nearby Universe.
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All authors J. L. Nilo-Castellón, L. Baravalle, D. Minniti, M. V. Alonso, G. Galaz, C. Villalon, R. Hinojosa, E. O Schmidt, C. Valotto, M. Soto, E. G. Rivera, V. Valdivia-Rojas, D. Alvarez-Rocha, P. Marchant Cortés, N. J. G. Cross

Instrumentation and Methods for Astrophysics · Cross-listed from physics.hist-ph

The influence of the Academy of Gondishapur on the formation of the House of Wisdom in Baghdad and the science of the Golden Age of Islam

Rizoi Bakhromzod

The purpose of this study is to determine the role of the Academy of Gondishapur in the formation of the Bayt al-Hikma (House of Wisdom) in Baghdad and the emergence of Islamic science in the 8th-10th centuries. The methodology combines comparative-historical and biographical analysis with a study of institutional continuity based on primary sources and contemporary scholarly literature. The results demonstrate that Gondishapur, the foremost scientific and medical centre of late Sasanian Iran, constituted the primary human, methodological, and institutional source for the Abbasid Bayt al-Hikma. The migration of specialists, especially the Bukhtishu dynasty, Yuhanna ibn Masawayh, and Hunayn ibn Ishaq, transferred Gondishapur's medical traditions, hospital organisation (bimaristans), and translation methodology to Baghdad. Gondishapur's experience also shaped the development of medical education and the compilation of pharmacopoeias within the Bayt al-Hikma. A comparative structural analysis of the two institutions reveals both institutional borrowings and the original features of the Baghdad model. The article concludes that the transmission of Gondishapur's heritage to the Bayt al-Hikma constituted sustained institutional continuity, laying the foundations for the large-scale synthesis of Greek, Persian, and Indian knowledge in the Arabic language.
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Earth and Planetary Astrophysics

The influence of composition gradients on giant planet radii

Henrik Knierim and Ravit Helled

The radius of a giant planet is a key physical property. It encapsulates the outcome of its mass, composition, and thermal state, serving as a critical link between observations and the theory of planetary interiors. While traditional interior models assume distinct core-envelope structures, recent gravity measurements of Jupiter and Saturn reveal complex interiors with deep composition gradients. Here, we combine an analytic framework with numerical evolution simulations to elucidate how internal structures with composition gradients affect the planetary radius. We demonstrate that the spatial redistribution of heavy elements does not inherently alter the planetary size; rather, it is the resulting difference in total entropy over time that drives observable radius variations. We show that this mechanism naturally establishes two distinct evolutionary regimes. During the first few gigayears of evolution, composition gradients trap thermal energy deep within the interior, significantly affecting the planetary evolution and internal structure. However, as the planet cools and contracts, this “thermal memory” fades and the total entropy no longer depends on the primordial conditions. Consequently, the planetary radius decouples from the internal distribution of heavy elements, becoming solely a function of the total mass and bulk composition. Our results present the physical origin of the mass-radius-composition relation and suggest that the use of simplified interior models for giant exoplanets is legitimate only after the planet has surpassed this evolutionary threshold. Our analysis establishes a thermodynamic constraint on the planetary structure: while composition gradients can temporarily modulate cooling, they cannot permanently sustain radius inflation, as the addition of heavy elements, regardless of their distribution, inevitably leads to planetary contraction.
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Astrophysics of Galaxies

Euclid: Discovery of 31 new quasars at $6.6 < z < 7.8$

D. Yang, J. F. Hennawi, F. Guarneri et al. (+211 more)

We report the discovery of 31 new high-$z$ quasars in the redshift range $6.6 < z < 7.8$. These quasars were selected from approximately 3000 deg$^2$ of sky covered during the first 1.5 years of the Euclid Wide Survey, representing the initial results of the Euclid high-$z$ quasar search. Our candidate selection employed multiple machine-learning and probabilistic techniques applied to the Euclid $I_E$, $Y_E$, $J_E$, and $H_E$ images, supplemented by ancillary $z$-band data when available. Spectroscopic follow-up observations were carried out with Keck, Magellan, and the Large Binocular Telescope (LBT). Among the new discoveries, there are 12 quasars at $z \geq 7$, more than doubling the number of previously known quasars at $z \geq 7$. The newly discovered quasars exhibit $21.2 < J_E < 23.2$ ($-25.5 < M_{1450} < -23.6$), extending quasar studies to the faint end of the quasar luminosity function (QLF) at $z \gtrsim 7$. The quasar with the highest-$z$, EUCL J172902.75+641018.1 at $z \approx 7.77$, sets the new redshift record for the most distant quasar ever reported. These discoveries demonstrate Euclid's transformative role in high-$z$ quasar discovery and set the stage for future follow-up studies of the early galaxies hosting quasars, supermassive black hole growth, and the intergalactic medium in the epoch of reionisation.
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All authors D. Yang, J. F. Hennawi, F. Guarneri, J. Wolf, S. Belladitta, J.-T. Schindler, A. C. N. Hughes, E. Bañados, D. J. Mortlock, J. Yang, F. Wang, X. Fan, K. Jahnke, D. Stern, C. J. Willott, A. J. Barth, H. J. A. Rottgering, R. G. Varadaraj, R. Decarli, A.-C. Eilers, M. Ezziati, Y. Fu, J. Huang, X. Jin, Y. Kang, L. N. Martinez-Ramirez, Y. Matsuoka, M. Onoue, R. Pello, R. P. Remigio, W. L. Tee, B. Venemans, G. Vietri, B. Wang, L. J. Abbo, H. Atek, S. Bisogni, S. E. I. Bosman, R. A. A. Bowler, C. J. Conselice, F. B. Davies, C. M. Gutierrez, Y. Harikane, K. Rubinur, C. C. Lovell, M. Magliocchetti, J. Matthee, F. Ricci, M. Scialpi, D. Scott, L. Spinoglio, F. Tarsitano, Y. Toba, F. Walter, J. R. Weaver, G. Zamorani, B. Altieri, A. Amara, S. Andreon, H. Aussel, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, J.-C. Cuillandre, H. Degaudenzi, G. De Lucia, C. Dolding, H. Dole, M. Douspis, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, S. Ferriol, F. Finelli, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. Gwyn, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, M. Jhabvala, S. Kermiche, B. Kubik, K. Kuijken, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, H. J. McCracken, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, J. J. Mohr, A. Mora, M. Moresco, L. Moscardini, E. Munari, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, G. D. Racca, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, H.-W. Rix, E. Romelli, M. Roncarelli, C. Rosset, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, M. Sauvage, M. Schirmer, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, F. M. Zerbi, E. Zucca, G. Fabbian, M. Huertas-Company, J. Martín-Fleitas, P. Monaco, V. Scottez, M. Viel

Astrophysics of Galaxies

Euclid: A UV-faint quasar in a highly luminous star-forming host galaxy at $z \approx 7.7$

S. Belladitta, R. Decarli, E. Bañados et al. (+180 more)

Constraining the co-evolution of supermassive black holes and their host galaxies in the first billion years after the Big Bang is essential for understanding the formation of the earliest cosmic structures. Here, we present IRAM/NOrthern Extended Millimeter Array (NOEMA) observations of the $z \approx 7.7$ quasar EUCL\,J125308.55+705432.3, recently discovered in the first data release of the Euclid Wide Survey. We report the most distant detections of [CII] 158$\mu\mathrm{m}$ and cold dust emission in a quasar host to date. The [CII] emission line sets the systemic redshift at $z=7.6980\pm0.0004$. The source exhibits luminosities of $L_{\rm FIR}=3.6\times10^{12}\,L_{\odot}$ and $L_{[CII]}=2\times10^9\,L_{\odot}$, respectively, a dust mass of 1.4$\times 10^{8}\,M_{\odot}$, and a dynamical mass in the range 0.33-1.3$\times10^{10}\,M_{\odot}$. Remarkably, despite being nearly two magnitudes fainter in the rest-frame UV ($M_{1450}=-24.06$) than previously known $z\approx7.5$ quasars (<M$_{1450}$> $\sim-$26.5), EUCL\,J125308.55+705432.3 exhibits the brightest [CII] emission among them. This indicates that the host galaxy is actively star-forming, with a star-formation rate $>250\,M_{\odot}\,\mathrm{yr}^{-1}$, consistent with recent findings that UV-faint quasars at $z>6$ preferentially reside in [CII]-luminous galaxies. The UV-faintness likely reflects dust obscuration or sub-Eddington accretion, rather than lower host mass, suggesting these systems are at a different stage in their evolution compared to UV-bright quasars. These IRAM/NOEMA observations highlight the power of combining Euclid's wide-area quasar discovery potential with submillimetre follow-up observations to characterise the host galaxies of early supermassive black holes across a broader redshift and luminosity range than previously accessible.
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All authors S. Belladitta, R. Decarli, E. Bañados, F. Walter, D. Yang, F. Guarneri, K. Jahnke, S. Bisogni, S. E. I. Bosman, X. Fan, Y. Fu, J. F. Hennawi, Y. Matsuoka, D. J. Mortlock, M. Onoue, J.-T. Schindler, L. Spinoglio, D. Stern, F. Wang, G. Vietri, C. J. Willott, J. Wolf, J. Yang, R. A. A. Bowler, K. I. Caputi, D. L. Clements, C. M. Gutierrez, H. J. A. Rottgering, D. Scott, F. Shankar, G. Zamorani, A.-C. Eilers, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, M. Brescia, S. Camera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, J.-G. Cuby, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, M. Douspis, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, F. Faustini, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, R. Laureijs, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Melchior, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, H.-W. Rix, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, M. Schirmer, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, F. M. Zerbi, E. Zucca, J. García-Bellido, J. Martín-Fleitas, P. Monaco, V. Scottez, M. Viel

Astrophysics of Galaxies

PKS 2155-304: Long-Term Optical Photometric Monitoring and Variability Analysis

J. L. Weiss, I. Andruchow, E. J. Marchesini et al. (+6 more)

Through the detailed study of the optical flux behaviour in blazars over time, it is possible to infer the conditions responsible for their observed emission. PKS 2155-304, a BL Lac object detected from radio to TeV energies, is among the brightest blazars in the southern hemisphere. We present optical monitoring spanning over two decades using telescopes at Complejo Astronómico El Leoncito and Estación Astrofísica de Bosque Alegre, Argentina. Differential light curves in the B, V, R, and I bands reveal significant variability on weekly and longer timescales, with occasional changes on sub-four-hour scales. The optical spectral index remained negative, consistent with non-thermal emission, and hardened over the past nine years. Evidence for quasiperiodic behaviour on 20-30 day timescales was found, while correlations with X-ray fluxes were weak, suggesting distinct emission components in the two bands. These results highlight the pronounced optical variability of PKS 2155-304 and provide insight into its multi-band emission mechanisms
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All authors J. L. Weiss, I. Andruchow, E. J. Marchesini, S. Cellone, L. Zibecchi, J. P. Varela, L. Mammana, E. Jofré, R. Petrucci

Instrumentation and Methods for Astrophysics

Simulation-based dynamic pointing analysis of AtLAST under wind loading and fast-scan conditions

Aleksej Kiselev, Martin Timpe, Matthias Reichert et al. (+2 more)

The Atacama Large Aperture Submillimeter Telescope (AtLAST) is a next-generation 50-m class single-dish facility concept designed for high-throughput, wide-field mapping at millimetre and submillimetre wavelengths. Its science goals require fast telescope motion while maintaining stringent dynamic pointing stability under realistic environmental and operational conditions. We present an end-to-end dynamic pointing analysis of the current AtLAST design, coupling a flexible structural model of the telescope mount with the intended cascaded main-axis control architecture, pointing-error evaluation, and measured site wind excitation. A key feature of the study is the use of high-rate wind measurements obtained at the AtLAST candidate sites before telescope construction. The measured wind time series are used as dynamic input to evaluate tracking under wind loading for multiple elevation angles, wind-speed classes, and wind angles of attack. The resulting wind-induced dynamic pointing error remains within the allocated tracking-stability budget for all budgeted wind conditions, confirming the adequacy of the current structural concept and main-axis control approach with respect to wind-driven pointing stability. Fast mapping is investigated separately using a Lissajous-daisy scan close to the kinematic limits of the mount. In contrast to the wind-loaded tracking case, the scan-induced response is more strongly linked to finite control bandwidth and trajectory-following accuracy, particularly in elevation. The analysis therefore identifies two distinct dynamic pointing regimes and provides guidance for future control optimization, feedforward strategies, and active compensation concepts.
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All authors Aleksej Kiselev, Martin Timpe, Matthias Reichert, Tony Mroczkowski, Claudia Cicone

Cosmology and Nongalactic Astrophysics

The heating rate of the Intergalactic Medium by Lyman-$\alpha$ photon scattering

Avery Meiksin

The strength of the 21-cm Cosmic Dawn radio absorption signature against the Cosmic Microwave Background or against a bright background radio source depends on the temperature of the neutral hydrogen in the intergalactic medium. While x-rays from forming galaxies will likely dominate the heating rate, recent models suggest scenarios in which heating by the scattering of Lyman-$\alpha$ photons sourced by the galaxies contributes non-negligibly as well, and may even dominate. The efficiency of Lyman-$\alpha$ photon heating for a point source at high redshift using a numerical solution to the exact radiative transfer equation is provided here. It is found to be a factor of several smaller than the rate computed in the commonly used diffusion approximation to the radiative transfer equation.
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Cosmology and Nongalactic Astrophysics

The giant radio source 0917+75: Origin and properties

G. Giovannini, N. Biava, M. Girardi et al. (+11 more)

Context. Several author have studied the giant radio source GRS0917 + 75 , but its origin remains unclear. Aims. This source is unusual, because of its large size and its location outside a rich cluster of galaxies. We aim to understand and discuss the properties and nature of this source and its connection to the environment. Methods. We conducted optical observations to obtain new spectroscopic data. We also acquired a LOFAR image at 144 MHz to derive information at low radio frequency. Moreover, we performed a new analysis of archival VLA data in the L and C bands for a multifrequency study of the source properties in the radio band. Results. From the observational data, we classify GRS0917 + 75 as a giant radio galaxy with a size of 1.5 Mpc and an estimated age of about 100 Myr. The optical parent galaxy is a bright low-excitation radio galaxy, the brightest member of a very poor group belonging to a large supercluster. GRS0917 + 75 is a peculiar low-power Fanaroff-Riley Class I giant radio galaxy with a bright central emission but no jet-like features. Conclusions. The existence of giant radio galaxies such as GRS0917 + 75 could explain the origin of relativistic particles and magnetic fields in low-density environments.
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All authors G. Giovannini, N. Biava, M. Girardi, W. Boschin, R. Barrena, A. Bonafede, L. Feretti, C. Ferrari, F. Govoni, M. Iacobelli, M. Murgia, E. Orru', R. Pizzo, V. Vacca

Cosmology and Nongalactic Astrophysics

Strong-lensing effects in high-redshift massive black-hole binary population inference

Yan-Heng Jin and Wen-Biao Han

High-redshift massive black-hole binary (MBHB) mergers provide a probe of black-hole seed formation and early galaxy assembly, but the population detected by LISA can be modified by galaxy-scale strong lensing. We quantify this effect for MBHB mergers at $10\leq z\leq20$ and assess its impact on the inference of intrinsic formation-channel fractions. We use four channels, corresponding to light- and heavy-seed scenarios with delayed and non-delayed mergers, and compute 4-year LISA-detectable event numbers with and without strong lensing. To bracket the uncertain lens population, we compare a conservative velocity-dispersion-function (VDF) prescription with an optimistic halo-mass-function (HMF)-based prescription. We consider a reference mixture with equal seed-channel weights and additional mixtures in which the intrinsic seed population is weighted toward selected formation channels, and jointly infer the formation fractions and the strength of the lensing contribution. Strong lensing does not affect all channels equally: it can change the detected channel mixture as well as the total number of detections. This effect is weak for the conservative VDF prescription, but becomes significant in the high-lensing-rate HMF case, where neglecting strong lensing can bias the recovered formation fractions. The inference precision depends on the underlying intrinsic channel composition, while the lensing contribution is more accurately recovered in the high-lensing-rate case. These results indicate that galaxy-scale strong-lensing effects and event-count information should be included when using high-redshift MBHB detections to infer intrinsic formation-channel fractions.
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High Energy Astrophysical Phenomena

Exploring the Magnetic Field Structure of the Milky Way with Pulsars in the SKA Era

Jun Xu, J. L. Han and Weicong Jing

The magnetic field structure of the Milky Way can offer critical insights into the origin of galactic magnetic fields. Measurements of magnetic structures of the Milky Way are still sparse in far regions of the Galactic disk and halo. Pulsars are the best probes for the three-dimensional structure of the Galactic magnetic field, primarily owing to their highly polarized short-duration radio pulses, negligible intrinsic Faraday rotation compared to the contribution from the medium in front, and their widespread distribution throughout the Galaxy across the thin disk, spiral arms, and extended halo. In this article, we give an overview of Galactic magnetic field investigation using pulsars. The sensitive SKA1 design baseline (AA4) will increase the number of known pulsars by a factor of around three, and the initial staged delivery array (AA*) will probably double the total number of the current pulsar population. Polarization observations of pulsars with the AA* telescopes will give rotation measures along several thousand lines of sight, enabling detailed exploration of the magnetic structure of both the Galactic disk and the Galactic halo.
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2607.03314 · 3 Jul · Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no: AASKAII/JunXu01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes. An earlier version of this chapter was published in The Open Journal of Astrophysics with arXiv ID: arXiv:2512.16159

Abstract PDF $MAG ×7$GALAC ×6$PLSR ×6$HALO ×3 +3

Cosmology and Nongalactic Astrophysics

Euclid: Measuring the intrinsic alignment of galaxies around cosmic voids in the \Euclid Flagship simulation\

P. Vielzeuf, M.-C. Cousinou, A. Pisani et al. (+149 more)

We present a methodology to measure the intrinsic alignment (IA) signal of galaxies in the vicinity of cosmic voids using the \Euclid-like Flagship cosmological simulation from the Euclid Consortium. The IA signal is quantified and compared with the predictions of the linear alignment (LA) model, providing one of the first detailed investigations of this effect in underdense large-scale environments. While the IA signal around cosmic voids has received little attention to date, it may constitute a non-negligible systematic in forthcoming cosmological analyses that exploit void-lensing measurements. Our analysis examines red and blue galaxy populations separately, enabling a comparison of their alignment behaviour in void environments with the corresponding trends measured in galaxy-galaxy correlations. We find that the redshift evolution of the IA amplitude in cosmic voids is broadly consistent with that measured in the general galaxy population for both colour-selected samples. Additionally, our modelling allows us to estimate the linear bias of voids, $b_{\rm V}(z)$ which characterises how cosmic voids trace the underlying dark-matter density field, for voids with radii in the range $10 < R_{\rm V}/(h^{-1} {\rm Mpc}) < 15$. The measured bias exhibits a positive trend with redshift, consistent with theoretical predictions for the clustering of underdense regions. These results highlight the importance of accurately modelling IA in void studies, both to mitigate systematic effects in void-lensing cosmology and to further improve our understanding of galaxy-environment interactions in low-density regions of the Universe.
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All authors P. Vielzeuf, M.-C. Cousinou, A. Pisani, S. Escoffier, E. J. Gonzalez, W. d'Assignies, E. Jullo, M. Ghodsi Yengejeh, A. Kovács, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, C. Carbone, V. F. Cardone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, H. Degaudenzi, S. de la Torre, G. De Lucia, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, S. Farrens, F. Faustini, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, M. Kilbinger, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, S. Maurogordato, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, C. Rosset, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, T. Castro, M. Sereno, M. Viel, D. Navarro-Gironés

Astrophysics of Galaxies

Physically motivated AGN emissivity profiles and their effects on quasar microlensing signatures. 1. Multi-epoch accretion disc size inference

Scott Hagen and Carina Fian

Quasar microlensing is uniquely sensitive to the size-scale of the accretion flow, offering one of the few direct probes of the accretion structure on micro-arcsecond scales. However, microlensing-based measurements in the optical and UV often find sizes systematically larger than expected from standard Shakura-Sunyaev disc theory, commonly referred to as the disc-size problem similar to that seen in continuum reverberation campaigns. But this assumes that all the emission comes from a single compact disc, neglecting the diffuse emission from the BLR which originates on much larger spatial scales. In this paper we directly quantify the effect of large-scale diffuse emission on the observed microlensing signatures. We adapt the physically motivated agnsed model to construct energetically self-consistent emissivity profiles in any given bandpass. Since this also predicts the full SED, we combine these SEDs with cloudy to give a diffuse BLR component. We convolve these models with representative microlensing magnification maps, and generate mock microlensing light curves to directly assess the inferred source size under different physical conditions. While the detailed shape of the disc emissivity profile has only a higher-order effect on the microlensing profile, the inclusion of the BLR makes a significant impact since this naturally smooths out the caustic network over larger scales. This introduces a significant bias when interpreted purely as a compact disc. However, the strength of this bias depends predominantly on the fractional contribution of the diffuse emission to the SED in the bandpass being considered, as this sets the effective half-light radius, giving an important wavelength dependence. We conclude that part of the excess in microlensing-inferred accretion disc sizes could arise from interpreting a composite (disc+BLR) picture as a single compact disc.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics

Overcoming the low signal-to-noise problem for hybrid mode-selective photonic lantern-based wavefront correction using machine learning

Nathan K Long, Barnaby Norris, Daniel S Dahl et al. (+10 more)

Hybrid mode-selective photonic lanterns transform an input complex point-spread function into several single-mode outputs, where a selected core feeds the fundamental mode to a photonic science instrument, while the remaining cores are used for wavefront sensing in a closed-loop adaptive optics system. A neural network maps the intensities of the wavefront sensing cores to an estimated wavefront correction, which is applied to an upstream deformable mirror. However, there exists a trade between maximizing the amount of light reserved for the photonic instrument and the reduced signal-to-noise ratios for the wavefront sensing cores. We explore wavefront correction for the Seidr instrument, a part of the Asgard Suite for the Very Large Telescope Interferometer. We evaluate different neural network architectures, comparing wavefront estimation performance for different wavefront error types, as a first step toward addressing the signal-to-noise trade-off. Results show transformer neural networks as a promising solution for temporal photonic lantern-based wavefront estimation.
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All authors Nathan K Long, Barnaby Norris, Daniel S Dahl, Christopher H Betters, Julia J Bryant, Nick Cvetojevic, Sergio Leon-Saval, Frantz Martinache, Marc-Antoine Martinod, Akira Rodziewicz-Ryan, Adam K Taras, Jin Wei, Peter G Tuthill

Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics

Seidr update: photonic 'black magic' for high-contrast interferometry using kernel-nulling and photonic lanterns

Nathan K Long, Daniel S Dahl, Christopher H Betters et al. (+13 more)

Seidr is a new interferometric beam combiner within the Asgard Suite, utilizing infrastructure common to the BIFROST instrument at the Very Large Telescope Interferometer. Seidr combines hybrid mode-selective photonic lantern injection modules with a kernel-nulling photonic chip backend to enable deep H-band nulling for high-contrast studies of exoplanets, exomoons, and circumstellar dust. This instrument update summarizes Seidr's current design maturity and recent simulations of the point source - to - lantern outputs. We also outline progress on our neural network-based wavefront estimation scheme, which uses the photonic lantern outputs to sense phase fluctuations, designed to feed back to Baldr's deformable mirror, and improve nuller light injection.
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All authors Nathan K Long, Daniel S Dahl, Christopher H Betters, Julia J Bryant, Nick Cvetojevic, Michael J Ireland, Stefan Kraus, Sergio Leon-Saval, Frantz Martinache, Marc-Antoine Martinod, Barnaby Norris, Jyotirmay Paul, Akira Rodziewicz-Ryan, Adam K Taras, Jin Wei, Peter G Tuthill

Earth and Planetary Astrophysics

Refined rotational state and shape model of (98943) Torifune ahead of the Hayabusa2# flyby

P. Fatka, P. Pravec, P. Scheirich et al. (+4 more)

The Hayabusa2# mission will perform a high-speed flyby of near-Earth asteroid (98943) Torifune on 5 July 2026, offering a rare opportunity to compare a pre-encounter spin and shape model derived from convex light-curve inversion with spacecraft imaging. We refined Torifune's rotational state and shape model using previously published dense light curves, new photometry data obtained in late 2025, and selected sparse photometry data from the Asteroid Terrestrial-impact Last Alert System (ATLAS). A key methodological contribution is a per-measurement weighting scheme that accounts for heterogeneous data quality and cadence through light-curve scatter, rotational-phase-dependent brightness, and correlation-time downweighting of closely spaced measurements. We also estimated uncertainties with an apparition-constrained block bootstrap, resampling complete light curves while preserving the dense/sparse composition of the dataset and retaining coverage of each apparition. This procedure provides realistic uncertainties for the determined sidereal period, pole direction, and shape parameters. We refine the sidereal period to P_sid = 5.0215221^{+0.0000011}_{-0.0000007} h and confirm a prograde spin state with the axis near the north ecliptic pole. The nominal pole solution is (\lambda, \beta) = (314\degree, +84\degree), with a 5.4\degree angular uncertainty. The dynamically equivalent ellipsoid has a/b = 1.66^{+0.03}_{-0.07}, whereas its polar axis remains less well constrained, with b/c = 1.49^{+0.44}_{-0.29}. All quoted uncertainties correspond to the two-sided 95% intervals of the block-bootstrap distributions. The forthcoming Hayabusa2# flyby should enable direct evaluation of which elements of this pre-encounter convex inversion model are robust, particularly the pole orientation and global silhouette, and may help constrain the remaining uncertainty in the polar dimension of the body.
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All authors P. Fatka, P. Pravec, P. Scheirich, P. Kušnirák, K. Hornoch, H. Kučáková, M. Hirabayashi

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Dark energy genesis: modeling dissipative effects in primordial cosmology

Pietro Pellecchia, Alejandro Perez and Salvatore Ribisi

In various approaches to quantum gravity, spacetime geometry is understood to emerge from more fundamental discrete structures at the Planck scale. As sometimes posited, their presence could lead to dissipative effects in the smooth effective sector. In this paper, we develop the idea of non-conservation in gravity, by introducing an effective cosmological model within unimodular gravity, in which a varying cosmological constant arises as a consequence of dissipation. We show that this requires to incorporate hidden degrees of freedom – termed quantum gravity defects – that act as an effective bath for the matter fields. To illustrate the viability of the framework, we study the case of an Ohmic bath inspired by the Caldeira-Leggett model for Brownian motion, leading to a diffusion equation for the matter energy density. The results show that, starting from a primordial universe with no dark energy, dissipation can account for the generation of a small positive cosmological constant.
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Astrophysics of Galaxies

Advancing extragalactic spectral line studies with the Square Kilometre Array Observatory

Jacco Th. van Loon, Viviana Casasola, Manuela Bischetti et al. (+6 more)

We present an overview of the Square Kilometre Array Observatory (SKAO) science potential in the area of extragalactic spectral lines besides 21-cm neutral hydrogen. It highlights the main points from the SKAO Science Book chapters on individual topics, but is augmented by additional prospects. The SKAO will push studies and use of masers, kilomasers, megamasers, molecular and radio-recombination-line emission and absorption to a wider variety of environments, including to very high redshift where it may detect the first molecule (HeH$^+$). It will open the door to measurements of hydrogen and helium isotopes, probing the conditions for star formation and Big Bang nucleosynthesis. While the planned SKAO of the 2030s (AA*) is destined to forge major progress, an SKAO as initially envisaged (AA4) will truly transform the landscape, and an extension towards higher frequencies (up to 24 GHz) would enable water maser and ammonia surveys in nearby galaxies and systematic molecular gas inventories at redshift 5.
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All authors Jacco Th. van Loon, Viviana Casasola, Manuela Bischetti, Sandra Etoka, Hans-Rainer Klöckner, Mamta Pandey-Pommier, Mark Sargent, Nick Seymour, Andrea Tarchi

Instrumentation and Methods for Astrophysics

FINER: development of the wideband millimeter-wave receiver system and preparations for first light on the Large Millimeter Telescope

Akio Taniguchi, Yoichi Tamura, Takeshi Sakai et al. (+38 more)

The recent discovery of an excess of luminous galaxies in the early Universe necessitates sensitive and wideband millimeter spectroscopy to understand their rapid growth. To address this, we present the development of the Far-Infrared Nebular Emission Receiver (FINER) for the Large Millimeter Telescope (LMT). The FINER frontend comprises two receivers covering 120-350 GHz (corresponding to ALMA Bands 4+5 and 6+7). The warm optics are designed to enable simultaneous two-band observations. Combined with the 10.24-GHz-wide digital spectrometer array, the system aims to deliver an instantaneous bandwidth approximately five times wider than current ALMA capabilities. We report that the 210-350 GHz receiver has already achieved commissioning-level performance, with sideband rejection further enhanced by the digital sideband separation technique. With installation expected in 2026, we discuss parallel preparations, including integrated testing and commissioning plans for first-look targets.
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All authors Akio Taniguchi, Yoichi Tamura, Takeshi Sakai, Masato Hagimoto, Takuya Hashimoto, Akio K. Inoue, Shun Ishii, Haoran Kang, Masato Kato, Ryohei Kawabe, Kotaro Kohno, Takafumi Kojima, Kianhong Lee, Sho Masui, Akinobu Miyake, Taku Nakajima, Tai Oshima, Wenlei Shan, Tatsuya Takekoshi, Kunihiko Tanaka, Kotomi Taniguchi, Kaoru Tsuji, Issei Watanabe, Tom J. L. C. Bakx, Yoshinobu Fudamoto, Kazuyuki Fujita, Yuichi Harikane, Bunyo Hatsukade, David H. Hughes, Takahiro Iino, Yuki Kimura, Hiroyuki Maezawa, Yuichi Matsuda, Ken Mawatari, Shunichi Nakatsubo, Hideo Sagawa, Peter F. Schloerb, Shigeru Takahashi, Akiyoshi Tsujita, Hideki Umehata, Min S. Yun

Cosmology and Nongalactic Astrophysics

Cosmology with HI Intensity Mapping

Laura Wolz, Gabriele Autieri, José Luis Bernal et al. (+18 more)

The redshifted spectral emission from neutral hydrogen (HI) at rest wavelength 21 cm can be used as a tracer of large-scale structure and its evolution. Within the HI intensity mapping method, sufficient signal-to-noise is achieved by integrating the line emission within large voxels over a wide sky area and line of sight depth which allows access to the largest scales of the matter distribution. The resulting tomographic maps usually feature low angular and high redshift resolution. The SKAO will be able to conduct HI intensity mapping experiments observing up to 20,000 square degrees over a wide range of redshifts. For SKA-Mid, we will employ the array in a fast-scanning single-dish mode using Band 1 and 2 to access 0<z<3, mapping an enormous volume with fast survey speed, allowing for the possibility of a commensal survey producing high angular resolution maps via the on-the-fly imaging of the visibilities. For SKA-Low, we will focus on deep observations to detect the HI signal in a frequency band matching 3<z<6. In this chapter, we will give an overview of HI intensity mapping with the SKAO, including an outline of planned surveys, a discussion of observational challenges, and methodology for power spectrum methodology and forecasts. We present predictions on the constraining power on LambdaCDM cosmology from HI intensity mapping data via power spectrum, and other observables such as bi-spectrum and HI stacking. We also demonstrate the synergy power of HI intensity mapping with other cosmological surveys.
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All authors Laura Wolz, Gabriele Autieri, José Luis Bernal, Maria Berti, Philip Bull, Stefano Camera, Isabella P. Carucci, Zhaoting Chen, Steven Cunnington, José Fonseca, Keith Grainge, Jiakang Han, Wenkai Hu, Dionysios Karagiannis, Mario G. Santos, Marta Spinelli, Liantsoa F. Randrianjanahary, Cora Uhlemann, Matteo Viel, Bernhard Vos-Ginés, Jingying Wang

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Odd-parity ringdown gravitational waves of a spherically symmetric black hole with perfect fluid accretion

Rikuto Ohashi, Yasutaka Koga, Hiroyuki Nakano et al. (+2 more)

The ringdown waves from a black hole offer a clean probe of strong-field gravity, but a matter distribution that may be present around a realistic black hole renders the background spacetime dynamical and the ringdown frequencies time-dependent. We study the odd-parity ringdown of a Schwarzschild black hole that grows through the dilute, steady, spherically symmetric accretion of a perfect fluid. Working to first order in the accretion rate, we compute the ringdown waveform directly in the time domain on this dynamical background. Since the odd-parity matter perturbation decouples from the metric perturbation, the wave mode can be described by a purely tensorial mode on the accreting background. In particular, the ratio of the imaginary to the real part of the frequency cancels both the secular variation caused by the growth of the black hole and the redshift factor, so that its deviation from the Schwarzschild value purely reflects the surrounding environment. The time dependence of the frequency, on the other hand, reflects the accretion rate and allows us to define a second observable tied to it. We argue that measuring these observables across multiple modes may provide significant information to constrain the surrounding environment of the black hole.
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All authors Rikuto Ohashi, Yasutaka Koga, Hiroyuki Nakano, Kota Ogasawara, Chul-Moon Yoo

Earth and Planetary Astrophysics · Cross-listed from cs.CE

Uncertainty Quantification Study of a Re-entry Breakup

Tommy Williamson, Beatriz Jilete, Emma Stevenson et al. (+3 more)

The uncertainty associated with breakup events that occur during atmospheric re-entry is severe. Limited attempts to gain a better knowledge of this environment have included the use of breakup recorder-type sensor capsules that are designed to escape the demising debris cloud and survive in order to transmit data. This work models a breakup recorder undergoing this process as a rigid body experiencing hypersonic aerothermodynamic loads alongside collision dynamics with components of the demising container vehicle. The re-entry of the Edoardo Amaldi Automated Transfer Vehicle (ATV3) and the recorder placed on board, the Re-Entry Breakup Recorder 4 (REBR4) is studied in the present work. After a deterministic exploration of the nature of the dynamics of the problem, uncertainty quantification is performed to investigate the effects of initial spacecraft state, REBR detachment conditions and spacecraft fragmentation states. From this data, inferences about the nature of the real re-entry event indicate that detachment of the recorder from the cargo bay prior to main breakup events is more likely than the alternate hypothesis of the container vehicle experiencing high rotation rates.
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All authors Tommy Williamson, Beatriz Jilete, Emma Stevenson, Stijn Lemmens, Massimiliano Vasile, Marco Fossati

Instrumentation and Methods for Astrophysics

DHARA: Data Handling and Automated Reduction pipeline for AIMPOL

Namita Uppal, Shashikiran Ganesh, Santosh Joshi et al. (+3 more)

We present an automated data-reduction and analysis for optical linear polarimetric data obtained from a dual-beam polarimeter. The pipeline is optimized for observations acquired with the ARIES Imaging POLarimeter mounted at the Cassegrain focus of the 1.04-m Sampurnanand Telescope at ARIES. It is implemented using interactive Python routines that process raw images to derive the Stokes parameters, from which the degree of polarization and polarization angle are computed along with their uncertainties. The pipeline framework is designed to handle the reduction of both single-source and crowded-field observations. The identification of extraordinary (e-ray) and ordinary (o-ray) image pairs is a crucial step and is performed using different strategies for single-source and crowded-field data, while subsequent stages, such as photometric and polarimetric analysis, follow a common procedure. We validate the pipeline using observations of polarized standard stars acquired over multiple epochs between 2017 to 2025, and compare the results with values reported in the literature. To demonstrate the applicability of the pipeline to crowded-field observations, we apply it to polarimetric data of the Alessi~1 open cluster and compare with previously published results derived using traditional reduction methods. In both cases, the polarization parameters derived using the pipeline agree with literature values within $2\sigma$ uncertainties. Although developed for AIMPOL, the pipeline is readily adaptable to any dual-channel imaging polarimeter in which the e-ray and o-ray images are recorded in a FITS image from a single CCD.
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All authors Namita Uppal, Shashikiran Ganesh, Santosh Joshi, Dmitry Blinov, Konstantinos Tassis, Sadhana Singh

Cosmology and Nongalactic Astrophysics

Neutrino mass constraints in the Schwarzschild-de Sitter black-hole dark energy model with ACT DR6 and DESI DR2 data

Sheng-Han Zhou, Tian-Nuo Li, Guo-Hong Du et al. (+4 more)

Recent DESI observations have posed new challenges to $\Lambda$CDM, showing a preference for dynamical dark energy and yielding neutrino mass constraints within $\Lambda$CDM that approach the lower bound allowed by neutrino oscillation experiments. In this work, we investigate cosmological constraints on the key neutrino parameters, $\sum m_\nu$ and $N_{\rm eff}$, within the Schwarzschild-de Sitter black-hole dark energy (SdSDE) framework. We use cosmic microwave background (CMB) data from Planck and ACT DR6, baryon acoustic oscillation data from DESI DR2, and type Ia supernova data from DES-Dovekie and PantheonPlus. We find that SdSDE scenarios prefer a positive neutrino mass whenever $\sum m_\nu$ is allowed to vary. Using CMB+DESI+DES-Dovekie data, we obtain $\sum m_\nu=0.207^{+0.047}_{-0.052}~{\rm eV}$ for SdSDE+$\sum m_\nu$, reduced to $\sum m_\nu=0.162^{+0.055}_{-0.056}~{\rm eV}$ when $N_{\rm eff}$ is also varied. This arises from the positive correlation between $N_{\rm eff}$ and $\sum m_\nu$, together with the systematic preference of SdSDE for values of $N_{\rm eff}$ below the standard value. Furthermore, the best-fit $\chi^2$ comparison shows that $\Lambda$CDM with extended neutrino parameters is strongly preferred over the corresponding SdSDE extension. Overall, the positive neutrino mass preference induced by SdSDE may reflect parameter compensation rather than an improved global fit, a possibility that should be further tested with future high-precision observational data.
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All authors Sheng-Han Zhou, Tian-Nuo Li, Guo-Hong Du, Yi-Min Zhang, Zhao-Yu Li, Jing-Fei Zhang, Xin Zhang

Solar and Stellar Astrophysics

The recent anomalously weak polar field does not imply a weak field at solar cycle 25 minimum

Zi-Fan Wang, Jie Jiang, Yukun Luo et al. (+3 more)

The ongoing solar cycle 25 has progressed past its peak of sunspot numbers, being stronger than the previous cycle 24. However, the present polar field is rather weak compared to previous cycles at the same evolution phase, particularly in the northern hemisphere, where it has been decreasing since mid-2025 till present. A prominent poleward surge is observed to cause the decrease of the polar field. This raises concerns to the polar field at cycle 25 minimum, which is the precursor to the strength of the next cycle 26. To predict whether the polar field at cycle 25 minimum will be weak as expected, we use observation-based statistical properties to predict the active region emergence during the latter half of cycle 25, and use a surface flux transport model to simulate the evolution of the large-scale magnetic field. We predict the polar field at cycle 25 minimum to be $-5.62\pm1.61$G in the north and $5.51\pm1.48$G in the south, both stronger than those at cycle 24 minimum. This is because the poleward surge causing the temporal decrease of the polar field originates from a group of active regions that produces net increase to the polar field, instead of active regions with non-Joy's tilt. Our results suggest the weak polar field at present is unlikely to cause a weak minium and an exceptionally weak cycle 26, clarifying that the short term evolution should not be simply correlated to the long term properties of the solar large-scale field.
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All authors Zi-Fan Wang, Jie Jiang, Yukun Luo, Ruihui Wang, Xinchun Ma, Jingxiu Wang

Astrophysics of Galaxies

A steep mass transition for bar-driven ISM structuring revealed by PHANGS-JWST

Eric Emsellem, Jessica Sutter, Ryan Chown et al. (+26 more)

Galactic bars play a critical role in the secular evolution of their hosts by reorganising the ISM. We use a sample of 57 star-forming disc galaxies observed with JWST at 3 and 7.7 $\mu$m to probe how the spatial distribution of PAH emission, as a structural marker of the cold ISM, depends on stellar mass and bar presence. We find evidence for a "watershed" at a stellar mass of $10^{10}$ Msun, marking a fundamental transition in the bar-driven distribution of PAH emission. This confirms trends previously predicted by numerical simulations and observed via ionised gas or UV light. While lower-mass galaxies exhibit a disordered and clumpy distribution of PAH emission regardless of bar presence, higher-mass barred hosts display well-structured dynamical features traced by PAH emission with significant gas reservoirs (e.g., discs and rings) within the central 15% of the bar radius (Rb). Furthermore, we observe a systematic depletion of PAH emission within the [0.2-0.8] Rb range in barred systems with stellar masses above $10^{10}$ Msun. Such central discs, rings, and associated radial dips ("bar deserts") appear to be a mass-dependent phenomenon: ubiquitous in massive galaxies but mostly absent in lower-mass counterparts. In contrast to the structured features in massive hosts, the disorganised ISM in lower-mass galaxies masks commonly observed bar-driven signatures. This suggests that tracer selection and dust obscuration may significantly bias observed bar fractions. Our study underlines two regimes of secular evolution, with different impacts and observability of bar-driven processes: it reaffirms bars as primary drivers of rapid secular evolution in galaxies above $10^{10}$ Msun$, while their impact is significantly reduced or delayed below this threshold. It further underscores the need to account for these processes when modelling galaxy evolution in cosmological simulations.
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All authors Eric Emsellem, Jessica Sutter, Ryan Chown, Adam Leroy, Debosmita Pathak, Eva Schinnerer, Thomas Williams, Karin Sandstrom, Oscar Agertz, Francesco Belfiore, Amelia Fraser-McKelvie, Kirsten Larson, Janice Lee, Jay Gonzàlez Lobos, Sharon Meidt, Miguel Querejeta, Sophia Stuber, Pierrick Verwilghen, Oleg Egorov, Damian Gleis, Jonathan Henshaw, Justus Neumann, Yixian Cao, Daniel Dale, Daizhong Liu, Elias Oakes, Marina Ruiz Garcìa, Dave Thilker, Elizabeth Watkins