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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 9 April

Earth and Planetary Astrophysics

A practical re-weighting scheme of data fitting: application to asteroids orbit determination with Gaia

Dmitri. E. Vavilov, Ziyu. Liu, Daniel. Hestroffer et al. (+1 more)

The method of weighted least squares is widely used in parameter estimation problems such as asteroid orbit determination. A key difficulty is the treatment of observational uncertainties, especially when combining heterogeneous datasets with differing precision. We propose a simple reweighting scheme that adjusts the contribution of each measurement group to ensure a statistically consistent least-squares solution. It consists of three steps: (i) estimating error standard deviations for each observational subset, (ii) rescaling their weights by the corresponding variances, and (iii) a weighted least-squares fit with the adjusted weights. We apply this to heliocentric orbit fitting of asteroids using ground-based astrometry and high-precision Gaia measurements. We validated the method by fitting each orbit to a restricted set and comparing with the complete set of measurements. For 7 objects, the reweighted solutions provide significantly improved agreement with older data. The most dramatic case is asteroid (21) Lutetia, where increasing the effective uncertainty of Gaia observations by a factor of 17 yields a substantially better fit, indicating the importance of accounting for systematic biases in high-precision datasets. We further apply the scheme to near-Earth asteroid 2024 YR4, grouping observations by visual magnitude. The reweighted orbit produces smaller uncertainty regions and a more stable solution, reducing predicted impact probabilities by roughly an order of magnitude. All computed probabilities remain below 0.5%, under the 1% International Asteroid Warning Network (IAWN) alert threshold. This reweighting procedure provides a practical way to combine heterogeneous measurements, improving the reliability of orbit determination and impact-risk assessment. The method is general and can be readily applied to other parameter estimation problems involving mixed-precision data.
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All authors Dmitri. E. Vavilov, Ziyu. Liu, Daniel. Hestroffer, Josselin. Desmars

Earth and Planetary Astrophysics

The Fate of Frozen Carbonated Water at Europa-like Conditions

Swaroop Chandra, William T.P. Denman and Michael E. Brown

We present the results of experiments probing the retention of CO2 in crystalline water ice, frozen sodium chloride (NaCl) brines, and flash-frozen carbonated water using diffuse reflectance infrared spectroscopy. Characteristic absorptions alluding to the formation of clathrate hydrates in crystalline ices and frozen brines are observed. NaCl in frozen brines does not affect qualitatively affect the formation of clathrate hydrates. Generation and stability of clathrates in crystalline ice transiently subjected to pressure-temperature (P-T) conditions in the stability region is observed, despite conditions being unviable at the onset of freezing. Retention of CO2 in flash-frozen carbonated water is observed to be dependent on the temperature of the substrate during freezing. The state of CO2 retained in the resulting ices differs from clathrate hydrates, as inferred from the respective infrared spectra. Both mechanisms of CO2 retention are stable up to 140 K and under evacuated conditions. In the context of Europa, the P-T states traversed by the samples plausibly represent the typical conditions around endogenous CO2 if it is indeed transported from the subsurface ocean to the surface while being retained in ice/frozen brines and/or liquid emerging on the surface. However, the absorptions of CO2 in the laboratory infrared spectra do not match those detected on the leading side of Europa by the NIRSpec instrument on board JWST. Therefore, it is unlikely that the endogenous CO2 observed at the surface of Europa is sourced directly from the ocean, unless additional processes affect the observed bands of CO2 on Europa.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc

Evaluating Deep Learning Models for Multiclass Classification of LIGO Gravitational-Wave Glitches

Rudhresh Manoharan and Gerald Cleaver

Gravitational-wave detectors are affected by short-duration non-Gaussian noise transients, commonly referred to as glitches, which can obscure astrophysical signals and complicate downstream analyses. While recent work has demonstrated the effectiveness of deep learning models for glitch classification using image-based time-frequency representations, comparatively less attention has been given to systematic evaluations of machine-learning architectures operating directly on tabular glitch metadata. In this work, we present a comprehensive benchmark of classical and deep learning models for multiclass glitch classification using numerical features derived from the Gravity Spy dataset. We compare gradient-boosted decision trees with a diverse set of neural architectures, including multilayer perceptrons, attention-based models, and neural decision ensembles, and evaluate them in terms of classification performance, inference efficiency, parameter efficiency, data-scaling behavior, and cross-model interpretability alignment. We find that while tree-based methods remain strong baselines for tabular data, several deep learning models achieve competitive performance with substantially fewer parameters and exhibit distinct inductive biases and scaling behavior. A cross-model attribution analysis further reveals partially consistent feature-importance hierarchies across architectures, providing new insight into interpretability structure in tabular models. These results clarify trade-offs between performance, complexity, data efficiency, and interpretability in tabular gravitational-wave analyses and provide practical guidance for deploying machine-learning models in detector characterization pipelines.
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Instrumentation and Methods for Astrophysics

Development of the New Optical Sensor for IceCube-Gen2

Delaney Butterfield and Chris Wendt

A new digital optical module (DOM) has been developed for the proposed expansion to the IceCube detector at the South Pole, IceCube-Gen2. The "Gen2-DOM" has 4 times the integrated photon sensitivity of the current IceCube DOMs and has built off the design features of the IceCube Upgrade modules. The Gen2-DOM has up to 18 4" photomultiplier tubes (PMTs) in a borosilicate glass pressure vessel, arranged in a uniform 4$\pi$ angular distribution. The mechanical design has been optimized to fit into a reduced borehole diameter which, in turn, will reduce drilling costs during installation. Each PMT has a dedicated readout board, designed to increase sensitivity to high-energy events aligned with the science goals of IceCube-Gen2. Internal storage enables multi-level triggering schemes with reduced overall flow of data on the long cables. Twelve prototypes of the Gen2-DOM will be deployed in the IceCube Upgrade in the 2025-2026 austral summer. This article will focus on the current status of design development and initial performance testing results.
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Astrophysics of Galaxies

Colloquium: Radio astronomy with the Arecibo 305-m telescope: In contemporaneous context

Tapasi Ghosh and Chris Salter

Most scientific research begins in the context of the then-contemporary state of knowledge of the field and moves toward a deeper understanding of the subject. This colloquium presents the Arecibo telescope$^{'}$s contribution to radio astronomy from the point of view of its contemporary impact and relevance and how that evolved over the 57 years of its long life. Sometimes, serendipitous discoveries at Arecibo and elsewhere brought revolutionary changes to the field. Further, significant upgrades to the reflector, optics, receiving, and data-taking systems helped clear a pathway for a leap ahead. Charting these movements through time and without any claim to completeness, this Colloquium presents a progression through Arecibo telescope$^{'}$s role in the history of radio astronomy.
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Solar and Stellar Astrophysics

EPISODE IV: Ice Inventory in the Envelope of EC 53

Jaeyeong Kim, Jeong-Eun Lee, Chul-Hwan Kim et al. (+9 more)

We present the 1.6$-$28 $\mu$m spectra of the young protostar EC 53, obtained with JWST NIRSpec IFU and MIRI MRS during the quiescent and burst phases of its periodic brightness variations. To isolate ice absorption features, we modeled and removed the mid-infrared silicate dust absorption using a dedicated continuum-fitting procedure. In the optical depth spectrum, we first fit the broad H$_2$O ice features and then decomposed the major ice components, including NH$_3$, CO$_2$, CH$_3$OH, CO, and CH$_4$, by matching laboratory profiles for both pure and H$_2$O-mixed ices. The 4.62 $\mu$m and 6.85 $\mu$m bands are attributed to OCN$^-$ and NH$_4^+$ ions, respectively. Minor or tentative contributions from complex species (HCOOH, H$_2$CO, CH$_3$COOH, CH$_3$CHO, CH$_3$CH$_2$OH, and NH$_2$CHO) are also considered to our global ice analysis. The silicate-corrected spectra reveal no measurable change in any ice absorption band between the two phases, indicating that moderate and short-period accretion bursts in EC~53 do not significantly alter the physical or chemical state of the ices within its envelope. The derived abundances of these major species relative to H$_2$O significantly exceed the values typically observed toward other embedded protostars. Finally, we place the ice inventory of EC~53 in the context of other protostellar systems observed with JWST, highlighting that its chemically rich, thermally quiescent ice reservoir provides a benchmark for studying ice evolution under episodic accretion.
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All authors Jaeyeong Kim, Jeong-Eun Lee, Chul-Hwan Kim, Seokho Lee, Giseon Baek, Seonjae Lee, Yao-Lun Yang, Yuri Aikawa, Gregory J. Herczeg, Doug Johnstone, Joel D. Green, Woong-Seob Jeong

High Energy Astrophysical Phenomena

Chasing Gamma-Ray Signals from Binary Neutron Star Coalescences with the Cherenkov Telescope Array: Prospects and Observing Strategies

S. Abe, J. Abhir, A. Abhishek et al. (+457 more)

The detection of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced LIGO and Advanced Virgo (GW170817), together with its electromagnetic counterpart, the short gamma-ray burst GRB~170817A, heralded the birth of multi-messenger astronomy. The detection of TeV emission from GRBs motivates follow-up observations with the Cherenkov Telescope Array Observatory (CTAO), ideal for detecting such signals due to its unprecedented sensitivity, rapid response, and wide-field survey capabilities. The aim of this work is to evaluate GeV–TeV GW follow-up strategies for CTAO using a multi-step simulation pipeline and to estimate the expected rate of joint GW-GRB detections during observing run O5. Using a simulated sample of BNS systems with corresponding GW detections, gamma-ray emission is simulated through phenomenological prescriptions based on the observed population of short GRBs, including off-axis jet scenarios. CTAO observations are simulated to account for instrument response, sky tiling strategies, integration times, and varying observing conditions. Strategies with variable and constant integration times are investigated. We find that, via an optimized follow-up strategy, about 5% of simulated GW-associated short GRBs produce GeV–TeV radiation detectable by CTAO. Detectability is strongly influenced by the jet opening angle and viewing angle, suggesting that even rough estimates of the viewing angle in GW alerts could enhance targeting. This framework motivates future follow-ups of GW-detectable events, including neutron star-black hole mergers, and further supports the development of advanced strategies incorporating galaxy distributions and synergies with future detectors such as the Einstein Telescope.
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All authors S. Abe, J. Abhir, A. Abhishek, F. Acero, A. Acharyya, R. Adam, A. Aguasca-Cabot, I. Agudo, I. Albanese, J. Alfaro, C. Alispach, R. Alves Batista, E. Amato, G. Ambrosi, D. Ambrosino, F. Ambrosino, L. Angel, C. Aramo, A. Arbet-Engels, C. Arcaro, C. Arena, T. T. H. Arnesen, K. Asano, H. Ashkar, C. Bakshi, C. Balazs, M. Balbo, A. Baquero Larriva, V. Barbosa Martins, J. A. Barrio, C. Bartolini, I. Batkovic, R. Batzofin, N. Bavdaz, J. Becerra Gonzalez, G. Beck, W. Benbow, E. Bernardini, M. G. Bernardini, J. Bernete, A. Berti, B. Bertucci, V. Beshley, P. Bhattacharjee, S. Bhattacharyya, C. Bigongiari, A. Biland, E. Bissaldi, M. Bla\ na, O. Blanch, J. Blazek, C. Boisson, G. Bonnoli, Z. Bosnjak, E. Bottacini, M. Bottcher, E. Bronzini, G. Brunelli, J. Buces Saez, A. Bulgarelli, T. Bulik, L. Burmistrov, P. G. Calisse, A. Campoy-Ordaz, B. K. Cantlay, G. Capasso, A. Caproni, R. Capuzzo-Dolcetta, M. Cardillo, S. Caroff, A. Carosi, E. Carquin, S. Casanova, E. Cascone, F. Cassol, G. Castignani, F. Catalani, D. Cerasole, M. Cerruti, P. M. Chadwick, S. Chaty, A. W. Chen, Y. Chen, M. Chernyakova, A. Chiavassa, G. Chon, J. Chudoba, L. Chytka, G. M. Cicciari, A. Cifuentes Santos, C. H. Coimbra Araujo, J. L. Contreras, B. Cornejo, J. Cortina, A. Costa, G. Cotter, P. Cristofari, O. Cuevas, Z. Curtis-Ginsberg, G. D'Amico, F. D'Ammando, P. D'Avanzo, P. Da Vela, L. David, F. Dazzi, M. de Bony de Lavergne, V. De Caprio, E. M. de Gouveia Dal Pino, B. De Lotto, M. de Naurois, V. de Souza, L. del Peral, M. V. del Valle, C. Delgado, D. della Volpe, D. Depaoli, A. Dettlaff, L. Di Bella, T. Di Girolamo, A. Di Piano, F. Di Pierro, R. Di Tria, L. Di Venere, R. Dima, A. Dinesh, E. Do Souto Espiñeira, D. Dominis Prester, A. Donini, D. Dorner, J. Dorner, M. Doro, L. Ducci, V. V. Dwarkadas, J. Ebr, C. Eckner, K. Egberts, L. Eisenberger, D. Elsasser, G. Emery, C. Escanuela Nieves, P. Escarate, M. Escobar Godoy, J. Escudero Pedrosa, P. Esposito, D. Falceta-Goncalves, E. Fedorova, S. Fegan, K. Feijen, Q. Feng, G. Ferrand, E. Fiandrini, A. Fiasson, M. Filipovic, V. Fioretti, L. Foffano, G. Fontaine, Y. Fukazawa, Y. Fukui, G. Galanti, G. Galaz, S. Gallozzi, V. Gammaldi, M. Garczarczyk, C. Gasbarra, D. Gasparrini, M. Gaug, G. Ghirlanda, J. G. Giesbrecht Formiga Paiva, N. Giglietto, F. Giordano, M. Giroletti, R. Giuffrida, J.-F. Glicenstein, P. Goldoni, J. M. Gonzalez, J. Goulart Coelho, T. Gradetzke, J. Granot, R. Grau, D. Green, J. G. Green, J. Grube, J. Hackfeld, D. Hadasch, A. Hahn, P. Hamal, W. Hanlon, S. Hara, V. M. Harvey, T. Hassan, K. Hayashi, L. Heckmann, N. Hiroshima, B. Hnatyk, R. Hnatyk, D. Horan, P. Horvath, D. Hrupec, S. Hussain, M. Iarlori, T. Inada, F. Incardona, S. Inoue, F. Iocco, A. Iuliano, Jahanvi, M. Jamrozy, P. Janecek, F. Jankowsky, C. Jarnot, I. Jaroschewski, P. Jean, V. Jilek, J. Jimenez Quiles, W. Jin, E. Joshi, J. Jurysek, V. Karas, H. Katagiri, J. Kataoka, S. Kaufmann, T. Keita, D. Kerszberg, M. Kherlakian, D. B. Kieda, R. Kissmann, T. Kleiner, Y. Kobayashi, K. Kohri, D. Kolar, N. Komin, A. Kong, K. Kosack, D. Kostunin, G. Kowal, H. Kubo, J. Kushida, A. La Barbera, N. La Palombara, B. Lacave, M. Lainez, A. Lamastra, J. Lapington, S. Lazarevic, J.-P. Lenain, F. Leone, E. Leonora, G. Leto, E. Lindfors, S. Lombardi, F. Longo, R. Lopez-Coto, M. Lopez-Moya, A. Lopez-Oramas, J. Lozano Bahilo, P. L. Luque-Escamilla, E. Lyard, O. Macias, P. Majumdar, M. Makariev, D. Mandat, S. Mangano, A. Marchetti, M. Mariotti, S. Markoff, I. Marquez, G. Marsella, O. Martinez, G. Maurin, D. Mazin, D. Melkumyan, S. Menon, E. Mestre, D. M.-A. Meyer, D. Miceli, M. Miceli, M. Michailidis, T. Miener, J. M. Miranda, R. Moderski, M. Molero, C. Molfese, E. Molina, K. Morik, A. Morselli, E. Moulin, A. L. Muller, K. Munari, T. Murach, A. Muraczewski, H. Muraishi, T. Nakamori, R. Nemmen, J. Niemiec, D. Nieto, M. Nievas Rosillo, L. Nikolic, K. Noda, D. Nosek, V. Novotny, S. Nozaki, A. Okumura, R. A. Ong, R. Orito, M. Orlandini, E. Orlando, S. Orlando, J. Otero-Santos, I. Oya, M. Ozlati Moghadam, A. Pagliaro, M. Palatiello, A. Pandey, G. Panebianco, D. Paneque, F. R. Pantaleo, J. M. Paredes, B. Patricelli, A. Pe'er, M. Pech, M. Pecimotika, M. Peresano, E. Peretti, J. Perez-Romero, G. Peron, F. Perrotta, M. Persic, O. Petruk, F. Pfeifle, E. Pietropaolo, M. Pihet, L. Pinchbeck, F. Pintore, G. Pirola, C. Pittori, F. Podobnik, M. Pohl, V. Pollet, G. Ponti, E. Prandini, G. Principe, M. Prouza, E. Pueschel, G. Puhlhofer, M. L. Pumo, M. Punch, A. Quirrenbach, S. Raino, R. Rando, S. Recchia, A. Reimer, O. Reimer, I. Reis, A. Reisenegger, W. Rhode, M. Ribo, C. Ricci, T. Richtler, J. Rico, L. Riitano, V. Rizi, E. Roache, G. Rodriguez Fernandez, P. Romano, G. Romeo, J. Rosado, A. Rosales de Leon, A. Roy, I. Sadeh, L. Saha, T. Saito, M. Sanchez-Conde, P. Sangiorgi, H. Sano, R. Santos-Lima, V. Sapienza, S. Sarkar, F. G. Saturni, A. Scherer, F. Schiavone, P. Schipani, P. Schovanek, F. Schussler, O. Sergijenko, H. Siejkowski, A. Simongini, V. Sliusar, A. Slowikowska, I. Sofia, H. Sol, S. Spinello, A. Stamerra, T. Starecki, R. Starling, T. Stolarczyk, Y. Suda, A. Sunny, T. Suomijarvi, R. Takeishi, S. J. Tanaka, F. Tavecchio, T. Tavernier, Y. Terada, M. Teshima, V. Testa, W. W. Tian, Y. Tian, L. Tibaldo, O. Tibolla, S. J. Tingay, C. J. Todero Peixoto, F. Tombesi, D. Tonev, F. Torradeflot, D. F. Torres, N. Tothill, G. Tovmassian, G. Tripodo, A. Trois, A. Tsiahina, A. Tutone, L. Vaclavek, M. Vacula, C. van Eldik, J. Vandenbroucke, V. Vassiliev, M. Vazquez Acosta, M. Vecchi, S. Vercellone, S. D. Vergani, I. Viale, A. Viana, A. Vigliano, J. Vignatti, C. F. Vigorito, J. Villanueva, E. Visentin, V. Voitsekhovskyi, S. Vorobiov, I. Vovk, T. Vuillaume, R. Walter, M. Wechakama, M. White, A. Wierzcholska, M. Will, F. Wohlleben, A. Wolter, F. Xotta, T. Yamamoto, R. Yamazaki, T. Yoshikoshi, M. Zacharias, G. Zaharijas, R. Zanmar Sanchez, D. Zavrtanik, M. Zavrtanik, A. Zech, V. I. Zhdanov, J. Zuriaga-Puig

Earth and Planetary Astrophysics

Positive YORP effect induced by lateral heat conduction in a crater

Zehua Qi, Yining Zhang, Hailiang Li et al. (+2 more)

The YORP effect plays an important role in the spin evolution of asteroids. Although craters are ubiquitous surface features, their influence on YORP torque has received limited attention. In this paper, we investigate the YORP torque of a circular crater on a spherical asteroid, focusing specifically on how lateral thermal conduction breaks symmetry to produce a net torque. Using three-dimensional finite element simulations, we calculate the resulting spin and obliquity accelerations and examine their dependence on the crater's location, depth, and thermal parameters. Our results show that the crater-induced spin torque is consistently positive, and craters at different latitudes drive the spin axis toward obliquity equilibria at 0, 90 or 180 degree. We demonstrate that the spin torque arises primarily from the lateral heat conduction inside the asteroid that occurs only in 3D model, while the contributions from self-heating and shadowing effects are negligible. While the YORP effect induced by internal heat conduction may be overtaken by torque components arising from shadowing and crater orientation, particularly on large asteroids, our numerical results show that for small craters, this spin torque amounts to approximately 10 to 100 percent of the normal YORP torque. Its persistent positivity may help explain the observed prevalence of positive spin accelerations in asteroids.
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All authors Zehua Qi, Yining Zhang, Hailiang Li, Yangbo Xu, Li-Yong Zhou

Astrophysics of Galaxies

GLIMPSED: Direct evidence for a fast active galactic nucleus-driven outflow from a z=6.64 little red dot host galaxy

Damien Korber, Rui Marques-Chaves, Daniel Schaerer et al. (+15 more)

We report the discovery of GLIMPSED-329380, a z=6.64 galaxy behind Abell S1063, which shows signs of an extreme ionised outflow driven by an active galactic nucleus (AGN). The deep JWST/NIRSpec medium grating observations show spatially resolved structures of a host galaxy containing the very fast outflow and an AGN, which we analyse separately. The outflow, mainly traced by broad [O III]{\lambda}5008 and H{\alpha} emissions in the host, reaches a full-width-at-half-maximum velocity of ~5350km/s, velocities only observed in AGN-dominated systems. From the Balmer decrement, we observe that while the narrow emission lines show no dust attenuation, the outflowing gas is dusty. We use emission lines diagnostics to infer gas abundances within the host galaxy. The oxygen abundance is 12+log(O/H)~7.96 (~18% solar) and the host is slightly nitrogen-enriched with log(N/O) ~ -0.68. Unless the extreme outflow turns out to be very dusty, the mass loading factor (>5-10%), and the kinetic energy (>1e43erg/s) of the extreme outflow does not hint at a significant impact on the galaxy. The AGN component shows many similarities with little red dots (LRDs): a characteristic 'V shape', exponential profile in hydrogen lines, numerous detection of forbidden [Fe II] lines, a Balmer break, and a broad absorption feature at ~4550Å. This detection of a fast outflow in an LRD, rare in surveys dominated by low-resolution (e.g. PRISM) spectra, provides direct evidence of AGN activity in these systems.
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All authors Damien Korber, Rui Marques-Chaves, Daniel Schaerer, Gabriel Brammer, Archana Aravindan, Arghyadeep Basu, Qinyue Fei, Emma Giovinazzo, Vasily Kokorev, Alberto Saldana-Lopez, Maxime Trebitsch, Hakim Atek, John Chisholm, Ryan Endsley, Seiji Fujimoto, Lukas Furtak, Richard Pan, Rohan P. Naidu

High Energy Astrophysical Phenomena

Ghosts of eruptions past: Searching for historical Galactic supernovae using variable thermal dust echoes and machine learning

Justin Vega, Kishalay De, Ashish Mahabal et al. (+4 more)

The Galactic core-collapse supernova (SN) rate is estimated at $\approx 1-3$ per century; however, no optically visible SN has been discovered in the past 400 years. Although records of the last optically detected SN (Cassiopeia A) are debated, it is revealed today via its bright, variable mid-infrared (MIR) dust echoes – offering the possibility of identifying dust-obscured, missed events via their dust echoes. We present the first all-sky, untargeted search for thermal dust echoes of luminous Galactic transients using difference imaging on 12 years of time-resolved NEOWISE co-adds (spanning $2009-2022$) followed by statistical detection of variable extended sources. We use echo features around Cas A, together with archival catalogs to train a convolutional neural network to classify transient candidates as dust echoes, point sources, artifacts, and high proper motion stars. Our model achieves $\approx 94$% accuracy in distinguishing echoes from other variable sources. Applying the classifier to $\approx 11$ million transient candidates, we search for spatial over-densities of echoes across the Galactic plane. We find that Cas A is the only region exhibiting echoes at the WISE sensitivity threshold of $W2$ surface brightness of $\approx 20$ Vega mag arcsec$^{-2}$ – reflecting its unique combination of young age and luminous shock breakout. We present the largest catalog of time-resolved echo positions of Cas A (20477 within 10$^\circ$) that are being used for studies of the surrounding interstellar medium with the James Webb Space Telescope. Our results lay the groundwork for the imminent Roman space telescope surveys – which will achieve $\approx 100\times$ higher sensitivity and $\approx 30\times$ better spatial resolution at wavelengths of $\lesssim 2.5\,\mu$m.
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All authors Justin Vega, Kishalay De, Ashish Mahabal, Jacob E. Jencson, Viraj R. Karambelkar, Armin Rest, Megan Masterson

Astrophysics of Galaxies

The Hubble sequence in JWST CEERS from unbiased galaxy morphologies

Elizaveta Sazonova, Cameron R. Morgan and Michael Balogh

Whether the "Hubble sequence" of galaxy morphologies exists up to z~4 is still disputed, and one of the challenges is characterizing galaxy structure consistently across a wide range of redshifts. To enable a fair comparison across cosmic time, we constructed "absolute" images of galaxies spanning 0.15<z<4.5 and 8<log $M_{\star}$<11 from HST CANDELS and JWST CEERS surveys, by matching the effective resolution and surface brightness limit of galaxies, accounting for cosmological dimming and evolution in size and mass-to-light ratio. We measured the structural parameters of 2825 galaxies and used the UMAP technique to study the evolution of the morphological phase space. We find a continuous sequence spanning late-type to early-type galaxies, with no redshift gradient - indicating that a Hubble-like sequence is established by z~4. We show that our approach recovers a cleaner separation between early- and late-type galaxies than visual classifications. By tracing progenitors using empirical mass assembly histories, we find that progenitors of low-mass galaxies are predominantly star-forming disks at all epochs. Progenitors of massive galaxies follow two distinct paths: a stable star-forming disk population with little structural evolution, and an early-type population that builds up rapidly from irregular progenitors and quenches within a few Gyr, consistent with a compaction-driven quenching scenario.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Tidal Response of Compact Objects

Sumanta Chakraborty and Paolo Pani

The tidal response of compact objects provides a powerful probe of their internal structure and of the surrounding gravitational field. We provide a comprehensive and unified overview of tidal effects in black holes, neutron stars, and exotic compact objects, with emphasis on both static and dynamical responses to external fields, encoded in Love numbers and dissipation numbers. We discuss the vanishing of static bosonic Love numbers for black holes in vacuum General Relativity, their modifications in alternative theories, in non-standard models of compact objects, and in the presence of matter, as well as their role in testing deviations from Einstein's theory and environmental effects. A fundamental distinction between bosonic and fermionic perturbations is highlighted, as the latter yield nonzero static Love numbers even for black holes in General Relativity. For neutron stars, we overview the dependence of tidal Love numbers on the equation of state, the emergence of quasi-universal relations, and the impact of rotation, nonlinearities, and dynamical effects. Exotic compact objects typically feature nonvanishing static tidal Love numbers – a striking observational signature that differentiates them from black holes. We further review how tidal effects influence the gravitational-wave signals from binary inspirals, and explore their implications for gravitational-wave astronomy. In particular, we stress their significance for current and future detectors as tools to test General Relativity, constrain the nuclear equation of state, and probe the fundamental nature of compact objects and their environments.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Minimum mass, maximum charge and hyperbolicity in scalar Gauss-Bonnet gravity

Dario Rossi, Leonardo Gualtieri and Thomas P. Sotiriou

We study the loss of hyperbolicity of perturbation equations for black hole solutions of scalar Gauss-Bonnet gravity. We consider a class of coupling functions allowing for static black hole solutions with arbitrary small masses. For masses below a minimum value, such solutions become unphysical, because the perturbation equations become elliptic; this arguably corresponds to the loss of validity of the effective field theory. We analyse the dependence of this minimum mass on the parameters of the theory, finding that with an appropriate choice of the coupling function, such mass can be chosen arbitrarily small. However, this does not correspond to larger deviations from general relativity, since observable quantities like the black hole scalar charge are bounded by above.
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Instrumentation and Methods for Astrophysics

Choice of optical transformation for photonic circuit wavefront sensors

Jonathan Lin

Coronagraph designs which use photonic integrated circuits have the highest theoretical throughput for off-axis signals, and therefore the highest potential exoplanet yield for future high-contrast direct imaging campaigns. Using the rejected starlight, the photonic integrated circuit may also provide simultaneous wavefront sensing, allowing for the correction of non-common-path aberrations. This work considers how a photonic circuit should be configured to maximize its sensitivity to phase aberrations. Two cases are considered: in the first, the photonic circuit is coupled directly to an electric field in a piecewise manner, while in the second, the circuit is coupled to the field via an optical mode sorter. In either case, this work constructs a unitary matrix which can be applied by a photonic circuit to produce maximum sensitivity.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Love numbers of black holes and compact objects

María J. Rodríguez, Luca Santoni and Adam R. Solomon

The Love numbers of a gravitating body are response coefficients encoding its tidal deformability. In compact binary systems, they appear in the gravitational waveform during the inspiral phase and will be measurable by upcoming gravitational-wave observatories. This review provides a comprehensive and pedagogical account of the theoretical foundations of Love numbers and surveys the most recent advances in the study of tidal effects in compact objects, with particular emphasis on black holes and neutron stars. We begin with a gentle introduction to tidal effects in Newtonian gravity, leading into a discussion of how to robustly define tidal responses in general relativity using the effective field theory and post-Newtonian frameworks. After an overview of the perturbation theory of black holes and neutron stars, we review the computation of Love numbers and dissipative response coefficients in a wide range of settings, including the static, dynamical, and nonlinear tidal responses of Kerr black holes and neutron stars in four-dimensional general relativity. We further discuss the extension of these results to charged black holes and a number of "new physics" scenarios, including higher-dimensional black holes and other black objects, (anti-) de Sitter black holes, supergravity black holes, and theories beyond general relativity. Finally we provide an overview of the tantalizing zoo of hidden symmetries of general relativity that have been uncovered in the attempt to explain the famous vanishing of static black hole Love numbers.
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Astrophysics of Galaxies

Temperature asymmetry in the Milky Way's hot circumgalactic medium induced by the Magellanic Clouds

Alexandru Oprea, Filippo Fraternali, Else Starkenburg et al. (+2 more)

The Milky Way is surrounded by a hot diffuse circumgalactic medium (CGM) with temperatures of millions of degrees. Recent X-ray observations with the eROSITA satellite discovered a significant temperature asymmetry of this hot CGM, with the southern hemisphere being on average hotter than the northern one by a relative difference of ${\Delta} T/T \approx 12\%$, where $T$ is averaged over the entire CGM. In this Letter, we investigate whether the passage of the Magellanic Clouds can be responsible for this asymmetry by means of a hydrodynamical/N-body simulation. In the simulation, the Magellanic Clouds induce a relative motion of the Milky Way's disc of up to 40 km/s. This motion leads to compression of the CGM gas in the southern hemisphere, resulting in an overall temperature increase in that region. We estimate a south-north temperature difference of ${\Delta} T/T \approx 13-20\%$, consistent with the observations. We find that this temperature asymmetry is a recent phenomenon that began ~100 Myr ago.
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All authors Alexandru Oprea, Filippo Fraternali, Else Starkenburg, Thor Tepper-Garcia, Joss Bland-Hawthorn

Cosmology and Nongalactic Astrophysics

Primordial Neutron Stars

Gordan Krnjaic, Duncan Rocha and Huangyu Xiao

We propose a novel cosmological scenario in which baryonic neutron stars could plausibly form in the early universe. If baryogenesis initially produces an excessively-large baryon asymmetry, $Y_B \gg 10^{-10},$ the baryonic mass inside the horizon can exceed the minimum neutron star mass before big bang nucleosynthesis (BBN). While this large asymmetry is present, non-relativistic baryons can dominate the universe and enhanced density perturbations on small scales can gravitationally collapse Hubble patches shortly after horizon re-entry. For some initial perturbations, just below the threshold for black hole formation, this collapse will be arrested only by nuclear pressure, possibly resulting in neutron star formation. Afterwards, there must be a large entropy injection to restore the observed baryon asymmetry, $Y_B \sim 10^{-10}$, and preserve the successful predictions of standard BBN. Unlike neutron stars that form from stellar collapse, primordial neutron stars can, in principle, be as light as $\sim 0.1 M_\odot$, limited only by the nuclear equation of state.
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High Energy Astrophysical Phenomena

High-dimensional inference for the $\gamma$-ray sky with differentiable programming

Siddharth Mishra-Sharma, Tracy R. Slatyer, Yitian Sun et al. (+1 more)

We motivate the use of differentiable probabilistic programming techniques in order to account for the large model-space inherent to astrophysical $\gamma$-ray analyses. Targeting the longstanding Galactic Center $\gamma$-ray Excess (GCE) puzzle, we construct differentiable forward model and likelihood that make liberal use of GPU acceleration and vectorization in order to simultaneously account for a continuum of possible spatial morphologies consistent with the GCE emission in a fully probabilistic manner. Our setup allows for efficient inference over the large model space using variational methods. Beyond application to $\gamma$-ray data, a goal of this work is to showcase how differentiable probabilistic programming can be used as a tool to enable flexible analyses of astrophysical datasets.
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All authors Siddharth Mishra-Sharma, Tracy R. Slatyer, Yitian Sun, Yuqing Wu

Astrophysics of Galaxies

Bypassed Core Formation in Milky Way-Mass SIDM Halos: Implications for the Local Group Past-Pericenter Scenario

Zhichao Carton Zeng, Odelia V. Hartl, Louis E. Strigari et al. (+4 more)

We consider a scenario in which the Milky Way (MW) and M31 have had a previous pericentric passage, and investigate its compatibility with self-interacting dark matter (SIDM). Using initial conditions sampled from Local Group (LG) analogues in the IllustrisTNG simulation, we perform controlled re-simulations of the MW-M31 orbit, evolving the system under both standard cold dark matter (CDM) and various SIDM cross-sections. We find that the deep baryonic potential of the MW preconditions the halo's thermal structure, establishing an initial negative temperature gradient. This drives SIDM halos to bypass the standard core-formation phase and enter immediate core-collapse, resulting in monotonically increasing central densities. In full orbital simulations, the compact stellar component (disk/bulge) of the MW analog remains robust against tidal disruption for pericenter distances as close as $r_{\rm peri}\lesssim20$ kpc during an encounter at cosmic time $\sim8$ Gyr. The diffuse stellar halo is comparatively more susceptible, facing disruption for $r_{\rm peri}\lesssim100$ kpc. Our results demonstrate a dichotomy in structural evolution: the compact disk/bulge is sensitive to intrinsic SIDM thermodynamics but dynamically robust against the pericenter encounter, whereas the diffuse stellar halo is largely independent of the specific SIDM model but more vulnerable to orbital tidal disruptions.
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All authors Zhichao Carton Zeng, Odelia V. Hartl, Louis E. Strigari, Annika H. G. Peter, Xiaolong Du, Charlie Mace, Andrew Benson

Earth and Planetary Astrophysics · Cross-listed from q-bio.QM

Resolving satellite-in situ mismatches in Net Primary Production using high-frequency in situ bio-optical observations in the subpolar Northwest Atlantic

Kitty Kam, Emmanuel Devred, Stephanie Clay et al. (+5 more)

Net primary productivity (NPP) plays a central role in biological carbon pump (BCP) and global carbon cycling, but NPP estimates in high-latitude regions remain highly uncertain despite their disproportional contribution to the global carbon sink. Previous studies identified discrepancies among satellite and in situ-derived NPP estimates, but the drivers of disagreement remain poorly resolved due to limited high-frequency observations. Here, we present continuous depth-resolved estimates of in situ NPP in the subpolar Northwest Atlantic (56{\deg}N), reconstructed from daily bio-optical profiles collected between May and October 2016, and a 40-years dataset of photosynthesis parameters derived from ^{14}C photosynthesis-irradiance (P-I) incubation experiments. Comparing with two satellite-based models showed satellite models overestimated NPP by factors of 2.5 to 4 from the study period. Statistical analyses identified the parameterization of the P-I relationship as the primary source of disagreement between satellite and in situ NPP estimates. Given the importance of NPP to estimates of the biological carbon pump, our findings highlight the need for regionally appropriate P-I parameterization in NPP models, particularly in high-latitude regions.
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All authors Kitty Kam, Emmanuel Devred, Stephanie Clay, Mohammad M. Amirian, Andrew Irwin, Dariia Atamanchuk, Uta Send, Douglas W.R. Wallace

Astrophysics of Galaxies · Cross-listed from physics.flu-dyn

Inverse Energy Cascade in Turbulent Taylor-Couette Flows

Changquan Zhou, Hua-Shu Dou, Lin Niu et al. (+1 more)

The inverse energy cascade in turbulent Taylor-Couette flow is studied in line with the results of the large eddy simulation. The simulation results show that the inverse energy cascade first occurs within the core region of the flow channel of the Taylor-Couette flow at higher Reynolds number. It is uncovered that this phenomenon is induced by the pulsed zero shear stress resulting from the singularities of the Navier-Stokes equation. In the core area between the two cylinders, the shear stress is nearly zero at higher Reynolds number. The turbulence generated there has high turbulent energy due to discontinuity of the tangential velocity. Since the energy transfer between the fluid layers is inhibited due to the low shear stress, the turbulent energy cannot be transferred along the radial direction, and small-scale vortices with high turbulent energy are produced. These small-scale vortices are located with the large-scale vortices and cannot be dissipated owing to low shear stress. A peak in the energy spectrum at middle frequency (or wave number) is formed due to the concentration of the small-scale vortices. As the number of the singular points of the Navier-Stokes equation increases with the increasing Reynolds number, the region with zero shear stress expands along the radial direction, intensifying nonlinear instability and energy accumulation. This, in turn, leads to more prominent peaks in the energy spectrum, resulting in a more pronounced inverse energy cascade.
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All authors Changquan Zhou, Hua-Shu Dou, Lin Niu, Wenqian Xu

Cosmology and Nongalactic Astrophysics

Disentangling cosmic distance tensions with early and late dark energy

Tanisha Jhaveri, Tanvi Karwal, Thomas Crawford et al. (+4 more)

Recent cosmological data reveal tension between parameters inferred from measurements of the cosmic microwave background (CMB), baryon acoustic oscillations (BAO), and supernovae (SN) under $\Lambda$CDM. Typical dynamical dark energy parameterizations (such as $w_0w_a$) that seek to jointly resolve these tensions have an equation of state parameter that crosses into the phantom regime, leading to potential instabilities for physical models. We show that the BAO (early-time) and SN (late-time) sides of the tension can instead be treated independently. Early dark energy (EDE) can reduce the tension between CMB-BAO data by changing the calibration of the sound horizon at the drag epoch $r_d$, with a $\Delta\chi^2 = -{9.4}$ relative to $\Lambda$CDM, raising $H_0$ to 70.87 $\rm km s^{-1}Mpc^{-1}$. EDE alone cannot bring consistency between CMB, BAO, and SN data, but combining with a thawing-quintessence component of dark energy reduces tensions between the three datasets, with $\Delta\chi^2=-12.6$ relative to $\Lambda$CDM without a phantom component, vs. $\Delta\chi^2=-15.8$ for $w_0 w_a$ with one. We consider different SN datasets, using the most recent DES Dovekie catalog as our default while assessing differences with the original DESY5 and Pantheon+ catalogs. While the significance of adding thawing quintessence changes, the EDE solution to the CMB-BAO tension remains nearly unaffected. Moreover, though we do not include direct Hubble constant measurements in these $\Delta\chi^2$ values, the EDE solution reduces the Hubble tension with the Local Distance Network value from $7\sigma$ in $\Lambda$CDM to $2-3\sigma$ depending on the SN dataset, nominally the equivalent of an extra $\Delta\chi^2 \sim -40$ or more.
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All authors Tanisha Jhaveri, Tanvi Karwal, Thomas Crawford, Wayne Hu, Ali Rida Khalife, Lennart Balkenhol, Fei Ge

Cosmology and Nongalactic Astrophysics

The Heavy Tailed Non-Gaussianity of the Supermassive Black Hole Gravitational Wave Background

Juhan Raidal, Juan Urrutia, Ville Vaskonen et al. (+1 more)

We study the non-Gaussian features of the gravitational wave (GW) background generated by a population of inspiraling supermassive black hole (SMBH) binaries. We show that the SMBH GW amplitude distribution (GWAD) features a universal heavy power-law tail $\propto A^{-4}$, while the low-amplitude tail depends on the SMBH merger rate and the energy-loss mechanisms of the binaries. The distribution of the induced timing residuals inherits this heavy tail. As a result, the ensemble averaged statistical moments of order three and higher diverge, limiting their usefulness as measures of non-Gaussianity, and the GW background from SMBH binaries exhibits the single loud source principle, according to which the strongest signals are more likely to be caused by a small number of loud sources. We confirm that the variance-averaged Gaussian approximation accurately describes the timing residual statistics. This approximation justifies a factored likelihood structure that combines standard Gaussian-process PTA posteriors with the non-Gaussian population prior, enabling consistent incorporation of non-Gaussian effects into SMBH model inference. We provide a fast and flexible Python implementation to compute the distribution of timing residuals from a given SMBH merger rate or GWAD.
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All authors Juhan Raidal, Juan Urrutia, Ville Vaskonen, Hardi Veermäe

Cosmology and Nongalactic Astrophysics

Probing non-Gaussianity during reheating with SIGW in the LISA band

Gabriele Perna and Guillem Domènech

We analyse the effects of a non-standard evolution of the Universe during the reheating epoch on the spectrum of scalar-induced gravitational waves (SIGWs) accounting for the presence of primordial non-Gaussianity. We show that given values of $w$ and $c_s^2$ leave characteristic features in the spectrum which can be detectable by third generation interferometers like LISA. In addition, we argue that the specific reheating dynamics can suppress or even enhance the spectrum, with crucial consequences for its detectability. We perform a Fisher forecast for different values of $w$ and different scans to assess the detectability of the signal when different values of the amplitude and central frequency are considered.
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Earth and Planetary Astrophysics

The effect of dust on vortices II: Streaming instabilities

Nathan Magnan and Henrik Nils Latter

One of the main questions in planet formation theory is how to cross the metre-scale barrier. In this two-part series, we assess the merits of vortex-based theories by investigating the effect of backreacting dust on vortices. Specifically, this second paper focuses on the 'turbulent' vortex theory, according to which the streaming instability (SI) might be active in vortices. We re-purpose the dusty vortex models derived in paper I as background flows for a linear stability analysis. To simplify the perturbation equations, we build an analogue of the shearing box that follows vortex streamlines instead of Keplerian orbits. This allows us to study the evolution of small wavelength perturbations. We find that inertial waves and dust density waves can propagate in vortices, but that they are not sinusoidal in time. We then extend resonant drag instability theory to these non-modal waves. This allows us to demonstrate that a close cousin of the SI remains active in vortices, a result that greatly strengthens the case for vortex-induced planetesimal formation. Our results also complement past simulations - which showed that the dust's backreaction makes vortices unstable - by providing insights into the nature of (some of) the unstable modes. The caveat is that our work is restricted to the limit of dilute well-coupled dust and to the linear phase of the instability. Finally, our 'vortex SI' extends to 2D. We explain the mechanism of this 'zonal flow RDI', but remain unsure whether it is the unknown instability seen in 2D vortex simulations.
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Earth and Planetary Astrophysics

The effect of dust on vortices I: Laminar models

Nathan Magnan and Henrik Nils Latter

One of the main questions regarding planet formation is how to cross the metre-scale barrier. Several theories rely on the formation of dust clumps dense enough to collapse under their own gravity. Vortices are promising candidate sites of clump formation because they can concentrate dust 'laminarly' by capturing particles, and 'turbulently' by creating the ideal conditions for the streaming instability. In this two-part series, we assess the validity of both pathways by investigating the effect of backreacting dust on vortices. This first paper focuses on the laminar pathway. We use multiple timescale analysis to create two models of vortex evolution. They differ in their assumptions regarding how much gas crosses the vortex's boundary: the first one assumes that the vortex's mass is constant, whereas the second one assumes that the gas density is constant. These two options epitomize the two ways in which vortices can respond to dust concentration. Essentially, as dust gets closer to the vortex centre, it loses angular momentum. To compensate, the gas must either move away from the vortex centre or change its vorticity (and therefore its shape). This choice neatly emerges from the conservation of a quantity akin to potential vorticity. Interestingly, we find that vortices that adjust their vorticity all evolve towards elliptically unstable shapes. And since the elliptical instability destroys the vortex, we conclude that dust imposes an upper bound on vortex lifetimes. If vortex destruction happens before the dust reaches the Hill density, the 'laminar' vortex pathway to planetesimal formation fails.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Squashed Pyramid Interferometer Network (SPIN): Direct Access to Chirality of Cosmological Gravitational Waves

Dmitri E. Kharzeev, Azadeh Maleknejad and Saba Shalamberidze

The cosmological gravitational wave background provides a powerful window on parity-violating physics at energies far beyond the reach of terrestrial experiments. However, any colocated planar detector network is insensitive to isotropic circular polarization, independent of its relative orientation. In this Letter, we show that this no-go result can be evaded by a new class of colocated 3D interferometer designs, which we call Squashed Pyramid, whose non-coplanar configuration geometrically isolates chirality. The design can be viewed as a minimal extension of the Einstein Telescope geometry, obtained by introducing a slightly tilted arm relative to the ET planar configuration. The coplanar correlation channel is blind to circular polarization, whereas the colocated non-coplanar channel is insensitive to the unpolarized background and acquires a response only in the presence of nonzero net helicity. Squashed Pyramid interferometer networks therefore furnish a unique probe of cosmological gravitational wave chirality, opening a realistic terrestrial pathway to test parity violation and fundamental symmetry breaking in the early Universe.
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Cosmology and Nongalactic Astrophysics

A GPU-Accelerated JAX Framework for Robust Parametric Component Separation and Clustering Optimization for CMB Polarization Satellites

Wassim Kabalan, Arianna Rizzieri, Wuhyun Sohn et al. (+6 more)

We present a novel, JAX-powered implementation of a parametric component-separation method for CMB polarization data, explicitly designed to handle spatially varying foreground Spectral Energy Distributions (SEDs). The approach models this variation across the sky by grouping sets of pixels that share common foreground spectral parameters, scanning over thousands of such configurations to evaluate the trade-off between model complexity and residual systematic contamination. Built within the FURAX framework – a JAX-powered environment for CMB data analysis – our pipeline extends the fgbuster parametric formalism. It enables fully vectorized, GPU-accelerated evaluation of the spectral likelihood, map reconstruction, and diagnostic metrics across tens of thousands of pixel subset configurations, noise realizations, and sky regions. Our implementation achieves up to $\sim 100\times$ speed-up over the scipy TNC optimizer used in fgbuster when running on GPUs, as well as giving more robust results. When applied to LiteBIRD-like simulations with spatially varying foreground SEDs, our optimized K-means configuration reduces the 68% upper limit on the tensor-to-scalar ratio $r$ by $\approx 30\%$ relative to a fixed, previously derived multi-resolution configuration, while maintaining competitive statistical uncertainties.
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All authors Wassim Kabalan, Arianna Rizzieri, Wuhyun Sohn, Artem Basyrov, Alexandre Boucaud, Benjamin Beringue, Pierre Chanial, Ema Tsang King Sang, Josquin Errard

Cosmology and Nongalactic Astrophysics

Coupled Dark Energy and Dark Matter for DESI: An Effective Guide to the Phantom Divide

Stefan Antusch, Stephen F. King and Xin Wang

Motivated by the recent Dark Energy Spectroscopic Instrument (DESI) DR2 preference for dynamical dark energy, we study interacting dark energy models in which a canonical quintessence field couples to cold dark matter through a field-dependent mass $m(\phi)$. In such scenarios, the effective equation of state inferred under the assumption of non-interacting dark sectors, $w_{\rm eff}(z)$, can differ from the intrinsic scalar-field equation of state $w_\phi(z)$, making an apparent phantom crossing $w_{\rm eff}<-1$ possible without introducing a phantom scalar. We show that a viable realization of this mechanism requires the scalar field to originate from a frozen phase deep in the radiation era, in order for the effective coupling to remain sufficiently suppressed before recombination to evade cosmic microwave background constraints, and for the late-time evolution to become strong enough to reproduce the apparent behavior of $w_{\rm eff}(z)$ preferred by DESI. We identify the general conditions that allow these requirements to be satisfied simultaneously, and present an illustrative phenomenological realization in which $w_{\rm eff}(z)$ evolves from $w_{\rm eff}\approx -1.2$ at $z \approx 1.0$ to $w_{\rm eff}\approx -0.9$ at $z\approx 0.4$. These conditions and requirements serve as a guide for designing future models of this kind which can safely navigate the phantom divide at $w=-1$ in an effective way without phantom fields.
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High Energy Astrophysical Phenomena

Optical images of Kerr-Sen black hole illuminated by thick accretion disks

Yu-Kang Wang, Chen-Yu Yang and Xiao-Xiong Zeng

This paper investigates the shadow and polarization images of a Kerr-Sen black hole illuminated by geometrically thick and optically thin accretion disks. We adopt two classes of accretion models, namely the phenomenological radiatively inefficient accretion flow (RIAF) model and the analytical ballistic approximation accretion flow (BAAF) model. Based on radiative transfer theory, we examine the effects of the spin parameter $a$, black hole charge $Q$, and observer inclination angle $\theta$ on the shadow images. Both models show that, as the charge $Q$ increases, the photon rings and the central dark regions shrink simultaneously. Meanwhile, frame dragging gives rise to a pronounced brightness asymmetry, which becomes more significant with increasing $a$ and $\theta$. The main difference between isotropic and anisotropic radiation is that, in the latter case, the higher order images are brighter in the upper and lower polar regions. For the BAAF model, because the conical approximation renders certain regions geometrically thinner, the spatial extent of the higher order images is narrower than that in the RIAF model, and the separation between the direct image and the higher order images is more distinct. In the polarization images, the spatial distribution of the polarization vector directions is mainly determined by gravitational lensing and frame dragging, whereas the intensity near the photon ring and the scale of the higher order images are significantly influenced by $Q$.
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