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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 23 June

Astrophysics of Galaxies

Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect

Timothy Robishaw, Marta Nowotka, Tao-Chung Ching et al. (+7 more)

Zeeman splitting in spectral lines – both in emission and absorption – provides direct estimates of magnetic field strength and direction in magnetized gas in our own Milky Way and in external galaxies. We discuss the potential for using the Square Kilometre Array (SKA) to measure the Zeeman effect in targets spanning an enormous range of distance: from cometary comas in the solar system, through Galactic molecular clouds, HI filaments in the cold neutral medium, high-velocity clouds, the Fermi Bubbles, and photodissociation regions (PDRs) traced by radio recombination lines, to OH masers and megamasers in nearby and distant starburst galaxies, and to cold neutral gas in damped Ly-alpha absorbing systems at cosmological redshifts. We update the sensitivity calculations of Robishaw et al. (2015) and indicate, for each science goal, whether it will be achievable with Array Assembly 4 (AA4) of SKA-Mid, with the staged delivery of AA*, or only with the full SKA buildout. Zeeman measurements will probe the magnetic field in situ in the warm and cold neutral interstellar medium, complementing SKA Faraday rotation programs; radio recombination lines, stackable across hundreds of transitions, extend this reach to HII regions and PDRs. In external galaxies, SKA-Mid will enable Zeeman studies of OH kilomasers in nearby starburst systems, substantially expand the census of megamaser Zeeman detections beyond the Arecibo sky, and probe magnetic fields in damped Lyman-alpha systems to field limits well below those currently achievable, opening a new window on the role of magnetic fields in galaxy formation and cosmic evolution.
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All authors Timothy Robishaw, Marta Nowotka, Tao-Chung Ching, James A. Green, Anita M. S. Richards, Sandra Etoka, Malcolm Gray, Susan E. Clark, Tyler L. Bourke, Vincent Fish

Instrumentation and Methods for Astrophysics

The Impact of Host Galaxy Properties on Supernova Classification with Hierarchical Labels

V. Ashley Villar, Sebastian Gomez, Edo Berger et al. (+1 more)

With the advent of the Vera C. Rubin Observatory, the discovery rate of supernovae (SNe) will surpass the rate of SNe with real time spectroscopic followup by three orders of magnitude. Accurate photometric classifiers are essential to both select interest events for followup in real time and for archival population-level studies. In this work, we investigate the impact of observable host galaxy information on the classification of SNe, both with and without additional light curve and redshift information. We find that host galaxy information alone can successfully isolate relatively pure (>90%) samples of Type Ia SNe with or without redshift information. With redshift information, we can additionally produce somewhat pure (>70%) samples of Type II SNe and superluminous supernovae. Additionally with redshift information, host galaxy properties do not significantly improve the accuracy of SN classification when paired with complete light curves. In the absence of redshift information, however, galaxy properties significantly increase the accuracy of photometric classification. As a part of this analysis, we present the first formal application of a new objective function, the weighted hierarchical cross-entropy, to the problem of supernova classification. This objective function more naturally accounts for the hierarchical nature of supernova classes and, more broadly, transients. Finally, we present a new set of SN classifications for the Pan-STARRS Medium Deep Survey of SNe that lack spectroscopic redshift, increasing the full photometric sample to >4400 events.
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All authors V. Ashley Villar, Sebastian Gomez, Edo Berger, Alex Gagliano

Astrophysics of Galaxies

Opening new parameter space windows on galaxy/AGN co-evolution with SKA radio continuum surveys

Isabella Prandoni, Mark T. Sargent, Matteo Bonato et al. (+11 more)

In this chapter we provide an overview of the science enabled by the SKAO, focusing on galaxy/AGN co-evolution studies. In particular we discuss a number of radio continuum `reference' surveys with the SKAO, highlighting the role they can play in advancing this research field with respect to the pre-SKAO era. Alongside well-explored scenarios for wedding cake-like, tiered extragalactic surveys at specific frequencies, we also address the scope for complementary efforts to obtain deep multi-frequency imaging over parts of (an) extragalactic field(s). In addition to providing key information on the physical properties of the emitting sources, such multi-frequency imaging will make important contributions to the calibration of observables from surveys with sparser radio spectral coverage. In this context, we explore possible pathways that can fully exploit the SKAO from initial (AA*) to baseline capabilities (AA4). Finally, we highlight observational synergies with other major facilities – for wide field and targeted follow-up science – that will be operational in the 2030s, and for which joint coverage of extragalactic fields will generate significant legacy value
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All authors Isabella Prandoni, Mark T. Sargent, Matteo Bonato, Dharam V. Lal, Mahdiyar Mousavi-Sadr, Masoumeh Ghasemi-Nodehi, Nicholas Seymour, Fatemeh S. Tabatabaei, Gianfranco De Zotti, Ivano Baronchelli, Elisabetta Liuzzo, Nicola Marchili, Marcella Massardi, Rosita Paladino

Astrophysics of Galaxies

Galactic Hubs: New Insights and SKA View of AGN Feedback in Galaxy Groups

T. Pasini, M. Brienza and C. J. Riseley

Over the last two decades, significant effort has been devoted to understand the physical processes involved in galaxy evolution. In this context, AGN feedback has emerged as the leading explanation for several longstanding astrophysical questions, including the origin of scaling relations between supermassive black holes and their host galaxies. Galaxy clusters have been particularly put under the lens, thanks to the combination of high-resolution X-ray and radio observations which allowed to investigate the link between thermal and non-thermal emission. On the other hand, research in the lower-mass regime of galaxy groups remains limited. This is mostly due to observational limitations in the high-energy regime, which prevents the study of the non-thermal emission in the context of its surrounding environment. Nevertheless, this is a key topic for galaxy evolution, as the vast majority of radio-loud AGN in the nearby Universe are hosted in galaxy groups. Recently, modern radio facilities such as LOFAR, uGMRT and MeerKAT have obtained interesting results in this regime. Examples include signatures of overheating caused by AGN, groups with largely evacuated environments due to powerful and prolonged feedback activity, and remnant plasma displaced by large-scale sloshing motions. This chapter reviews these advances while identifying gaps in our understanding. We will explore how SKA promises to close these gaps and revolutionise the field through its unparalleled combination of high resolution and sensitivity across a wide frequency range. Moreover, its unique capabilities, in synergy with state-of-the-art and upcoming surveys carried out by new instruments, will facilitate the construction of unprecedentedly large samples of groups, dramatically enhancing the statistical power of future studies.
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Earth and Planetary Astrophysics

Coupled atmospHere Interior modeL Intercomparison (CHILI). I. Evolutionary Modelling – Primordial Magma Oceans of Earth and Venus

Harrison Nicholls, Joshua Krissansen-Totton, Tim Lichtenberg et al. (+22 more)

Earth and Venus represent two evolutionary outcomes arising from initially molten 'magma ocean' periods, followed by lifetimes of chemical and geophysical divergence. Their physics is common to all rocky planets and is accessible to simulations that adopt coupled interior-atmosphere modelling approaches. Our understanding of planet histories and interpretation of current states is dependent on this modelling, yet existing codes vary in their approximations. Here, we present the first results from the Coupled atmospHere Interior modeL Intercomparison (CHILI) project; benchmarking planetary evolution codes in the context of Earth and Venus to identify key model sensitivities. Our 'nominal' Earth models predict magma ocean solidification timescales within 4 Myr of thermal evolution, and are consistent with empirical constraints on Earth's early history. Venus scenarios exhibit more diverse behaviours where prolonged magma ocean stages can be conditionally sustained for 50 Myr. Cooling timescales correlate with initial hydrogen and carbon budgets, but model-specific treatments of volatile partitioning and vertical energy transport introduce substantial inter-model variance. Different parametrisations of mantle geodynamics, convection, melting curves, rheological properties, and radiative transfer give rise to divergent evolutionary behaviours. Discrepancies in atmospheres generated by magma ocean outgassing underscore these differences, although C-H-O compositions with surface pressures exceeding 100 bar are favoured. This intercomparison identifies critical sensitivities in volatile partitioning, escape processes, mantle viscosity, and melting. Validating these treatments is essential for enabling deep insight into the early histories of the Solar System's terrestrial planets, and for drawing meaningful interpretations from ongoing observational exoplanet campaigns.
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All authors Harrison Nicholls, Joshua Krissansen-Totton, Tim Lichtenberg, Laura Schaefer, Keiko Hamano, Maxime Maurice, Henri Samuel, Alexandra Papesh, Carlos Ortiz-Quintana, Junellie Perez, Yamila Miguel, Denis Sergeev, Philipp Baumeister, Spanan Dash, Leoni Janssen, Jonathan Keathley, Alexandre de Larminat, Emmanuel Marcq, Lena Noack, Hugo Pelissard, Bo Peng, Emma Postolec, Ramses Ramirez, Mariana Sastre, Andrea Zorzi

Astrophysics of Galaxies

Unlocking the Full Potential of SKAO Extra-galactic Science with High-multiplex Optical Spectroscopy

Kenneth J Duncan, Natasha Maddox, Daniel J. B Smith et al. (+9 more)

Parallel to the transformation in radio continuum and H I observations from SKAO pathfinders and precursors over the past decade has been the development of a new generation of multi-object spectrographs that will be equally transformational in a broad range of scientific areas. For all extragalactic radio source populations, this spectroscopy is essential for providing precise redshifts, separating star-formation and AGN activity, identifying accretion modes and revealing detailed host galaxy properties. It is only with the detailed emission line and optical continuum diagnostics from spectroscopy that we can begin to link the AGN and star-formation activity revealed by the radio continuum to the kinematic and chemical histories of galaxies. Crucially, extensive spectroscopy also unlocks the full potential of H I observations by enabling statistical measures of the H I content of galaxies out to $z = 1$ and beyond, through spectral stacking analyses, as well as comprehensively tracing the local environment and large-scale structure to enable studies of environmental effects on the baryon cycle. We outline the scientific synergies enabled by combining SKAO continuum and H I surveys with current optical spectroscopic surveys, as well as identifying the needs and scientific potential of future spectroscopic surveys dedicated to the radio source population with both existing and planned optical facilities.
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All authors Kenneth J Duncan, Natasha Maddox, Daniel J. B Smith, Marina I Arnaudova, Catherine L Hale, Sophia Flury, Luke Holden, Matt J Jarvis, Elizabeth A. K. Adams, S. Ilani Loubser, Mamta Pandey-Pommier, Anastasia Ponomareva

Earth and Planetary Astrophysics

Stellar Wind Driven Alfvén Wing Dynamics in Planetary and Exoplanetary Magnetospheres

Sakshi Gupta, Arnab Basak and Dibyendu Nandy

Magnetized obstacles embedded within a plasma flow generate magnetohydrodynamic structures known as Alfvén wings, which act as primary conduits for the transfer of momentum and energy between the body and the surrounding medium. This study employs three-dimensional resistive magnetohydrodynamic simulations to explore how these wings and the magnetosphere respond to diverse stellar wind conditions. Our results, gleaned from a large number of systematic simulations spanning a wide range of stellar wind speed and magnetic field – and planetary dipole field – show that the global magnetospheric configuration is highly sensitive to the upstream Alfvén Mach number. We find that increasing stellar wind speed leads to a systematic closure and narrowing of Alfvén wing structures, while stronger stellar magnetic fields facilitate their opening. Analysis of the Alfvén wing morphology demonstrates a distinct dependence of wing opening angle on stellar wind speed, with internal wing analysis showing a reduction in plasma velocity and significant magnetic-flux accumulation. Our results exhibit a clear interdependence between the day-side magnetopause stand-off distance and the night-side magnetotail current sheet length. We find a linear scaling between the magnetotail dynamics and upstream forcing parameters. This study bridges the gap between solar system observations and (exo)planetary systems by demonstrating how Earth-like magnetospheres might transform into wing-dominated configurations during extreme stellar events or within the sub-Alfvénic regimes of close-in (exo)planets. Our findings can aid the interpretation of Alfvén wing signatures in observational data and enhance our understanding of how (exo)planetary magnetospheres respond to dynamic stellar wind forcing.
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High Energy Astrophysical Phenomena

Probing Merger Shocks in Galaxy Clusters in the SKA Era

Arpan Pal, Ruta Kale, Gabriella Di Gennaro et al. (+8 more)

Galaxy cluster mergers represent the most energetic phenomena in the Universe since the Big Bang releasing gravitational potential energy of $\sim 10^{63-64}$ erg, injecting turbulence and driving shocks through the intracluster medium (ICM). These merger shocks can accelerate cosmic ray electrons and compress magnetic fields, sometimes producing Mpc-scale synchrotron radio structures known as radio relics. Radio relics are powerful tracers of merger dynamics, particle acceleration, and magnetic field evolution, yet fundamental questions about the underlying physics and their time evolution remain unresolved. In this chapter, we review the current understanding of cluster merger shocks and their radio signatures, presenting the observational evidence from the SKA pathfinders and precursors, linking radio relics to shocks alongside outstanding theoretical challenges. We also consider related shock-influenced phenomena: radio phoenices from revived fossil AGN plasma and Gently Re-Energised Tails. Further, we outline the directions of investigation using the sensitivities of the SKA-Low and Mid complemented with X-ray observations that will allow us to make significant progress in understanding the cluster merger shocks. Detailed studies of individual targets in continuum and polarization and studies of populations of relics using wide surveys will both provide insights to the micro-physics and cosmic evolution of merger shocks. We present SKAO capabilities across staged deployments starting from AA0.5 to AA4 and identify science verification targets that will illuminate the physics of cluster merger shocks in the SKA era
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All authors Arpan Pal, Ruta Kale, Gabriella Di Gennaro, Francesco de Gasperin, Swarna Chatterjee, Majidul Rahaman, Ramananda Santra, Mamta Pandey-Pommier, Abhirup Datta, Kenda Knowles, Nasmi S. Anand

Astrophysics of Galaxies

The dependence of Circumgalactic Medium properties on halo assembly histories in the IllustrisTNG simulations

Yiyuan Zhang, Houzun Chen and Xi Kang

While halo mass is the dominant factor shaping the embedded galaxies, the properties of the circumgalactic medium (CGM) also depend on halo assembly history. To investigate this, we calculate the formation times for TNG50 halos with masses between $10^{10.5}$ and $10^{12.5} M_\odot$, classifying them into `early-' and `late-forming' populations. It is found that across all mass bins, early-formed halos generally host galaxies with higher stellar mass and higher metallicity, with lower CGM gas mass and lower specific star formation rate (sSFR) at $z\sim0$. For the CGM metallicity, `early' halos with masses below $10^{12}\mathrm{M_\odot}$ show systematically higher gas phase metallicities, whereas in the $10^{12-12.5}\mathrm{M_\odot}$ bin the trend reverses. When examining the origins of the CGM gas, it is found that fresh accretion is insensitive to assembly history, whereas the `late' galaxies experience more wet mergers. These differences in gas properties arise from processes after the formation time, given that the CGM gas masses show no significant differences at formation time. Finally, our analysis of CGM kinematics shows that for halos below $10^{12}\mathrm{M_\odot}$, the cold gas in late-forming halos carries higher specific angular momentum and simply has a higher degree of rotational support, while the same properties in the $10^{12-12.5}\mathrm{M_\odot}$ bin shows no significant dependence on assembly history.
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Cosmology and Nongalactic Astrophysics

Interferometric HI Intensity Mapping of the Late Time Universe with SKA-Mid

Aishrila Mazumder, Zhaoting Chen, Junaid Townsend et al. (+6 more)

We discuss the progress towards using the SKA-Mid for interferometric neutral hydrogen (HI) intensity mapping surveys. By mapping the distribution of cosmic HI distribution through the 21cm line, SKA-Mid will be able to measure the HI power spectrum at small angular separations in interferometric mode. We review the measurements made from the precursor MeerKAT telescope, using the MeerKAT DEEP2 as well as the MIGHTEE survey data, yielding tentative detection as well as upper limits on HI clustering. The methodology for MeerKAT can be naturally extended to SKA-Mid. Forecasts suggest that SKA-Mid AA4 will be able to measure the HI power spectrum with high statistical significance across a wide range of redshifts from $z\sim1.0$ to $z\sim 3.0$, around nonlinear scales $k\sim 1.0\,{\rm Mpc}^{-1}$. The precise measurements can be used to constrain the properties of HI galaxies, providing a novel window into probing galaxy evolution at $1.0\lesssim z \lesssim 3.0$.
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All authors Aishrila Mazumder, Zhaoting Chen, Junaid Townsend, Suman Chatterjee, Zhixing Li, Sourabh Paul, Reza Ansari, Laura Wolz, Mario G. Santos

Cosmology and Nongalactic Astrophysics

Imaging the 21-cm Signal from the Cosmic Dawn & Epoch of Reionization and the Connection with the Global Signal

Satadru Bag, Michele Bianco, Samir Choudhuri et al. (+12 more)

The original baseline design for SKA-Low was motivated by the ability to produce tomographic images of the redshifted 21-cm signal, thus allowing the research field to move beyond the simple statistic of the power spectrum. In this chapter we review the imaging capabilities of SKA-Low, the wide variety of methods proposed for quantatively analysing image data, as well as the connection with the global 21-cm signal.
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All authors Satadru Bag, Michele Bianco, Samir Choudhuri, Saswata Dasgupta, Abhirup Datta, Kanan K. Datta, Ivelin Georgiev, Sambit K. Giri, Ian Hothi, Akanksha Kapahtia, Suman Majumdar, Garrelt Mellema, Arnab Mishra, Samit Kumar Pal, Feiyu Zhao

Astrophysics of Galaxies

Traversing the Galactic Centre in space and time

Michal Zajaček, Bożena Czerny, Martin Mondek et al. (+5 more)

The Galactic Center is often identified with its central supermassive black hole, Sgr A*. Yet the black hole governs gravitationally only the innermost few parsecs of the Milky Way, while the surrounding Nuclear Star Cluster, Nuclear Stellar Disc and Central Molecular Zone (CMZ) shape the dynamics of stars and gas on progressively larger scales. Understanding how these components interact is essential not only for reconstructing the history of our own Galaxy, but also for interpreting galactic nuclei more generally.
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All authors Michal Zajaček, Bożena Czerny, Martin Mondek, Samik Mitra, Matúš Labaj, Tomáš Ondro, Jan Janík, Jiří Dušek

Cosmology and Nongalactic Astrophysics

Euclid preparation. First investigation of the impact of cross-contamination on spectroscopic redshift measurements with pixel-level simulations

Euclid Collaboration: F. Passalacqua, S. Anselmi, P. Monaco et al. (+298 more)

We present a study on simulated data focused on understanding the performance of the spectroscopic redshift measurements with the Near-Infrared Spectrometer and Photometer (NISP) instrument on Euclid. Simulations include scenarios with different levels of cross-contamination arising from overlapping spectra of nearby sources, which represents one of the main drawbacks of slitless spectroscopy. We present a new analysis based on pixel-level simulations of the NISP images, with the data processed using the Euclid spectroscopic pipeline. We first consider an idealised case with non-overlapping spectra to assess the accuracy and reliability of the redshift measurement as a function of the flux of the H-alpha emission line and galaxy size. We then introduce more realistic contamination scenarios, distinguishing between two contributions: contamination from H-alpha emitters, which are the Euclid targets for cosmological analyses, and contamination from all other galaxies. In the second case, we analyse the impact of cross-contamination with an increasing number of contaminants, from the brighter to the fainter galaxies. Given that our results show no clear evidence that sources fainter than magnitude 20 degrade redshift measurements, we conservatively restrict our analysis to galaxies with magnitudes up to 24. In particular, we provide a preliminary estimate that contamination from galaxies within the same redshift range as the target sample contributes to about 4% of the total degradation due to cross-contamination from all galaxies.
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All authors Euclid Collaboration: F. Passalacqua, S. Anselmi, P. Monaco, C. Sirignano, S. Dusini, N. Fourmanoit, M. Fumana, E. Lecrivain, K. S. McCarthy, M. Moresco, F. Oppizzi, A. Renzi, M. Scodeggio, L. Stanco, A. Troja, S. Bruton, C. Carbone, S. de la Torre, B. R. Granett, G. Lavaux, S. Lee, K. Markovic, W. J. Percival, I. Risso, C. Scarlata, E. Sefusatti, Y. Wang, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, V. F. Cardone, J. Carretero, S. Casas, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Escoffier, M. Farina, S. Ferriol, S. Fotopoulou, M. Frailis, E. Franceschi, L. Gabarra, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, W. G. Hartley, S. V. H. Haugan, S. Hemmati, W. Holmes, F. Hormuth, A. Hornstrup, P. Hudelot, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, V. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, C. J. R. McPartland, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, C. Moretti, L. Moscardini, E. Munari, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, G. D. Racca, F. Raison, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, C. Rosset, E. Rossetti, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, P. Simon, G. Sirri, J. Steinwagner, C. Surace, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, D. Vibert, J. Weller, G. Zamorani, E. Zucca, V. Allevato, M. Ballardini, A. Boucaud, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, J. A. Escartin Vigo, R. Maoli, J. Martín-Fleitas, S. Matthew, R. B. Metcalf, M. Pöntinen, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, M. Archidiacono, F. Atrio-Barandela, P. Bergamini, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, M. Bonici, S. Borgani, M. L. Brown, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, M. Y. Elkhashab, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Fontana, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, S. Joudaki, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, A. Loureiro, J. Macias-Perez, C. Mancini, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, G. Morgante, S. Nadathur, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, D. Paoletti, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, G. Rodighiero, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, M. Tucci, D. Vergani, G. Verza, P. Vielzeuf, N. A. Walton

Astrophysics of Galaxies

Only obscured yet luminous active galactic nuclei are closely associated with galaxy mergers: Direct observational evidence from type 2 active galactic nuclei

Yongmin Yoon, Yongjung Kim, Dohyeong Kim et al. (+2 more)

To establish a more comprehensive understanding of the connection between galaxy mergers and active galactic nuclei (AGNs), it is essential to disentangle the contributions of intrinsic AGN luminosity and dust extinction to the merger-AGN connection. Since tidal features identified in deep images serve as direct evidence of recent mergers, we studied the fraction of AGN hosts with tidal features ($f_T$) for a large sample of 748 type 2 AGNs at $z<0.063$. Specifically, we examined $f_T$ as a function of $E(B-V)$, derived from the Balmer decrement, and the internal-extinction-corrected luminosity of the [O III] $\lambda$5007 emission line ($L_{\text{[O III]}}$), which is a proxy for bolometric AGN luminosity. Our main finding is that $f_T$ is only significantly higher for AGNs that are simultaneously luminous and heavily dust-obscured. Specifically, AGNs with $\log L_{\text{[O III]}}\gtrsim41.5$ and $E(B-V)\gtrsim0.7$ exhibit a high $f_T$ of $\sim0.7$. In contrast, AGNs with either low luminosity ($\log L_{\text{[O III]}}\lesssim41.0$) or low dust obscuration ($E(B-V)\lesssim0.3$) show a low $f_T$ of $\lesssim0.2$. This trend suggests that galaxy mergers preferentially trigger AGNs that are simultaneously luminous and dust-obscured, whereas AGNs that are either luminous but unobscured or dust-obscured but less luminous are not strongly associated with merger-driven triggering. Based on several assumptions, our result can also be interpreted, despite certain caveats, within the framework of a merger-initiated evolution model for AGNs, suggesting that AGNs that are both obscured and luminous are temporally closer to merger events than those with lower luminosities and less dust obscuration.
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All authors Yongmin Yoon, Yongjung Kim, Dohyeong Kim, Jaejun Cho, Woowon Byun

Cosmology and Nongalactic Astrophysics

Exploring the Cosmic Dawn through the 21 cm Forest and High-redshift Radio Sources with the SKA

Junsong Cang, Benedetta Ciardi, Barun Maity et al. (+12 more)

The 21~cm forest, seen as absorption features in the spectra of distant radio sources, is produced by intervening neutral hydrogen and offers a direct probe of the neutral intergalactic medium during the epoch of reionization (EoR). Because it is sensitive to small-scale structure and gas temperature, it can constrain the thermal history of the early Universe and physics that affects structure formation. Detecting individual absorption lines is challenging, mainly because of their weakness and the scarcity of high-redshift radio-bright sources. Recent progress, however, has made 21~cm forest studies increasingly feasible: new statistical observables can improve sensitivity within realistic observing times, updated radio-source counts have revised expectations for suitable background quasars, and deep-learning methods can extract physical information more efficiently. In addition, new approaches have been developed to separate astrophysical effects from early galaxies from fundamental-physics effects on small-scale structure. With the Square Kilometre Array (SKA), the 21~cm forest will therefore provide a promising route to study early heating, possible exotic energy injection, dark matter properties, neutrino mass, the running spectral index, and baryon–dark-matter relative velocity. This chapter reviews recent developments in 21~cm forest research and discusses observational strategies and prospects for constraining the first galaxies and fundamental physics with SKA-Low.
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All authors Junsong Cang, Benedetta Ciardi, Barun Maity, Atsushi J. Nishizawa, Qi Niu, Yue Shao, Abinash Kumar Shaw, Hayato Shimabukuro, Tomáš Šoltinský, Tian-Yang Sun, Tsutomu T. Takeuchi, Yidong Xu, Kohji Yoshikawa, Bin Yue, Xin Zhang

Cosmology and Nongalactic Astrophysics

Measuring local primordial non-Gaussianity from the clustering of DESI DR1 LRGs and QSOs

Z. Brown, B. Levi, H. Randall et al. (+42 more)

We report the first measurement of primordial non-Gaussianity (PNG), parameterized by $f_{\mathrm{NL}}$, in the configuration space two-point correlation function (2pcf). We employ simulation based modeling and a novel approach for the mitigation of imaging systematics. We apply this method to samples of luminous red galaxies (LRG) and quasars (QSO) observed by the Dark Energy Spectroscopic Instrument (DESI) during the first year of its observations (DR1). The observed 68% CL interval on $f_{\mathrm{NL}}$ is $-3^{+22}_{-21}$ using LRGs, and $ 0^{+17}_{-16}$ using QSOs. The joint measurement yields $f_{\mathrm{NL}} = -3^{+12}_{-12}$ at $\ [68\%]$ CL. Our pipeline imposes a Gaussian prior on the value of $p$ (which defines the PNG bias via the Universality relation), with $p_{\rm LRG} = 1.0 \pm 0.1$ and $p_{\rm QSO} = 1.6\pm 0.1$. The observed constraining power of DESI tracers significantly exceeds that of previous large-scale structure (LSS) surveys, and encouragingly, approaches the sensitivity of CMB probes of PNG.
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All authors Z. Brown, B. Levi, H. Randall, E. Chaussidon, R. Demina, A. G. Adame, S. Avila, V. Gonzalez-Perez, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, Biprateep Dey, P. Doel, J. E. Forero-Romero, E. Gaztanaga, Satya Gontcho A Gontcho, G. Gutierrez, C. Hahn, K. Honscheid, D. Huterer, M. Ishak, R. Joyce, D. Kirkby, C. Lamman, M. Landriau, M. Manera, A. Meisner, R. Miquel, S. Nadathur, W. J. Percival, I. Perez-Rafols, A. Ross, G. Rossi, L. Samushia, E. Sanchez, M. Schubnell, J. Silber, D. Sprayberry, G. Tarle, B. A. Weaver, H. Zou

Astrophysics of Galaxies

Weak Lensing with the SKAO: Radio Shear Measurement

Priyamvad Tripathi, Marzia Rivi, Simon Prunet et al. (+2 more)

Cosmic shear measurements have traditionally been dominated by optical surveys, which offer higher resolution, better sensitivity, higher galaxy number density, and wider area coverage than their radio counterparts. With the advent of upcoming radio surveys, particularly those planned with the SKA-Mid, we would reach the high sensitivity and resolution required for weak lensing studies, allowing radio observations to begin competing with optical surveys in this domain. However, radio observations are affected by fundamentally different instrumental and astrophysical systematics, meaning that shape and shear measurement techniques developed for optical surveys cannot be straightforwardly applied. Fully realizing the weak lensing potential of these next generation radio surveys therefore requires the development and validation of methods tailored specifically for radio datasets. In this chapter, we present a simulation pipeline to generate realistic observations of isolated radio galaxies based on the SKA-Mid AA4 array configuration. We apply three recent radio shape measurement techniques: SuperCALS, RadioLensfit, and DeepShape, to assess their performance on these simulations. Our results show that RadioLensfit and DeepShape yield the most accurate shape estimates, although RadioLensfit is significantly more computationally intensive. We also perform shear recovery on simulated data using RadioLensfit and DeepShape, finding multiplicative and additive shear biases of order a few $10^{-2}$ and $10^{-4}$, respectively. Finally, we highlight the challenge of source separation, which will play a critical role in the success of future radio weak lensing analyses.
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All authors Priyamvad Tripathi, Marzia Rivi, Simon Prunet, Ian Harrison, André Ferrari

Solar and Stellar Astrophysics

Beyond the Tayler instability: A new global instability of toroidal magnetic fields in stars

Mikhail E. Gusakov, Laura Becerra, Elena M. Kantor et al. (+2 more)

Stellar toroidal magnetic fields are known to be unstable to the Tayler instability. Here we demonstrate the existence of a complementary current-driven instability of essentially arbitrary toroidal-field configurations in stably stratified nonrotating stars with the following properties: (i) in ideal magneto-hydrodynamics, it grows on the Alfvén timescale $\tau_{\rm A}$; (ii) under certain conditions, it may reveal itself by driving shellular differential rotation about an arbitrary axis perpendicular to the magnetic-field symmetry axis; (iii) it is large-scale in the angular directions $\theta$ and $\varphi$, and develops at radial wave-numbers $k \lesssim \mathcal{N}\tau_{\rm A}/R$, where $\mathcal{N}$ is the Brunt-Väisälä frequency and $R$ is the stellar radius. Thus, unlike the Tayler instability, the proposed instability is intrinsically global. Consequently, it may be less susceptible to dissipative suppression than the Tayler instability and can prevail over it in some regimes. This instability may have broad implications for magnetic field generation in stars and could modify scenarios of magnetic field amplification within the Tayler-Spruit dynamo, contributing to models of efficient angular-momentum transport and chemical mixing in stellar interiors.
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All authors Mikhail E. Gusakov, Laura Becerra, Elena M. Kantor, Andreas Reisenegger, Juan Alejandro Valdivia

Astrophysics of Galaxies · Cross-listed from math.PR

Toeplitz Determinants and Admissible Correlation Intervals

Thomas Erben

For a homogeneous one-dimensional random field, positive semidefiniteness of finite Toeplitz correlation matrices imposes non-trivial constraints on admissible correlation coefficients. The widths of the corresponding admissible intervals are closely related to determinants of principal Toeplitz submatrices. Using the classical Desnanot–Jacobi determinant identity, I derive a simple determinantal representation for the widths of admissible correlation intervals. As an immediate consequence, I recover the product expressions for admissible interval widths previously stated by Schneider & Hartlap (2009). The argument places these relations into the general framework of classical Toeplitz determinant theory.
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Solar and Stellar Astrophysics

Evolution of Stars During the Main Sequence and the Transition to the Red Giant Phase

Ravid Achituv and reem sari

We derive a simple analytical description for the structure and evolution of $3$–$10 M_\odot$ stars throughout main-sequence hydrogen burning. We obtain an analytical relation for the convective core mass, $\frac{M_\star}{M_c}=1+2.1\left(\frac{\mu_c}{\mu_e}\right)^2$, where $\mu$ is the mean molecular weight of the core and envelope. Using this relation, we analytically derive the hydrogen abundance profile outside the convective core. We find that $\mu(m)\propto m^{-0.7}$, and show that this profile is important for an analytical description of these stars. Within this region of variable $\mu$, the temperature, density, and pressure are well approximated by power laws of radius. We derive analytical expressions for the core and stellar radii, stellar luminosity, and effective temperature as functions of $\mu_c$. We provide a simple physical explanation for the main-sequence hook, defined by the minimum in effective temperature. We show that the hook occurs when the hydrogen mass fraction in the core is $x_c\simeq0.045$, and stress that the same convective-core burning physics governs the subsequent evolution. In that sense, at the hook hydrogen is not yet fully exhausted. During late main-sequence evolution, we find that the ratio of nuclear luminosity between the core and the surrounding hydrogen-rich shell is $\simeq4000x_c$. Hence, the main sequence terminates only once $x_c\simeq2.5\times10^{-4}$, when the surrounding layers become as luminous as the core itself and $M_c\simeq0.11 M_\star$. Although this terminal core mass is numerically similar to the Sch"onberg–Chandrasekhar limit, we show that the two are physically unrelated, since the core remains far from isothermal even at this stage. We validate all analytical results using MESA simulations.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ed-ph

Simulated Gravitational Lensing in the Undergraduate Lab

Daniel FitzGreen

This paper presents a method for fabricating acrylic lenses that simulate the gravitational deflection of light. The fabricated lenses reproduce key features of strong gravitational lensing, while the simulation is further extended to the weak- and microlensing regimes with images analogous to modern astronomical observations. The simulated mass of the lens is measured from the quantitative analysis of the lensed images in each gravitational lensing regime. These independently measured masses are mutually consistent and agree with the values predicted from the machined lens curvature.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det

Anomalously long-delayed afterpulses in large-area photomultipliers

Nikita Ushakov, Bayarto Lubsandorzhiev, Arslan Lukanov et al. (+2 more)

We report the observation of anomalously long-delayed afterpulses in photomultipliers of the Baksan Large Neutrino Telescope project$~-$ 10-inch R7081-100, 8-inch R5912-100, 20-inch R12860 photomultipliers produced by Hamamatsu Photonics, and 20-inch N6205 photomultipliers produced by NNVT. The mean delay times relative to the main pulses are approximately $85~\mu$s, $73~\mu$s, $260~\mu$s, and $90~\mu$s, respectively. The probability of such afterpulses does not exceed 0.1% per photoelectron, and their amplitudes are strictly confined to the single-photoelectron level, regardless of the amplitude of the main pulse. The delay time of these afterpulses shows no significant dependence on the PMT operating voltage.
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All authors Nikita Ushakov, Bayarto Lubsandorzhiev, Arslan Lukanov, Andrei Sidorenkov, Dmitrii Voronin

Cosmology and Nongalactic Astrophysics

Inflation in a nutshell: From basics to latest advances

Zhi-Chong Qiu and Qing-Guo Huang

Inflation is an elegant paradigm for the very early Universe. It not only offers a simple solution to the flatness and horizon puzzles of the standard hot Big Bang model, but also generates quantum fluctuations that seed CMB anisotropies and the formation of large-scale structure. In particular, both the spatial flatness of the Universe and a nearly Gaussian, scale-invariant power spectrum of the curvature perturbation predicted by inflation have been confirmed by various observations. Recently, a larger spectral index of curvature perturbation is preferred when combining with ACT DR6, and particularly when further including the $H_0$ prior from SH0ES, and then the Starobinsky inflation model is disfavored at more than $95\%$ confidence level. Even though modified reheating histories and non-minimal couplings have been proposed to achieve a larger value of the spectral index, the model with higher-order curvature corrections to Starobinsky inflation offers a concise and well-motivated explanation.
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Astrophysics of Galaxies

Unlocking the Hidden Potential of ALMA Calibrators: A Pilot Blind Search for Galactic Molecular Gas in ALMA Band 1

Kanako Narita and Bunyo Hatsukade

We present a pilot blind absorption line search using calibrator observations with the Atacama Large Millimeter/submillimeter Array (ALMA) Band 1 receiver (35 GHz to 50 GHz). Radio-loud quasars, commonly used for calibration, provide stable and bright background sources that are ideal for absorption line studies of diffuse interstellar gas. To enable a systematic analysis beyond previous targeted studies, we developed an automated pipeline, from archival data download to statistical identification of absorption line candidates, and applied it to archival ALMA Band 1 observations corresponding to 16 distinct calibrator sources. We statistically identify significant absorption line candidates along the analyzed sightlines. This pilot study demonstrates the feasibility of blind absorption line searches with ALMA Band 1 calibrator data and provides a scalable framework for future large-scale archival surveys.
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Earth and Planetary Astrophysics

An Agnostic Machine Learning Model of Photosynthetic Habitability

Callum Gray, Cassandra Hall, Stefano Santabarbara et al. (+5 more)

The search for exoplanet biosignatures is guided by whether planetary environments can sustain photosynthesis. As such, the Photosynthetic Habitable Zone (PHZ) was recently proposed, as the overlap between the canonical habitable zone and the orbital range where stellar irradiance is sufficient to drive photosynthesis. Existing PHZ estimates rely on empirical light-response curves from Earth phytoplankton, and thus include implicit Earth-centric biases. We introduce an agnostic PHZ derived from a generalized model of photosynthesis grounded in thermodynamics and redox chemistry, without reference to model organisms. The model is built on a generic photochemical reaction in which photon capture couples oxidation of a donor molecule to the reduction of CO2. The optical properties and CO2 reduction rate are optimized against irradiance spectra for exoplanets orbiting main-sequence stars, using a genetic algorithm that mimics evolution by natural selection. Our simulations predict that photosynthetic organisms compensate for reduced flux by evolving larger light-harvesting structures. As a result, photosynthetic viability declines only linearly with orbital distance, despite stellar flux falling off quadratically. As such, the agnostic PHZ expands well beyond previous Earth-based estimates. Earth-like (visible light) oxygenic photosynthesis is flux-limited at the outer habitable zone for cool M-dwarf stars; however, both anoxygenic photosynthesis and a hypothetical, NIR-driven oxygenic photosynthesis are viable across the entire habitable zone for M, K, and G stars. This implies that M-dwarf exoplanets could sustain robust oxygenic photosynthesis, though it would be different to that found on Earth, presenting reflectance biosignatures in the NIR band rather than the visible.
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All authors Callum Gray, Cassandra Hall, Stefano Santabarbara, Klaus Schmidt-Rohr, Andrew Ringham, Edward Gillen, Thomas J. Haworth, Christopher D. P. Duffy

Astrophysics of Galaxies

Statistical Properties of Molecular Clouds in the Milky Way: Insights from Three-Isotopologue CO Observations of the MWISP Project

Xin Zhou, Ji Yang, Qing-Zeng Yan et al. (+5 more)

We present a comprehensive statistical analysis of molecular cloud (MC) properties using the MWISP survey's 12CO, 13CO, and C18O (J = 1–0) data toward the inner (l = 45$^\circ$–60$^\circ$) and outer (l = 120$^\circ$–130$^\circ$) Galaxy. From a strict selection of 24,724 identified MCs, a final sample of 3,161 well-resolved MCs is established. We investigate the distributions of observational, morphological, and derived physical parameters, as well as their environmental dependencies and intercorrelations. Our analysis reveals that MCs are typically oblate and tend to align with the Galactic disk. A critical evaluation using a nearby subsample confirms significant distance-dependent selection effects for some parameters, nevertheless, the direction of changes in these parameters can indicate distance influence. We also examine several specific subsamples, revealing the distinct characteristics of MCs in the G120 spiral shock region, MCs in the G50 interarm spurs, C18O-bright MCs, and MCs with supra-Larson velocity dispersion. For instance, MCs with supra-Larson velocity dispersion are predominantly small and likely young clouds inheriting turbulence from the diffuse ISM. Notably, a comparison across tracers reveals that typical MCs have a turbulent, diffuse, 12CO-bright gas structure in their outer layers that does not contribute directly to star formation. In contrast, 13CO-bright gas represents a turning point where gravity becomes significant; C18O-bright gas is about gravity-dominated. Comprehensive correlation analysis confirms a flatter $\sigma_v$-size relation than classic Larson's law and a strong mass-size relation. Incorporating dimensional analysis, we derive minimal sets of eigenparameters from which most other observational and physical parameters can be estimated. This highlights the underlying scaling relations that governing cloud properties.
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All authors Xin Zhou, Ji Yang, Qing-Zeng Yan, Yan Sun, Lixia Yuan, Yang Su, Xuepeng Chen, Shaobo Zhang

Instrumentation and Methods for Astrophysics

The Space Debris Tracking and Surveillance program of the IAC80 telescope

Olga Zamora

The increasing population of artificial objects in Earth orbit poses significant risks to operational spacecraft and ground infrastructure, making Space Surveillance and Tracking (SST) a critical activity. Since 2015, the IAC80 telescope at the Teide Observatory has been contributing to European SST efforts through a dedicated space debris tracking program. Originally designed for astronomical observations, the IAC80 has been progressively adapted to perform automated monitoring of satellites and debris objects in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geostationary Earth Orbit (GEO). This work presents an overview of the IAC80 SST system, including the telescope and site characteristics, the optical instruments currently in use, and the automation tools developed to enable autonomous operations. Particular emphasis is placed on the real-time data reduction pipeline, SATRED, which performs calibration, automatic satellite trail detection, and astrometric measurements during observations. The trail detection algorithm combines robust background estimation, contour extraction, and geometric characterization to provide reliable positional and photometric information. The IAC80 system routinely delivers accurate measurements, with astrometric precision better than one arcsecond and the capability to acquire a large number of observations per night, particularly for MEO and GEO targets. These results demonstrate the effectiveness of adapting classical astronomical facilities for operational SST applications and highlight the role of the IAC80 telescope as a reliable contributor to the European Space Surveillance and Tracking network.
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Solar and Stellar Astrophysics

Discovery of a nebula associated with a high proper motion sdB star

R. Ortiz, F. Bijarchian, M.A. Guerrero et al. (+2 more)

All B-type subdwarf stars (hereafter sdB) should have low flux of ionizing photons, making them incapable of producing a noticeable circumstellar photoionized shell. However, a few sdB stars have been associated with circumstellar nebulae, resembling in some cases a planetary nebula. These discoveries spark doubts about the nature of the physical processes behind the formation of the nebula. In this paper, we describe the newfound parabolic-shaped nebula associated with the high proper motion sdB star TYC 3315-1807-1. The apex of the Halpha nebula is situated approximately 0.5 arcmin in the direction of the stellar proper motion. A wider parabolic-shaped nebula is also detected in WISE W1 infrared images at 3.4 micron, whereas GALEX images show extended far-UV emission around the star within the optical and mid-IR emissions. Like most other sdB stars with associated nebulae, TYC 3315-1807-1 moves at a high-speed (102 km/s) across the Galactic plane. The low luminosity of TYC 3315-1807-1 cannot provide its wind with the momentum necessary to form and keep a bow shock. The nebula around TYC 3315-1807-1 is rather suggested to be a Mach wave partially excited by shocks and photoionization or the encounter of the star with an over-density clump in the ISM.
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All authors R. Ortiz, F. Bijarchian, M.A. Guerrero, M. Akhlaghi, M. Serra-Ricart

Solar and Stellar Astrophysics

Evaluating the Sensitivity of the Age Inferences of Red Giant Stars to Machine Learning Methodology

Jamie Tayar, Carli Mankowski, Lara Tunca et al. (+22 more)

Stellar ages are vital for understanding the formation of our galaxy, but they are among the most challenging parameters to measure. Many authors address this by using machine learning models trained on stars of known age. Here we used data for 351,995 stars from Milky Way Mapper Data Release 19 to explore the sensitivity of the inferred ages to 1) neural network hyperparameters, 2) machine learning architecture, and 3) training set. We find that the resulting ages are generally insensitive to the neural network hyperparameters or the machine learning architecture, but are somewhat sensitive to the training set chosen. We also find that ages for the oldest, coolest, and lowest metallicity stars in the sample are most sensitive to the methodology used and the training set chosen. In general, our analysis suggests that even simple neural network models are sufficient for accurate age inference, but future work expanding the available training sets will be an important component of predicting reliable ages for the full galactic population.
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All authors Jamie Tayar, Carli Mankowski, Lara Tunca, Dante Jordan, Mia Severino, Sydney McArthur, Zeina Benton, Sophia Armstrong, Alexa Leddy, Emily Bower, Zabdiel Sanchez, Colin Avery, Emily Cummings, Joshua Donley, Rachel Freeman, David R. Fulcher, Vanessa Hervie, James Ivey, Hyde Kenney, William MacMillan, Jake Mahoney, Eve Maramba, Erin Philip, Yazmeen Simpson, Ethan Strojie

High Energy Astrophysical Phenomena

Magnetized Coulomb crystals in neutron star crusts

Cheng-Jun Xia, Toshiki Maruyama, Nobutoshi Yasutake et al. (+1 more)

We investigate the properties of magnetized Coulomb crystals in neutron star crusts using a fully three-dimensional geometry with periodic boundary conditions. The electron density profiles are fixed via the Thomas-Fermi approximation, and the nonuniform magnetic fields are treated with the equivalent magnetic charge method. The study focuses on Coulomb crystals composed of $^{12}$C at an ion number density $n_d = 10^{-9}\ \text{fm}^{-3}$, subjected to various external magnetic fields. Nuclei are described by a Gaussian wave function, where the width $b$ encapsulates the effects of zero-point ion vibrations and finite temperature. Our findings show that the crystal softens as $b$ increases. The Madelung constant $K_M$ fluctuates with the external magnetic field $B_{z0}$ at $B_{z0}\leq 3\times 10^{14}$ G. At higher field strengths, $K_M$ increases until $B_{z0} \approx 3\times 10^{15}$ G and then decreases. The body-centered cubic (BCC) lattice is slightly more stable than the face-centered cubic (FCC) lattice when $B_{z0} < 3\times 10^{15}$ G, whereas the FCC lattice may become more stable at larger $B_{z0}$. The elastic constants $c_{11}-c_{12}$ and $c_{44}$ are computed and tabulated, which grow with $B_{z0}$ for $3\times 10^{14}\ \mathrm{G}\lesssim B_{z0}\lesssim 2\times 10^{15}$ G and then decline toward zero as the field strength increases further. For $B_{z0}\gtrsim 10^{16}$ G, it becomes difficult to identify a stable lattice structure. These results provide valuable insights into the role of strong magnetic fields in shaping the properties of Coulomb crystals in compact stars.
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All authors Cheng-Jun Xia, Toshiki Maruyama, Nobutoshi Yasutake, Toshitaka Tatsumi