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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 6 October

Astrophysics of Galaxies

Euclid Quick Data Release (Q1). Exploring the complexity of quenching processes across time, environment, and mass through recently quenched galaxies

Euclid Collaboration: Z. Mao, L. Pozzetti, A. Enia et al. (+307 more)

Recently quenched galaxies (RQGs) provide insights into galaxy quenching. We present a photometric and spectroscopic analysis of RQGs using the first Euclid Quick Data Release (Q1). Using rest-frame UVJ colours, we classify star-forming (SFGs), quiescent (QGs), and recently quenched galaxies at 0.2<z<3.0, separating RQGs into fast- and slow-quenching types (fRQGs and sRQGs) following model evolutionary tracks. The relative fractions of RQGs and their quenching efficiencies both decrease with cosmic time. At early epochs, fast quenching is more efficient in massive galaxies, whereas it becomes efficient only at low masses at later epochs. Slow quenching becomes more efficient at z<1.5, progressing from high to intermediate masses with cosmic time. Most RQGs at z<0.5 reside in low-density environments, while they also exist in high-density environments at z>0.5, suggesting earlier quenching in dense regions. RQGs show intermediate properties between SFGs and QGs in stellar mass, star-formation rate, specific star-formation rate, Sersic index, and radius. Most RQGs exhibit regular morphologies, excluding merger as a primary mechanism. We find that fRQGs retain disc-like morphologies, whereas sRQGs are more concentrated, suggesting different stages of morphological transformation. Our analysis suggests that multiple mechanisms drive quenching. Stacked spectra of galaxies with spectroscopic redshifts confirm old, passive populations in QGs, while sRQG spectrum shows weak Ha emission, indicating residual star-formation activity or AGN contribution. The recently-quenched nature of RQGs is confirmed by strong Balmer absorption lines in stack DESI spectra. The stacked Euclid QG spectrum agrees with previous templates and stellar population models older than 5Gyr at z<1. These results demonstrate Euclid's potential for studying galaxy quenching, to be further enhanced by future releases.[Abrg.]
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All authors Euclid Collaboration: Z. Mao, L. Pozzetti, A. Enia, S. Quai, W. G. Hartley, M. Bolzonella, F. Gentile, G. De Lucia, M. Moresco, N. Borghi, C. Saulder, C. Nipoti, M. Talia, P. Corcho-Caballero, L. Gabarra, Abdurro'uf, L. Wang, L. Bisigello, E. Daddi, M. Siudek, C. D'Eugenio, G. Zamorani, F. Calura, H. Fu, R. Ragusa, F. Shankar, M. Hirschmann, O. Cucciati, T. Kodama, S. Belli, L. Spinoglio, J. R. Weaver, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, C. Dolding, H. Dole, F. Dubath, X. Dupac, M. Farina, R. Farinelli, S. Ferriol, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. Gwyn, S. V. H. Haugan, S. Hemmati, J. Hoar, W. Holmes, A. Hornstrup, M. Huertas-Company, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, 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, S. Maurogordato, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, P. Monaco, A. Mora, C. Moretti, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, I. Risso, E. Romelli, M. Roncarelli, H. J. A. Rottgering, B. Rusholme, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, F. M. Zerbi, I. A. Zinchenko, E. Zucca, V. Allevato, M. Ballardini, E. Bozzo, C. Burigana, A. Cappi, T. Castro, J. A. Escartin Vigo, R. Maoli, J. Martín-Fleitas, R. B. Metcalf, A. A. Nucita, M. Pöntinen, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, D. Bertacca, M. Bethermin, F. Beutler, L. Blot, H. Böhringer, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, T. E. Collett, T. Contini, A. R. Cooray, S. Davini, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, P.-A. Duc, V. Duret, M. Y. Elkhashab, Y. Fang, A. Finoguenov, F. Fontanot, A. Franco, K. Ganga, T. Gasparetto, R. Gavazzi, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, C. Hernández-Monteagudo, H. Hildebrandt, J. Hjorth, L. K. Hunt, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, S. J. Liu, X. Lopez Lopez, A. Loureiro, G. Maggio, E. A. Magnier, C. Mancini, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, G. Morgante, K. Naidoo, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, G. W. Pratt, M. Radovich, G. Rodighiero, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, C. Scarlata, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, F. Tarsitano, G. Testera, R. Teyssier, A. Troja, A. Venhola, D. Vergani, G. Verza, S. Vinciguerra, N. A. Walton, A. H. Wright

Cosmology and Nongalactic Astrophysics · Cross-listed from physics.comp-ph

Convergence of Roberts flow dynamos in Eulerian and Lagrangian codes

Nikyta Shchutskyi, Axel Brandenburg and Matthieu Schaller

Standard benchmark tests for numerical magnetohydrodynamics codes focus on one- and two-dimensional problems that ignore the possibility of dynamos, i.e., an exponential instability converting kinetic energy into magnetic energy. They also tend to ignore magnetic helicity conservation that can have dramatic effects in periodic domains. The existence of magnetic diffusion is crucial for dynamos, as was exemplified by the impossibility of finding dynamo solutions when using Euler potentials, which is a perfectly valid approach in the absence of magnetic diffusion. The Roberts flows~I, II, III, and IV are two-dimensional flows that support three-dimensional dynamos, all of which are also large-scale dynamos in the sense that their planar averages are of significant strengths, even though flow~II is pointwise non-helical. Here we demonstrate the numerical convergence properties of solutions obtained using discretisation schemes of second, sixth, and tenth order in the mesh width in the Pencil Code, compare the results with the SPH-based SWIFT code, and present a list of averaged quantities that facilitate their use in characterising the solutions as benchmarks. In addition, we present a procedure to obtain two-dimensional time-independent magnetic field visualisation for all Roberts flows, and perform per-pixel comparison between the Pencil and SWIFT codes. The rich combination of features makes Roberts flows an excellent dynamo benchmark for the direct numerical simulations of magnetohydrodynamics equations.
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Instrumentation and Methods for Astrophysics

A method for multimodal analysis of TAIGA experiment data using essential features

Alexander Kryukov, Julia Dubenskaya, Elena Fedotova et al. (+6 more)

The aim of processing and analyzing experimental data from physical experiments is to obtain physically significant information about the phenomenon under study. This goal is achieved by multi-stage processing of experimental data, during which noise associated with measurements is suppressed and the dimensionality of the input data is reduced. In this paper, we propose a new method based on the use of neural networks such as autoencoders to extract essential features. The special value of the proposed approach lies in the possibility of its application to the analysis of multimodal data received simultaneously from several installations. We will apply this approach to a multimodal data (MMD) of the experiment TAIGA. Currently, the analysis of the MMD is carried out independently for each installation separately. Therefore, the development of methods for the joint analysis of MMD from TAIGA-type installations is an urgent task in cosmic ray physics and gamma-ray astronomy. Based on Monte Carlo simulation, it is shown that the proposed method allows for effective MMD analysis. It can also be used for MMD analysis at other experimental complexes.
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All authors Alexander Kryukov, Julia Dubenskaya, Elena Fedotova, Elizaveta Gres, Stanislav Polyakov, Eugene Postnikov, Alexander Razumov, Pavel Volchugov, Dmitry Zhurov

Astrophysics of Galaxies

CHemical Evolution in MassIve star-forming COres (CHEMICO). II. Molecular ions, electron fraction, and cosmic-ray ionisation rate

F. Fontani, E. Roueff, V.M. Rivilla et al. (+5 more)

Molecular ions are crucial in initiating and regulating the formation of molecules in the interstellar medium, and are expected to be sensitive tracers of evolution in star-forming regions. Within the framework of the project `CHemical Evolution of MassIve star-forming COres' (CHEMICO), we investigate the temporal evolution of molecular ions towards three high-mass star-forming cores that represent three sequential evolutionary stages. CHEMICO is based on an unbiased spectral line survey of the bandwidth at 3, 2, and 1.2~mm carried out with the 30m telescope of the Insitut de Radioastronomie millimétrique. We detect 19 molecular ions, including isotopologues. From a local thermodynamic equilibrium analysis, we derive the following main results: (i) Overall, the physical parameters of sulphur-bearing ions are the most sensitive to evolution, whereas those of nitrogen-bearing ions are the least; (ii) The molecular abundances that exhibit the most pronounced temporal variations are those of SO+, DCO+, and N2D+; (iii) A simple analytic approach tailored for warm gas conditions provides cosmic-ray ionisation rates of H2 several orders of magnitude above the canonical values measured in the interstellar medium and with a marked increase with evolution; (iv) The abundance ratio of protonated-to-neutral species increases with the proton affinity of the neutral regardless of the evolutionary stage of the source, indicating that proton-transfer appears to proceed similarly in both cold and warm interstellar environments. Molecular ions exhibit distinct evolutionary trends in high-mass star-forming regions, with sulphur-bearing species and the abundances of N2D+, DCO+, and SO+ emerging as particularly sensitive tracers of evolution. Measured electron fractions and cosmic-ray ionisation rates are in line with an internal production of cosmic-rays that becomes increasingly efficient with time.
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All authors F. Fontani, E. Roueff, V.M. Rivilla, Á. López-Gallifa, L. Bizzocchi, L. Colzi, H. Martín-Caballero, P. Caselli

High Energy Astrophysical Phenomena

Can LISA See Inside the Little Red Dots?

Samuel Gómez Gómez, Xisco Jimenez Forteza, Carlos Palenzuela et al. (+1 more)

The Little Red Dots (LRDs) are compact, broad-line sources that appear to contain accreting black holes (BHs) embedded in dense gas. Proposed models for their central environments (including quasi-stars, radiative BH envelopes and super-Eddington accretion discs) predict gas densities at the radii probed by an extreme-mass-ratio inspiral that differ by many orders of magnitude. We compute the inspiral of a $10$–$30\Msun$ BH for a range of LRD interior models, including environmental effects from the gas, and test with a mismatch criterion whether the resulting waveforms can be distinguished from vacuum and from one another. Dense interiors (Bondi-like free-fall cavities and radiative envelopes) produce measurable deviations from vacuum in essentially every detectable event. Convective quasi-star interiors are measurable for $\MBH\lesssim10^5\Msun$ and $z\lesssim0.6$, while a co-rotating disc leaves no measurable imprint. In favorable cases the models are also mutually distinguishable. None of the 14 JWST LRDs at $z>3.9$ would be detectable with a $10\Msun$ companion, but 30 of 31 LRDs at $z<0.9$ would be if their black holes are $\sim100$ times less massive than their virial estimates, and in many of them the interior's imprint would be measurable. Across the LRD population to $z=6$, a 4-yr LISA mission would yield $0.08$–$0.8$ detectable events for $10^5\Msun$ hosts and $10\Msun$ companions ($1.5$–$15$ for $30\Msun$) if LRD nuclei host inspirals at the rate of ordinary galactic nuclei. In dense clusters, where captures are plunges, this falls to $\lesssim10^{-4}$.
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All authors Samuel Gómez Gómez, Xisco Jimenez Forteza, Carlos Palenzuela, Rosalba Perna

Solar and Stellar Astrophysics

Turbulent viscosity in line-driven stellar winds

Matías Montesinos, Michel Cure, Ignacio Araya et al. (+1 more)

Radiation-driven winds from massive stars generate powerful outflows known to be intrinsically turbulent. Despite this, standard hydrodynamic models have historically restricted the application of macroscopic turbulent viscosity to rotationally supported disks, neglecting its dynamic role in the supersonic expansion regime of the wind. We evaluated the dynamical relevance of macroscopic turbulent momentum transport in accelerating line-driven stellar outflows of rotating B supergiants. We introduced a generalized strain-limited viscous prescription within a stable, time-dependent 1D m-CAK hydrodynamic framework using the FARGO3D code. We compared inviscid, constant-viscosity, and strain-limited models to analyze their effects on the radial velocity, density stratification, mass-loss rate, and angular momentum transport. The strain-limited prescription produces a radially structured viscosity that primarily acts as a broad radial braking term. With the viscosity bounded through a prescribed maximum mixing length, the viscous acceleration remains subdominant to the total radiative acceleration but is dynamically relevant to the advective acceleration. In the strongest-viscosity model, the terminal velocity decreased by $\sim 39\%$ and the mass-loss rate by $\sim 58\%$ relative to the inviscid model in the stationary state. The flow remains radiatively driven, and angular momentum transport remains dominated by advection, maintaining a quasi-conserving $v_\phi \propto r^{-1}$ scaling. Turbulent viscosity exerts a measurable dynamic effect on supersonic line-driven winds. When bounded by the local macroscopic strain, it modifies the radial momentum balance and the resulting mass-loss rate without forcing the wind into a disk-like regime of strong viscous angular momentum redistribution.
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All authors Matías Montesinos, Michel Cure, Ignacio Araya, Roberto O. J. Venero

Cosmology and Nongalactic Astrophysics

Measuring the Clustering of tSZ-Selected Galaxy Clusters with SPT-3G

E. S. Martsen, D. Anbajagane, L. E. Bleem et al. (+96 more)

We present a measurement of the spatial clustering of galaxy clusters selected via the thermal Sunyaev-Zel'dovich (tSZ) signal. Using a cluster catalog derived from five years of SPT-3G Main field survey data, we define a sample spanning $0.25 < z < 1.1$, as well as two subsamples spanning $0.25 < z < 0.67$ and $0.67 < z < 1.1$. We detect cluster clustering at $12.8\sigma$, the highest significance detection in a tSZ-selected sample to date. We detail our analytic modeling and theoretical covariance models, including validations performed on synthetic data created from numerical simulations. The measurements and inference pass a variety of null tests, and show minimal sensitivity to common spatially varying systematics that impact optical clustering measurements, such as depth, stellar density, and extinction. We use our pipeline to place constraints on the halo bias of our sample, $b_{\rm{h}} = 5.30\pm{0.24}$, and the normalization of our mass-observable relation, $\rm{lnA}_{sz} = 0.43^{+0.17}_{-0.21}$. We also demonstrate the useful synergies between cluster clustering and abundance measurements, which manifest in the breaking of high-dimensional parameter degeneracies. Samples of clusters selected using the tSZ effect serve as a unique probe of clustering that is insensitive to common systematics, relative to conventional galaxy datasets, and the detection significance of this measurement will increase substantially with existing data from the SPT-3G Ext-10k survey and upcoming data from SPT-3G+ and the Simons Observatory.
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All authors E. S. Martsen, D. Anbajagane, L. E. Bleem, B. A. Benson, E. Anderes, A. J. Anderson, B. Ansarinejad, M. Archipley, L. Balkenhol, D. R. Barron, P. S. Barry, K. Benabed, A. N. Bender, F. Bianchini, S. Bocquet, F. R. Bouchet, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Carron, C. L. Chang, P. M. Chichura, A. Chokshi, T.-L. Chou, A. Coerver, T. M. Crawford, C. Daley, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, D. Dutcher, C. Feng, K. R. Ferguson, N. C. Ferree, K. Fichman, A. Foster, N. Frontiere, S. Galli, A. E. Gambrel, A. K. Gao, F. Ge, S. Gradis, F. Guidi, S. Guns, N. W. Halverson, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, A. Hryciuk, N. Huang, T. Jhaveri, F. Kéruzoré, A. R. Khalife, M. Klein, L. Knox, K. Kornoelje, C.-L. Kuo, P. Larsen, K. Levy, Y. Li, A. E. Lowitz, C. Lu, G. P. Lynch, T. J. Maccarone, A. S. Maniyar, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, Y. Omori, A. Ouellette, Z. Pan, P. Paschos, K. A. Phadke, K. Prabhu, W. Quan, M. Rahimi, A. Rahlin, C. L. Reichardt, M. Rouble, J. E. Ruhl, A. C. Silva Oliveira, A. Simpson, J. A. Sobrin, A. A. Stark, J. Stephen, C. Tandoi, C. Trendafilova, J. D. Vieira, A. G. Vieregg, A. Vitrier, Y. Wan, N. Whitehorn, W. L. K. Wu, M. R. Young, J. A. Zebrowski

High Energy Astrophysical Phenomena

Predictions for Short Gamma-Ray Burst Detections by COSI

Eliza Neights, Eric Burns, Nicolò Parmiggiani et al. (+21 more)

The Compton Spectrometer and Imager (COSI) is a soft gamma-ray telescope scheduled to launch in 2027. COSI will trigger onboard the spacecraft in response to short-duration transients, including gamma-ray bursts, and it will promptly disseminate alerts which include localizations to the community. This will enable rapid follow-up observations of the afterglow and associations with transients identified by other instruments. By simulating COSI observations of short gamma-ray bursts (sGRBs) and processing them with the trigger algorithm which will run onboard the spacecraft, we estimate the sensitivity of COSI to sGRBs. We then convolve this with a simulated set of sGRBs representing the intrinsic population in the universe to predict the rate that will be detected by COSI. We find that COSI is expected to trigger on $\sim$47-89 sGRBs per year with $\sim$7-10 localized to within 2.5{\deg}. With the gravitational wave sensitivity anticipated in the O5 run, we predict 0-3 joint detections with gravitational waves.
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All authors Eliza Neights, Eric Burns, Nicolò Parmiggiani, Yong Sheng, Savitri Gallego, Aldo Aguilar-Nadalini, Aaron C. Trigg, Sylvain Guiriec, Koothodil Abhijith Augustine, Matthew G. Baring, Anna L. Butterworth, Hsiang-Kuang Chang, Che-Yen Chu, Niccolò Di Lalla, Christopher Fryer, Hadar Lazar, Israel Martinez-Castellanos, Marion Sudvarg, Péter Veres, Steven E. Boggs, Dieter H. Hartmann, Carolyn A. Kierans, John A. Tomsick, Andreas Zoglauer

Astrophysics of Galaxies

Early onset of the hot circumgalactic medium around Milky Way galaxies

Víctor Rufo-Pastor, Oscar Agertz, Santi Roca-Fábrega et al. (+6 more)

Hot coronae are key regulators in Milky Way (MW)-type galaxy formation and are thought to emerge once a galaxy's dark matter halo crosses a critical mass threshold, $M_{\mathrm{vir}}\sim10^{12} {\mathrm{M}}_\odot$, so that accretion shocks can heat infalling gas to virial temperatures, $T_{\mathrm{vir}}$. Here we investigate the roles of stellar feedback and accretion shocks in establishing the circumgalactic medium (CGM) around MW-mass galaxies using the VINTERGATAN cosmological simulation suite. We find that stellar feedback drives the early formation of a hot CGM, with $T_{\mathrm{CGM}}\sim T_{\mathrm{vir}}$. By contrast, in feedback-free simulations, accretion shocks alone do not produce a CGM with comparably high average temperatures at early epochs ($z>2$), independent of gas metallicity. We show that CGM virialisation (defined when halo-gas cooling time exceeds the free-fall time) begins with the emergence of a hot corona ($T>10^5$ K) that can appear as early as $z\approx3$ at virial radius, $R_{\mathrm{vir}}$, when feedback is included. This is much earlier than predicted by accretion-shock theory or feedback-free models ($z\lesssim1$). While accretion shocks alone produce an inside-out virialisation pattern, feedback can alter this behaviour, driving a rapid transition ($\lesssim0.5$ Gyr) that is either outside-in or nearly simultaneous throughout the halo. Finally, these early-forming coronae are largely stable from formation through to the present day, but can appear to evolve simply because the definition of $R_{\mathrm{vir}}$ grows with time. This 'CGM pseudo-evolution' is analogous to the pseudo-evolution of dark matter haloes and should be taken into account when interpreting the evolution of hot coronae.
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All authors Víctor Rufo-Pastor, Oscar Agertz, Santi Roca-Fábrega, Martin P. Rey, Joss Bland-Hawthorn, Justin I. Read, Thor Tepper-García, Corentin Cadiou, Anatole Storck

Solar and Stellar Astrophysics

Re-calibrated analytic stellar evolution formulae for the main sequence: Extension to massive stars and variations in $[\alpha/\mathrm{Fe}]$

Conor M Byrne, Elizabeth R Stanway and Jan J Eldridge

Analytic formulae are an efficient way to approximate the evolution of a star of a given mass and chemical composition, and are widely used in the literature to compute large grids of evolutionary models for stellar population synthesis. Such formulae rely on calibration to detailed stellar evolution models, and existing versions are based on a sparse, limited grid in comparison to modern simulations. By calibrating against the latest generation of single-star evolution models calculated within the Binary Population and Spectral Synthesis (\bpass) framework, we revise and extend pre-existing equations to include the evolution of massive ($M\gtrsim50\,$\msun) stars and changes in chemical abundances in the form of variations in \afe. We introduce additional terms which allow for a better approximation of the main-sequence lifetimes, and the luminosities and radii at the beginning and end of the main sequence. These revised equations describe the main-sequence age, zero-age and terminal-age radius and luminosity with mean errors of less than 10 per cent or 0.05 dex, for all except the terminal age radius, which shows RMS errors of 20 per cent and 0.1 dex. For \afe\ enriched stellar populations, we advise using a matched-iron value for metallicity in the equations, consistent with the expectation that iron is the dominant opacity source affecting the evolution of main-sequence stars.
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2610.08930 · 6 Oct · Accepted for publication in MNRAS. 18 pages, 13 figures, 1 table, plus appendices (12 pages, 7 tables 12 figures) Python functions to evaluate the equations are available at https://warwick.ac.uk/fac/sci/physics/research/astro/people/conorbyrne/byrne26_equations.py and a Fortran version is available at https://warwick.ac.uk/fac/sci/physics/research/astro/people/conorbyrne/byrne26_equations.f90

Abstract PDF $EVO ×6$STAR ×5$MTLC ×1

Earth and Planetary Astrophysics

Searching for hot water world candidates with CHEOPS: II. A low-density super-Earth orbiting the K dwarf TOI-2211

J. A. Egger, P. Cortés-Zuleta, D. Kubyshkina et al. (+98 more)

Small exoplanets on close-in orbits are exposed to high levels of stellar irradiation, which can effectively remove low-mass primordial H/He envelopes through atmospheric escape. Under these conditions, planets whose masses and radii are incompatible with both bare rocky interiors and extended H-dominated atmospheres are therefore expected to host high mean molecular weight atmospheres, making them promising candidates for volatile-rich hot water worlds. We present the first detailed characterisation of the low-density super-Earth TOI-2211 b (P~3.09 d), a recently validated transiting planet orbiting a K type star (G mag: 9.1). Combining TESS and CHEOPS photometry with radial velocity measurements from HARPS, ESPRESSO, and KPF, we precisely constrain the planet's radius and mass to $1.457 \pm 0.047$ R$_\oplus$ and $2.69 \pm 0.56$ M$_\oplus$. We also identify an outer, non-transiting planetary candidate (P~15.6 d, Msin(i) $ = 8.53 \pm 1.04$ M$_\oplus$) in the radial velocity data. We investigate the internal structure of the transiting planet and assess the stability of the inferred volatile envelopes through a detailed evaporation analysis, thereby identifying TOI-2211 b as a promising hot water world candidate. TOI-2211 b therefore joins the small but growing sample of these close-in low-density super-Earths, which represent particularly interesting targets for testing current planet formation and evolution theories. Additionally, we investigate the full architecture of the planetary system using a generative model of planet formation and evolution, with the resulting posterior distributions showing a clear over-density consistent with the observed orbital period and minimal mass of the non-transiting planetary candidate identified in the radial velocity data.
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All authors J. A. Egger, P. Cortés-Zuleta, D. Kubyshkina, H. P. Osborn, S. Marques, I. Crossfield, A. Deline, S. Ulmer-Moll, A. E. Simon, G. Scandariato, A. C. M. Correia, Y. N. E. Eschen, D. Gandolfi, V. Adibekyan, A. Bonfanti, C. Pezzotti, P. H. Premnath, S. G. Sousa, T. G. Wilson, L. Fossati, R. Eltschinger, Y. Alibert, D. Degen, G. Lacedelli, T. Zingales, B. Akinsanmi, R. Alonso, T. Bárczy, D. Barrado, S. C. C. Barros, W. Baumjohann, W. Benz, N. Billot, L. Borsato, A. Brandeker, C. Broeg, M. Buder, A. Castro-González, A. Collier Cameron, C. Corral Van Damme, Sz. Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, O. D. S. Demangeon, B.-O. Demory, A. Derekas, B. Edwards, D. Ehrenreich, A. Erikson, A. Fortier, M. Fridlund, K. Gazeas, M. Gillon, M. Güdel, M. N. Günther, J. Hasiba, A. Heitzmann, Ch. Helling, K. G. Isaak, L. L. Kiss, D. Kitzmann, J. Korth, K. W. F. Lam, J. Laskar, A. Lecavelier des Etangs, A. Leleu, M. Lendl, M. Lund, D. Magrin, P. F. L. Maxted, B. Merín, C. Mordasini, M. Munari, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, A. Peel, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, D. Ségransan, A. M. S. Smith, M. Stalport, S. Sulis, Gy. M. Szabó, S. Udry, V. Van Grootel, J. Venturini, E. Villaver, N. A. Walton, S. Wolf

High Energy Astrophysical Phenomena

PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field V: Unraveling X-ray Spectral Variability

Samantha Creech, Francesca Civano, Daniel Wik et al. (+13 more)

As one of the first deep time-domain surveys in the hard X-ray band, the NuSTAR campaign in the JWST North Ecliptic Pole Time Domain Field (NEP-TDF) offers a prime opportunity to measure variability in a faint population of Active Galactic Nuclei (AGN) in the medium-to-high redshift universe. In the X-ray band, AGN variability is generally caused by changes in the brightness of the corona ($F_{int}$ variability) or changes in the column density of obscuring material near the SMBH ($N_H$ variability). Broad-band spectroscopy ($\sim$0.5-24 keV) is required to reliably disentangle these two phenomena. With simultaneous NuSTAR and XMM-Newton coverage—as well as 1.8 Ms of Chandra monitoring—the X-ray surveys in the NEP-TDF are ideally situated for this purpose. This work presents the first spectral modeling of the 52 NuSTAR-identified sources discovered in the latter half of the campaign, as well as a spectroscopic variability study of the entire 112-source NuSTAR NEP-TDF catalog. Seven variable candidates are identified. We find that $\gtrsim 1000$ total counts split across many ($\gtrsim 10$) epochs are needed in order to detect variability. Additionally, variable sources are compared to the survey sensitivity in order to inform population synthesis models of how variations can affect the detectability of faint AGN, which dominate the SMBH accretion history. Lastly, the timescale of $N_H$ variability is investigated as a probe for the obscurer location. Significant variability is slightly more common on $> 100$ day timescales, suggesting that the torus may have only slight dominance in driving $N_H$ variability in faint AGN.
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All authors Samantha Creech, Francesca Civano, Daniel Wik, Núria Torres-Alba, Ross Silver, Xiurui Zhao, Tonima Ananna, Gibson Bowling, Norman A. Grogin, Anton M. Koekemoer, Peter Maksym, Sylvia Mesicek, Rafael Ortiz III, Payaswini Saikia, Steven Willner, Rogier Windhorst

Cosmology and Nongalactic Astrophysics

The BUFFALO Survey : The Subhalo Mass Function for Abell 2744 with Strong+Weak Gravitational Lensing

Nency R. Patel, Mathilde Jauzac, Anna Niemiec et al. (+16 more)

We present a combined strong and weak gravitational lensing mass model of the massive merging galaxy cluster Abell 2744 (z = 0.308). The mass reconstruction combines strong-lensing constraints in the cluster core with weak-lensing measurements derived from deep imaging with the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST), enabling a reconstruction of the projected mass distribution from the core to the cluster outskirts. Using the resulting mass map, we identify cluster substructures and construct the subhalo mass function (SHMF) for Abell 2744. To interpret the observed substructure population, we apply identical detection methods to projected mass maps of massive galaxy clusters from the BAryons and HAloes of MAssive Systems (BAHAMAS) simulations. We observe a systematic excess of detected substructures in Abell 2744 compared to BAHAMAS. We interpret this excess as likely reflecting Abell 2744's exceptionally disturbed dynamical state, characterised by complex ongoing mergers, rather than tension with $\Lambda$Cold Dark Matter ($\Lambda$CDM) or self-interacting dark matter (SIDM) predictions. Although confirming this interpretation will require extending the analysis to a larger sample of clusters spanning a range of dynamical states.
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All authors Nency R. Patel, Mathilde Jauzac, Anna Niemiec, Guillaume Mahler, David Lagattuta, David Harvey, Johannes Schwinn, Andrew Robertson, Lukas J. Furtak, Sownak Bose, Alastair Edge, Anton Koekemoer, Jose Diego, Andreas Faisst, Eric Jullo, Marceau Limousin, Richard Massey, Derek Perera, Sut-Ieng Tam

High Energy Astrophysical Phenomena

A Newly Identified Transient Ultraluminous X-ray Source in M31

Ferdinand, Murray Brightman, Jean-Marie Hameury et al. (+9 more)

Ultraluminous X-ray sources (ULXs) are off-nuclear X-ray sources with luminosities exceeding the Eddington limit of typical stellar-mass compact objects. While most known ULXs are relatively persistent sources, transient ULXs have emerged as a distinct population that offer unique insight into extreme, super-Eddington accretion. We report the discovery and X-ray characterization of a newly identified transient ULX in M31. First detected serendipitously on 2021 June 9, the source reached a peak unabsorbed $0.3 - 10$ keV luminosity of $\sim10^{39}\ \rm erg\ s^{-1}$. Its spectral evolution suggests increasing advection at later epochs, opposite to the expected transition from a super-Eddington slim disk toward a standard thin disk during the decay of the outburst. The observed X-ray light curve can be reproduced using the disk-instability model of Hameury & Lasota, with characteristic timescales of $\sim41-61$ days. The inferred mass-accretion rate is super-Eddington for a $1.4\,M_{\odot}$ neutron star but approximately Eddington for a $10\,M_{\odot}$ stellar-mass black hole. Nearby optical sources from the Hubble Source Catalog suggest a possible giant donor with an age of $\log_{10}({\rm age/yr})\sim8.5$ and a mass of $\sim3.2\,M_{\odot}$, when compared with stellar isochrones with an assumed $A_V=1.58$. We estimate a transient ULX occurrence rate in M31 of $0.18\pm0.10\ {\rm yr^{-1}}$. This rate is lower than those reported for other galaxies in previous studies. M31 ULX-3 expands the small population of known transient ULXs in M31 and highlights the importance of continued, regular X-ray monitoring of nearby galaxies.
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All authors Ferdinand, Murray Brightman, Jean-Marie Hameury, Elias Kammoun, Dominic J. Walton, Matthew J. Middleton, Hannah Earnshaw, Felix Fürst, Wynn V. Jacobson-Galán, Jacob E. Jencson, Margaret Lazzarini, Mark T. Reynolds

Solar and Stellar Astrophysics

Debye cooling of ultramassive white dwarfs

David Barba-González and Sivan Ginzburg

Recent observations of cold and massive white dwarfs are beginning to probe Debye cooling: an accelerated cooling phase driven by the vanishing heat capacity $C_V(T)$ of the crystallized interiors at low temperatures $T$, due to the quantum nature of phonon oscillations. We analyse this regime by calculating, both analytically and numerically, the instantaneous cooling time $\tau(L)\equiv -\textrm{d}t/\textrm{d}\ln L$, which is a proxy for the number density of white dwarfs at a given luminosity $L$. We find that cooling accelerates ($\tau$ shortens) at $L\lesssim 10^{-4}\,\textrm{L}_{\odot}$ due to a combination of Debye cooling and the simultaneous convective coupling of the degenerate core to the surface, with neither process causing significant acceleration on its own. Specifically, strong magnetic fields can inhibit convective coupling, leading to an almost flat $\tau\propto L^{1/7}$ instead. We parametrize the uncertainty in the solid microphysics by generalizing the Helmholtz free energy such that $C_V\propto T^\delta$ at low temperatures. The currently observed decreasing luminosity function in the Debye regime is tentatively consistent with $\tau(L)$ of non-magnetic white dwarfs with $\delta=3$, corresponding to the standard Debye model. Larger samples could probe, in addition to magnetism, deviations $\delta<3$, which diverge appreciably before the Galactic disc's age $t\approx 10\textrm{ Gyr}$ for masses $M\gtrsim 1.0\,\textrm{M}_{\odot}$. For $\delta>3$, in contrast, the cooling curves converge because the heat capacity becomes dominated by the degenerate electrons $C_V\propto T$.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

An early $Z'$ dominance: dark matter, gravitational waves & collider probes

Basabendu Barman, Nayan Das, Partha Kumar Paul et al. (+1 more)

In the minimal anomaly-free gauged B$-$L extension of the Standard Model (SM), we consider a scenario in which the energy density of the new Abelian gauge boson dominates the Universe prior to big bang nucleosynthesis (BBN), resulting in an early matter-dominated (EMD) era. Taking one of the three right-handed neutrinos to be a decaying dark matter (DM) candidate, we investigate its production during this EMD phase. We show that the region of parameter space consistent with the relic abundance lies within the projected sensitivity of several gravitational wave (GW) experiments, where the GW signal arises from cosmic strings formed during the spontaneous breaking of the gauged B$-$L symmetry. We further constrain the viable parameter space using bounds from collider experiments, beam dump experiments, BBN, and ultra high energy neutrino observations, demonstrating the complementarity of multi-messenger probes in exploring physics beyond the SM as well as non-standard cosmological histories prior to BBN.
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All authors Basabendu Barman, Nayan Das, Partha Kumar Paul, Narendra Sahu

Cosmology and Nongalactic Astrophysics

Full-Shape Analysis of the Redshift-Space Galaxy Trispectrum in the EFTofLSS

Beatriz Tucci and Oliver H. E. Philcox

The effective field theory of large-scale structure (EFTofLSS) program for spectroscopic galaxy surveys has been remarkably successful for cosmological inference from the galaxy power spectrum and bispectrum. However, a full-shape cosmological analysis including the galaxy trispectrum has not yet been performed. In this work, we develop the tree-level EFTofLSS model of the galaxy trispectrum, including all relevant ingredients: galaxy bias, stochasticity, infrared resummation, Fingers-of-God (FoG) counterterms, Alcock-Paczynski distortions, binning effects, and covariance. We validate the model by performing cosmological inference using the one-loop galaxy power spectrum, tree-level bispectrum, and tree-level trispectrum measured from dark-matter halos in 25 AbacusSummit $N$-body simulations, whose large effective volume ($V=200h^{-3}\text{Gpc}^3$) allows us to test the precision of our model and determine scale cuts in both real-space and redshift-space. We also study the cosmological information content of the galaxy trispectrum in a DESI-like volume, finding that its inclusion can improve constraints e.g., on $\omega_{\rm cdm}$ by up to $15\%$. We further find that the maximum scale cut can be extended to $k_{\max}=0.12h\mathrm{Mpc}^{-1}$ depending on the tracer, thanks to our improved treatment of FoG effects. This provides a path towards using the three-dimensional large-scale structure to constrain new-physics scenarios with distinctive signatures in the trispectrum, in particular primordial non-Gaussianity.
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Astrophysics of Galaxies

Modeling the nanohertz gravitational wave background with the t-process: Improved frequentist analysis of gravitational-wave power

B. E. Moreschi, K. A. Gersbach, G. Shaifullah et al. (+2 more)

Pulsar timing array (PTA) collaborations have recently reported evidence for a gravitational wave background (GWB) signal in the nanohertz band, which most likely originates from the incoherent superposition of GWs emitted by a population of supermassive black hole binaries (SMBHBs). Since the number of binaries emitting in each frequency bin is finite, and since individual loud sources can dominate the GWB, the power spectral density (PSD) of the background is expected to deviate significantly from the smooth power law that describes an idealized population. PTA searches usually describe the PSD either with a power law or with a free spectrum model, which fits the PSD in each frequency bin as a free parameter. In this paper, we explore the t-process as a third model; it assumes a power law as the underlying spectrum but leaves each frequency bin free to deviate from it. We compare the performance of these three models on simulated datasets, injecting $100$ realizations of a realistic SMBHB population, to evaluate how well each model recovers a complex PSD. Using Bayesian and frequentist tools, we find that the t-process model gives the most precise PSD results, with uncertainties $43\%$ and $26\%$ narrower than those obtained with the power law and the free spectrum, respectively, while the improvement in accuracy is smaller. Moreover, using the t-process model, we compute isotropic and anisotropic signal-to-noise ratios with median gains of about $46\%$ over the power law and $65\%$ over the free spectrum in the first nine frequency bins. The t-process also returns lower anisotropy p-values and among the frequency bins with $p<0.01$, it allows to localize the loudest binary within the angular resolution of the sky maps in $14.3\%$ of the cases, compared to the $10\%$ for the power law and the $6.2\%$ for the free spectrum.
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All authors B. E. Moreschi, K. A. Gersbach, G. Shaifullah, S. R. Taylor, A. Sesana

Astrophysics of Galaxies

KDG 162: A Nearby Isolated Star-forming Dwarf Galaxy

Gagandeep S. Anand, Igor D. Karachentsev, Meredith J. Durbin et al. (+6 more)

The nearby dwarf galaxy KDG 162 (also known as KK 153) has recently attracted attention as a potentially gas-rich, isolated, and low-mass dwarf galaxy. However, many of these characterizations depend on the true distance to KDG 162. Here we present new Hubble Space Telescope (HST) imaging that resolves individual stars down to 3 magnitudes below the tip of the red giant branch. Using this HST imaging, we determine a distance to KDG 162 of D = 3.48 $\pm$ 0.12 Mpc, somewhat higher than previous determinations. We find KDG 162 to be relatively isolated and lying at the edge of first infall onto the M81 group. We use its stellar content to measure its recent star formation history and find that only a modest amount of star formation can be attributed to within the last $\sim$500 Myr. The present-day stellar mass outweighs the H I mass by a factor of 2$\times$. The properties of KDG 162 add to an increasingly detailed picture of nearby and isolated low-mass galaxies. In the future, deeper observations would allow for reaching more age-sensitive populations, enabling the recovery of its star-formation history back to ancient times.
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All authors Gagandeep S. Anand, Igor D. Karachentsev, Meredith J. Durbin, R. Brent Tully, Rachael Beaton, Andrew Dolphin, Serafim S. Kaisin, Lidia N. Makarova, Edward J. Shaya

High Energy Astrophysical Phenomena

Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny

Willem B. Hoogendam, David O. Jones, Christopher J. Storfer et al. (+26 more)

We present photometric and spectroscopic follow-up observations of the strongly-lensed H-poor superluminous supernova (SLSN) 2025wny at $z = 2.0155$. We use integral-field Keck-II/KCWI spectroscopy to obtain rest-frame ultraviolet spectra spanning $11$ to $61$ days after maximum light. We use Pan-STARRS photometry to constrain the brightest image's magnification, finding $\mu_A=19.4\pm1.6$, a factor of $\sim$2-4 higher than mass-modeling estimates. We fit the Pan-STARRS photometry with a magnetar energy-injection model including $^{56}$Ni decay using the Modular Open Source Fitter for Transients (MOSFiT); the model can reproduce the near-maximum light curve with parameters typical of local universe SLSNe-I, including a magnetar spin period $P_{\rm spin}=4.1^{+0.7}_{-1.0}\,\mathrm{ms}$ and magnetic field $B_{\perp}=2.4^{+1.1}_{-0.8}\times10^{14}\,\mathrm{G}$; however, the late-time plateau suggests an additional power source. Spectroscopically, iron-group element line blanketing is virtually absent in the rest-frame UV spectra, and the absorption features match previously identified SLSN-I features from abundance tomography. Based on narrow ISM line metallicity estimates, SN 2025wny exploded in a sub-solar-metallicity galaxy. From host-galaxy lines in our rest-frame UV-to-optical spectrum we estimate high-velocity outflows of $\sim$575 km s$^{-1}$ and an exceptionally high Ly$\alpha$ escape fraction of $f_{esc}^{Ly\alpha}=0.23\pm0.03$. SN 2025wny matches lower-redshift SLSNe reasonably well. Upcoming surveys like LSST and Roman will discover additional high-redshift SLSNe, further testing whether SLSNe-I explosions remain consistent at the population level in the early universe.
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All authors Willem B. Hoogendam, David O. Jones, Christopher J. Storfer, Luca Izzo, Kyle W. Davis, Miranda Y. Kong, Katie Auchettl, Aadya Agrawal, David R. Aguilera-Dena, Kenneth C. Chambers, Siyuan Chen, Thomas de Boer, Ryan J. Foley, Matthew Grayling, Jason T. Hinkle, Jens Hjorth, Mark E. Huber, Chien-Cheng Lin, Thomas B. Lowe, Eugene A. Magnier, Kaisey S. Mandel, C. Tanner Murphey, Gautham Narayan, Gregory S. H. Paek, Kishore C. Patra, Haille M. L. Perkins, Armin Rest, Benjamin J. Shappee, Richard J. Wainscoat

Solar and Stellar Astrophysics

Coronal Mass Ejections from the Young Sun: Deceleration-Powered Solar Energetic Particles as a Self-Extinguishing Forcing of the Early Earth

Olga A. Panasenco

At $\sim$3.9~Ga (stellar age $\sim$0.6~Gyr), the young Sun was far more magnetically active than today. It launched $\sim$$10^2$ large, fast coronal mass ejections (CMEs) per year into a denser, more magnetized wind. We follow these eruptions to Earth's atmosphere with a semi-analytic model chain. We find that a CME launched at $v_0\sim3\text{--}4\e{3}\unit{km\,s^{-1}}$ dissipates $\Delta E_k\sim6\e{25}\unit{J}$ as it decelerates, an amount set only by its launch and final speeds. Diffusive shock acceleration converts $\sim$10% of this energy into solar energetic particles (SEPs), whose deposition depth depends mainly on a spectral break energy $E_b$. We show that the stronger field moves the Alfvén surface, inside which the magnetic field controls the wind, from $\sim$10–25$\,\Rsun$ to $\sim$40–60$\,\Rsun$, so CME shocks deliver over ten times the particle fluence of flares. Because the forcing is powered by deceleration, it follows the measured wind history ($\dot M\propto t^{-2.3}$) and declines as $\sim t^{-3}$. It was $\sim$50–100 times stronger at 3.9~Ga than at 2~Ga and several hundred times today's level. This decline, strongest when the Sun was faintest, is what greenhouse solutions of the faint young Sun (FYS) problem usually impose by hand. The magnitude is small: SEP-driven $\mathrm{N_2O}$ adds at most a few $\unit{W\,m^{-2}}$ to a 20–40$\unit{W\,m^{-2}}$ greenhouse requirement, and only if a fractal organic haze extends its lifetime. Counting energy deposited below a survival level near 1~hPa, we find the particles fix $\sim$$4\e{10}$–$4\e{11}\unit{mol\,N\,yr^{-1}}$, which could supply prebiotic feedstock to surface pools. The largest uncertainties are $E_b$, the event rate, the survival depth, and the $\mathrm{N_2O}$ lifetime.
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Astrophysics of Galaxies

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) – IV. Methyl cyanide isotopologues toward BHR71-IRS1

P. Nazari, A. Coutens, J. K. Jørgensen et al. (+16 more)

Methyl cyanide is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around low- and high-mass protostars. However, very few observations exist with a broad enough frequency coverage and sufficiently high sensitivity to systematically characterize its minor isotopologues toward such regions. We add to this number by analyzing data toward BHR71-IRS1 taken as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ~33 GHz frequency range. We studied as many isotopologues of methyl cyanide as possible toward BHR71-IRS1. We found the column densities and excitation temperatures via spectral fitting and assuming local thermodynamic equilibrium. We then compared the derived column density ratios with those toward IRAS 16293-2422 A and B, V883 Ori, G31.41+0.31, and Sgr B2(N2b). We detect CH3CN, CH3CN $v_8$=1, 13-CH3CN, CH3-13-CN, CH3C-15-N, CH2DCN, and CHD2CN. The column density ratio of 13-CH3CN/CH3-13-CN is around unity, in agreement with previous observations. The CH2DCN/CH3CN ratios are similar for all the low-mass objects but are ~1 order of magnitude higher than those toward Sgr B2(N2b). This could be due to a warmer pre-stellar phase or a different formation timescale of Sgr B2(N2b). The D/H ratios found from methyl cyanide isotopologues agree well with those of methanol toward BHR71-IRS1, likely pointing to the formation and deuteration of methyl cyanide in a similar star-formation phase as methanol (i.e., the pre-stellar phase). We find an increase in the methyl cyanide D/H ratios with the number of deuterium atoms, which suggests that the deuterated isotopologues may form later in the pre-stellar phase. Future COMPASS studies will increase the sample size of low-mass systems with methyl cyanide analysis and potentially examine some of the trends observed here statistically.
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All authors P. Nazari, A. Coutens, J. K. Jørgensen, A. Belloche, A. L. Plunkett, S. Maret, D. Harsono, M. N. Drozdovskaya, J.-E. Lee, F. Cruz-Sáenz de Miera, J. Ferrer Asensio, M. L. R. van 't Hoff, J.-H. Jeong, Á Kóspál, B. A. McGuire, S. Spezzano, Y.-L. Yang, H.-S. Yun, S. Zeng

Cosmology and Nongalactic Astrophysics

Mitigating prior-volume effects in galaxy clustering by adopting Mpc over Mpc/h units

Andrea Pezzotta, Alejandro Pérez-Fernández, Giosuè Gambardella et al. (+4 more)

We investigate prior-volume effects in Bayesian analyses of galaxy clustering based on state-of-the-art models, such as the EFT and the VDG$_\infty$ model. We show that these effects are largely driven by imposing priors on the model parameters defined in ${\rm Mpc}/h$ units, thereby introducing a spurious correlation with the Hubble parameter $h$, and that they can be strongly mitigated by adopting a more physically motivated formulation in ${\rm Mpc}$ units. We test this approach using a set of synthetic data vectors designed to reproduce the clustering signal expected in a Stage-IV survey across a range of cosmological models, including $\Lambda$CDM, $K$CDM, $w$CDM, and $w_0w_a$CDM. We find that the resulting constraints are largely free from shifts induced during the marginalisation process, even in the challenging $w_0w_a$CDM runs, reducing discrepancies with the fiducial values from several standard deviations to well within $1\sigma$. The performance of this approach is comparable to that of alternative mitigation strategies, such as the adoption of invariant priors or the reparametrisation of nuisance parameters in terms of growth and geometrical amplitudes. For the latter, we find that using $\sigma_{12}$ in place of the commonly adopted $\sigma_8$ to describe the amplitude of density fluctuations improves the performance of the reparametrisation technique, even at high redshifts, where constraints on the dark-energy equation of state are weaker. We further show that these conclusions hold with the inclusion of additional BAO constraints, and for data sets with reduced statistical power. These results add to the benefits of working with ${\rm Mpc}$ units, avoiding an explicit dependence on $h$, with direct relevance for the analyses of Stage-IV galaxy surveys.
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All authors Andrea Pezzotta, Alejandro Pérez-Fernández, Giosuè Gambardella, Ariel G. Sánchez, Alexander Eggemeier, Martin Crocce, Benjamin Camacho-Quevedo

Instrumentation and Methods for Astrophysics

Space-based Cosmic Neutrino Measurements

John F. Krizmanic

Space-based neutrino detection employs celestial bodies, the Earth, moon, and the sun, as neutrino targets and particle cascade generators. These cascades, or showers, have an immense content of charged particles, mainly electrons and positrons, that can form signals that can be detected by orbiting or balloon-borne (for the Earth) experiments. Here the focus will be on the using the Earth as the neutrino target and using the atmosphere to generate optical and radio signals from extensive air showers (EAS). Cascades in the Earth itself can also generate Askaryan radiation in ice, where the radio transparency allows the signal from in ice neutrino-induced showers to eventually refract out of the Earth's surface. These different techniques also have different neutrino-flavor detection sensitivities and duty cycles, i.e. experimental live time fractions. For example, optical measurements need to be performed close to astronomical night and are also affected by the level of moonlight and distribution of clouds in the the viewing direction of the EAS. The radio technique can be operate with nearly 100% efficiency, as long as sources of anthropogenic and other backgrounds are minimal. Given the distances for viewing the neutrino-induced signals from sub-orbital or low Earth orbit (LEO) altitudes, the neutrino energy thresholds for detection are currently above $\sim$ 1 PeV for optical Cherenkov detection and 100 PeV for radio detection. In this chapter, the nature of the cosmic neutrino interactions, shower development, and optical and radio signal generation and detection will be detailed. This will be done by discussing experiments that have used such signals to set limits on the very-high and ultra-high energy cosmic neutrino flux. We will also discuss the design and simulated performance of the next generation of space-based cosmic neutrino detection experiments.
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Cosmology and Nongalactic Astrophysics

Halo Mass Function Constraints on Early Galaxy and AGN Populations in the JWST Era

Elan Yogeswaren and Robert Schaefer

The discovery by the James Webb Space Telescope (JWST) of massive galaxies and luminous active galactic nuclei (AGN) at high redshift provides an increasingly sensitive test of the connection between cosmological structure formation and the astrophysical processes that make dark matter halos observable. We develop a framework connecting the linear matter power spectrum to the mass variance, peak height, halo mass function (HMF), cumulative halo abundance, and observable galaxy and AGN populations. We use the Sheth-Tormen (ST) HMF as the baseline and compare it with an illustrative Bolshoi-Klypin-calibrated modification (KST) to quantify the sensitivity of predictions to the calibration of the HMF against cosmological N-body simulations. We apply the framework to three complementary tests: the baryonic and stellar mass reservoir available to massive galaxies, the abundance of halos capable of hosting luminous AGN, and the rest frame ultraviolet luminosity function of high redshift galaxies. Because the most massive systems occupy the rare, high peak tail of the halo distribution, modest changes in inferred host mass, baryonic conversion efficiency, black-hole occupation or duty cycle, and HMF calibration can produce large changes in predicted abundances. The ST-KST comparison shows that uncertainty in the high redshift halo population can materially affect the inferred host supply, particularly toward large z (10). Comparison with representative JWST massive galaxy, AGN, and UV luminosity function measurements demonstrates that matching the properties of an individual source is not sufficient for population consistency; the corresponding host halos must also exist in adequate numbers. Current observations provide increasingly stringent quantitative stress tests of both cosmological halo abundances and the baryonic and black hole physics at cosmic dawn.
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Cosmology and Nongalactic Astrophysics

When, Why, and How CMB Compression Fails

Davide Pedrotti, William Giarè, Hanyu Cheng et al. (+1 more)

We test when compressed CMB likelihoods can be reliably used to constrain new physics beyond $\Lambda$CDM, formulating concrete criteria for when, why, and how CMB compression fails. We derive our conclusions by exploring a broad set of models that modify different aspects of the cosmological evolution, including late-time dark-energy dynamics, non-standard late-time dark-matter evolution through interactions or decay, and dark-matter models with persistently non-standard redshift evolution. For each case, we compare the results obtained from data combinations based on the full Planck-CMB likelihood with their counterparts based on a compressed CMB likelihood calibrated in $\Lambda$CDM. We find that the compression remains accurate for late-time dark-energy extensions that preserve the dark-matter background evolution and do not introduce significant additional perturbative effects. By contrast, modifying the dark-matter evolution breaks the mapping between the present-day matter density and the matter density at the epochs relevant to the CMB, causing the compressed constraints to fail even when the modification acts exclusively at late times. In these cases, the compressed likelihood can drastically alter the geometry of the multidimensional posterior distributions, shifting their centers, producing strongly anisotropic deformations, reordering principal modes, and generating genuine mixing and rotation of their eigendirections. These multidimensional distortions propagate into substantially incorrect marginalized constraints on cosmological parameters, with differences between the full and compressed analyses reaching nearly an order of magnitude in some of the cases studied here.
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All authors Davide Pedrotti, William Giarè, Hanyu Cheng, Eleonora Di Valentino

Astrophysics of Galaxies

Galaxy merger-driven signatures in massive black hole pair hosts across cosmic time

Pranav Satheesh, Aklant K. Bhowmick and Laura Blecha

Galaxy mergers can drive gas toward galactic nuclei, enhancing both star formation and black hole accretion in post-merger galaxies. Here we use the IllustrisTNG-50 simulation and two boxes from the BRAHMA simulation suite, all of which adopt different black hole formation models, to characterize merger-associated signatures in candidate massive black hole (MBH)-pair hosts. In all three simulations, we select post-merger galaxies whose progenitors both host MBHs and quantify their enhancements in star formation and black hole accretion relative to matched non-merging controls. In TNG50, we find substantial merger-triggered enhancements in both specific star formation rate (sSFR) and specific black hole accretion rate (sBHAR) at $0 \leq z < 3.3$, reaching $\sim 1.4\times$ and $\sim 1.5-1.7\times$ the controls, respectively. The BRAHMA runs employ more physically motivated seed formation models, seeding BHs in lower-mass galaxies and at higher redshifts than TNG50. In BRAHMA, merger-driven enhancements in sSFR and gas fractions are comparable to those in TNG50 at $z \lesssim 3.3$ and persist to the highest redshifts probed by BRAHMA ($z \sim 6$). Despite this, BRAHMA shows no significant merger-driven enhancement in sBHAR across its entire redshift range. In a similar vein, TNG50 pair hosts show an enhanced AGN fraction relative to matched controls, whereas BRAHMA shows only a weak excess among the most rapidly accreting MBHs.
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Cosmology and Nongalactic Astrophysics

Boosted Odds: Lower-Point Probes of Parity Violation with Momentum Fields

Yong Sheng Yap, William R. Coulton, Jiamin Hou et al. (+1 more)

Parity-violating initial conditions are uniquely compelling signatures of inflationary dynamics beyond the single-field slow-roll paradigm, and their effects on the distribution of late-time observables can be easily separated from that of gravitational nonlinearities and galaxy formation physics. In this work, we propose using the momentum field, $\mathbf{p} = (1+\delta)\mathbf{v}$, and, in particular, the density-density-momentum bispectrum as a novel probe of primordial parity violation. This class of bispectra greatly complements traditional searches using four-point statistics of the density field, furnishing new observables that can be sensitive to parity-violating physics. At the same time, its lower dimensionality substantially reduces the complexity associated with analysing high-dimensional data vectors and their covariance. We show that the sensitivity of the density-density-momentum bispectrum to parity violation effects persists even if we can only observe the projection of the momentum field along the line-of-sight. We perform a Fisher forecast for the parity-violating amplitude of the ultra-squeezed template in the cross bispectrum of kinetic Sunyaev-Zel'dovich (kSZ) anisotropies and galaxy clustering, and we find that our approach give competitive constraints when compared to existing methods. Our method can be easily co-opted to existing pipelines to study parity violation and, as the galaxy-galaxy-kSZ bispectrum is a key cosmological probe, take advantage of the significant existing efforts dedicated to mitigating systematics and covariance modelling.
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All authors Yong Sheng Yap, William R. Coulton, Jiamin Hou, Steven Gratton

Instrumentation and Methods for Astrophysics

Nancy Grace Roman Space Telescope Wide Field Instrument: Grism Saturation Response to Bright Sources during Thermal-Vacuum Testing

Lipika Chatur, Dana R. Louie, Joshua E. Schlieder et al. (+3 more)

The Nancy Grace Roman Space Telescope launched on August 30th, 2026 and is expected to begin its science mission in 2027. Although Roman's core science will focus primarily on faint and distant sources, as a survey telescope, it will also observe many bright sources that can saturate the detector pixels. Our goal is to study the behavior caused by bright sources dispersed through the grism and to assess how detector properties may impact scientific analysis. We analyze detector saturation behavior in Roman's Wide Field Instrument (WFI) using Thermal Vacuum Test 2 (TVAC2) bright-source grism data. When bright sources are dispersed through the grism, we find that the faint and diffuse combined orders cause significant structured stray light. We also find that pixels neighboring saturated pixels continue to exhibit linear growth behavior before reaching saturation limits, in contrast to the non-linearity reported for non-dispersed bright point sources.
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All authors Lipika Chatur, Dana R. Louie, Joshua E. Schlieder, Robert F. Wilson, Evan Bray, Scott Rohrbach

High Energy Astrophysical Phenomena

Unveiling the Accretion Architecture of GS 1354–64: A Broadband X-ray and Polarimetric Study of its 2025–2026 Outburst

Kaushik Chatterjee

A comprehensive multi-satellite analysis of the dynamically confirmed black hole candidate GS 1354-64 during its highly active 2025-2026 outburst is presented. Leveraging simultaneous broadband spectroscopy, fast timing, and X-ray polarimetry, I map the evolution and geometry of the accretion flow. During the initial Compton-dominated hard state rise, strong, narrow Type-C quasi-periodic oscillations (QPOs) evolving from 0.08 Hz to 1.73 Hz with high fractional RMS (~8-10%) are detected, showing a strong anti-correlation with the inner disk radius (R_in) and a linear correlation with the coronal photon index (Gamma), supporting disk migration driving the precessional frequency while cooling the corona. An anomalous, highly ionized (Fe XXVI) equatorial disk wind is also observed, suggesting strong localized radiation pressure prior to the state transition. In the luminous, thermal-dominated soft state, individual-epoch reflection modeling indicated a rapidly spinning black hole (a* ~ 0.94-0.99) at inclination i ~ 45-53 deg; joint spectral modeling across these epochs refines this to i ~ 51 deg and a* ~ 0.998, with the disk pinned to the ISCO. The QPOs shifted to higher frequencies (~4.7-6.2 Hz) and weakened (RMS ~3-6%). Joint spectro-polarimetric modeling of this epoch reveals a steep, energy-increasing polarization degree, ruling out a spherical or lamppost geometry in favor of a highly asymmetric, radially extended slab-like corona. The suppression of the high-RMS QPO, combined with the strict energy-independence of the polarization angle, indicates the corona stabilized into an extended, symmetric slab, consistent with the collapse of the puffed-up spherical corona seen in the hard state.
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