Cosmology and Nongalactic Astrophysics
CNN+FoF: application of deep learning to the identification of dark matter haloes
Soumadeep Maiti, Carlos M. Correa, Andrea Fiorilli et al. (+4 more)
We present a deep-learning-based approach for identifying dark matter
haloes in cosmological N-body simulations. Our framework consists of a volumetric Convolutional Neural Network to classify individual simulation particles as either
halo or non-
halo members, followed by a highly optimised and parallelised Friends-of-Friends clustering
algorithm that groups the classified
halo members into distinct
haloes. The training data comprise simulations generated using GADGET-4, with labels obtained with the ROCKSTAR
halo finder. Our models incorporate two main
halo mass definitions, $M_{200\mathrm{b}}$ and $M_{\text{vir}}$, with similar performance. For
haloes defined by the ROCKSTAR $M_{200\mathrm{b}}$ criterion, the classification network demonstrated stable performance across multiple simulation resolutions. For the highest resolution, it achieved over $98\%$ across all primary performance metrics when identifying
halo particles. Furthermore, the FoF
algorithm yielded
halo catalogues with a purity generally exceeding $99\%$ and a stable completeness of $94\%$ for masses above $5\times10^{11} \, M_\odot$. Our pipeline recovered the centre-of-mass positions, velocities and
halo masses with high fidelity, yielding a
halo mass function consistent to within $5\%$ of the reference while faithfully reconstructing the internal density profiles. The primary objective of this study is to offer a faster and scalable alternative to conventional
halo finders, achieving a speed-up of approximately one order of magnitude relative to ROCKSTAR. While traditional N-body simulations remain dominated by the time required to solve gravitational dynamics, this post-processing acceleration becomes essential when coupled with fast field-level emulators, offering a promising pathway towards efficient, end-to-end forward modelling in modern simulation-based inference.
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All authors Soumadeep Maiti, Carlos M. Correa, Andrea Fiorilli, Andrés N. Ruiz, Dante J. Paz, Alejandro Pérez Fernández, Ariel G. Sánchez
High Energy Astrophysical Phenomena
A fast radio burst cyclone in technicolour: evidence of plasma lensing
Pavan A. Uttarkar, Ryan M. Shannon, Kelly Gourdji et al. (+9 more)
Fast
radio bursts (FRBs) are bright, energetic,
radio pulses of extragalactic origin. A dichotomy has emerged in the population: some produce repeat bursts, while the majority do not. Most repeating sources only show rare repetitions, and none have been studied extensively over the wide bandwidths necessary to disentangle the physical processes that produce emission from distortions to bursts caused by intervening ionised gas. Here we present
radio observations of the most active repeating source, FRB 20240114A. Using an ultrawideband receiving system, we have detected 5526 repetitions, revealing an extreme spectral and temporal variability in the burst emission. The bursts exhibit longer-term broadband variations in central emission frequency over multiple months, and narrowband bursts that have correlations in central frequencies on time scales of milliseconds to minutes. The spectral and temporal properties are consistent with the source undergoing magnification by foreground
plasma lenses, potentially embedded in a turbulent circumsource medium. This extreme example highlights the role of
plasma lenses in the observed properties of burst emission and can explain the diversity in activity and energetics of the entire FRB population.
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All authors Pavan A. Uttarkar, Ryan M. Shannon, Kelly Gourdji, Adam T. Deller, Pravir Kumar, Navin Sridhar, Marcus E. Lower, Artem Tuntsov, Atharva D. Kulkarni, Simon C.-C. Ho, Yuanming Wang, Joscha N. Jahns-Schindler
High Energy Astrophysical Phenomena
Foiling Black Hole Foils: Revealing Horizon Alternatives with Baryonic Atmospheres
Shokoufe Faraji and Avery E. Broderick
Event horizons are a defining feature of black holes. Consequently, there have been many efforts to probe their existence in astrophysical black hole candidates, spanning ten orders of magnitude in mass. Nevertheless, horizons remain an obstacle to unifying general relativity and
quantum mechanics, most sharply presented by the information paradox. This has motivated a proliferation of horizonless alternatives (black hole foils) that avoid event horizons and are therefore presumably benign. We explore the fate of accreting material in the context of spherically symmetric horizonless compact objects in the steady state regime. We find that for typical accreting astronomical targets, foils can develop an optically thick, convectively stable baryonic atmosphere, immediately implying the creation of an emitting photosphere at modest
redshift even when the surface
redshift is extreme. The emergent photosphere luminosity is driven toward the
accretion powered
equilibrium value and is only weakly sensitive to the foil
redshift. Moreover, local gas-surface interaction provides a microphysical lower bound on the effective base temperature, insulating the atmosphere from arbitrarily cold foils. The unknown properties of the foil enter only through local boundary conditions controlling
baryon processing and thermal coupling at the surface, making the solutions broadly applicable to horizonless alternatives that do not invoke significant additional nonlocal interactions. Thus, under minimal assumptions (GR exterior and local surface interactions), spherically symmetric horizonless foils in accreting systems are generically observationally exposed: the absence of a thermal photosphere directly constrains or rules out broad classes of such models.
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Earth and Planetary Astrophysics
Multi-Arrival Infrasound from Meteoroids: Fragmentation Signatures versus Propagation Effects in a Fine-Scale Layered Atmosphere
Igor P. Chunchuzov, Oleg E. Popov, Elizabeth A. Silber et al. (+1 more)
Infrasonic signatures of meteoroid fragmentation are frequently ambiguous: do multiple arrivals signify a complex breakup or merely the distorting effects of a layered atmosphere? Resolving this ambiguity is critical for accurate energy estimates and source reconstruction. In this study, we address this challenge by analyzing a unique regional
dataset of well-constrained meteoroid events observed by the Southern Ontario Meteor Network and the co-located Elginfield Infrasound Array. We employ pseudo-differential
parabolic equation (PPE) simulations to quantify how fine-scale
gravity-wave structures in the stratosphere and lower thermosphere modify acoustic waveforms at ranges <300 km. Our modeling reveals that while fine-scale layering can stretch signals and generate diffuse oscillatory tails, it does not produce discrete, high-amplitude pulse splitting at ranges below ~140 km. By applying these results to the rare multi-arrival event 20060305, we demonstrate that its distinct double arrival at 100 km range is inconsistent with atmospheric multipathing and provides definitive evidence of separate fragmentation episodes. These findings establish new diagnostic criteria for separating source physics from propagation artifacts, improving the reliability of infrasound as a monitoring tool for natural bolides, space debris re-entries, and catastrophic launch failures.
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All authors Igor P. Chunchuzov, Oleg E. Popov, Elizabeth A. Silber, Sergey N. Kulichkov
Earth and Planetary Astrophysics
Vertical Temperature Structure in Io's Atmosphere from ALMA SO$_2$ Observations
Timothy N. Proudkii, Katherine de Kleer, Imke de Pater et al. (+4 more)
The structure of Io's atmosphere is controlled by competing processes, from volcanic outgassing and sublimation to radiative cooling and
plasma heating. Yet, the lack of an observationally-derived temperature profile has left this balance unconstrained. We used four epochs of Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 (275-373 GHz) and Band 8 (385-500 GHz) SO$_2$ spectroscopy to retrieve Io's vertical atmospheric temperature profiles. To mitigate longstanding degeneracies common in atmospheric
retrievals, we performed a simultaneous multi-line analysis combined with line-of-sight disk-resolved Doppler velocity maps and a forward model that included a sub-beam velocity-dispersion term. This modeling approach enabled the separation of thermal and dynamical line-shape contributions. On the leading hemisphere, we retrieved a cold, quasi-isothermal lower atmosphere ($\sim$124-137~K up to $\sim$0.5~nbar), followed by a thermospheric rise reaching hundreds of kelvins by $\sim10^{-2}$~nbar. On the trailing hemisphere, our fits yielded qualitatively similar profiles but consistently retrieved lower SO$_2$ column densities. The lower column densities confined line formation to the first few kilometers, making the trailing hemisphere spectra statistically consistent with an isothermal atmosphere. Across
datasets, we retrieved fractional gas coverages of $\sim$35-50$\%$ and sub-beam velocity dispersions of $\sim$25-85$\mathrm{~m~s^{-1}}$, encoding line-of-sight velocity dispersion within a beam element in excess of the disk-resolved Doppler velocity map. Together, these
retrievals deliver the first vertically resolved temperature profiles of Io's atmosphere, reveal robust vertical structure on the dayside leading hemisphere, and offer new constraints on Io's thermal energy balance.
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All authors Timothy N. Proudkii, Katherine de Kleer, Imke de Pater, Alexander E. Thelen, Statia Luszcz-Cook, Emmanuel Lellouch, Arielle Moullet
High Energy Astrophysical Phenomena
Helium superluminous SN 2021bnw : an explosion of a massive star with a pre-outburst
Alexandra Kozyreva, Matteo Bugli, Alexey Mironov et al. (+1 more)
Superluminous
supernovae (SLSNe) remain an intriguing topic in
supernova (SN) transient astronomy. While the majority of SLSNe are shown to be explained by energy streaming from the newly born magnetar, there are others which are powered by different mechanisms. We analyse the pseudo-bolometric light curve of the nearby helium-rich SLSN 2021bnw. We built models and run hydrodynamics radiative-transfer simulations with STELLA. Our best-fit models include 15-22.5 Msun of ejecta enriched with 1.7 Msun of 56 Ni and carrying energy of 4 foe, and colliding w ith 7 Msun of circumstellar matter which match the observed light curve very well. The early data can be explained as cooling of an expanding shell with the mass of 0.5 Msun and kinetic energy of 0.7 foe. We tend to exclude a pulsational pair-instability (PPISN) origin for SLSN 2021bnw. Instead we conclude that SLSN 2021bnw was preferably a core-collapse explosion of a
star with the initial mass of not less than 61 Msun aided by magnetorotational effects.
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All authors Alexandra Kozyreva, Matteo Bugli, Alexey Mironov, Petr Baklanov
Instrumentation and Methods for Astrophysics
A Response to paper Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates by Watters et al. (2026)
Beatriz Villarroel, Alina Streblyanska, Stephen Bruehl et al. (+1 more)
We respond to the critique by Watters et al. (2026) of the statistical analyses in Villarroel et al. (2025) and Bruehl & Villarroel (2025). We argue that the critique conflates object-level validation with ensemble-level statistical inference and relies on a reduced, heterogeneously filtered subset originally constructed for a different scientific purpose. We further question whether the aggressively filtered subset used in Watters et al. (2026) demonstrates a meaningful improvement in sample purity, given the twenty-fold reduction in sample size. Our simple, visual check does not suggest that it does. The subset further lacks complete temporal information and is seriously statistically underpowered for testing the reported Earth-shadow deficit. We emphasise that the horizontal separation metric used for plate assignment and time reconstruction as in Watters et al. (2026) depends on the inclusion of the cos(Dec) factor to ensure
geometric consistency. Any omission would alter plate assignment and inferred observation times. Moreover, the analyses presented in Watters et al. (2026) do not include uncertainty estimates or error propagation, limiting the interpretability of the claimed null results. We conclude that the principal findings reported in Villarroel et al. (2025) and Bruehl & Villarroel (2025) are not invalidated by the analyses presented in Watters et al. (2026).
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All authors Beatriz Villarroel, Alina Streblyanska, Stephen Bruehl, Stefan Geier
High Energy Astrophysical Phenomena
Three-Dimensional Kinematics of the Oxygen-rich Supernova Remnant G292.0+1.8
Adele L. Plunkett, P. Frank Winkler, Knox S. Long et al. (+1 more)
Studying the remnants of young core-collapse
supernovae (SNe) can yield insight into the chemical composition of their progenitors and the geometry of the explosions. The
supernova remnant (SNR) G292.0+1.8 is one of only three known oxygen-rich SNRs in the
galaxy-remnants of core-collapse for which relatively pure fragments of ejecta can be seen. Several dozen ejecta
knots from G292.0+1.8 were the subject of a proper motion analysis, based on [O III] 5007-Angstrom images taken over a 22-year baseline by Winkler et al. 2009 (arXiv:0810.1935). They determined that the transverse velocities of the filaments are linearly proportional to their distances from a common expansion center, thus the O-rich filaments have been traveling with little deceleration since the initial
supernova event,about 3000 years ago. In this paper, we use optical spectra of G292.0+1.8, all taken from the Cerro Tololo Inter-American Observatory (CTIO), to measure radial velocities for 93
knots. Assuming un-decelerated expansion, as indi- cated by the proper motions, the radial velocity should be proportional to the distance from the center along the line of sight, just as the proper motions are proportional to the transverse distance. Therefore, we can map the three-dimensional structure and kinematics of the SNR. We find that the
knots generally follow a broad bi-conical distribution, suggesting that the
supernova explosion produced broad jets of ejecta. This structure is similar to that seen in some other young core-collapse
supernova remnants.
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All authors Adele L. Plunkett, P. Frank Winkler, Knox S. Long, Dan Milisavljevic
Solar and Stellar Astrophysics
The eruptive young star IRAS 21204+4913
M.A. Burlak, A.V. Dodin, A.V. Zharova et al. (+7 more)
The results of photometric, polarimetric, and spectroscopic observations are presented for the young
star IRAS 21204+4913, whose visible brightness has increased by $\approx 5^{\rm m}$ since October 2025. The
star's absorption spectrum in the $0.36 - 0.75 \mu$m range resembles those of A - F
giants and supergiants, but it also exhibits molecular TiO bands. The brightening was accompanied by a significant increase in the degree of polarization of the
stellar radiation (to $\approx 16 \%$ in the I-band), likely due to scattering by
dust in an expanding circumstellar shell. The P Cygni profile of the H$\alpha$ line implies a dusty wind velocity of $\approx 300$ km/s. We believe that the outburst of IRAS 21204+4913 is caused by an increase in the
accretion rate of protoplanetary disk's matter onto the young
star with a mass of $\lesssim 0.5$ M$_\odot$ to $\gtrsim 3\times 10^{-5}$ M$_\odot$ yr$^{-1}$. Furthermore, IRAS 21204+4913 displays several unusual features: the dependence of the width and radial velocity of absorption lines on the excitation potential, emission in the TiO molecular bands, and a comparably bright outburst that occured in 1948. Several T Tauri
stars and a group of Herbig-Haro objects are found in the vicinity of the
star.
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All authors M.A. Burlak, A.V. Dodin, A.V. Zharova, S.G. Zheltoukhov, N.P. Ikonnikova, S.A. Lamzin, B.S. Safonov, I.A. Strakhov, A.A. Tatarnikov, A.M. Tatarnikov
Astrophysics of Galaxies
Mechanisms Affecting Galaxies Nearby and Environmental Trends (MAGNET)
Benedetta Vulcani, Gabriella De Lucia, Daria Zakharova et al. (+28 more)
[ABRIDGED]
Galaxy evolution is shaped by internal and external mechanisms that regulate the
baryon cycle and
star formation activity. We present a theoretical framework based on the
GAlaxy Evolution and Assembly (GAEA) semi-analytic model. We extracted portions of simulated volumes that include isolated
galaxies, pairs, group, and filament members at z ~ 0, specifically avoiding massive clusters.
Galaxies were classified using both intrinsic (
halo-based) and observational (2D projected) parameterizations, reconstructing their environmental histories from z = 2 and identifying mergers,
tidal interactions, ram pressure stripping (RPS), and starvation. 2D information decreases isolated and group fractions while doubles pairs. More than half of
galaxies remain unaffected by the investigated processes since z = 2. Among affected
galaxies, mergers dominate at high
stellar masses (40-60% at log(M*/Msun) > 10.5).
Tidal interactions are less frequent, and their incidence increases with
stellar mass. RPS dominates in groups and filaments at intermediate masses (~50%), while starvation ranges from 20 to 30%. The incidence of the different mechanisms depends strongly on both mass and environment, though their imprints on global properties are often subtle. Distinct evolutionary pathways emerge: log(M*/Msun) < 9.5,
galaxies in groups and filaments have a faster mass growth than
galaxies in the other environments, especially those undergoing starvation, mergers and, to less extent, RPS. Differences are reduced moving to higher masses, where no clear dependence on physical mechanism emerge, even though at these masses a clear
star formation suppression is evident in mergers and starved
galaxies. This theoretical investigation provides essential context for the recently started multi-wavelength program Mechanisms Affecting
Galaxies Nearby and Environmental Trends (MAGNET), which we introduce here.
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All authors Benedetta Vulcani, Gabriella De Lucia, Daria Zakharova, Paolo Serra, Lizhi Xie, Stefania Barsanti, Bianca Maria Poggianti, Alessia Moretti, Marco Gullieuszik, Yannick Bahé, Fabio Fontanot, Jacopo Fritz, Fabio Gastaldello, Massimo Gaspari, Michaela Hirschmann, Yara Jaffe, Konstantinos Kolokythas, Alessandro Ignesti, Augusto Lassen, Alessandro Loni, Lorenzo Lovisari, Antonino Marasco, Sphesihle Makhathini, Sean McGee, Moses Mogotsi, D.J. Pisano, Mpati Ramatsoku, Oleg Smirnov, Rory Smith, Stephanie Tonnesen, Marc Verheijen
Cosmology and Nongalactic Astrophysics
Mimicking the large-scale structure of the Local Universe. Synthetic pre-labelled galaxies in large-scale structures
M. Alcázar-Laynez, S. Duarte Puertas, S. Verley et al. (+6 more)
Current observational and simulated large-scale structure (LSS) catalogues often lack consistency in assigning
galaxies to specific structures, due to the absence of a universally accepted classification criterion. With the aim to generate synthetic empirical data for fine-tuning LSS classification
algorithms, as well as to train machine learning (ML)/deep learning (DL) models for the same purpose, this work presents a purely geometrical simulation based on statistical spatial properties found in LSS surveys, using the spectroscopic main
galaxy sample of the Sloan Digital Sky Survey (SDSS) catalogue up to a
redshift of z~0.1 as a specific use case. A parallelism between the LSS and the Voronoi tessellation was utilised, in which the nodes, links, surfaces, and
cells of the diagram correspond to clusters, filaments, walls, and voids, respectively. The simulation used random positions within voids as seeds for tessellating the 3D space. The resulting structures were randomly populated with
galaxies that adhere to the statistical properties of their observational respective structures. As the
galaxies were generated, they were tagged with their corresponding structure. In each simulation, six LSS mock catalogues were generated, following the statistical behaviour observed in the SDSS catalogue, depending on the structure they belong to. The Malmquist bias and the Fingers of God effect were simulated as well. We present a novel geometrical LSS simulator, where generated
galaxies mimic the statistical properties of their observational belonging structure. The simulator was tuned to mimic the SDSS catalogue, although any other catalogue can be considered. With the generated catalogue, it is possible to adjust the LSS classification
algorithms, train and test ML/DL models, and
benchmark several LSS classification methods using this pre-labelled data to contrast their results and performance.
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All authors M. Alcázar-Laynez, S. Duarte Puertas, S. Verley, G. Blázquez-Calero, A. Jiménez, A. Lorenzo-Gutiérrez, D. Espada, M. Argudo-Fernández, I. Pérez
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Enhanced Cosmic-Ray Antinuclei Fluxes with Dark Matter Annihilation into SUEPs
Mattia Di Mauro, Caleb Gemmell, Austin Batz et al. (+4 more)
Standard-Model (SM) hadronic parton showers initiated by secondary
cosmic-ray production or dark matter (DM) annihilations robustly predict very low antinuclei yields and a strong additional suppression for heavier antinuclei. We show that an important exception can arise if DM annihilates into a confining dark sector that produces Soft Unclustered Energy Patterns (SUEPs). The hallmark of SUEPs is the emission of very large multiplicities of soft dark
mesons ($\pi_D$), which can overcome the usual phase-space suppression of antinuclei formation in parton showers, provided that the dark
mesons decay promptly into SM
quarks, i.e. within a SM hadronization length. We study several
benchmark realizations and find that for DM masses $m_{\rm DM}\sim\mathcal{O}(10~\mathrm{TeV})$, dark
meson masses $m_{\pi_D} \sim 400~\mathrm{GeV}$, $\pi_D$ dominantly decaying to $t\bar t$, and a SUEP temperature $T_{\rm SUEP}\simeq 0.1\,m_{\pi D}$, DM annihilation into SUEPs can yield tens of antideuterons and a few antihelium–3 events at AMS-02 at kinetic energies of $\mathcal{O}(\mathrm{GeV}$/n) and a few antideuterons and antihelium-3 events in GAPS at energies below 0.5 GeV/n. A future confirmation of an antinuclei signal by the AMS-02 or GAPS experiments could provide hints for hidden confining dynamics and would significantly constrain the relevant SUEP parameters.
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All authors Mattia Di Mauro, Caleb Gemmell, Austin Batz, David Curtin, Fiorenza Donato, Nicolao Fornengo, Graham D. Kribs
Astrophysics of Galaxies
AGN in massive galaxies identified via optical broadband variability: lessons from VST-COSMOS for future LSST science
B. Bichang'a, D. De Cicco, S. Kaviraj et al. (+4 more)
We study the properties of 56 massive (M$_{\rm{\star}}$ > 10$^{10}$ M$_{\odot}$)
galaxies at $z<1$ that host AGN, detected via their broadband optical variability in the VST-COSMOS survey. VST-COSMOS provides a nearly-identical single visit depth ($r$ $\sim$ 24.6 mag) and temporal baseline (eleven years) as the forthcoming Legacy Survey of Space and Time (LSST), albeit in a much smaller 1 deg$^2$ footprint (four orders of magnitude smaller than that of the LSST). We compare the properties (morphologies, the presence of interactions, rest-frame colours and environment) of our AGN to
galaxies in a control sample, which are drawn from the non-variable population and matched in
redshift and
stellar mass to their AGN counterparts. The fraction of AGN with early-type morphology ($\sim$55 per cent) and the fraction that is interacting ($\sim$23 per cent) are similar to what is observed in the controls, suggesting that these AGN are not primarily triggered by interactions. Similarly, the AGN and controls do not show strong differences in their rest-frame $(u-z)$ colours or local environment, suggesting that neither the recent
star formation histories nor the surroundings of the AGN are strongly atypical of the general
galaxy population. This study provides a glimpse into forthcoming AGN science using the LSST. With vastly improved statistics, LSST will offer unprecedented insights into AGN demographics, host-
galaxy evolution and the processes that fuel supermassive black holes, potentially reshaping our understanding of their place in the Universe.
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All authors B. Bichang'a, D. De Cicco, S. Kaviraj, I. Lazar, A. Watkins, G. Martin, D. Kakkad
Astrophysics of Galaxies
Magnetohydrodynamic Precipitation
G. M. Voit, B. D. Wibking and D. Yaldiz
Circumgalactic gas around massive
galaxies generally has a volume-filling component – an atmosphere – with a temperature determined by the potential-well depth of the
galaxy's
halo. If the atmosphere is near hydrostatic
equilibrium and is stable to convection, then it can remain nearly homogeneous, as long as it is not too dense. But if its density is great enough, it becomes prone to producing a rain of cold clouds that fall toward the
galaxy's center and accrete onto its central black hole. Here we explain how relatively weak
magnetic fields enhance a
galactic atmosphere's tendency to produce cold clouds and how the cold gas becomes organized into vertically elongated, highly magnetized filaments descending at sub-Keplerian speeds. It is intended to complement recent numerical simulations of the process and to serve as a guide to interpreting both simulations and observations of the filamentary gas in hot
galactic atmospheres.
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Solar and Stellar Astrophysics
Detection horizon for the neutrino burst from the stellar helium flash
Pablo Martínez-Miravé, Irene Tamborra and Georg Raffelt
Low-mass
stars ($M\lesssim 2\,M_\odot$) ignite helium under degenerate conditions, eventually causing a
nuclear run-away – the helium flash. The alpha-capture process on $^{14}$N produces a large amount of $^{18}$F, whose subsequent decay spawns an intense $\nu_e$ burst (with average energy of $0.38$ MeV) lasting about a day. We show that, in addition, a strong $1.7$ MeV
neutrino line is generated by electron capture on $^{18}$F. Detection is hindered by large backgrounds in state-of-the-art
neutrino observatories, such as JUNO. In next-generation facilities, such as the Jinping
neutrino experiment, the horizon for a detection with a local significance of $3 \sigma$ would be extended to almost $3$ pc. Although helium flashes occur a few times per year in our
Galaxy, there are no
stellar candidates approaching the tip of the red
giant branch within $10$ pc. Hence, to date, asteroseismology remains the most promising tool for probing the most energetic thermonuclear event in the life of a low-mass
star.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
The Sun Can Strongly Constrain Spin-Dependent Dark Matter Nucleon Scattering Below the Evaporation Limit
Thong T.Q. Nguyen and Tim Linden
The Sun is a promising target for dark matter (DM) searches due to its ability to accumulate DM particles via scattering and catalyze their self-annihilation. However, at low DM masses, DM particles can also "evaporate" due to subsequent collisions with the hot thermal
plasma of the Sun. While several modeling studies have calculated the competitive dynamics of DM evaporation and annihilation, observational studies have typically assumed a fixed 4 GeV "evaporation limit", below which DM evaporates before it can annihilate. In this paper, we consider the competitive effects of DM evaporation and annihilation on
spin-dependent DM nucleon cross-section limits, finding that
Solar observations can continue to exceed terrestrial constraints by between 1-5 orders of magnitude for DM masses between 2-4 GeV, and can even provide world leading constraints below 0.2 GeV where direct detection is limited.
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High Energy Astrophysical Phenomena
Orbital eccentricity can make neutron star g-mode resonances observable with current gravitational-wave detectors
János Takátsy, Lorenz Zwick, Pankaj Saini et al. (+1 more)
Dynamical tides can provide us vital information about the properties of
neutron star (NS) matter. This is particularly true for g-modes, whose frequency and
tidal coupling are highly sensitive to the composition of NSs, especially in their centers, where microphysical models are the least reliable. However, due to their weak coupling to external
tidal fields, their effect on the gravitational-wave (GW) signal of binary inspirals can be difficult to observe. Here we show that the detectability of these tides can be significantly enhanced by binary NSs with moderate eccentricities. This is primarily due to higher eccentric harmonics in the early phase of the binary
evolution experiencing larger phase shifts, which they transport to the sensitive band of GW detectors. In addition, g-mode tides in eccentric binaries undergo several epicyclic resonances, which also amplify the total phase shift. We demonstrate that these effects increase the detectability of g-mode dynamical tides by more than an order of magnitude for eccentricities of $e_\mathrm{10Hz}\sim0.2-0.4$, making it possible to put robust constraints on g-mode properties using current GW detectors, while all relevant models could potentially be constrained with eccentric binary NSs with Einstein
Telescope.
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All authors János Takátsy, Lorenz Zwick, Pankaj Saini, Johan Samsing
High Energy Astrophysical Phenomena
Measuring Pulsar Distances from Chirping Orbital Periods
Brady Egleston, Reza Ebadi and Ronald Walsworth
The observed orbital period time derivative (or orbital "chirp") of a millisecond binary
pulsar (MSP) encodes information about both the intrinsic properties of the binary system and its environment. Orbital chirp has contributions from intrinsic energy loss due to gravitational wave emission, kinematic effects due to motion in the plane of the sky, and dynamical effects due to
galactic acceleration, with the latter two contributions depending on the MSP distance. We use orbital chirp data to infer distances to 21 MSPs; and for four of which we obtain smaller uncertainties than those reported in previous distance measurements. We incorporate multiple realistic
galactic acceleration models to assess the sensitivity of the inferred distances to the choice of
galactic gravitational potential, finding a significant dependence for four MSPs.
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Astrophysics of Galaxies
The dependence of triggering mechanisms on radio AGN sub-types: the role of galaxy mergers
Freya Barwell, Clive N. Tadhunter, Jonathon C. S. Pierce et al. (+10 more)
Powerful,
radio-loud active
galactic nuclei (AGN) are associated with one of the most important forms of AGN feedback, and understanding how they are triggered is key to properly incorporating them into models of
galaxy evolution. Here, we present the results of a deep Isaac Newton
Telescope/Wide Field Camera imaging survey which, when combined with Gemini/Gemini Multi-Object Spectrograph South images, gives a 98 per cent complete sample of 112 3CR
radio galaxies with
redshifts $z$ < 0.3, alongside a
stellar mass matched control sample. Our results provide strong evidence for significant differences ($\sim$3$\sigma$) between the triggering mechanisms of the different sub-types of powerful
radio AGN. The high-excitation
radio galaxies (HERGs) show a high rate of morphological disturbance (62$^{+6}_{-7}$ per cent) – an excess of $\sim$4$\sigma$ compared with the control sample – consistent with them being predominantly triggered in
galaxy mergers and interactions. In contrast, the low-excitation
radio galaxies (LERGs) show a much lower rate of morphological disturbance (36$^{+7}_{-6}$ per cent), consistent with the control sample, and suggesting a different dominant triggering mechanism, such as the
accretion of gas from the hot X-ray
haloes of the host
galaxies or
galaxy clusters. We also demonstrate that, when considering the
radio morphology, the FRII HERG sources preferentially reside in disturbed morphologies, a difference of $\sim$3$\sigma$ to the FRII LERG objects. This suggests that the FRII LERG sources do not solely represent a `switched-off' phase in the HERG lifecycle of the same parent
galaxy population as the FRII HERGs.
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All authors Freya Barwell, Clive N. Tadhunter, Jonathon C. S. Pierce, Aaron E. Watkins, Yjan Gordon, Luke R. Holden, Lydia Makrygianni, Dustin T. Mason, Adam J. Singleton, Rebecca J. Houghton, Summer A. J. McLaughlin, Cristina Ramos Almeida, Javier Román
Astrophysics of Galaxies
The diverse nature of spiral arms in the Auriga Superstars cosmological hydrodynamic simulations
Robert J J Grand, Francesca Fragkoudi, Rüdiger Pakmor et al. (+4 more)
The dynamical nature and formation mechanism(s) of
galactic spiral arms remain long-standing problems in astrophysics. Most theoretical work is based on analytic calculations or idealised simulations, which has yielded several theories of spiral structure. The radial profile of the spiral arm rotation speed - the pattern speed - is a key observable prediction of these theories. However, observations that infer spiral pattern speeds reveal a mixed picture with no clear consensus. Here, we expand on theoretical efforts by examining the pattern speed profiles in the Auriga Superstars set of high-resolution cosmological magnetohydrodynamic simulatons of Milky Way-mass spiral disc
galaxies. These simulations combine
galaxy formation in a cosmological environment with the high dynamical fidelity afforded by an $\sim 800$ $\rm M_{\odot}$
star particle resolution, giving $\sim 100$ million
star particles in the disc. We show that several different spiral arm theories are realised among our simulations, including large-scale kinematic density waves,
manifold spirals, dynamic (co-rotating) spirals, and overlapping modes. In particular, we demonstrate that a strong
tidal interaction leads to clear kinematic density waves, and that
manifold spirals are present in a strongly-barred
galaxy. Interestingly, we find that the same
galaxy may show qualitative
evolution of their spiral pattern speed profiles, indicating that the nature of spiral arms can evolve on potentially sub-Gigayear timescales. Our results demonstrate that in the absence of a strong external encounter or a strong bar,
galactic spiral structure is highly transitional and complex with no clear long-lived underlying wave.
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All authors Robert J J Grand, Francesca Fragkoudi, Rüdiger Pakmor, Facundo A Gómez, Freeke van de Voort, Rebekka Bieri, Sophie Townson
Astrophysics of Galaxies
Barium Stars Across the Milky Way: Probing Their Origins via the GALAH Survey
Jaden Levine, Catherine Manea, Keith Hawkins et al. (+4 more)
Barium
stars are unusually enriched in barium ([Ba/Fe] >= 1.0 dex) and not predicted by current
Galactic chemical
evolution models. Previous observations of barium
stars have found evidence that they form through mass transfer from a companion asymptotic
giant branch (AGB)
star or through radiative levitation. The chemical abundance and kinematic information of barium
stars may help constrain AGB
stellar nucleosynthesis, binary
star evolution, and internal evolutionary processes that affect surface abundances. Using ~450,000
stars from the
GALactic Archaeology with Hermes (GALAH) survey, we identify nearly 3000 new barium-rich
stars and separate them into hot (Teff > 6000 K) and cool (Teff < 6000 K) populations. Cross-matching with
Gaia DR3, we find that 47.7% of our barium
stars within 1 kpc have elevated re-normalized unit weight error (RUWE >= 1.4), compared to 16.3% of a comparable sample of the GALAH field, suggesting multiplicity plays an important role in the formation of both populations of barium
stars. A subset of hot barium
stars exhibit low RUWE (RUWE < 1.2) and [alpha/Fe] < -0.2, supporting radiative levitation as an origin as well. We determine
Galactic memberships using both kinematics and chemistry and find that barium
stars exist in the thin disk, thick disk, and
halo though they are slightly more prevalent at lower
metallicities. Overall, we show evidence for barium
stars produced by mass transfer and for those produced by radiative levitation, with both formation mechanisms occurring ubiquitously across the
Galaxy.
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All authors Jaden Levine, Catherine Manea, Keith Hawkins, Kendall Sullivan, Kate H. R. Rubin, Zachary Maas, Andrew C. Nine
Earth and Planetary Astrophysics
Searching for Extragalactic Exoplanets: A Survey of the Sagittarius Dwarf Galaxy Stream with TESS
William Schap, Jason Dittmann and Elizabeth Lada
To date no
exoplanets have been detected outside the Milky Way, and their extragalactic occurrence rates are poorly constrained. Using available data from TESS we perform the first transit survey of the Sagittarius
dwarf galaxy stream using 15,176 main sequence
stars identified as likely members. We calculate an upper limit of $<$1.01% for hot Jupiters with radii of 1-2 R$_{Jup}$ and periods of 0.6-10 days after detecting zero
planets. We compare our calculated occurrence rate upper limits to the upper limits found in the Milky Way globular clusters M4 and 47 Tuc. Our 1-$\sigma$ occurrence rate upper limit of $<$0.37% for the Sagittarius
dwarf galaxy stream, for
planets with radii of 1.5-2 R$_{Jup}$ and periods $<$10 days, is lower than the $<$0.57% upper limit measured in 47 Tuc. Similarly, our 2 sigma upper limit of $<$0.78% for
planets with radii of 1.4-2 $_{Jup}$ and periods $<$8 days is below the $<$0.81% upper limit measured in M4. We predict that a future analysis of TESS data with a high detection efficiency for hot Jupiter transit depths would require $\eta_{extragalactic}$ $\geq$ 11,467 target
stars to detect a
planet of extragalactic origin. Therefore, we predict that a future investigation of TESS data which includes additional extragalactic
stellar streams will be able to either detect the first extragalactic origin
planet or provide evidence that older, lower
metallicity extragalactic environments may experience a lower hot Jupiter occurrence rate than is observed for the Milky Way.
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Cosmology and Nongalactic Astrophysics
ABCMB: A Python+JAX Package for the Cosmic Microwave Background Power Spectrum
Zilu Zhou, Cara Giovanetti and Hongwan Liu
We present ABCMB, a differentiable Einstein-Boltzmann solver for the
cosmic microwave background (CMB). ABCMB is an analysis-ready code package capturing important effects to linear order in $\Lambda$CDM cosmology. It computes the CMB power spectrum and includes effects like
lensing, polarization, massive
neutrinos, and a state-of-the-art treatment of Big Bang Nucleosynthesis and recombination. ABCMB has sub-percent-level agreement with CLASS and can be run on a GPU with competitive, and sometimes even faster, run times, owing to ABCMB's favorable run time scaling with maximum multipole moment. It is refactored compared to previous codes and takes advantage of object-oriented programming to improve extensibility, meaning new physics can be added to it without the need for modifying source files. ABCMB provides accurate and stable gradients to the user, making Fisher analyses straightforward, and enabling the use of efficient gradient-based sampling methods.
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