Astrophysics of Galaxies
Cross Subtype Transferability of Machine Learning Photometric Redshift Relations in Low Redshift Seyfert AGN
Uzay Aydin
Photometric
redshift estimation for active
galactic nuclei (AGN) is complicated by the combined effects of host-
galaxy light,
nuclear emission,
dust attenuation, and broadband spectral diversity. We investigate whether machine learning photo-z relations trained on one low-
redshift Seyfert subtype remain valid when transferred to another, and whether probabilistic subtype classification can be used to identify sources for which a specialised regressor is reliable. Using spectroscopically selected Seyfert I and Seyfert II samples from SDSS, matched to AllWISE photometry over 0 < z_spec <= 0.6, we constructed a common 45-feature representation from SDSS ugriz and WISE W1-W4 data. Random Forest and XGBoost regressors were evaluated within each subtype, followed by controlled cross-subtype transfer tests,
redshift and sample size-matched experiments, feature ablations, and an independent classifier-gated regression test. The subtype specific models achieved strong within-sample performance, with the Seyfert II model reaching R2 = 0.965 and sigma_NMAD = 0.0169. However, transfer between Seyfert I and Seyfert II produced a clear and asymmetric degradation in accuracy that persisted after matching the samples and restricting the photometric inputs. A probabilistic Seyfert classifier further identified subsets for which the Seyfert II regressor was more reliable, while extrapolation beyond the
redshift range represented in training produced systematic underestimation. These results demonstrate that AGN photo-z performance depends strongly on the population and
redshift domain represented in the training data, supporting subtype-aware calibration and applicability-based source selection.
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High Energy Astrophysical Phenomena
Cosmic Ray Electron Evolution in Supernova Remnants: Log-Parabola Distribution
Joshua J. Ziegler, Justin D. Finke and J. Martin Laming
The shock fronts of
supernova remnants (SNRs) are believed to be significant sites of acceleration of
cosmic ray particles. Previous researchers have shown that a particle distribution similar to a log-parabola can be generated when particles have an energy-dependent escape. We explore the acceleration of electrons at SNR shock fronts, and show that modeling this energy-dependent particle escape model can produce spectral energy distributions consistent with observations of two
lepton-radiation-dominated SNRs: RX J1713.7-3946 and SN 1006. The model includes the
evolution of both the electron distribution and
photon spectra as a result of the combined effects of the SNR
evolution and electron energy loss. The electron-escape energy dependence is quite weak, but the electron distribution and
photon spectra turn out to be very sensitive to changes in the electron escape. We also explore how sensitive the spectra and electron distributions are to the parameters used in the log-parabola model.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
String-inspired Gauss-Bonnet Gravity Inflation and ACT
S.D. Odintsov, V.K. Oikonomou, Pyotr Tsyba et al. (+2 more)
In this article we present a systematic observational verification of the ghost-free string-inspired $f(R,\mathcal{G})$ model, where the Gauss-Bonnet invariant is non-minimally coupled to an auxiliary scalar field $\chi$ through the coupling function $h(\chi)$. Previous studies confirmed the theoretical viability of this framework using phenomenological parameter choices. In this work, for the first time, a systematic comparison with observational data from Planck 2018 and the Atacama Comsology
Telescope is carried out via a
Bayesian MCMC analysis using the Cobaya code. We explore an extended set of sixteen models constructed from four types of the Hubble parameter combined with power-law, exponential, hybrid, and inverse logarithmic coupling functions $h(\chi)$. The hybrid coupling $h(\chi) = \gamma e^{b_1\chi}\chi^{b_2}$, introduced in this context, allows for interpolation between the power-law and exponential forms, providing additional flexibility in controlling the Gauss-Bonnet contribution at different stages of inflation. All sixteen models reproduce the red spectral tilt of scalar perturbations consistent with CMB observations, yielding $n_s \approx 0.97$ at $N = 60$ e-folds. We find that the preference for the
dataset is systematically determined by the choice of Hubble parametrization rather than by the coupling function. The parameter $\mu\approx0.1$ remains stable in all configurations, suggesting its fundamental role within the ghost-free formalism.
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All authors S.D. Odintsov, V.K. Oikonomou, Pyotr Tsyba, Olga Razina, Dauren Rakhatov
Cosmology and Nongalactic Astrophysics
Testing $\Lambda$CDM versus dynamical dark energy in one year: A DESI spectroscopic follow-up program for Rubin supernovae
Jannik Truong, Greg Aldering, Saul Perlmutter et al. (+2 more)
Combined cosmological probes currently indicate that best-fit values in the $w_0-w_a$ parametrization of dynamical dark energy deviate from $\Lambda$CDM by $\sim3\sigma$. In this work, we present a
supernova survey capable of measuring dynamical dark energy at the $>5\sigma$ level with just one year of data, starting in 2027. We first show that with the present values of $w_0$ and $w_a$, new SNe Ia at
redshifts $z\lesssim0.6$ near dark energy-matter equality would add the most constraining power. This is well within reach of the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument (DESI). Because cosmology measurements with SNe Ia quickly become systematics-limited, we focus on eliminating key systematics by using only a spectroscopically confirmed and volume-limited sample. In our proposed survey, SN alerts from Rubin would actively re-prioritize the scheduling of already-planned DESI tile visits. This would yield 7 500 near-peak transient spectra in one year without delaying DESI's primary survey. We forecast that if current best-fit $w_0-w_a$ values persist, combining just our volume-limited subset of 2 300 new SNe Ia at $z<0.3$ with current SN, BAO, and CMB data would push the tension with $\Lambda$CDM beyond $5\sigma$. This applies across a wide range of assumed uncertainties. To further circumvent systematics, we explore how DESI enables spectroscopic standardization via machine learning, offering a path toward a cosmology measurement independent of light-curve-based standardization. Finally, we discuss how early results from this program could inform future dark energy experiments.
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All authors Jannik Truong, Greg Aldering, Saul Perlmutter, David Rubin, David Schlegel
Instrumentation and Methods for Astrophysics
Pulsar Selection Criteria and Performance Evaluation of Autonomous X-ray Pulsar Navigation Systems
Sui Chen, Emilie Parent, Nanda Rea et al. (+1 more)
Current space missions primarily depend on Earth-based Guidance,
Navigation, and Control (GNC) systems involving human-in-the-loop operations. X-ray
pulsar-based
navigation offers a promising alternative by using the very precise periodic X-ray emissions from
pulsars for fully autonomous state estimation. This study presents a comprehensive analysis of
pulsar selection criteria that significantly influence overall
navigation performance. Observational data from the NICER mission is used to derive realistic estimates of measurement noise. Key mission-level constraints, including pulsed flux,
pulsar visibility,
geometric configuration, and long-term timing stability, are integrated into the
pulsar selection process, addressing limitations of existing studies. An extended Kalman filter (EKF) is used for onboard spacecraft state estimation. The proposed system is evaluated in two scenarios: a Low Earth Orbit (LEO) satellite at 600 km altitude and an interplanetary transfer from Earth to Jupiter. Simulation results show that including the Crab
pulsar yields position errors below 7 km in LEO and 20 km during interplanetary transfer with an instrument effective area of 200~cm$^2$; however, the Crab's limited timing stability leads to filter divergence after 20 days without timing model updates. In contrast, more stable
pulsars enable long-term autonomy but with reduced accuracy. These results highlight the trade-offs involved in
pulsar selection for autonomous
navigation and the need to balance competing objectives. Overall, this study demonstrates the feasibility of X-ray
pulsar-based
navigation and marks a key step towards fully autonomous spacecraft operations.
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All authors Sui Chen, Emilie Parent, Nanda Rea, Francesco Topputo
Solar and Stellar Astrophysics
Discovery of the First Octupole Pulsation Mode in a delta Scuti Star: A Stationary l = 3 Sectoral Mode
S. A. Rappaport, R. Jayaraman, G. Handler et al. (+8 more)
Aims. We are attempting to better understand how
stellar pulsations in close binary systems are affected, and possibly induced, by
tidal, Coriolis, and centrifugal forces. Methods. We analyzed TESS data for some 50,000 potential eclipsing binaries selected by machine learning
algorithms in order to search for pulsation multiplets split by integer multiples of the orbital frequency. Results. We report on the discovery of an octupole pulsation mode in the binary
star system TIC 287869463, which contains a delta Scuti
star. This mode is actually a combination of Y3+3 and Y3-3 modes that are perturbed into a new eigenmode of the
star via
tidal, Coriolis, and centrifugal forces, which we call a Y33+ mode. The mode is stationary on the
star. To our knowledge, this is the first time that such an l = 3 mode identification has been securely made in any delta Scuti
star, and the first stationary l = 3 sectoral mode of this type seen in any
star, including the Sun. The l = 3 pulsations appear as a combination of two components at 34.94617 per day and 39.31127 per day, split by exactly six times the frequency of the orbital motion to within better than 1 part in 100,000. We extract the pulsation frequencies from the TESS data spanning more than three years, and model the system to gain a better understanding of this novel asteroseismic discovery. The pulsation frequencies are found to be steadily increasing with time, but always maintaining a split equal to six times the orbital frequency. Conclusions. We discuss the implications for the broader class of "tidally tilted pulsators" and "tri-axial pulsators" that have been discovered to date. We conclude that these previous categories can all be interpreted as linear combinations of spherical harmonics whose axes coincide with the orbital axis and form new eigenmodes of the
star via
tidal, Coriolis, and centrifugal perturbations
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All authors S. A. Rappaport, R. Jayaraman, G. Handler, D. Kurtz, V. Zhang, R. Gagliano, B. Powell, J. Fuller, T. Borkovits, V. Kostov, J. Daszyńska-Daszkiewicz
Instrumentation and Methods for Astrophysics
Design of a mission to measure the shape and substructure of the 511 keV gamma-ray line from the center of the Milky Way
Kun Hu, Matthew Fritts, Daniel Becker et al. (+23 more)
The 511 keV electron-positron annihilation feature near the
galactic center has been detected for more than half a century, yet its origin remains a mystery. In this paper, we describe a concept for a balloon-borne 511 keV $\gamma$-ray mission called the 511-Spectrometer Mission. The mission will use Transition-Edge Sensor (TES) arrays with thick metal absorbers that are thermally coupled to the TES. The strength of the approach is a projected energy resolution of 200 eV Full Width Half Maximum (FWHM) at 511 keV, enabling detailed studies of the shape and substructure of the 511 keV emission from the
galactic center region. A first mission equipped with 8,192 $\gamma$-ray detectors and a fully active shield and collimator could detect the
galactic center with ~35 $\sigma$ statistical significance. We present the mission concept as well as first results obtained with a prototype detector equipped with $1.35\times1.35\times2$ mm$^{3}$ Bi absorbers. The detector has a
quantum efficiency of 15% for 511 keV
photons in photoelectric effect interactions. In tests with a $^{137}$Cs source, these prototype detectors show an energy resolution of 525 eV FWHM at 662 keV. We end with a discussion of follow-up missions that use coded mask imaging, or use concentrating or focusing optics to scrutinize the sources of 511 keV $\gamma$-rays on smaller angular scales.
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All authors Kun Hu, Matthew Fritts, Daniel Becker, Daniel Schmidt, Fang Zhou, Adrika Dasgupta, Fabian Kislat, Mark Keller, Sohee Chun, Argen Gian Detoito, Ephraim Gau, Xiaoyue Jin, Douglas Bennett, Dana Braun, Johnathon Gard, John A. B. Mates, Jason Nobles, Danny Radomski, Nicole Rodriguez Cavero, Ryan Snodgrass, Daniel Swetz, Joel Ullom, Shravan Vengalil Menon, Joel Weber, Kasun Wimalasena, Henric Krawczynski
Instrumentation and Methods for Astrophysics
SAGUI: SED-based Segmentation of Multi-band Galaxy Images – Application to JADES in GOODS-South
Rafael S. de Souza, Andressa Wille, Shravya Shenoy et al. (+11 more)
We present sagui, a modular framework for the analysis of multi-band imaging data in spatially resolved
galaxies, with synergies to integral-field spectroscopy (IFS). Building on the spectro-spatial paradigm introduced by capivara for IFS data, sagui extends this approach to imaging
datasets, enabling a coherent, pixel-level treatment of spatial and spectral information across multiple bands. The method follows a two-stage strategy: a starlet-based decomposition is first used to identify and mask spatial structures across multiple scales while suppressing noise, and a spectral-similarity analysis then partitions the image into coherent pixel groups that preserve spectral consistency. In addition to compact and high-contrast structures, the framework incorporates a dedicated statistical treatment, based on a copula transform, to identify and recover faint, diffuse low-surface-brightness components. We demonstrate the method across a diverse range of
galaxy morphologies, highlighting its ability to characterize complex spatial structures, including clumps, bars, interacting systems, and low-surface-brightness features. As a case study, we apply it to eleven morphologically diverse
galaxies from the James Webb Space
Telescope Advanced Deep Extragalactic Survey in the GOODS–South field. sagui is released under an MIT license and is available at https://rafaelsdesouza.github.io/sagui/.
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All authors Rafael S. de Souza, Andressa Wille, Shravya Shenoy, Aarya A. Patil, Alberto Krone-Martins, Ana L. Chies-Santos, Celine Boehm, Reinaldo R. Rosa, Thallis Pessi, Emille E. O. Ishida, Kristen C. Dage, Lilianne Nakazono, Phelipe Darc, Rupesh Durgesh
Astrophysics of Galaxies
Analysis of synthetic OVI absorption associated with galaxy groups in SIMBA and TNG50 simulations
Tanmay Singh, Sanchayeeta Borthakur, Dylan Nelson et al. (+2 more)
We compare OVI absorption in synthetic spectra from
galaxy groups in the SIMBA and TNG50 cosmological hydrodynamic simulations against those observed from the COS-IGrM survey. We select 14
galaxy groups from each simulation with $12.89 \le \log(M_{\rm halo}/M_\odot) \le 13.61$, closely matching COS-IGrM, and create 90,000 synthetic spectra per group. We demonstrate the utility of synthetic absorption spectroscopy when comparing simulations with QSO absorption-based observations. We investigate absorber properties such as radial distributions and kinematics with respect to the group and nearest
galaxy. The OVI covering fraction ($f_{\rm OVI}$) in TNG50 ($20.62 \pm 2.56\%$) and SIMBA ($5.98 \pm 0.82\%$) are both systematically lower than COS-IGrM ($44 \pm 5\%$). Kinematic analysis reveals that vast majority ($\sim 95\%$) of absorbers in both the simulations are gravitationally bound. In TNG50, strong absorbers ($\log N_{\rm OVI} > 15$) are located near
star-forming
galaxies ($\log {\rm sSFR} > -11$) within $\sim 200$kpc, suggesting physical connection to
stellar feedback, whereas SIMBA shows no comparable trend. Furthermore, in TNG50 occurrence of OVI absorbers at small impact parameters increases with
stellar mass of nearest
galaxy, but shows no dependence on total
stellar mass of group. In contrast, SIMBA shows no clear correlation with nearest
galaxy's
stellar mass, though groups with higher total
stellar mass exhibit higher detection rate at larger impact parameters. Differences observed in simulations may arise from feedback models and resolution effects. Finally, we show absorber analysis methodology is important factor when comparing simulations with absorption spectroscopy observations.
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All authors Tanmay Singh, Sanchayeeta Borthakur, Dylan Nelson, Romeel Davé, Tyler McCabe
Instrumentation and Methods for Astrophysics
Machine Learning Supports Existence of Previously Unrecognized Transient Astronomical Phenomena in Historical Observatory Images
Stephen Bruehl, Brian Doherty, Alina Streblyanska et al. (+1 more)
Transient,
star-like point sources that appear and vanish over short timescales are described in astronomical images prior to launch of Sputnik. We have reported that transient numbers diminish significantly in Earth's shadow (shadow deficit) and are more likely within (plus/minus) one day of
nuclear testing (
nuclear window). These findings remain debated with some arguing that transients identified via existing automated pipelines are simply plate defects. Therefore, we use machine learning (ML) to enhance transient identification accuracy and validate the phenomenon. The model was trained against 250 transient image pairs taken 30 minutes apart that were classified as real versus plate defect by expert visual review; the model demonstrated good discrimination (out-of-fold AUC$=$0.81; sensitivity$=$0.71, specificity$=$0.71). After deployment in a
dataset of 107,875 previously-identified transients, the model assigned each a probability of being real. After controlling for ML-identified artifacts, transient counts were significantly elevated for dates within a
nuclear window (p$=$.024); transients with the highest probability of being real were more likely to occur within a
nuclear window (p$<$.0001). The shadow deficit was significant (p$<$.0001) and largest in the highest probability transients relative to lower probability transients (p$=$.003). Results strongly support existence of an unrecognized population of transient objects in historical astronomical plates warranting further study.
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All authors Stephen Bruehl, Brian Doherty, Alina Streblyanska, Beatriz Villarroel
Solar and Stellar Astrophysics · Cross-listed from physics.plasm-ph
System Size Dependence of Collisionless Reconnection Rate
Yi-Min Huang, Naoki Bessho, Li-Jen Chen et al. (+2 more)
It is a widely accepted paradigm that collisionless
magnetic reconnection proceeds at a universal fast rate of $\sim0.1$ when normalized to a properly defined reconnecting
magnetic field and Alfvén speed, effectively independent of the macroscopic system size. This conclusion, derived primarily from kinetic simulations of classical Harris current sheets with kinetic-scale thickness, stands in contrast to results from forced reconnection and island coalescence, where the rate significantly depends on the system size. Here, we reconcile this disparity by performing a rigorous scaling study using both particle-in-
cell and
Hall magnetohydrodynamic simulations. We demonstrate that when the global
magnetic configuration is self-consistently preserved by scaling the initial current sheet thickness proportionally with the system size, the “universal” fast rate disappears. Instead, the reconnection rate decreases as the system size increases. These results indicate that dependence on macroscopic scales is not peculiar to specific geometries but is a fundamental property of collisionless reconnection, effectively unifying the Harris sheet with other configurations exhibiting size-dependence.
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All authors Yi-Min Huang, Naoki Bessho, Li-Jen Chen, Judith T. Karpen, Amitava Bhattacharjee
Earth and Planetary Astrophysics
Linking System of Jets to the Non-Gravitational Acceleration of 3I/ATLAS
Toni Scarmato and Abraham Loeb
Building on the jet morphology and periodic wobble analysis of 3I/ATLAS in Scarmato & Loeb (2026), we link observed jet position angles (PAs) and the non-gravitational acceleration components (A1,A2,A3) in the 3D RTN (radial, transverse, normal) frame relative to the Sun. We: (i) compute RTN directions from heliocentric state vectors and project them on the sky at the measured astromet ric pointings; (ii) compare projected RTN PAs to three persistent jets (Jet1-Jet2-Jet3) and quantify angular offsets; and (iii) estimate order-of-magnitude thrust and accelerations from HST/WFC3-UVIS F350LP net counts via transformations from photometry to cross-section,
dust mass, mass-loss rate, and thrust. We explicitly document the uncertainties through background handling, phase-function systematics, and
geometric degeneracies along the line of sight. For U.T. 2025-11-30.80903, Jet2 is aligned with the projected transverse direction to within 0.5 degs, while Jet3 is the closest to the pro jected normal direction with a moderate offset (about 25 degs). For UT 2025-12-27, Jet2 exhibits a monotonic PA drift over 24 minutes with a larger oscillation amplitude.
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Earth and Planetary Astrophysics
Laser-based mass spectrometry for the detection of signatures of life within our Solar System
Andreas Riedo, Salome Gruchola, Nikita J. Boeren et al. (+5 more)
The search for signatures of life beyond Earth has been a major goal of space research and astrobiology for decades. The combination of expanded knowledge on
Solar System bodies from past missions and advancements in in-situ detection technologies may place humanity on the verge of discovering extraterrestrial life. Here, we highlight the current measurement capabilities of
Laser Ionisation Mass Spectrometry for the detection of several classes of signatures of life of high relevance to current astrobiology-focused missions. This includes the detection of microstructures within complex geological hosts by chemical depth profiling, sulphur isotope fractionation signatures, and the detection of various classes of organic molecules. The recorded mass spectrometric data can be fed into network and machine learning analysis routines, which are powerful tools for the unbiased detection of signatures of life, including agnostic detection of biosignatures. We demonstrate that
Laser Ionisation Mass Spectrometry is a novel and promising technology for future application. on space exploration missions devoted to life detection.
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All authors Andreas Riedo, Salome Gruchola, Nikita J. Boeren, Peter Keresztes Schmidt, Luca N. Knecht, Youcef Sellam, Marek Tulej, Peter Wurz
Astrophysics of Galaxies
Magnetic properties of the Abell 3391-3395 system revealed using wide-field MeerKAT polarimetry
V. Gustafsson, M. Brüggen, C. Tasse et al. (+1 more)
Magnetic fields in cluster outskirts and the intercluster medium are poorly constrained because diffuse synchrotron emission is hard to detect at low surface brightness. Faraday rotation measures (RMs) of polarized background sources can probe foreground large-scale structure. The nearby interacting Abell 3391-3395 system hosts a well-established X-ray bridge, making it an excellent target for studying magnetization in the intercluster environment. We characterize the magnetized environment of Abell 3391/95 and its surroundings by constructing a dense RM grid from wide-field polarimetry. We observed Abell 3391/95 with MeerKAT in full polarization using a three-pointing mosaic. The data were calibrated with direction-independent and direction-dependent techniques and imaged using visibility-plane mosaicing for a large field of view at high sensitivity. Using Faraday synthesis, we formed Faraday cubes and measured RMs for polarized background sources. We defined on- and off-target regions using contours from a wavelet-filtered eROSITA image. We identified 434 polarized sources within the field, with a polarized source density ranging from about 30 sources per square degree in the outer regions to about 110 sources per square degree in the central field, and a field-averaged density of 73 sources per square degree. The clusters show a statistically significant enhancement of RM scatter relative to the off-target region. In contrast, the bridge shows comparatively low RM scatter, while an RM structure-function analysis on matched angular scales yields a tentative indication of larger RM differences in the bridge than off-target. Combined with low per-source depolarization, this suggests a bridge
magnetic field relatively ordered on ~10 kpc scales, but less ordered on larger scales. The non-detection of diffuse synchrotron emission in the bridge yields improved upper limits on the emissivity.
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All authors V. Gustafsson, M. Brüggen, C. Tasse, S. P. O'Sullivan
Astrophysics of Galaxies
Stellar feedback SPICEs up [C II] emission in the first galaxies
Aniket Bhagwat, Tiago Costa, Benedetta Ciardi et al. (+1 more)
The bright [C II] 158 micron line is widely used to trace
star-forming gas and feedback-driven
outflows in high-
redshift galaxies. Using the SPICE simulations, we investigate how bursty versus smooth
stellar feedback shapes
galaxy properties at z > 5 as traced by [C II] emission. All models exhibit a tight correlation between [C II] luminosity (L_[CII]) and
star formation rate (SFR), though bursty feedback yields systematically lower L_[CII] at fixed SFR and larger intrinsic scatter. [C II] emission is more extended than rest-frame UV light by factors of ~2-4, consistent with ALMA observations. While
outflows are ubiquitous and mass
outflow rates scale with L_[CII] (reaching ~10 Msun/yr), the net mass flux remains inflow-dominated in [C II]-bright systems. The emission is dominated by low-velocity (|v_rad| < 200 km/s) cold gas, with fast
outflows contributing little, causing [C II]-based kinematics to overestimate cold gas velocities and underestimate fast components by factors of ~2-5. Consequently, inferred mass-loading factors and wind energetics are biased low, and large line widths primarily reflect the gravitational potential rather than
outflow speeds. Although [C II] spatial and spectral properties alone do not distinguish feedback models, gas kinematics provides a strong diagnostic: smooth feedback promotes earlier disk settling, yielding higher V/sigma and disk fractions (~48% vs. ~28% for bursty feedback at z = 5). Overall, [C II] robustly traces
star formation but is a biased tracer of feedback-driven
outflows, highlighting the need for multiwavelength constraints on the multiphase ISM.
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All authors Aniket Bhagwat, Tiago Costa, Benedetta Ciardi, Fabrizio Arrigoni Battaia
Astrophysics of Galaxies
New constraints on stellar feedback through [O III] emission: interpreting ALMA and JWST observations with SPICE simulations
Benedetta Casavecchia, Aniket Bhagwat, Benedetta Ciardi et al. (+2 more)
ALMA and JWST have recently detected emission lines from the interstellar medium of
star-forming
galaxies during the Epoch of Reionization, reaching
redshifts up to z = 14. Among these, [OIII] lines provide a powerful diagnostic of metal enrichment, gas ionization, and the impact of
stellar feedback in
galaxies at z > 6. Modeling this emission in cosmological simulations is challenging due to the wide range of spatial scales and physical processes involved. To address this, we have developed a post-processing pipeline that implements a sub-grid model for [OIII] line emission within the SPICE radiation-hydrodynamical simulations. These simulations explore three
supernova feedback prescriptions: bursty-sn, smooth-sn, and the hypernova-based hyper-sn. We investigate how these feedback models affect metal enrichment, the neutral gas fraction, and the size and morphology of ionized
halos traced by [OIII] emission in both the optical and far-infrared. We find that [OIII] emission predominantly originates from gas that is both shock-heated and radiatively ionized. We also examine the mass-
metallicity relation and the correlation between neutral gas fraction and [OIII] luminosity. Our results show that the bursty-sn model efficiently ionizes gas but enriches
galaxies less effectively by z = 5, leading to fewer bright [OIII] emitters compared to the smooth-sn model. Both bursty-sn and hyper-sn produce suppressed luminosity functions. Spatially resolved [OIII] emission further indicates that smooth-sn tends to generate more compact
galaxies and slightly higher V/{\sigma} values, although there is significant overlap between models. Overall, our findings demonstrate that [OIII] emission is a sensitive tracer of
stellar feedback at high
redshift and highlight the importance of observations probing fainter luminosities, where feedback effects are strongest.
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All authors Benedetta Casavecchia, Aniket Bhagwat, Benedetta Ciardi, Celine Peroux, Tiago Costa
Cosmology and Nongalactic Astrophysics
Model-independent reconstruction of cosmic thermodynamics and dark energy dynamics
Afaq Maqsood and Tanima Duary
We perform a model-independent investigation of the thermodynamic
evolution of the Universe by reconstructing the expansion history from observational data using Gaussian Process regression. We consider three independent combinations of
datasets, namely CC32+DESI DR2+Pantheon+, CC32+DESI DR2+Union3, and CC32+DESI DR2+DES Y5, allowing us to assess the impact of different
supernova samples on the reconstruction. From the reconstructed Hubble parameter and its derivatives over the
redshift range 0 to 2, we evaluate key thermodynamic quantities associated with the apparent horizon, including the diagnostic function $P(z)$, the
entropy production rate $\dot{S}_{\mathrm{tot}}$, and its second derivative $\ddot{S}_{\mathrm{tot}}$. We find that $P(z)$ remains positive across all
redshifts, ensuring the validity of the generalized second law of thermodynamics. Correspondingly, $\dot{S}_{\mathrm{tot}} > 0$ throughout, while $\ddot{S}_{\mathrm{tot}} < 0$ at low
redshifts, indicating that the Universe evolves toward stable thermodynamic
equilibrium. To assess methodological robustness, the reconstruction is performed using multiple covariance kernels, including the Squared Exponential and Matérn kernels with $\nu = 5/2, 7/2,$ and $9/2$, all of which yield consistent results within uncertainties. We also reconstruct the dark energy equation of state in a fully model-independent manner and find it to be consistent with a cosmological constant at the present epoch, with no statistically significant deviation from $\Lambda$CDM.
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Astrophysics of Galaxies
Investigating the formation channel of GW231123: Population III stars or hierarchical mergers?
Federico Angeloni, Konstantinos Kritos, Raffaella Schneider et al. (+5 more)
The gravitational wave event GW231123, with component black hole masses lying within or above the pair-instability mass gap, poses a significant challenge to current
stellar evolution models. In this work, we describe how we investigated its origin by coupling the
galaxy formation model GAMESH with the cluster population synthesis code RAPSTER and using two distinct binary population synthesis codes, SEVN and BSEEMP. This framework allowed us, for the first time, to reconstruct the life cycle of GW231123-like candidates within the same cosmological simulation, enabling a self-consistent comparison between different formation channels. Although both population synthesis codes can in principle produce black holes compatible with GW231123, we find that isolated binary
evolution fails to reproduce the inferred merger
redshift. In SEVN, massive black hole binaries form with semi-major axes > 10^3 Rsun , preventing coalescences within a Hubble time. In BSEEMP, candidates arise only at extremely low
metallicities (Z = 10^{-10}), which contribute negligibly to the
star formation rate density in our overdense simulated volume. Our results therefore strongly support a dynamical hierarchical origin. The observed black hole masses are naturally reproduced through successive mergers in dense globular clusters. The high dimensionless
spins reported by the LIGO-Virgo-KAGRA Collaboration are consistent with this hierarchical population. We found a local merger rate density of 0.78 Gpc^{-3} yr^{-1}, with a peak at z = 4 - 6, tracing the maximum formation rate of globular clusters in metal-poor environments (Z = 0.006). Overall, GW231123 may represent a
benchmark event for a robust population of hierarchical black holes formed in the early Universe.
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All authors Federico Angeloni, Konstantinos Kritos, Raffaella Schneider, Emanuele Berti, Luca Graziani, Stefano Torniamenti, Michela Mapelli, Ataru Tanikawa
High Energy Astrophysical Phenomena
SAETASS: Solver for Astroparticle Equation of Transport Analysis in Spherical Symmetry
José María García-Morillo, Stefano Menchiari and Rubén López-Coto
In order to model astrophysical environments characterized by radial stratification, such as
supernova remnants or expanding superbubbles; correctly understanding the transport of non-thermal particles in astrophysical
plasmas is essential. While large-scale
Galactic propagation codes exist, they are often optimized for Cartesian or cylindrical geometries and lack the efficiency of one-dimensional spherically symmetric problems. In this work, we present SAETASS (Solver for Astroparticle Equation of Transport Analysis in Spherical
Symmetry), a novel, open-source numerical tool designed to solve the time-dependent transport equation for astroparticles. The solver is built upon a conservative finite-volume framework that ensures exact particle conservation and numerical stability. To manage the interplay between diverse physical processes, SAETASS employs a modular operator-splitting architecture. Radial advection and continuous momentum losses are treated using a second-order, shock-capturing MUSCL-Hancock scheme, while the diffusive operator is integrated via an implicit, batched Crank-Nicolson
algorithm. This approach allows for the robust handling of steep gradients, spatial discontinuities and regularity conditions at the origin. We rigorously validate the code through a suite of tests for pure advection,
diffusion and losses. Finally, we demonstrate the solver's capabilities by modelling
cosmic-ray
proton transport in a real astrophysical scenario. Our results successfully recover established steady-state limits while revealing relevant pre-
equilibrium temporal dynamics across Kolmogorov, Kraichnan and Bohm
diffusion regimes. SAETASS provides the community with a lightweight, flexible tool for investigating particle acceleration and propagation in complex, radially dependent astrophysical environments.
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Astrophysics of Galaxies
Extending the ALMA survey of the SCUBA-2 CLS UDS field: Tracing the obscured formation of spheroids across z~1-4
Ian Smail, Steven Gillman, Ugne Dudzeviciute et al. (+1 more)
We investigate the properties of 870-um selected
galaxies at z~1-4 with FIR luminosities of LIR~1e11-1e13Lo, encompassing systems that dominate obscured activity at the peak of
cosmic star formation, to identify variations in
star-formation processes as a function of
dust mass and
redshift. We revisit ALMA 870-um continuum maps from the ALMA/SCUBA-2 UDS (AS2UDS) survey, lowering the source selection threshold from 4.3 sigma to 3.1 sigma to enlarge the sample with S870~1mJy. To reduce contamination from noise peaks, we match submm sources to a K-selected
galaxy sample and apply cuts on photometric
redshift and near-infrared (H-K) colour. This yields 84 sources in our extended AS2UDS survey, AS2UDSx, with S870=0.3-2.2mJy, doubling the sample at S870~1mJy relative to the original study. Using this expanded sample, we find that submm
galaxies with S870~1mJy at z>~2.5 share properties with brighter, more active populations, while those at z<~2.5 are distinct, with lower gas fractions, shorter depletion times, and
stellar morphologies from JWST imaging that show less structured
dust obscuration, resembling less-active field
galaxies. This indicates a shift in the characteristics of 870-um-selected
galaxies at S870~1mJy and z~2, likely driven by the stability of their gas discs. Brighter and higher-z
galaxies can sustain dense, globally unstable discs through efficient gas
accretion, powering compact obscured starbursts. In contrast, fainter systems at z<~2.5 lack this
accretion, leading to more stable discs and more extended
dust continuum emission. This suggests a natural division around S870~1mJy and z~2: lower-z, fainter sources represent the most active secularly-driven extended
star-forming discs, while similar and brighter, higher-z submm
galaxies form a distinct population of compact starbursts within massive, unstable, gas-rich discs, consistent with progenitors of massive spheroids.
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All authors Ian Smail, Steven Gillman, Ugne Dudzeviciute, A.M. Swinbank
Astrophysics of Galaxies
Other red dots: A possible GLIMPSE of normal AGB stars at Cosmic Noon through extreme lensing
Lukas J. Furtak, Adi Zitrin, Erik Zackrisson et al. (+18 more)
We report the discovery of four extremely faint ($m_{\mathrm{F444W}}\gtrsim29$) red point sources in recent ultra-deep JWST/NIRCam images of the strong
lensing galaxy cluster Abell S1063. All four sources sit in lensed arcs, on the
symmetry points very close to the critical curves for their host-
galaxies'
redshifts ($z\sim1-4$). Remarkably, these point sources appear in most arcs that are sufficiently faint close to the critical curve's position ($<21\,\mathrm{nJy}\,\mathrm{arcsec}^{-2}$ in F115W). This suggests that – unlike previous caustic-crossing events or lensed
stars – thanks to the unprecedented depth of the GLIMPSE observations paired with the extreme
lensing magnification (up to $\mu\sim10^4$) we might be resolving the lower-mass ($M\sim1-11\,\mathrm{M}_{\odot}$) red
stellar population. Concretely, we detect three likely extremely magnified asymptotic
giant branch (AGB)
stars ($T_{\mathrm{eff}}\sim3200-3750$ K), and one yellow super-
giant star ($T_{\mathrm{eff}}\sim6750$ K) – possibly a yellow hyper-
giant or a Cepheid. In addition to offering the first glimpse at low-mass extremely magnified
stars, these detections open a possible window into
stellar populations,
evolution, and chemical enrichment at high
redshifts, and could pave the way for using lensed
stars such as these as standard candles to populate the distance ladder at cosmological
redshifts.
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All authors Lukas J. Furtak, Adi Zitrin, Erik Zackrisson, Vasily Kokorev, Anthony J. Taylor, Joseph F. V. Allingham, John Chisholm, Jose M. Diego, Hakim Atek, Kristen B. W. McQuinn, Ryan Endsley, Richard Pan, Gabriel Brammer, Qinyue Fei, Seiji Fujimoto, Tiger Y.-Y. Hsiao, Patrick L. Kelly, Damien Korber, Ashish K. Meena, Rohan P. Naidu, Alberto Saldana-Lopez
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Flavomons in Matter Gradients: Ray Tracing and Amplitude Evolution
Damiano F. G. Fiorillo and Georg G. Raffelt
Flavor instabilities develop in
neutrino plasmas through the emission of flavomons, collective excitations of the
flavor field. Matter gradients can sweep flavomons across the unstable wave-number range, halting their amplification. This effect is parametrically small for fast modes, where it was first identified, but we show that it strongly alters
neutrino-mass-induced instabilities below the
supernova shock, while leaving those outside largely unaffected. Dispersion relations alone, which are inevitably local, cannot determine the cumulative amplification of slow instabilities. Using the WKB approximation, we derive the covariant
evolution equation for the flavomon amplitude along geometrical-optics rays, enabling a global treatment of instability growth and seeding.
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Solar and Stellar Astrophysics
White dwarf + M dwarf Detached Binaries in Long Period Radio Transients: Observed Binary Parameters, Evolution, and Population Constraints
Antonio C. Rodriguez, Kareem El-Badry, Iris de Ruiter et al. (+4 more)
Long period
radio transients (LPTs) are the slowest
radio-pulsing sources ever found, with the current population spanning periods of seven minutes to over six hours. Two of the thirteen published LPTs, ILT J1101+5521 and GLEAM-X J0704–37, have been associated with an M
dwarf closely orbiting a white
dwarf (WD) through optical spectroscopy. Here, we present new Keck I/LRIS optical spectroscopy of ILT J1101+5521, which reveals H$\alpha$ emission from the M
dwarf and confirms an orbital period nearly matching the
radio period (2.092 hr).
Radio pulses in both systems arrive just after maximum M
dwarf redshift, assuming the
radio period matches the orbital period. Based on
Gaia proper motions and systemic velocities, we find that these systems are kinematically hotter and less concentrated in the
Galactic plane than other LPTs. Both systems harbor unusually massive and cool WDs, with $M_\mathrm{WD} \approx 0.84-1.0 M_\odot$ and $T_\mathrm{eff} \approx 5200-7300$ K, implying that their carbon-oxygen cores are nearly entirely crystallized. Both systems are unusually close to being face-on binaries ($i=13^\circ-28^\circ$), signaling that the production of coherent
radio pulses may be a strongly inclination-dependent phenomenon. We present MESA models that show that the M
dwarf in each system will fill its Roche lobe within $\sim1$ Gyr, becoming a cataclysmic variable. Finally, we place lower limits on the space density of WD + M
dwarf LPTs ($\rho \gtrsim 10^{-8}\;\mathrm{pc}^{-3}$); based on the broader population of WD + M
dwarf binaries, we estimate that there are 100 (1000) WD + M
dwarf LPTs within 2 kpc if current
radio findings are 100% (10%) complete. Current and upcoming
radio surveys will be sensitive to many such systems, and M
dwarf optical counterparts out to $\sim$2 kpc will be detectable with the Rubin Observatory Legacy Survey of Space and Time (LSST).
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All authors Antonio C. Rodriguez, Kareem El-Badry, Iris de Ruiter, Kaustubh Rajwade, Edo Berger, Liam Connor, Natasha Hurley-Walker
Astrophysics of Galaxies
Galaxies at z > 10: {\Lambda}CDM predicts increased Star Formation Efficiency
Francisco Prada, Peter Behroozi, Tomoaki Ishiyama et al. (+4 more)
We show that the rest-frame UV statistics and global properties of
galaxies at 7 <= z <= 14 are naturally reproduced within the standard {\Lambda}CDM framework when
galaxy formation is modeled with UniverseMachine applied to the high-resolution Uchuu N-body simulation. Our model matches the UV luminosity functions over five magnitudes and reproduces the
evolution of the UV (and inferred
star formation rate) density once internal
dust attenuation is included. Comparisons with spectroscopically confirmed JWST/HST
galaxies show good agreement with the
stellar mass-SFR and
stellar mass-UV luminosity relations. In contrast, earlier claims of insufficient
stellar masses at z=8 are inconsistent with our model and are likely driven by systematic uncertainties, including AGN contamination,
dust attenuation, and the lack of JWST/MIRI constraints. A key prediction is that the
star-formation efficiency increases with
redshift at fixed
halo mass, reaching 2-3 percent of
baryons converted into
stars by z=10-12. These results demonstrate that current JWST observations of early
galaxy populations can be explained within the {\Lambda}CDM framework.
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All authors Francisco Prada, Peter Behroozi, Tomoaki Ishiyama, Enrique Pérez, Anatoly Klypin, Xin Wang, José Ruedas
Earth and Planetary Astrophysics
Coupled orbital and interior structure evolution of lava planets
Mahesh Herath, Nicolas B. Cowan, Charles-Édouard Boukaré et al. (+1 more)
Lava
planets likely did not form in their current orbits, instead migrating inward via orbital decay, which influenced the
evolution of their magma oceans. We introduce a coupled thermal-orbital
evolution model to explore how rocky
planets migrate from the inner edge of the protoplanetary disk, with periods of 1-10 days, to orbital periods of less than a day. In our model, mantle melting is controlled by
tidal heating and
stellar flux, while orbits evolve via
tidal migration. The mantle's
tidal quality factor varies with its temperature and structure, creating a feedback loop between thermal
evolution and orbital decay. We use our numerical model to simulate the migration of seven known lava
planets: K2-141b, K2-360b, TOI-141b, TOI-431b, TOI-2431b, HD 3167b and GJ 367b. Migration occurs in two stages: an initial high-eccentricity stage reducing the semi-major axis by a factor of $\sim 2$, followed by a low-eccentricity stage reducing it by a factor of $\sim 5$. A successful migration from $\sim 0.1$ AU to a present-day orbit requires starting eccentricities $\ge 0.9$ and sustained eccentricity forcing with $e_{\mathrm{min}} \ge 10^{-2}$. The rate of migration depends on the state of the mantle: slow when mostly molten, fast when mostly solid. This pathway works for most lava
planets, but not for TOI-431b or GJ-367b, suggesting that multiple migration pathways are possible for lava
planets.
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All authors Mahesh Herath, Nicolas B. Cowan, Charles-Édouard Boukaré, Mathieu Dumberry
High Energy Astrophysical Phenomena
Nicolas Grimbaum Yamamoto and Thomas Hambye
High energy
neutrinos can be injected in the early Universe from the decay or annihilation of long lived
primordial relics. We analyse the possibility that the ultrahigh energy
neutrino event recently observed by the KM3NeT
neutrino telescope could have such an origin. This possibility has the advantage of leading to a sharp spectral feature in a way that the
neutrino flux can be small at all energies except at the KM3NeT event energy. Thus, along this scenario the tension with null results from other experiments is reduced with respect to the usual power law case analysed by the KM3NeT and IceCube experiments. At such energies and for an emission around the recombination time, interactions of these
neutrinos with background
neutrinos prove to be relevant and must be determined from the development of a dedicated code. These interactions, as well as final state radiation processes, modify the spectrum. Interestingly, it turns out that the scenario can also leave an imprint in the CMB that could be probed in the near future. Interestingly too, this scenario does not predict an associated $\gamma$-ray flux beyond observation. All in all we do find that the high energy
neutrino could be a
primordial high energy
neutrino, provided it has been produced around the recombination time or later.
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High Energy Astrophysical Phenomena
Binary Evolution Can Mimic the Pair-Instability Mass Gap in Black Hole Mergers
Aleksandra Olejak and Jakob Stegmann
The recent O4 catalogs from the LIGO-Virgo-KAGRA collaboration, which significantly increased the number of gravitational-wave (GW) detections, reveal features with potentially important astrophysical implications. One notable example is a hint of the so-called pair-instability mass gap. In particular, the observed decline in the number of black holes (BHs) with mass above 45Msun, together with indications of possibly higher
spins for BHs above this threshold, has been interpreted by Antonini et al. and Tong et al. as evidence for pair-instability
supernovae.In this work, we investigate whether mass transfer in binary systems can produce features in the BH component-mass distributions that mimic the inferred pair-instability limit. We use both the population synthesis code StarTrack and a simple semi-analytical framework to highlight the impact of mass transfer efficiency on the BH masses. We find that mass-ratio reversal during the first Roche-lobe overflow, followed by a highly non-conservative second mass-transfer phase, naturally limits the mass of the first-born BH and produces an apparent cutoff that mimics the lower edge of a mass gap. While the upper mass limit for the more massive BH is increased through
accretion during the first mass-transfer phase and is ultimately set by the pair-instability limit, the less massive BH is limited to the stripped primary mass. As a result, the fraction of systems in which the less massive BH exceeds 45Msun is negligible, below 0.0001 in our default models. While pair instability remains a possible interpretation of current GW data, similar features can naturally arise from binary
evolution without invoking a low pair-instability cutoff. The emerging evidence for predominantly positive effective
spins extending into the putative upper mass gap may further support a contribution from isolated binary
evolution to the high-mass tail.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Hunting Sterile Neutrino Dark Matter in the MeV Gap
Shivam Gola, Akash Kumar Saha and Manibrata Sen
We investigate the sensitivities of upcoming MeV gamma-ray
telescopes to sterile
neutrino dark matter in the mass range $(0.2-100)\,{\rm MeV}$. Sterile
neutrinos in this regime can produce observable
photon signals through radiative two-body decays and three-body decays with final-state radiation. We perform a Fisher
forecasting analysis incorporating realistic astrophysical background modeling and detector response to derive projected constraints on the sterile
neutrino decay rate. We find that future MeV instruments can improve existing limits by several orders of magnitude across a wide region of parameter space. Our results highlight the discovery potential of next-generation MeV
telescopes in probing sterile
neutrino dark matter.
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Astrophysics of Galaxies
GOALS-JWST: Resolved multi-phase molecular gas in IRAS 20551-4250 using JWST and ALMA
D. Kakkad, Y. Song, T. S.-Y. Lai et al. (+24 more)
Studying the content and distribution of molecular gas provides key insights into how feedback from Active
Galactic Nuclei (AGN) and
star formation influences
galaxy evolution, since molecular gas is the primary fuel for
star formation. Ultra-Luminous Infrared
Galaxies (ULIRGs) are ideal candidates to study how AGN and/or starbursts affect the interstellar medium due to their intense AGN and
star forming activity. We present spatially-resolved multi-phase molecular gas study of IRAS20551-4250, a nearby ($z=0.0429$) ULIRG, using JWST/MIRI-MRS and ALMA. Mid-infrared diagnostics do not rule out the presence of AGN in IRAS20551-4250. [OIII]$\lambda$5007 in VLT/MUSE data reveal ionised gas
outflows with $w_{80}^{\rm [OIII]} \sim 790$ km s$^{-1}$ and $\dot{M}_{\rm out}^{\rm[OIII]}<0.01$ M$_{\odot}$ yr$^{-1}$. No
outflows are observed in either molecular phases. JWST/MIRI-MRS data reveal several rotational transitions of warm H$_{2}$ (T$\sim500-1400$ K) within the central $\sim4\times4$ kpc$^{2}$ region. Excitation temperature maps suggest that the warm H$_{2}$ is primarily heated by UV radiation from the central source. The CO-based cold molecular component dominates the molecular gas mass, accounting for $>$95% of the total molecular gas mass. Warm H$_{2}$ maps show two
tidal tails and the velocity centroid maps show disturbed, non-rotational motions and a systematic gradient across the field-of-view, similar to that of ALMA CO-based cold molecular gas and consistent with a late-stage merger. Together, our analysis indicate that the molecular gas composition in IRAS20551-4250 is consistent with ongoing
star formation in the host
galaxy and the
outflows observed in ionised gas phase appear insufficient to expel the molecular gas or quench ongoing
star formation.
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All authors D. Kakkad, Y. Song, T. S.-Y. Lai, L. Armus, M. Malkan, K. L. Larson, A. S. Evans, P. N. Appleton, L. Barcos-Muñoz, M. Bianchin, T. Böker, T. Bohn, V. Buiten, V. Charmandaris, T. Diaz Santos, H. Inami, J. Kader, L. Lenkic, S. T. Linden, C. M. Lofaro, G. C. Privon, C. Ricci, M. Sanchez-Garcia, D. Sanders, N. Torres-Alba, V. U, P. van der Werf
Instrumentation and Methods for Astrophysics
Asteroid Mining to Sustain a Mars Colony: A Logistics Point of View
Serena Suriano, Shamil Biktimirov, Dmitry Pritykin et al. (+1 more)
Asteroid mining can become an enabling technology to establish a sustainable manned colony on Mars, which requires metallic materials more often than they are readily available in shipments from Earth. This paper describes a feasibility study of a supply chain that delivers metals extracted from metallic asteroids to Mars. The asteroids are selected to respect the $\Delta V$ limits imposed by up-to-date spacecraft. The study is conducted with reference to the state of the art in space transportation technologies and in-situ resource utilization. A possibility for mining on carbonaceous asteroids to produce the propellant required for return trips is also taken into account. Different supply chains are computed through a multi-objective optimization routine that considers the mission $\Delta V$, the mass of extracted metals and the mass of propellant produced on the asteroids. Schedules to visit the asteroids within reach are obtained and the total mass of the delivered material is evaluated for various mining rates. Finally, the use of the metallic material to build habitats and rovers on the Martian soil through additive manufacturing is discussed.
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All authors Serena Suriano, Shamil Biktimirov, Dmitry Pritykin, Anton Ivanov