Instrumentation and Methods for Astrophysics
Improving Generalization and Uncertainty Quantification of Photometric Redshift Models
Jonathan Soriano, Tuan Do, Srinath Saikrishnan et al. (+4 more)
Accurate
redshift estimates are a vital component in understanding
galaxy evolution and precision cosmology. In this paper, we explore approaches to increase the applicability of machine learning models for photometric
redshift estimation on a broader range of
galaxy types. Typical models are trained with ground-truth
redshifts from spectroscopy. We test the utility and effectiveness of two approaches for combining spectroscopic
redshifts and
redshifts derived from multiband ($\sim$35 filters) photometry, which sample different types of
galaxies compared to spectroscopic surveys. The two approaches are (1) training on a composite
dataset and (2) transfer learning from one
dataset to another. We compile photometric
redshifts from the COSMOS2020 catalog (TransferZ) to complement an established spectroscopic
redshift dataset (GalaxiesML). We used two architectures, deterministic neural networks (NN) and
Bayesian neural networks (BNN), to examine and evaluate their performance with respect to the Legacy Survey of Space and Time (LSST) photo-$z$ science requirements. We also use split conformal prediction for calibrating uncertainty estimates and producing prediction intervals for the BNN and NN, respectively. We find that a NN trained on a composite
dataset predicts photo-$z$'s that are 4.5 times less biased within the
redshift range $0.3<z<1.5$, 1.1 times less scattered, and has a 1.4 times lower outlier rate than a model trained on only spectroscopic ground truths. We also find that BNNs produce reliable uncertainty estimates, but are sensitive to the different ground truths. This investigation leverages different sources of ground truths to develop models that can accurately predict photo-$z$'s for a broader population of
galaxies crucial for surveys such as Euclid and LSST.
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All authors Jonathan Soriano, Tuan Do, Srinath Saikrishnan, Vikram Seenivasan, Bernie Boscoe, Jack Singal, Evan Jones
Instrumentation and Methods for Astrophysics · Cross-listed from eess.SY
AstroTimer: Rethinking Non-Access Stratum Timers in LEO Constellations
Arshiya Rezaie Hezaveh and Peng Hu
Low-Earth Orbit (LEO) constellations expand 5G coverage to remote regions but differ fundamentally from terrestrial networks due to rapidly changing
topologies, fluctuating delays, and constrained onboard resources. Existing 3GPP Non-Access Stratum (NAS) timers, inherited from terrestrial and geostationary (GEO) or medium Earth orbit (MEO) systems, fail to accommodate these dynamics, leading to signaling storms and inefficiency. This paper introduces AstroTimer, a lightweight, adaptive framework for sizing NAS timers based on LEO-specific parameters such as link variability, processing delays, and network-function placement. AstroTimer derives a closed-form timer model with low computational cost and optimizes both watchdog and backoff timers for the 5G registration procedure. Simulation results demonstrate that AstroTimer significantly reduces registration time, retry frequency, and user equipment (UE) energy consumption compared to 3GPP defaults, while preventing signaling overloads. The proposed approach provides an operator-ready foundation for reliable, efficient, and scalable non-terrestrial 5G/6G deployments.
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Instrumentation and Methods for Astrophysics
Detached eclipsing binary star science in the 2040s
Pierre F. L. Maxted, Dominic M. Bowman, Thomas G. Wilson et al. (+7 more)
Detached eclipsing binary
stars (DEBS) are currently the best source of accurate and precise fundamental
stellar parameters. This makes DEBS crucial targets for constraining the impact of various physical processes on
stellar structure and
evolution. Long-period binaries are particularly interesting because their separation minimises interactions between the components. This makes long-period binaries more comparable to single
stars. However, the current sample of DEBS with high precision
stellar parameters are dominated by short-period systems (e.g. ~90% of the
Gaia DR3 eclipsing binaries have periods < 5 days). Facilities capable of performing detailed studies of long-period DEBS will be essential to further improve our understanding of
stellar structure and
evolution. Such facilities would need to be able to obtain spectroscopic observations of more distant objects at high resolution and cadence. 2-8m class
telescopes with echelle spectrographs and an ability to monitor a large sample of
stars would be required.
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All authors Pierre F. L. Maxted, Dominic M. Bowman, Thomas G. Wilson, Sophie Rosu, Keivan G. Stassun, Simon J. Murphy, Ayush Moharana, Amaury H. M. J. Triaud, Axel Hahlin, John Southworth
Instrumentation and Methods for Astrophysics
STIS Cycle 30 Calibration Programs
D. Welty, R. Bohlin, J. Carlberg et al. (+8 more)
We discuss the suite of STIS calibration programs executed during HST Cycle 30, covering the period 2022 Nov 07 through 2023 Nov 05. For each of the 19 current regular calibration programs, we provide brief descriptions of the objectives, observations, analysis procedures, and results - with comparisons to the results from previous cycles and to desired accuracies, as well as references to more detailed analyses of the calibration data. Many of these calibration programs produce routine reference file deliveries or demonstrate the continuing applicability of existing reference files for processing STIS observations. This ISR provides a brief snapshot of the current instrument performance, similar to those given in annual reports for Cycles 7-10 and 17-21. Two Appendices briefly discuss the state of the onboard calibration lamps and the ongoing major effort to revise the flux calibration for the many STIS spectroscopic and imaging modes.
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All authors D. Welty, R. Bohlin, J. Carlberg, M. Dallas, S. Hernandez, A. Jones, S. Lockwood, S. Medallon, E. Rickman, D. Stapleton, T. Wheeler
Earth and Planetary Astrophysics · Cross-listed from eess.SY
Autonomous Mars Rover Module for Soil Sampling and Life Component Analysis
Bibek Adhikari, Rishab Rijal, Rakesh Yadav et al. (+2 more)
The search for extraterrestrial life has long been a primary focus of scientific exploration, driven by rapid advancements in technology and our understanding of the universe. The discovery of water on Mars has sparked significant interest, raising the question of whether life could exist on the
planet. This study proposes a novel approach to simulate and illustrate the detection of life using a proof-of-life module integrated into a Mars rover. The module is an autonomous system capable of traveling to designated regions, excavating soil, collecting samples, and performing biochemical testing onboard the rover itself. The project is inherently multidisciplinary, integrating mechanical systems such as a drill mechanism and a
vacuum system, alongside biochemical analysis for soil testing. The module is capable of successfully detecting the presence or absence of living components of life from the collected soil particles. This proof-of-life module serves as a proof-of-concept for autonomous life detection in extraterrestrial environments and lays the foundation for future exploration missions.
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All authors Bibek Adhikari, Rishab Rijal, Rakesh Yadav, Nikchey Khatri, Sandesh Dhakal
Astrophysics of Galaxies
Direct Abundance Maps and Radial Metallicity Gradients of two Galaxies at z~4-5 in the GARDEN Survey
L. Stanghellini, S. A. Kassin, C. Pacifici et al. (+26 more)
We investigate
galaxies in the GARDEN (
Galaxies at All
Redshifts Deciphered and Explained with the NIRSpec MSA) survey that exhibit auroral emission lines, enabling spatially resolved measurements of electron temperature and direct oxygen abundances. Two
galaxies in this survey have spectra suitable for this analysis: CANDELS 8005 at z=3.794 and CANDELS 7986 at z=4.702. For both
galaxies, we measure auroral and key nebular emission-line fluxes across their full extent, allowing direct-method oxygen abundance determinations in individual spatial pixels (spaxels). These observations demonstrate the viability of deep JWST/NIRSpec MSA spectroscopy for spatially resolved chemical analyses at high
redshift, aided by weak nebular continua and low interstellar extinction. We derive global direct abundances of 12 + log(O/H) = 8.008$^{+0.025}_{-0.027}$ for CANDELS~8005 and 7.89$^{+0.027}_{-0.028}$ for CANDELS~7986. Emission-line diagnostics indicate neither
galaxy hosts an active
galactic nucleus. A first-order kinematic analysis suggests a potential merger in CANDELS~8005. The direct abundances are consistent with strong-line estimates based on our data and recent high-
redshift calibrations. We build emission line, radial velocity, strong-line abundance indices, electron temperature, and direct abundance maps for both
galaxies, thanks to the excellent spatial resolution. From the direct abundance maps we measure linear radial
metallicity gradients of $-$0.111$^{+0.026}_{-0.025}$ dex kpc$^{-1}$ for CANDELS~8005 (statistically significant), and $-$0.0928$\pm$0.0880 dex kpc$^{-1}$ for CANDELS~7986, where the large uncertainties limit the significance of the result. These results provide a rare direct measurement of a radial
metallicity gradient at $z>0$ from direct-method abundances, offering key observational support for inside-out
galaxy growth with feedback-regulated chemical enrichment.
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All authors L. Stanghellini, S. A. Kassin, C. Pacifici, J. E. Morrison, M. E. Dickinson, E. Sukay, C. R. Mulcahey, L. E. Bergeron, M. W. Regan, C. N. A. Willmer, B. J. Weiner, N. Dencheva, D. Law, A. de la Vega, A. M. Koekemoer, C. Conselice, J. P. Gardner, Y. Guo, F. Hammer, A. Henry, B. W. Holwerda, J. Kartaltepe, R. A. Lucas, M. Puech, M. Rafelski, I. Shivaei, C. Welker, X. Xu, L. Y. A. Yung
Astrophysics of Galaxies
The multiple coherence scales of C IV at cosmic noon
H. Cortés-Muñoz, S. Lopez, N. Tejos et al. (+6 more)
The spatial and kinematic structure of the circumgalactic medium (CGM) remains poorly constrained observationally. In this article we compute the clustering of CIV absorption systems at
cosmic noon using
quasar pairs. We analyze VLT/UVES and Keck/HIRES high-resolution spectra (R = 45000) of a sample of 8 projected and 4 lensed
quasar pairs that probe transverse separations, $\Delta r$, from sub-kpc to a few Mpc, over the
redshift range 1.6 < z < 3.3. We detect and fit Voigt profiles to a total of 141 CIV systems, corresponding to 620 velocity components across all
quasar lines-of-sight. We compute the two-point correlation function of CIV, $\xi(\Delta v, \Delta r)$, where $\Delta v$ is the velocity difference between components across all available scales. We find a strong dependence of $\xi(\Delta r)$ with $\Delta r$ at all velocities. $\xi(\Delta r)$ reaches a sharp peak at the smallest scales analyzed here, $\Delta r\approx 0.1$ kpc, decreases steadily up to $\Delta r\approx 5$ kpc and remains flat up to $\Delta r\approx 500$ kpc, where it begins to decrease again. By fitting power-laws to the projected transverse correlation function $\Xi(\Delta r)$, we infer two coherence lengths: $r_1 = 654^{+100}_{-87}$ kpc, which we interpret as a representative size for the CIV enriched regions at $z\approx 2$, and $r_2 = 4.70^{+1.60}_{-1.19}$ kpc for the individual CIV-bearing "clouds". Projecting instead in $\Delta r$, we find consistent amplitudes of $\xi(\Delta v)$ with previous work using
quasars and extended background sources. Our results suggest that CIV may be a good tracer of not only the small, internal structure of the circumgalactic medium, but also of the way in which
galaxies cluster at
cosmic noon.
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All authors H. Cortés-Muñoz, S. Lopez, N. Tejos, J.-K. Krogager, D. Zamora, R. Cuellar, P. Anshul, F. Urbina, A. Afruni
Astrophysics of Galaxies
The mass distribution in and around the Local Group
Ewoud Wempe, Simon D.M. White, Amina Helmi et al. (+2 more)
Our
Galaxy, Andromeda and their companion
dwarf galaxies form the Local Group. Most of the mass in and around it is believed to be dark matter rather than gas or
stars, so its distribution must be inferred from the effect of
gravity on the motion of visible objects. Modelling efforts have long struggled to reproduce the quiet Hubble flow around the Local Group, as they require unrealistically little mass beyond the
haloes of the two main
galaxies. Here we revisit this using $\Lambda$CDM simulations of Local Group analogues with initial conditions constrained to match the observed dynamics of the two main
haloes and the surrounding flow. The observations are reconcilable within $\Lambda$CDM, but only if mass is strongly concentrated in a plane out to 10 Mpc, with the surface density rising away from the Local Group and with deep voids above and below. This configuration, dynamically inferred, mirrors known structures in the nearby
galaxy distribution. The resulting Hubble flow is quiet yet strongly anisotropic, a fact obscured by the paucity of tracers at high supergalactic latitude. This flattened geometry reconciles the dynamical mass estimates of the Local Group with the surrounding velocity field, thus demonstrating full consistency within the standard cosmological model.
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All authors Ewoud Wempe, Simon D.M. White, Amina Helmi, Guilhem Lavaux, Jens Jasche
Instrumentation and Methods for Astrophysics
Learning at the Edge: Tailed-Uniform Sampling for Robust Simulation-Based Inference
Chaipat Tirapongprasert and Matthew Ho
We introduce the Tailed-Uniform proposal distribution for generating training simulations in simulation-based inference. Instead of sampling parameters uniformly within bounded regions, we extend the distribution beyond prior boundaries with smooth Gaussian tails. This eliminates sharp transitions that cause neural posterior
estimators to fail when the posterior distribution intersects or extends beyond the prior bounds. We show these benefits on a toy problem and cosmological parameter inference from the matter power spectrum. Such an advantage grows in high dimensions, where boundaries dominate parameter space volume. All code is publicly available on Github at https://github.com/chaipattira/tailed-uniform-sbi.
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Astrophysics of Galaxies
An Enhanced Isothermal Jeans Approach to Constraining Dark Matter Self-Interactions from Galactic Kinematics
Zixiang Jia, Fangzhou Jiang, Shubo Li et al. (+3 more)
We present an improved semi-analytical model to predict density profiles of self-interacting dark matter (SIDM)
halos and apply it to constrain the self-scattering cross section using SPARC
galaxy rotation curves. Building on the isothermal Jeans approach, our model incorporates (i) velocity-dependent cross sections, (ii) an empirical treatment of core collapse, and (iii) enhanced robustness for identifying solutions. These advances allow us to fit a large sample of
galaxies, including systems with
baryon-dominated centers often excluded in earlier studies. We find that roughly 1/6 of
galaxies admit both a core-growth and a core-collapse solution, while the rest favor a unique evolutionary state. Joint constraints across the sample reveal clear velocity dependence: the allowed parameter space forms an L-shaped degeneracy, where both nearly constant, low cross sections ($\sigma_0\sim2\,{\rm cm}^2$/g, $\omega\gtrsim500\,$km/s) and strongly velocity-dependent models ($\sigma_0\sim100\,{\rm cm}^2$/g, $\omega\sim60\,$km/s) are viable. Adopting the core-growth interpretation yields best-fit values $\sigma_0\simeq5\,{\rm cm}^2$/g and $\omega\simeq250\,$km/s. Our constraints are remarkably consistent with previous results derived from a variety of independent probes. Compared to cold dark matter (CDM) models, SIDM outperforms simple adiabatic-contraction profiles and rivals empirical feedback-based CDM profiles, yet shows no correlation with
stellar-to-
halo mass ratio, a proxy for feedback strength, offering a distinct explanation for
dwarf galaxy diversity. Moreover, SIDM does not affect
galaxy-
halo scaling relations significantly and makes concentration systematically lower. Our results highlight SIDM as a compelling framework for small-scale structure, while future low-mass kinematic data will be crucial for breaking degeneracies in velocity-dependent cross-section models.
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All authors Zixiang Jia, Fangzhou Jiang, Shubo Li, Ran Li, Jing Wang, Ling Zhu
Cosmology and Nongalactic Astrophysics
Non-Equilibrium Relativistic Core Collapse of Self-Interacting Dark Matter Halos – Limits On Seed Black Hole Mass
Hua-Peng Gu, Fangzhou Jiang, Xian Chen et al. (+1 more)
Recent observations of supermassive black holes (SMBHs) at high
redshifts pose challenges to standard seeding mechanisms. Among competing models, the collapse of self-interacting dark matter (SIDM)
halos provide a plausible explanation for early SMBH formation. While previous studies on modeling the gravothermal collapse of SIDM
halos have primarily focused on non-relativistic
evolution under the assumption of hydrostatic
equilibrium, We advance this framework by relaxing the
equilibrium assumption and additionally incorporating general-relativistic effects. To this end, we introduce the Misner-Sharp formalism to the SIDM context for the first time. Our model reproduces the standard hydrostatic models in the early long-mean-free-path (LMFP) regime, but displays interesting distinct behavior in the late short-mean-free-path (SMFP) regime, where intense outward heat flux drives a rapid expansion of the outer envelope, removing mass from the core and significantly decelerating the collapse. Our general relativistic treatment enables us to follow
halo evolution to the final stage when the apparent horizon forms. Our simulation yields a seed black hole mass of approximately $3\times10^{-8}$ of the
halo mass at horizon formation, suggesting that additional mechanisms such as baryonic effects are critical for seeding black holes that are sufficiently massive to account for SMBHs in the early Universe.
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All authors Hua-Peng Gu, Fangzhou Jiang, Xian Chen, Ran Li
Solar and Stellar Astrophysics
Measuring Rotation Periods in Crowded Star Clusters with TESS: A Proof-of-Concept with NGC 3532
Matthew S. Stafford, Jason L. Curtis and Marcel A. Agüeros
The Transiting
Exoplanet Survey Satellite (TESS) has observed nearly the entire sky, producing full-frame images (FFIs) every 30 min (Cycles 1$-$2), 10 min (Cycles 3$-$4), and now 200 s (Cycle 5+), over 27-day sectors. Light curves extracted from FFIs can be used to measure
stellar rotation periods ($P_{\rm rot}$) in nearby open clusters, and are well-suited for studying low-mass
stars ($\lesssim$1.2 M$_\odot$) younger than $\approx$1 Gyr, whose $P_{\rm rot}$ are generally still $\leq$15 days. A challenge to exploiting TESS data fully is its 21$''$ pixel size, which can cause strong signals from a source to contaminate the signals of nearby sources in the crowded environments found, e.g., in the more distant and/or richest clusters. We conducted a test with the young ($\approx$350 Myr old), moderately distant (470 pc), and rich open cluster NGC 3532 ($N_\star$ > 3000), which has an extensive $P_{\rm rot}$ catalog from ground-based photometry, to examine the reliability of $P_{\rm rot}$ obtained from TESS data. We recovered 69% of the literature periods from at least one of the three TESS cycles in which NGC 3532 was observed before any quality analysis. We then used all available TESS data for low-mass members of NGC 3532 and, applying a set of quality cuts that combined information from TESS and from
Gaia, measured $P_{\rm rot}$ for 885 cluster
stars, adding 706 new $P_{\rm rot}$ to the existing catalog. We conclude that, when considered with appropriate caution, TESS data for
stars in crowded fields can yield reliable $P_{\rm rot}$ measurements.
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Astrophysics of Galaxies
The Impact of Star Formation Histories on the Inner Dark Matter Density Slopes of Galaxies
Jorge Sarrato-Alós, James Bullock, Arianna Di Cintio et al. (+3 more)
Aims. We aim to investigate the connection between
star formation histories (SFHs) and the inner dark matter density profiles of simulated
galaxies. In particular, we test whether the burstiness and temporal distribution of
star formation influence the formation of cored versus cuspy dark matter profiles. Methods. We homogeneously analysed simulated
galaxies from the NIHAO and FIRE-2 projects. For each
galaxy, we derived dark matter density profiles and measured the logarithmic slope in the inner region of the dark matter
halo (1-2% of R$_{\rm vir}$). To characterise
star formation burstiness, we introduced a criterion based on comparing the
star formation rate (SFR) averaged over two distinct timescales. We further quantified the temporal concentration of SFHs by computing $M_{\star, \rm post}$ / $M_{\star, \rm pre}$, the ratio of
stellar mass formed after versus before the epoch of reionisation at
redshift z $\sim$ 6.5. Results. Homogeneous analysis reveals that inner slope versus
stellar-to-
halo mass ratio trends for NIHAO and FIRE-2
galaxies are in much better agreement than reported in previous works. The burstiness and post-to-pre reionisation
stellar mass ratio of the SFH explain the scatter in the inner slope versus
stellar-to-
halo mass ratio relation, revealing that
galaxies with above average burstiness and more extended SFHs are more efficient at developing cored dark matter profiles. In contrast,
galaxies with smoother SFHs and earlier
stellar mass assembly tend to maintain cuspier dark matter profiles. We present an analytic expression that improves predictions for the inner slope using the parameter $M_{\star \rm,post}$ / $M_{\star \rm,pre}$, which reduces the mean squared error in both simulation suites relative to previous formulations based solely on the
stellar-to-
halo mass ratio.
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All authors Jorge Sarrato-Alós, James Bullock, Arianna Di Cintio, Christopher Brook, Fernando Valenciano, Andrea V. Macciò
Instrumentation and Methods for Astrophysics
Extragalactic Planetary Nebulae (xPNe). Chemical evolution and assembly histories of nearby galaxies using Oxygen and Argon abundances. From the local universe to cosmic dawn
Magda Arnaboldi, Ortwin Gerhard, Martin Roth et al. (+6 more)
How
galaxies formed and evolved in the expanding Universe is the main science goal of Near-Field Cosmology research. Studies of the properties of
galaxies' resolved
stars open a widow on their ancient
galactic components, probing
star formation during epochs more than 10 billion years ago. Extragalactic Planetary Nebulae (xPNe) can help decipher the signatures of mergers and interactions persisting over many dynamical times by tracing elemental abundances coupled with their kinematics and spatial distributions. With new facilities, reaching higher angular resolution, area coverage and sensitivity, one can use xPNe to map Oxygen and Argon element abundances, in addition to their kinematics, to extend the
Galactic Archeology investigation to the oldest
stellar aggregates in our Local Universe.
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All authors Magda Arnaboldi, Ortwin Gerhard, Martin Roth, Souradeep Bhattacharya, Johanna Hartke, Chiara Spiniello, Azlizan Soemitro, Claudia Pulsoni, Lucas Valenzuela
Earth and Planetary Astrophysics
Effect of different Non-Gravitational accelerations on the trajectory of Interstellar Comet 3I/ATLAS
Goldy Ahuja and Shashikiran Ganesh
Comet C/2025 N1 or 3I/ATLAS is the third confirmed interstellar object. It has passed perihelion on 2025 October 29, and is currently on a path to leave the
solar system. During its outbound journey, it will pass close to Jupiter at a distance of 0.358 au. NASA JPL Horizons has updated the non-gravitational parameters of the comet based on the CO$_2$ sublimation model, where $g(r)= 1/r^2$. In this research note, we use the non-gravitational accelerations from Horizons together with symmetric and asymmetric H$_2$O sublimation models derived using Find\_Orb software. We calculate the resulting perijove distances and compare them with our earlier results at epoch JD 2460867.5.
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Earth and Planetary Astrophysics
Post-Perihelion Integral Field Spectroscopy of the Interstellar Comet 3I/ATLAS
Willem B. Hoogendam, David O. Jones, Bin Yang et al. (+10 more)
The environs of other
stellar systems may be directly probed by analyzing the cometary activity of interstellar objects. The recently discovered interstellar object 3I/ATLAS was the subject of an intensive worldwide follow-up campaign in its pre-perihelion approach. Now, 3I/ATLAS has begun its post-perihelion departure from the
Solar System. In this letter, we report the first post-perihelion blue-sensitive integral-field unit spectroscopy of 3I/ATLAS using the Keck
Cosmic Web Imager on November 16, 2025. We confirm previously reported CN, Fe, and Ni outgassing along with detections of carbon chain molecules $\mathrm{C}_2$ and $\mathrm{C}_3$. We calculate production rates for each species. We find Fe and Ni production rates of $\mathrm{Q_{Fe}} = (9.55\pm3.96)\times10^{25}$ atoms s$^{-1}$, and $\mathrm{Q_{Ni}} = (6.61\pm2.74)\times10^{25}$ atoms s$^{-1}$, resulting in a ratio of $\log(\mathrm{Q_{Ni}} / \mathrm{Q_{Fe}}) = -0.16\pm0.03$, which matches
Solar System comets well and continues the pre-perihelion trend of declining $\log(\mathrm{Q_{Ni}} / \mathrm{Q_{Fe}})$ with $r_h$. We investigate the radial distributions of these elemental species and find characteristic $e$-folding radii of 3880$\pm$39 km for Ni, 6053$\pm$68 km for CN, 4194$\pm$45 km for $\mathrm{C}_2$, and 3833$\pm$45 km for $\mathrm{C}_3$. Compared to pre-perihelion measurements, these radii have increased by a factor of $\sim$6.5–7. Our post-perihelion observations reveal that 3I/ATLAS continues to exhibit cometary behavior broadly consistent with
Solar System comets.
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All authors Willem B. Hoogendam, David O. Jones, Bin Yang, Benjamin J. Shappee, James J. Wray, Karen J. Meech, Christopher Ashall, Dhvanil D. Desai, Jason T. Hinkle, Andrew M. Hoffman, Kyle Medler, Cameron Pfeffer, Ruining Zhao
Astrophysics of Galaxies
ReveaLLAGN 1: JWST Emission-Line Spectra Reveal Low-Luminosity AGN with UV-Deficient SEDs and Warm Molecular Gas
Kameron Goold, Anil Seth, Mallory Molina et al. (+20 more)
We present near- and mid-infrared spectra of eight Low-Luminosity Active
Galactic Nuclei (LLAGN), spanning nearly four orders of magnitude in black hole mass and Eddington ratio, obtained with JWST/NIRSpec and MIRI as part of the ReveaLLAGN program along with identical archival data of Cen A. The high spatial resolution of JWST cleanly separates AGN emission from host-
galaxy contamination, enabling detections of high-ionization potential lines more than an order of magnitude fainter than previously measured. Emission-line diagnostics reveal a transition at log($L_{bol}/L_{Edd}$) ~ -3.5, where the spectral energy distribution becomes increasingly deficient in ultraviolet
photons. We find that rotational H$_2$ excitation temperatures are elevated (~500 K higher) compared to both higher-luminosity AGN and
star-forming
galaxies, while the H$_2$(0-0)S(3)/PAH$_{11.3 \mu m}$ ratios are consistent with those observed in the AGN population. We discuss the possible roles of
outflows, jets, and X-ray dominated regions in shaping the interstellar medium surrounding LLAGN. Silicate emission at ~10 $\mu$m, localized to the
nuclear region, is detected in most ReveaLLAGN targets. This
dataset offers the first comprehensive JWST-based characterization of infrared emission lines in the
nuclear regions of LLAGN.
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All authors Kameron Goold, Anil Seth, Mallory Molina, David Ohlson, Nischal Acharya, Torsten Böker, Antoine Dumont, Michael Eracleous, Anja Feldmeier-Krause, Juan Antonio Fernández-Ontiveros, Elena Gallo, Andy D. Goulding, Kayhan Gültekin, Luis C. Ho, Nadine Neumayer, Richard M. Plotkin, Almudena Prieto, Jessie C. Runnoe, Shobita Satyapal, Glenn van de Ven, Jonelle L. Walsh, Feng Yuan, Nora Lützgendorf
Cosmology and Nongalactic Astrophysics
Calibrating redshift distributions at $z>2$ with Lyman-$\alpha$ forest cross-correlations
Qianjun Hang, Laura Casas, William d'Assignies et al. (+3 more)
We explore the feasibility of using Lyman-$\alpha$ (Ly$\alpha$) forests to calibrate the ensemble
redshift distribution of the high-
redshift tail ($2<z<3$) of photometric
galaxies. We use CoLoRe simulations to create mock DESI 5-year Ly$\alpha$ forests and Rubin Observatory LSST 10-year photometric
galaxies up to $z=3$, and measure the
galaxy redshift distribution via their angular cross-correlations. Due to large
redshift-space distortions in the Ly$\alpha$ forest, the conventional $n(z)$
estimator for clustering
redshifts does not apply, and we develope a theoretical framework to model the angular cross-correlation directly. Using the simulations, we explore effects of instrumental noise, continuum fitting, and contamination in the Ly$\alpha$ forest, cross-correlation angular scales ($\theta$), and
redshift bin size ($\Delta z$) on the signal-to-noise (SNR) of the measurements. We find that continuum fitting methods strongly impact the SNR of the measurements. With our baseline continuum fitting method, LyCAN, at angular scales $\theta\sim10$ arcmin and $\Delta z=0.1$, we measure the cross-correlation signal at $24\sigma$. If the shape of the
redshift distribution and
galaxy bias
evolution are known well for $z<2$, the cross-correlation can constrain the mean
redshift of the
galaxy sample to $\sigma_z/(1+\bar{z}) = 0.006$ at a mean
redshift of $\bar{z}=2$. This demonstrates that Ly$\alpha$ cross-correlation is a reliable and promising method to calibrate the high-
redshift tails of photometric Stage IV
galaxy surveys.
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All authors Qianjun Hang, Laura Casas, William d'Assignies, Wynne Turner, Andreu Font-Ribera, Benjamin Joachimi
Instrumentation and Methods for Astrophysics
Probabilistic Graphical Models in Astronomy
Abigail Sheerin and Giuseppe Vinci
The field of astronomy is experiencing a data explosion driven by significant advances in observational instrumentation, and classical methods often fall short of addressing the complexity of modern astronomical
datasets. Probabilistic graphical models offer powerful tools for uncovering the dependence structures and data-generating processes underlying a wide array of
cosmic variables. By representing variables as nodes in a network, these models allow for the visualization and analysis of the intricate relationships that underpin theories of hierarchical structure formation within the universe. We highlight the value that graphical models bring to astronomical research by demonstrating their practical application to the study of
exoplanets and host
stars.
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Astrophysics of Galaxies · Cross-listed from gr-qc
Galactic dark matter halos: From anisotropic fluids in general relativity to Horava-Lifshitz gravity
Paolo M Bassani
We deform the GR
Hamiltonian by adding an extra weight $+1$ density to the potential. We show that potential deformations of this type leave the (reduced) Dirac
algebra unchanged and the modification is naturally reinterpreted as an effective anisotropic stress-energy contribution. While the fluid reproduces an isothermal-like mass scaling, its pressure anisotropy prevents it from giving flat rotation curves in this reduced phenomenological toy model. We then turn to HL
gravity, where the absence of a local
Hamiltonian constraint leaves a non-vanishing local
Hamiltonian density, giving a controlled nonconservation law for the emergent
dust component. Generalizing earlier results, we identify a restricted class of LTB backgrounds for which the HL source term yields a positive scaling dark matter density, consistent with ghost freedom and with the continuous $\lambda \to 1$ limit, in which the effective
dust amplitude vanishes together with the deviation from GR. The analysis is conditional on a prescribed background: obtaining a fully backreacted areal-radius solution consistent with the HL field equations is left as a natural direction for future work.
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Cosmology and Nongalactic Astrophysics
Improving constraints on primordial non-Gaussianity from Quaia with a new cosmological observable: angular redshift fluctuations
José Ramón Bermejo-Climent, Carlos Hernández-Monteagudo, Alba Crespo-Pérez et al. (+4 more)
Angular
redshift fluctuations (ARF) are a new cosmological observable, recently proposed in the literature. It measures the 2D angular deviations of the average
redshift of a given matter tracer under an input
redshift shell. Since it depends on the
galaxy bias, it can be used to constrain
primordial non-Gaussianity through the scale-dependent bias effect. We analyze a sample of
quasars built upon the
Gaia satellite and unWISE data, Quaia, to measure the local non-Gaussianity parameter $f_{\rm NL}$. This sample is particularly suitable for measuring $f_{\rm NL}$ due to its large volume coverage. We measure the ARF power spectra from the Quaia catalog and combine their information with the 2D (projected)
galaxy density and their cross-correlation with the $Planck$ PR4 CMB
lensing maps
lensing to jointly constrain $f_{\rm NL}$. Assuming the universality relation, we measure $f_{\rm NL} = -3 \pm 14$ at 68% confidence level by combining Quaia
quasar angular density and ARF with the CMB
lensing. This result is the second tightest constraint on $f_{\rm NL}$ using LSS two-point statistics to date and the best measurement achieved using two-point projected summary statistics, improving by $\sim$25% the previous measurement from Quaia. Our results motivate the inclusion of ARF as an additional cosmological observable in future 2D analysis of upcoming
datasets from large surveys.
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All authors José Ramón Bermejo-Climent, Carlos Hernández-Monteagudo, Alba Crespo-Pérez, Jorge Martin Camalich, David Alonso, Giulio Fabbian, Kate Storey-Fisher
Cosmology and Nongalactic Astrophysics
Forecast on the generalised dark matter properties from a Euclid-like survey
Ziad Sakr and Jessica N. López-Sánchez
The Stage~IV Euclid mission will deliver spectroscopic
galaxy redshifts together with photometric positions and shapes, enabling cosmological analyses through spectroscopic
galaxy clustering (GCsp), photometric
galaxy clustering (GCph), weak-
lensing cosmic shear (WL), and their cross-correlation (XC). In this work we forecast the constraining power of a Euclid-like survey on the Generalised Dark Matter (GDM) parameters \(w_{\rm gdm}\) and \(c^{2}_{s,{\rm gdm}}\). Our analysis extends previous
forecasting pipeline used for standard cold dark matter. For GCsp, we adopt a semi-analytic nonlinear RSD model, with free terms for each bin. For the photometric probes, we compute the nonlinear GDM matter power spectrum using dedicated simulations, and we modify the
lensing and clustering window and the intrinsic-
alignment prescription. We consider several survey configurations and explore three fiducial values of \(\sigma_8\) motivated by current CMB and low-
redshift measurements. In an optimistic setting, for fiducial values \(\sigma_8 \simeq 0.81\) and \(\sigma_8 \simeq 0.77\), we find relative errors of \(4.01\%\) (GCsp), \(5.01\%\) (GCph+WL+XC), and \(1.96\%\) (all probes) on \(c^{2}_{s,{\rm gdm}}\), and \(3.26\%\) (GCph+WL+XC) and \(1.85\%\) (all probes) on \(w_{\rm gdm}\). For a lower fiducial value \(\sigma_8 \simeq 0.67\), that could strongly disfavor $\Lambda$GDM, we find constraints of \(5\%\) (GCsp), \(5\%\) (GCph+WL+XC), and \(2.45\%\) (all probes) on \(c^{2}_{s,{\rm gdm}}\), and \(3.43\%\) (GCph+WL+XC) and \(2.04\%\) (all probes) on \(w_{\rm gdm}\). We also found that, combining all probes, whether in the pessimistic or optimistic settings, a Euclid-like survey will be able to disentangle between the three scenarios. These results show that the survey will be able to constrain the GDM parameters and distinguish between normalisations of the matter fluctuations.(Abridged)
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Astrophysics of Galaxies
The scaling relations of galaxies with different morphology: comparison among WINGS, MANGA and Illustris data samples
Mauro D'Onofrio, Francesco Brevi, Cesare Chiosi et al. (+1 more)
We present a panoramic view of several scaling relations (ScRs) of
galaxies of different morphology. The ScRs are obtained from the data of two large surveys (WINGS and MANGA). We analyze the distribution (parameterized by the percent over the total) of
galaxies in each region of the diagnostic planes that are set up by means of suitable physical quantities. In addition to this, we discuss the origin of the differences observed in the ScRs between the two samples. Finally, we compare the observational data with the theoretical ones taken from two subsets of the Illustris large scale simulations (TNG50 and TNG100) and we discuss how the comparison should be performed for a correct statistical answer.
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All authors Mauro D'Onofrio, Francesco Brevi, Cesare Chiosi, Paola Marziani
Cosmology and Nongalactic Astrophysics
The shape function of the observed growth index
Ziad Sakr and Jinglan Zheng
The growth index $\gamma$ is a powerful trigger for detecting deviations from $\Lambda$CDM. However, its value is often determined by considering an asymptotic constant value that works for all
redshift, or else following a chosen parameterisation. Here we formulate the growth index as function of three quantities that could be directly related to observables in
redshift bins, $f\sigma_8(z_i)$, $f(z_i)$ and $H(z_i)$. We determine its value and its derivative at observed nodal center of
redshift bins and use the shape function method, after showing insightful connection with its underlying governing virtual-work conservation principle, to construct a
redshift dependence of the $\gamma$ without assuming a specific parameterization. We then use the resulting shape function to test if we can disentangle between different scenarios where there are discrepancies between its three constituent measured components. We also tested whether it can be used to rule out models of modified
gravity, or extended parametric models of the growth index that capture more general behaviors with an additional parameter as function of the scale factor or dark energy. Adopting forecasted measurements from next generation surveys on the three quantities used to construct $\gamma$, we find that reported discrepancies between them could be detected with our method, but at the bins where the errors and lost of precision from our addition of degrees of freedom is small with respect to the deviation of $\gamma$. The same could be concluded for first order extensions to $\gamma$ or common modified
gravity models, and to a lesser degree for dynamical dark energy models after supposing the latest DESI values. We conclude that this method is a strong tool to investigate cosmology in a model-independent way especially with forthcoming data delivered by further stage-IV surveys with more stringent uncertainties.(Abridged)
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Solar and Stellar Astrophysics
Fast Magnetoacoustic Wave Behavior within Gravitationally Stratified, Magnetically Inhomogeneous Media
Ryan T. Smith, James A. McLaughlin and Gert J. J. Botha
The nature of MHD waves within inhomogeneous media is fundamental to understanding and interpreting wave behavior in the
solar atmosphere. We investigate fast magnetoacoustic wave behavior within gravitationally stratified, magnetically inhomogeneous media, by studying a
magnetic environment containing a simple 2D X-type
magnetic null point. The addition of gravitational stratification fundamentally changes the nature of the system, including breaking the
symmetry. There are two main governing effects: the stratified density profile acts in combination with the inhomogeneous
magnetic field, creating a large gradient in the Alfven speed and hence a system replete with refraction. The system is investigated using both numerical simulations and a semianalytical WKB solution (via Charpit's method and a fourth-order Runge-Kutta solver) and we find strong agreement between both. The results show a fundamental difference between the stratification-free and stratified cases, including the formation of caustic surfaces and cusps, and we contextualize these results in the theoretical understanding of fast magnetoacoustic waves.
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Instrumentation and Methods for Astrophysics
CosmoSlider: An educational tool for cosmology
Andreas Nygaard, Steen Hannestad and Thomas Tram
Understanding how cosmological parameters influence the
cosmic microwave background (CMB) power spectra is a central component of modern cosmology education, but interactive exploration is often limited by computational cost or technical complexity. We present CosmoSlider, a lightweight visualization tool that enables real-time exploration of CMB power spectra as multiple cosmological parameters are varied simultaneously. The tool employs a neural-network emulator implemented using TensorFlow Lite, allowing rapid evaluation of spectra without relying on large grids of precomputed models or on-demand execution of Einstein–Boltzmann solvers. CosmoSlider is available both as an iOS application and as a web-based tool, making it accessible across platforms and suitable for use in classrooms, lectures, and self-guided study. By providing immediate visual feedback, CosmoSlider supports the development of intuition for the physical processes underlying CMB anisotropies and serves as a complementary resource to traditional theoretical instruction.
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Solar and Stellar Astrophysics
Drawing the line between explosion and collapse in electron-capture supernovae – I. Impact of conductive flame speeds and ignition conditions on the explosion mechanism
Alexander Holas, Samuel W. Jones, Friedrich K. Roepke et al. (+5 more)
Electron-capture
supernovae (ECSNe) are commonly thought to result in a collapse to a
neutron star. Recent work has shown that a thermonuclear explosion is also a possible outcome. The division between the two regimes has not yet been mapped out. In this study, we investigate the conditions under which the transition from thermonuclear explosion to collapse occurs, and what physical mechanisms drive each outcome. We conducted a parameter study of 56 3D hydrodynamic simulations of ECSN in ONe white
dwarfs using a level set based flame model implemented in the Leafs code. We varied both the ignition location and the central density at ignition to determine the conditions of the transition regime. Additionally, we explored two different laminar flame parameterizations and how they impact the simulation outcome. From our parameter study, we find a transition density in the range of $\log\rho_c^{ini}=10.0$ and $10.15$ g cm$^{-3}$, depending on the ignition location and utilized laminar flame speed parameterization. Importantly, we find that for sufficiently high central densities, the burned ashes can sink into the core and trap large amounts of
neutron-rich material in the bound remnant. In the transition regime between explosion and collapse, we find that the laminar flame speed plays a critical role by suppressing the formation of instabilities and thereby reducing the
nuclear energy generation needed to overcome the collapse. We find that a thermonuclear explosion is possible for a wide range of parameters, whereby a more off-center ignition allows for higher central densities to still result in an explosion. Both the conditions at ignition and the flame physics are critical in determining the outcome. Detailed 3D hydrodynamic simulations of the preceding
stellar evolution and the ignition process of the thermonuclear flame are necessary to accurately predict the outcome of ECSNe.
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All authors Alexander Holas, Samuel W. Jones, Friedrich K. Roepke, Rüdiger Pakmor, Christina Fakiola, Giovanni Leidi, Raphael Hirschi, Ken J. Shen