Astrophysics of Galaxies
Zhihui Li, Timothy Heckman, Max Gronke et al. (+8 more)
We build upon our previously developed multi-ion radiative transfer (RT) framework, PEACOCK, to investigate the kinematic and energetic structure of cool-to-warm
galactic winds in a sample of 50 nearby
star-forming
galaxies. Using self-consistent constraints derived from joint modeling of Ly-alpha and multiple ultraviolet metal lines, we analyze how bulk
outflows and turbulent motions contribute to the dynamics and energy budget of
galactic winds in the circumgalactic medium (CGM). We find that macroscopic turbulent velocities are often comparable to, and sometimes exceed, the coherent bulk
outflow velocity. The associated turbulent pressure frequently dominates over both microscopic pressure and ram pressure, indicating that
turbulence is a major contributor to the kinetic energy budget of the CGM wind. Wind kinematics, ionic column densities, and metal mass
outflow rates all scale systematically with
stellar mass and
star formation rate, demonstrating a strong coupling between
stellar feedback and CGM structure. Including turbulent motions strengthens these CGM-
galaxy scaling relations and favors an energy-driven feedback regime. The total kinetic energy flux of the cool-to-warm CGM correlates tightly with the mechanical energy injection rate from
star formation, implying that
stellar feedback provides sufficient power to sustain both coherent
outflows and
turbulence. Comparisons with phenomenological line-profile fitting methods further show that simplified treatments can introduce systematic biases in inferred wind properties. Together these results support a
turbulence-regulated picture of
galactic winds in which a substantial fraction of feedback energy is stored in turbulent motions within a multiphase CGM.
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All authors Zhihui Li, Timothy Heckman, Max Gronke, Xinfeng Xu, Alaina Henry, Evan Schneider, Matthew Abruzzo, Danielle Berg, Bethan James, Crystal Martin, John Chisholm
High Energy Astrophysical Phenomena
Data-Driven Trends and Subpopulations in the Gravitational Wave Binary Black Hole Merger Population with UMAP
A. J. Amsellem, I. Magaña Hernandez, A. Palmese et al. (+1 more)
The rapidly expanding Gravitational-Wave Transient Catalog (GWTC) necessitates the development of model-independent techniques to uncover trends and subpopulations within the binary black hole (BBH) population. We present the first usage of the Uniform
Manifold Approximation and Projection (UMAP)
algorithm, a novel dimensionality-reduction technique, for the purpose of analyzing BBH mergers in GWTC-3. We show that UMAP, paired with a clustering
algorithm, effectively partitions the population into four well-segregated subgroups principally via their primary and secondary mass components along with an outlier event, GW$190521\_030229$. UMAP clearly identifies objects in the ${\sim}10~M_\odot$ buildup in the BBH mass spectrum as their own group with aligned
spins and mass ratios of ${\sim}0.2{-}0.7$ while objects in or above the ${\sim}35~M_\odot$ overdensity are all in the same, largest group and display typically lower effective
spins as well as larger mass ratios (${\sim}0.5{-}0.9$) on average. With the aid of hierarchical population inference, we interpret these as subpopulations from different formation pathways, consistent with previous findings. We also find a transitional group of a handful of objects with masses in between the aforementioned buildups and broad support for anti-aligned
spins. We examine the low-mass UMAP subgroup, which exhibits anti-correlation between the mass ratio and effective
spin, and show that it drives such anti-correlation for the entire GWTC-3 sample. Overall, we demonstrate that UMAP is an interpretable, non-parametric framework that can not only be used for visualization but also for probing the astrophysics of the BBH population.
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All authors A. J. Amsellem, I. Magaña Hernandez, A. Palmese, J. Gassert
Astrophysics of Galaxies
Kinematically Coherent Multiphase Galactic Winds in Star-Forming Galaxies Revealed by Unified Radiative Transfer Modeling of UV Emission and Absorption Lines
Zhihui Li, Timothy Heckman, Max Gronke et al. (+8 more)
We present PEACOCK, a three-dimensional Monte Carlo radiative transfer (RT) framework designed to self-consistently model rest-frame ultraviolet emission and absorption lines arising from multiphase, clumpy
galactic winds. Applied to deep HST/COS spectra of 50 nearby
star-forming
galaxies, PEACOCK reproduces 220 observed profiles of Ly-alpha, Si II, C II, Si III, Si IV, and C IV spanning absorption, emission, and P-Cygni-like morphologies within a single CGM model. By combining Monte Carlo RT with deep-learning acceleration and nested sampling, the framework enables fully converged multi-line inference at a small fraction of the cost of traditional RT grids. Systematic experiments show that ion column densities, bulk
outflow velocities, and turbulent motions leave distinct imprints on line profiles, allowing the underlying gas properties to be constrained with minimal degeneracy. Purely radial accelerating flows often fail to reproduce the observed absorption morphologies, whereas macroscopic velocity dispersion naturally produces the broad asymmetric troughs seen in the data, indicating that turbulent motions are a key component of
outflow kinematics. The inferred kinematics reveal strong coherence among low- and high-ionization metal lines in both bulk and turbulent velocities, consistent with a dynamically coupled multiphase wind. In contrast, neutral hydrogen shows weaker correspondence with metals, suggesting incomplete mixing and a distinct kinematic structure. By unifying emission and absorption diagnostics across multiple ions, PEACOCK provides a physically grounded bridge between UV observations and theoretical models of
galactic winds.
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All authors Zhihui Li, Timothy Heckman, Max Gronke, Xinfeng Xu, Alaina Henry, Evan Schneider, Matthew Abruzzo, Danielle Berg, Bethan James, Crystal Martin, John Chisholm
Cosmology and Nongalactic Astrophysics
Comment on: "Third-order corrections to the slow-roll expansion: Calculation and constraints with Planck, ACT, SPT, and BICEP/Keck [2025 PDU 47 101813]"
Pierre Auclair and Christophe Ringeval
We point out that several terms in the third-order corrections to the slow-roll power spectra presented by Ballardini et al. [1] are incorrect. The authors of that work claim that their result differ from the ones originally presented by Auclair & Ringeval [2] due to some different approximation schemes. However, in our original work, all terms at all orders have been derived exactly and any difference between two expansions performed at the same pivot wavenumber signals a problem. As we show in this comment, Ballardini et al. [1] have misevaluated some definite three-dimensional integrals by integrating a truncated Taylor expansion instead of Taylor expanding an integral. Our claim is backed-up with a Monte-Carlo numerical integration of the incriminated three-dimensional integrals, which, unsurprisingly, matches the analytical value derived in Auclair & Ringeval [2].
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Solar and Stellar Astrophysics
Constraining turbulent solar flare acceleration regions by connecting kinetic modeling and X-ray observations
Morgan Stores, Natasha Jeffrey, Ewan Dickson et al. (+2 more)
Spatially-resolved X-ray observations are the key to understanding electron acceleration in
solar flares. Currently, the underlying processes that efficiently energize
solar flare particles are poorly constrained. Abundant
flare observations suggest that
turbulence plays a crucial role in transferring energy between the
magnetic field and energetic electrons. For the first time, we connect inhomogeneous acceleration from
turbulence and hard X-ray spectroscopy and imaging observations with kinetic modeling to constrain the properties of
flare acceleration. Observing three large
flares with RHESSI, or
Solar Orbiter/STIX, we extract X-ray imaging and spectroscopy observables. We compare with modeling results, mapping observables to electron acceleration and turbulent properties. We determine that extended regions of
turbulence are required to match multiple X-ray observables, suggesting electrons are accelerated over a large fraction (~25%) of the
flare loop; a property that is usually unconstrained from X-ray observations alone. Additionally, we determine acceleration timescales that vary between 7 and 22s by using fixed values for the turbulent scattering timescale and the velocity dependence of the acceleration
diffusion coefficient. These fixed values are effectively unconstrained, but yield acceleration timescales that will help to restrict possible viable
stochastic models.
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All authors Morgan Stores, Natasha Jeffrey, Ewan Dickson, James McLaughlin, Eduard Kontar
Astrophysics of Galaxies
Galaxy UV Legacy Project: Survey Description and First Insights Into NGC 4449 Recent History of Star Formation
E. Sabbi, B. Meena, P. Zeidler et al. (+18 more)
The
Galaxy UV Legacy Project (GULP) is a Cycle 28 Treasury program with the Hubble Space
Telescope (HST) designed to characterize resolved massive
stars, OB associations, and young
star clusters (YSCs) in 26 nearby
star-forming
galaxies. Utilizing the ACS/SBC F150LP and WFC3/UVIS F218W filters, combined with extensive archival observations, GULP provides an unprecedented panchromatic 8-band view from the Far-UV to the I-band. The target
galaxies were carefully selected to span a broad range of
metallicities, masses, morphological types, and
star formation rates, thereby enabling detailed studies of
star formation processes across different
galactic environments. This paper introduces the GULP survey, detailing its observational strategy, data processing, and initial scientific results for the irregular barred starburst
dwarf galaxy NGC 4449, used as a test case. We derived the physical parameters and ages for thousands of
stars using the Binary Populations And Spectral Synthesis (BPASS) models, and found that the younger
stars and clusters are predominantly concentrated along the
galaxy's central bar, and that over the past <50 Myr
star formation progressively migrated from northeast to southwest. We used the F150LP, F218W, and F275W filters to investigate how the UV-bump at lambda 2175 A correlates with the intensity of the UV radiation. The UV-bump is detected in many areas of the
galaxy, but is absent in the regions of most intense and recent
star formation. This strongly supports the scenario where UV radiation from young, massive
stars effectively destroys the small
dust grains responsible for the UV-bump.
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All authors E. Sabbi, B. Meena, P. Zeidler, V. Bajaj, D. Calzetti, J. J. Eldridge, P. Facchini, S. Linden, P. A. Crowther, A. Adamo, L. Bianchi, M. Cignoni, B. G. Elmegreen, D. M. Elmegreen, J. S. Gallagher III, M. Gennaro, E. K. Grebel, R. S. Klessen, A. Pasquali, L. J. Smith, A. Wofford
Astrophysics of Galaxies
The Baryonic Mass-Halo Mass Relation of Extragalactic Systems
Stacy McGaugh, Tobias Mistele, Francis Duey et al. (+4 more)
We combine data for extragalactic systems to quantify a relation between the observed baryonic mass $M_b$ and the enclosed dynamical mass $M_{200}$ inferred from kinematics or gravitational
lensing. Our sample covers nine orders of magnitude in baryonic mass, including
galaxies with kinematic or weak gravitational
lensing data and groups and clusters of
galaxies with new gravitational
lensing data. For rich clusters with $M_b > 10^{14}\;\mathrm{M}_{\odot}$, the observed
baryon fraction is consistent with the
cosmic value, $f_b = 0.157$. For lower masses, the
baryon fraction decreases systematically with mass. The variation is well described by $M_b/M_{200} = f_b \tanh(M_b/M_0)^{1/4}$ with $M_0 \approx 5 \times 10^{13}\;\mathrm{M}_{\odot}$. This relation is qualitatively similar to
stellar mass-
halo mass relations derived from abundance matching, but exhibits less scatter.
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All authors Stacy McGaugh, Tobias Mistele, Francis Duey, Konstantin Haubner, Federico Lelli, Jim Schombert, Pengfei Li
High Energy Astrophysical Phenomena
Discovery and Timing of the First Millisecond Pulsar in NGC 6316
Deven Bhakta, Scott M. Ransom, Megan DeCesar et al. (+1 more)
NGC 6316 is a poorly studied, distant, and massive globular cluster (GC) with prominent gamma-ray emission detected via the
Fermi Large Area
Telescope (LAT). Based on gamma-ray spectral studies, NGC 6316 is expected to host tens of millisecond
pulsars (MSPs). Using the Green Bank
Telescope (GBT) and Murriyang, CSIRO's Parkes
radio telescope (Parkes), we present the discovery and a 3.1 yr duration timing solution of the first millisecond
pulsar found in the cluster. PSR J1716$-$2808A has a rotational period of 2.45\,ms and is in a binary with a $\sim$0.1 M$_\odot$ companion with an orbital period of 0.42 d. This is a typical cluster MSP within a compact orbit with no evidence of eclipses. PSR J1716$-$2808A has a dispersion measure DM = 172.26 pc cm$^{-3}$, which is lower than predicted NE2001, YMW16 and NE2025 electron density model values. The MSP is located within half a core radius from the cluster center and has a negative period derivative, implying that it is on the back side of the cluster and is being accelerated towards us. Given the negative period derivative, we report an upper limit on the maximum line-of-sight cluster acceleration, $a_{l,\textrm{GC}}/c \approx -2.3\times10^{-18}$ s$^{-1}$, experienced by the
pulsar and constraints on the
magnetic field to be $<\sim$3$\times$10$^{8}$ G. The presence of external acceleration strongly supports the
pulsar to be within NGC 6316. We can better constrain NGC 6316's properties through longer-term timing of PSR~J1716$-$2808A or by finding more
pulsars within the cluster. Based on the gamma-ray
pulsar estimates and a cluster distance of 11.3 kpc, deeper, more sensitive searches would find many additional
pulsars.
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All authors Deven Bhakta, Scott M. Ransom, Megan DeCesar, Shi Dai
Astrophysics of Galaxies
WALLABY pilot survey: Blinded by the light – discovery of a fourth member in the ESO 179-013 system
Rayssa Guimarães Silva, Marco Grossi, Denise R. Gonçalves et al. (+12 more)
We present new ASKAP/WALLABY HI observations of the nearby
dwarf galaxy system ESO 179-013 (Kathryn's Wheel), the nearest known collisional ring
galaxy, located 10 Mpc away in the Local Void. The system is composed of three previously known
dwarf galaxies embedded in a large HI envelope, with a newly discovered fourth member identified through HI and
radio continuum emission behind a bright foreground binary.
Galaxy D exhibits the highest
star formation rate in the group and deviates from the HI mass-diameter relation, suggesting it is a compact, gas-rich
dwarf missed due to
stellar foreground contamination. The HI data reveal for the first time an extended HI envelope around the whole system, the neutral gas counterpart of the
star-forming ring and gas bridges among members, suggesting a more complex interaction history than the previously proposed collisional ring scenario. ESO 179-013 thus provides a rare opportunity to study hierarchical assembly and gas dynamics in underdense environments and demonstrates the power of blind HI surveys in identifying faint members of low-mass compact groups.
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All authors Rayssa Guimarães Silva, Marco Grossi, Denise R. Gonçalves, Edvige Corbelli, Barbara Catinella, Nathan Deg, Benne W. Holwerda, Roger Ianjamasimanana, Denis A. Leahy, Pavel E. Mancera Piña, Sriram Sankar, Kristine Spekkens, S. F. Rahman, Tobias Westmeier, O. Ivy Wong
Cosmology and Nongalactic Astrophysics
Unbiased Bayesian Inference of Peculiar Motions of Galaxies from Type Ia Supernovae Observations
Ujjwal Upadhyay, Tarun Deep Saini and Shiv K. Sethi
The peculiar motions of
galaxies are powerful cosmological probes that trace the growth of structures and the distribution of matter in the universe, providing a means to investigate the nature of dark energy and test
gravity on cosmological scales. However, their direct observation is extremely challenging, as it requires independent and precise distance measurements to
galaxies. We present a
Bayesian approach to estimate the radial component of peculiar velocities of
galaxies hosting Type Ia
supernovae (SNe Ia), relying solely on the background cosmological model and the precision of the SNe Ia data. Unlike other peculiar velocity
estimators based on Hubble residuals, our method does not assume local linearity of the magnitude-
redshift relation or a fixed cosmology, making it unbiased even for large peculiar velocities and self-consistently avoiding bias due to a wrong cosmology. We validate our method using simulated
supernova data with the precision of current and upcoming surveys, and further compare it with the linearized
estimator to test its efficacy. We show that our
estimator has lower bias than the standard
estimator and remains consistent even for larger values of $v_{\rm p}/cz$. We also present a
Bayesian derivation for the linearized
estimator generalized to include the
supernova magnitude covariance.
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High Energy Astrophysical Phenomena
Angular momentum drives proton-rich nucleosynthesis in hyperaccreting neutron stars in common envelopes
Alexander D. Hall-Smith, Sophie E. D. Abrahams, Alison M. Laird et al. (+3 more)
Interacting binaries can produce a wide range of exotic systems, including X-ray binaries and merging
neutron stars, through a mass transfer phase called Common Envelope (CE)
evolution. A CE phase can occur during rapid expansion as a
star as it moves off the main sequence. If the engulfed
star is a compact object (e.g.
neutron star), a CE phase can lead to hyperaccretion onto the
neutron star. Previous work focused on systems in which the accreting material has low angular momentum, studying turbulent
outflows. This study investigates the impact of angular momentum on accreting material leading to the formation of an
accretion disk. Disk
accretion systems lead to very different
nuclear burning conditions. This paper presents the results of nucleosynthesis modelling of material ejected from an
accretion disk surrounding a 1.5 M$_{\odot}$
neutron star in a CE with a 15 M$_{\odot}$ companion. As material is accreted towards the
neutron star, sufficient heating will occur to eject a fracton of the material back into the surrounding envelope, producing a nucleosynthetic yield signature that differs from other explosions. We find that significant mass fractions of rp-process products are synthesised, thereby providing another mechanism for rp-process contribution to
galactic chemical
evolution, following ejection of the CE. Furthermore, later stages of the CE
evolution the accrete helium leading to alpha-rich,
supernova-like nucleosynthesis, producing $^{44}$Ti and $^{56}$Ni. Further work on modelling both the
accretion disk wind, and the companion envelope ejection, is vital to understand the contributions of these scenarios to chemical
evolution.
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All authors Alexander D. Hall-Smith, Sophie E. D. Abrahams, Alison M. Laird, Christian Aa. Diget, Christopher Fryer, Samuel W. Jones
Astrophysics of Galaxies
MIGHTEE: The dark matter haloes, duty cycle and mechanical feedback from radio-AGN up to $z \sim 2.5$
Joel Hamlett, Catherine L. Hale, Matt J. Jarvis et al. (+3 more)
Radio-AGN are observed to be more strongly clustered than non-active
galaxies, though it is unclear whether this is simply due to their preference for massive host
galaxies, or if they reside in distinct environments beyond this mass dependence. Using data from three fields covered by the MIGHTEE survey, we measure the angular two-point cross-correlation functions with a large,
stellar mass-limited population of near-infrared selected
galaxies, overcoming limitations of previous single-deep-field studies. By fitting
halo occupation distribution models, we infer the
galaxy bias parameters, $b$, for
radio-AGN in three
redshift ranges with median
redshifts of $z_{med}=0.76^{+0.17}_{-0.28}$, $1.25^{+0.14}_{-0.17}$ and $1.75^{+0.44}_{-0.18}$, finding $b=1.94^{+0.07}_{-0.07}$, $2.50^{+0.11}_{-0.18}$ and $3.38^{+0.27}_{-0.38}$, respectively. The typical dark matter
halo mass decreases with increasing
redshift: $\log_{10}(\langle M_{h} \rangle/{M_\odot})=13.44^{+0.08}_{-0.08}$, $13.17^{+0.07}_{-0.06}$ and $13.03^{+0.09}_{-0.10}$, which we attribute to the increased abundance of cold gas required to fuel AGN activity at earlier times. The AGN duty cycle is determined to be $\sim5-9\%$, and we estimate that the total energy radiated by
radio-jets over $0<z<2.5$ is $\sim10^{53}$ J per
halo, which is sufficient to account for the observed excess heating of gas beyond that of gravitational collapse. Comparing the typical dark matter
halo masses to the values obtained for the control sample, we find that the
halo masses of
radio-AGN are $1.54^{+0.47}_{-0.33}$, $1.11^{+0.25}_{-0.20}$ and $1.82^{+1.04}_{-0.57}$ times greater than those of the
stellar mass- and
redshift-matched
galaxies. This difference could arise because AGN feedback suppresses
stellar mass growth while leaving
halo mass unchanged, or because
radio-AGN preferentially reside in earlier forming
haloes which are more strongly clustered.
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All authors Joel Hamlett, Catherine L. Hale, Matt J. Jarvis, David Alonso, Natalia Stylianou, Imogen H. Whittam
Astrophysics of Galaxies
Formation of mega-parsec giant radio sources from hosts residing in dark matter halos with normal hot baryonic gas fractions
Xiaodong Duan
Mega-parsec
giant radio sources (GRSs) have been known for decades. Their known population has soared from several hundred to more than $10^4$ in recent years. However, the formation mechanisms of GRSs remain elusive. In this work, we study the formation and properties of GRSs associated with dark matter
halos of different masses and normal gas density environment. We use magnetohydrodynamic simulations to study the formation of GRSs from hosts residing in dark matter
halos with masses of $10^{13}$, $10^{14}$ and $10^{15}$
solar masses, adopting normal hot baryonic gas fractions in ranges (0.02-0.1, 0.05-0.1, and 0.1-0.15) and varying density profiles. We inject jet energy of 0.06 percent of the central black hole's relativistic energy in their host
galaxies with power of 0.05 percent of the Eddington luminosity in most runs. The successful formation of GRSs from hosts in dark matter
halos with normal hot baryonic gas fractions indicates that an unusual low-density gas environment is not a prerequisite for their formation. The propagation of
radio lobes can be slower in
halos with sufficiently low or high central density and pressure, as a much lower central pressure cannot sufficiently collimate the jet and produces wider, less penetrating lobes, whereas an atmosphere with sufficiently high pressure enhances the interaction between the jet and the surrounding medium. Assuming equipartition between non-thermal electron and
magnetic energy, the
evolution of the simulated GRSs in the
radio power–linear size diagram shows that the
radio power of most simulated sources within
halo masses of $\rm 10^{13}$ and $\rm 10^{14} M_\odot$ can reach values comparable to observational data at similar physical scales. The simulated sources with a shorter jet duration than other sources become faint remnant sources when they propagate to GRS scales.
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Cosmology and Nongalactic Astrophysics
Efficient Numerical Evaluation of a Two-Loop Contribution to the Dark-Matter Trispectrum
Andrea Favorito
We study a two-loop contribution to the dark-matter trispectrum and evaluate it numerically using an infrared-safe integrand. The calculation is organized as an expansion around a fixed reference cosmology: the linear matter power spectrum of the target cosmology is written as a rescaled reference spectrum plus a small difference, and the trispectrum is expanded perturbatively in this difference. For the external momentum configuration considered here, truncating the expansion at third order reproduces the full numerical result with sub-percent accuracy over the range of scales studied, while higher-order terms are strongly suppressed. This reorganization reduces the number of cosmology-independent building blocks that must be computed compared with direct basis decompositions of the linear power spectrum. This provides a practical route to faster evaluations of higher-loop and higher-multiplicity correlators in the Effective Field Theory of Large-Scale Structure.
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Solar and Stellar Astrophysics
Velocity dispersion of Solar Energetic Particles in turbulent heliosphere
T. Laitinen and S. Dalla
Solar Energetic Particles (SEPs) are a signature of
solar eruptions, and to link them to acceleration mechanisms many studies investigate their injection time at the Sun, $t_{sun}$. We assess velocity dispersion analysis (VDA), an often-used method to derive $t_{sun}$. We use full-orbit simulations of 1–100 MeV SEP
protons in a novel model of the interplanetary
magnetic turbulence superposed on a Parker Spiral
magnetic field. The
turbulence is described analytically as dominant transverse fluctuations that are 2D with respect to the mean field, supplemented with a minor contribution of asymptotically slab
turbulence modes. We determine simulated SEP intensities for three
turbulence strengths and use VDA to obtain $t_{sun}$ and the apparent path length $s$ of the SEPs, employing an SEP onset threshold to mimic a realistic energetic
proton background before the SEP event. We find that
turbulence strongly affects $t_{sun}$ and $s$. For weak and moderate
turbulence, VDA estimates of $t_{sun}$ are 2-16 minutes after the actual
solar injection time, and the path lengths are 0.2-0.3 au longer than the Parker spiral. For strong
turbulence, the path lengths are $>5$ au, considerably longer than those typically obtained from SEP observations. We also investigate the effect of energy-dependence of the pre-event
proton background, and find that different background spectra result in 5-20-minute difference in VDA injection times, depending on the heliolongitude. We conclude that in many cases VDA-derived injection times include a significant contribution from
turbulence and/or the pre-event background and are not an accurate estimate of the acceleration time.
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Astrophysics of Galaxies
Ly{\alpha} Nebulae in HETDEX: The Largest Statistical Census Bridging Ly{\alpha} Halos and Blobs across Cosmic Noon
Erin Mentuch Cooper, Karl Gebhardt, Dustin Davis et al. (+20 more)
The Hobby-Eberly Dark Energy Experiment (HETDEX) is an untargeted ~540 deg^2 spectroscopic survey of Ly{\alpha} emission in the 1.9 < z < 3.5 Universe. In surface brightness, this survey reaches 1{\sigma} Ly{\alpha} sensitivities of approximately 2-5 x 10^-18 erg s^-1 cm^-2 arcsec^-2, allowing large samples of extended Ly{\alpha} nebulae (LAN) to be studied. We selected a sample of 70,691 Ly{\alpha}-emitting
galaxies (LAEs) with an emission-line signal-to-noise ratio greater than 6 and modeled the Ly{\alpha} emission as a point-source component with an optional exponential envelope. Half (~47.5%) of the LAE sample (33,612 objects) exhibits significant extended emission and is best fit by the two-component model. The fraction of resolved sources increases with Ly{\alpha} flux and luminosity. Their isophotal areas range from 10-130 arcsec^2 (median 15 arcsec^2), with integrated Ly{\alpha} fluxes from 6-2000 x 10^-17 erg s^-1 cm^-2 (median 20 x 10^-17 erg s^-1 cm^-2). Comparison between point-spread-function-weighted and isophotal flux measurements shows that the HETDEX pipeline underestimates the total Ly{\alpha} flux by ~30% on average, reflecting the substantial
halo contribution in extended sources. Approximately 420 LANs are found per deg^2 over 79.5 deg^2 of non-contiguous sky. About 12% of resolved sources show active
galactic nuclei signatures and are bright in Ly{\alpha} and continuum. The remaining 88% span a wide range of morphologies and often lack continuum counterparts. Exponential scale lengths show no strong correlation with Ly{\alpha} flux or luminosity (median 11.6 +/- 1.9 kpc). Only 2.9% of the full S/N > 6 LAE population with ancillary data have
radio counterparts, but 64% of those are found to be extended, with the
radio fraction increasing with Ly{\alpha} size.
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All authors Erin Mentuch Cooper, Karl Gebhardt, Dustin Davis, Robin Ciardullo, Chris Byrohl, Chenxu Liu, Maya H. Debski, Óscar A. Chávez Ortiz, Maximilian Fabricius, Daniel J. Farrow, Steven L. Finkelstein, Caryl Gronwall, Gary J. Hill, Maja Lujan Niemeyer, Brianna McKay, Shiro Mukae, Masami Ouchi, Huub Röttgering, Donald P. Schneider, Sarah Tuttle, Lutz Wisotzki, Gregory Zeimann, Sai Zhai
Astrophysics of Galaxies
The Collective Voice of Ly$\alpha$ Emitters: Insights from JWST Stacked Spectroscopy
R. Tripodi, L. Napolitano, L. Pentericci et al. (+20 more)
We present a spatially resolved stacked analysis of 287 LAEs at $z>4$ observed with JWST/NIRSpec prism spectroscopy. By constructing a two-dimensional stack from public surveys (CAPERS, CEERS, JADES, and RUBIES), we probe the average internal structure of typical LAEs on sub-kiloparsec scales. We find a clear radial decoupling between resonant and non-resonant emission: while EW(H$\beta$) and other optical lines decline with radius, EW(Ly$\alpha$) increases toward the outskirts, and the Ly$\alpha$ escape fraction rises from $\sim16\%$ in the center to $\gtrsim24\%$ at larger radii. This behavior suggests that resonant scattering redistributes Ly$\alpha$
photons into lower-density outer regions, where escape becomes more efficient. Optical diagnostics and $T_e$ measurements reveal low
metallicities ($12+\log(\rm O/H)\simeq7.7\pm0.2$), high ionization parameters, negligible
dust attenuation, and systematically elevated N/O ratios ($\log({\rm N/O})\sim-0.4$). The latter place typical LAEs among the growing population of nitrogen-enhanced high-
redshift galaxies, pointing to rapid and possibly feedback-driven chemical enrichment. The inferred ionizing
photon production efficiency, $\log(\xi_{\rm ion}/{\rm Hz\,erg^{-1}})\simeq25.1-25.2$, together with the high Ly$\alpha$ escape fractions, suggests that these systems are efficient, though not extreme, contributors to the ionizing
photon budget. Comparison with SPICE radiation-hydrodynamic simulations shows that bursty
supernova feedback models naturally reproduce the observed radial trends in Ly$\alpha$ escape, UV slope, and emission-line equivalent widths, linking the spatial redistribution of Ly$\alpha$ to
stochastic star formation and feedback-driven gas flows. Our results demonstrate that Ly$\alpha$ emission, chemical enrichment, and feedback are tightly connected in typical $z>4$ LAEs. (Shortened version for arXiv)
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All authors R. Tripodi, L. Napolitano, L. Pentericci, B. Pérez-Díaz, A. Bhagwat, F. D'Eugenio, F. Arevalo-Gonzalez, Pablo G. Perez-Gonzalez, A. Arroyo-Polonio, A. Calabrò, B. Ciardi, M. Dickinson, H. C. Ferguson, G. Gandolfi, M. Hirschmann, W. Hu, A. M. Koekemoer, M. Llerena, R. A. Lucas, M. S. Oey, C. Papovich, L. Y. A. Yung, X. Wang
Astrophysics of Galaxies
Molecular Clouds Resolved at the Onset of Cosmic Noon
Bjorn Emonts, Matthew Lehnert, Mingyu Li et al. (+10 more)
We present the discovery of seven molecular clouds in the
radio galaxy B2 0902+34 at
redshift z=3.4. These clouds are detected as CO(0-1) absorption features against the bright
radio continuum, and spectrally resolved using the Karl G. Jansky Very Large Array (VLA). The velocity dispersion of the individual absorption components ranges from 3-7 km/s, which is similar to values observed for molecular clouds in the Milky Way and nearby
galaxies, and imply cloud radii of R~10$^{1-2}$ pc. The absorbing clouds are found in a region of high obscuration inside a 30 kpc wide
stellar nebula, as revealed by rest-frame near-ultraviolet imaging performed with the Hubble Space
Telescope (HST). The fact that we spectrally resolve molecular clouds at the onset of
Cosmic Noon opens prospects for studying cloud chemistry and physics that drive the formation of
stars in the Early Universe.
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All authors Bjorn Emonts, Matthew Lehnert, Mingyu Li, Azia Robinson, Stephen Curran, Montserrat Villar-Martin, Chris Carilli, Raffaella Morganti, Ilsang Yoon, Pierre Guillard, George Miley, Reinout van Weeren, Zheng Cai
Cosmology and Nongalactic Astrophysics
WIMP Dark Matter Searches in Reticulum II Using MeerKAT
Shibre Semane, Geoff Beck, Sphesihle Makhathini et al. (+2 more)
In the last decade
radio astronomy has emerged as a powerful technique for detecting signatures of Weakly Interacting Massive Particles (WIMPs).
Dwarf spheroidal
galaxies (dSphs) are particularly promising targets for these searches due to their substantial dark matter (DM) dominance and minimal baryonic background emission. In this study, we utilize the exceptional sensitivity of the MeerKAT
radio telescope to search for synchrotron emission from WIMP annihilation/decay in the nearby Reticulum II dSph. Through rigorous data reduction and self-calibration, we establish constraints on WIMP properties that improve upon previous
radio studies, demonstrating the potential of MeerKAT and next-generation
radio telescopes in exploring increasing swathes of the WIMP parameter space.
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All authors Shibre Semane, Geoff Beck, Sphesihle Makhathini, Marco Regis, Gianni Bernardi
High Energy Astrophysical Phenomena
Survival of ultraheavy nuclei in astrophysical sources: applications to protomagnetar outflows
Nick Ekanger, Mukul Bhattacharya, Kohta Murase et al. (+1 more)
Outflows of rapidly rotating protomagnetars have been considered as attractive sites for the synthesis of
nuclei heavier than iron, but the question remains whether these
nuclei are able to survive against photodisintegration as they make their way out of their formation environments. In this work, we present new analytic fitting formulae for the photodisintegration cross sections applicable to heavy
nuclei beyond iron. We confirm that the results from the TALYS simulations are consistent with the theory of the
giant dipole resonance, and apply the obtained new formulae to investigate whether ultraheavy
nuclei entrained in protomagnetar
outflows can be disintegrated by thermal and nonthermal
photons before leaving the
stellar envelope. We explore two
outflow models: a spherical wind model and a jetted
outflow model. For
nuclei accelerated to the bulk speed of these
outflows, their survival depends on the model and engine properties. For spherical winds,
nuclei may survive for the first $\sim100\,{\rm s}$ post-core collapse, but as the wind Lorentz factor increases, the photodisintegration optical depth sharply rises and
nuclei may no longer survive. For the jetted
outflows arising from progenitors surrounded with
stellar envelopes,
nuclei can only survive before the jet breakout time in cases where the central engine has high
spin-down energy, that is, with a high
magnetic field strength and shorter
spin period. In progenitors with more extended envelopes, the jet break out time is much longer, allowing for nonthermal
photons to readily photodisintegrate
nuclei in high
spin-down energy cases. These results also outline some of the necessary, but not yet sufficient, conditions to source ultrahigh-energy
cosmic-ray
nuclei.
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All authors Nick Ekanger, Mukul Bhattacharya, Kohta Murase, Shunsaku Horiuchi
Instrumentation and Methods for Astrophysics
Generation of Imaging Air Cherenkov Telescope images using Diffusion Models
Christian Elflein, Stefan Funk, Jonas Glombitza et al. (+3 more)
Substantial amounts of air-shower simulations are needed to derive the instrument response for analyzing Imaging Air Cherenkov
Telescope (IACT) data. This process is both computationally intensive and requires repetition under varying observation conditions, due to detector aging, changes in the atmosphere, or the instrument hardware. Generative models offer an efficient alternative, significantly accelerating simulations while compactly storing extensive simulation libraries, and providing a differentiable surrogate model of the instrument. However, their applicability has so far been limited in gamma-ray astronomy, particularly for modeling hadronic showers that dominate the background and exhibit significant intrinsic fluctuations that are challenging to model. In this study, we present the first application of score-based
diffusion models to generate monoscopic $\gamma$-ray and
proton shower images with nearly 2,000 pixels and
benchmark the performance against Wasserstein GANs using H.E.S.S. simulations. We examine quality using both low-level parameters and well-established shower-shape observables, and take the first step towards analysis readiness by investigating $\gamma$-
hadron separation. While GAN-based approaches can reproduce $\gamma$-ray showers with high fidelity, they fail to generate
proton events of comparable quality, leading to a measurable degradation in analysis performance. In contrast, score-based
diffusion modles achieve significantly superior quality for $\gamma$-ray and
proton showers, accurately reproducing high-level correlations and generating events that are statistically indistinguishable from simulations at the analysis level. These results establish
diffusion-based models as the first analysis-ready surrogate model of a single IACT, opening new prospects for fast instrument response generation, detector optimization, and connected downstream tasks.
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All authors Christian Elflein, Stefan Funk, Jonas Glombitza, Vinicius Mikuni, Benjamin Nachman, Lark Wang
Solar and Stellar Astrophysics
Searching for outbursts from Symbiotic Binaries in GOTO and ATLAS data
G. Ramsay, K. Ackley, S. Belkin et al. (+46 more)
Symbiotic Binaries contain a white
dwarf accreting material from a red
giant star typically through a wind. We present the results of a search for outbursts from Symbiotic Binaries using photometric data obtained using the GOTO all-sky survey taken from 2023 onwards. After identifying ten candidate outbursting systems, we used ATLAS photometry to characterise their photometric behaviour before 2023, leaving five systems which showed photometric behaviour consistent with an outburst. The ATLAS data also provides colour information which gives insight to the nature of the outburst. The outburst from LMC N67 is the first reported Z And-type outburst from a Symbiotic binary in the LMC. In OGLE SMC-LPV-4044 and HK Sco we find previously unreported outbursts. QW Sge and V4141 Sgr show outbursts starting in 2024, which have already been reported and are ongoing. By better identifying and characterising Z And-type outbursts from many systems, it will be possible to better understand the physics of these events, which are still not fully understood.
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All authors G. Ramsay, K. Ackley, S. Belkin, P. Chote, D. Coppejans, M. J. Dyer, R. Eyles-Ferris, B. Godson, D. Jarvis, Y. Julakanti, L. Kelsey, M. R. Kennedy, T. L. Killestein, A. Kumar, A. Levan, S. Littlefair, J. Lyman, M. Magee, S. Mandhai, D. Mata Sánchez, S. Mattila, J. McCormac, J. Mullaney, D. O'Neill, C. Phillips, K. Pu, M. Pursiainen, A. Sahu, S. Moran, M. Shrestha, E. Stanway, R. Starling, Y. Sun, K. Ulaczyk, L. Vincetti, B. Warwick, E. Wickens, K. Wiersema, D. Steeghs, D. K. Galloway, V. S. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, B. Gompertz, J. Casares, D. Pollacco
High Energy Astrophysical Phenomena
Disentangling the Galactic binary zoo: Machine learning classification of stellar remnant binaries in LISA data
Irwin Khai Cheng Tay, Valeriya Korol and Thibault Lechien
The
Laser Interferometer Space
Antenna (LISA) will open a new observational window in the millihertz gravitational-wave band, enabling the detection of tens of thousands of compact
stellar remnant binaries across the Milky Way. Most of LISA's sources will be double white
dwarf (WDWD) systems, while
neutron star-white
dwarf (NSWD) binaries and higher-mass systems will be orders of magnitude rarer but of significant astrophysical interest. Disentangling these populations is challenging due to the strong overlap in their gravitational-wave features. In this work, we investigate the use of machine-learning techniques to classify LISA-detectable binaries based solely on LISA observables. Using mock catalogues of
Galactic binaries constructed from population-synthesis studies, we evaluate a range of machine-learning classifiers. We find that ensemble-based methods-particularly gradient-boosting
algorithms such as XGBoost-deliver the best performance on our highly imbalanced
dataset. WDWD systems are identified with a recall of $\sim 99\%$, reflecting their dominant presence, and high-mass binaries are also classified with high recall ($\ge 85\%$). In contrast, NSWD systems remain the most challenging population to distinguish: their features overlap strongly with those of WDWD binaries, making them particularly prone to misclassification. Despite this, XGBoost correctly identifies 85.6% of NSWD systems in our simulated LISA detections, outperforming simple statistical approaches based on kernel density estimation. We further demonstrate that machine-learning classification can effectively support the interpretation of LISA data, enabling the identification of eccentric binaries and extremely rare subclasses.
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Cosmology and Nongalactic Astrophysics
Enhancing Gravitational Lens Study with Deep Learning: A Study on Effects of Dropout Regularization
Juan J. Ancona-Flores, A. Hernández-Almada and V. Motta
Strong gravitational
lensing provides valuable insights into the mass distribution of
galaxies and the nature of dark matter. However, its modeling is computationally demanding due to the large volume of strong
lensing observations. In this work, we explore the application of Convolutional Neural Networks to infer physical parameters from simulated
galaxy-
galaxy lens systems, described by the Singular Isothermal Ellipsoid (SIE) profile for the
galaxy lens. We construct a
dataset of 76,396 synthetic
lensing images derived from the China Space Station
Telescope catalog and employ it to train a modified CNN model, based on AlexNet architecture, to predict four key SIE parameters, Einstein radius, axis ratio and ellipticity components. We analyze the network performance under three distinct dropout configurations to quantify their influence on generalization and parameter inference accuracy. The results indicate that the incorporation of dropout is critical for enhancing the precision and robustness of the estimated parameters, as demonstrated using a 4-fold cross-validation procedure. When dropout tools are included we obtain yields coefficients of determination up to $R^2 \sim 0.96$ for most SIE parameters and mean Peak Signal-to-Noise Ratios of up to $\sim 37$ dB. Relative to the configuration without dropout, the use of dropout reduces the relative errors in the inferred SIE parameters by approximately $60-76\%$, resulting in errors of at most $\sim 9\%$ at the $90\%$ confidence level for the majority of parameters. These findings highlight the potential of deep learning approaches to enable scalable, computationally efficient, and high-precision modeling of strong gravitational
lensing systems.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
A High Efficiency Superconducting On-chip Filterbank with Directional Filters for Integral Field Units in the Sub-millimeter Regime
Louis H. Marting, Kenichi Karatsu, Leon G.G. Olde Scholtenhuis et al. (+7 more)
Integrated superconducting spectrometers are developing to the point that they are enabling integral field units, providing large area spectral mapping capabilities for astronomy in the sub-millimeter band. However, these integral field units are only worthwhile if they have a high efficiency, but to date the efficiency of on-chip filterbanks has been quite poor. Here we demonstrate a filterbank with high efficiency by using directional filters. Using a cryogenic thermal load and a noise measurement in combination with a continuous-wave terahertz source to obtain the spectral response of the filters, we are able to accurately measure the filterbank efficiency, accounting for all quasi-optical elements within our setup. We experimentally obtain an average peak coupling efficiency to the detectors of 75% in a filterbank that sparsely samples between 125 GHz to 220 GHz using filters with a mean loaded quality factor of 19.6. Our results demonstrate that a filterbank with a high efficiency is achievable using directional filters, giving a clear route towards efficient integral field units.
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All authors Louis H. Marting, Kenichi Karatsu, Leon G.G. Olde Scholtenhuis, Shahab O. Dabironezare, Alejandro Pascual Laguna, Arend Moerman, David J. Thoen, A. J. van der Linden, Akira Endo, Jochem J.A. Baselmans
Cosmology and Nongalactic Astrophysics
Effects of Self-Interaction and of an Ideal Gas in Binary Mergers of Bosonic Dark Matter Cores
Carlos Tena-Contreras, Ivan Alvarez-Rios, Francisco S. Guzman et al. (+1 more)
We study binary mergers of dark matter cores in the Bose-Einstein condensate (BECDM) model. We include two scenarios: scalar self-interaction and the presence of a gravitationally coupled ideal gas. Using 3D simulations of the Gross-Pitaevskii-Poisson and Schrödinger-Poisson-Euler systems, we analyze the properties of the resulting remnants. We find that the final core-mass ratio reaches a stable average value after the merger. Repulsive self-interaction increases the mass of the final solitonic core, while attractive interaction enhances mass loss. In mergers involving an ideal gas, namely of
fermion-
boson stars, a stable solitonic core always forms in the bosonic component, even when the gas dominates, whereas the gas itself does not form a compact core. We explain these results using energy scalings and find that without self-interaction,
equilibrium cores follow $E \propto -M^3$, which leads to an almost universal merger fraction. Self-interaction changes this scaling, because repulsive $g$ moves the system toward a milder $E \propto -M^2$ scaling and increases mass retention, while attractive $g$ strengthens binding and favors mass ejection. In the case of interaction with an ideal gas, this component only modifies the gravitational background and does not change the intrinsic scaling of the bosonic part. These results show that the merger outcome is not universal but controlled by the interaction strength, while solitonic BECDM cores remain robust across diverse environments including gas.
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All authors Carlos Tena-Contreras, Ivan Alvarez-Rios, Francisco S. Guzman, Jens Niemeyer
Astrophysics of Galaxies · Cross-listed from nucl-ex
Implications for Type Ia Supernova Nucleosynthesis from an Experimentally Constrained $^{16}$O$(p,\alpha)^{13}$N Reaction Rate
M. Alruwaili, C. Fougeres, A. M. Laird et al. (+13 more)
The $^{16}$O$(p,\alpha)^{13}$N reaction plays a key role in shaping the $\alpha$-particle abundance during explosive oxygen burning in Type Ia
supernovae. By enhancing $\alpha$-production, this reaction directly affects the calcium-to-sulphur (Ca/S) and argon-to-sulphur (Ar/S) ratios, which serves as a tracer of progenitor
metallicity. However, recent work suggests that the rate must be enhanced by a factor of up to seven over the standard value to explain observed Ca/S ratios across a range of progenitor
metallicities. To explore this impact, available experimental cross-section data for the $^{16}$O$(p,\alpha)^{13}$N reaction have been compiled and critically evaluated. Significant discrepancies are identified in the low-energy region ($E_{\mathrm{cm}}$ = 5.7–7.0 MeV), primarily due to limitations of the activation method. To resolve this, the first direct measurement at astrophysical energies has been performed using the MUSIC active-target detector. The new $^{16}$O$(p,\alpha)^{13}$N thermonuclear reaction rate is found to be approximately 1.5 times higher than the REACLIB rate in the temperature range T = 3–4 GK, with more constrained uncertainties that resolve the previously large spread among existing data. The suggested factor of seven enhancement is excluded and these results indicate that this reaction alone cannot fully explain the variation in the Ca/S and Ar/S ratios observed across different progenitor
metallicities. Therefore, future work should focus on reducing the uncertainties in other key oxygen-burning reactions, particularly $^{16}$O+$^{16}$O and $^{12}$C+$^{16}$O. Further reducing the constraints on the $^{16}$O$(p,\alpha)^{13}$N rate is also needed to fully determine to whether a
nuclear physics solution to this discrepancy is possible.
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All authors M. Alruwaili, C. Fougeres, A. M. Laird, H. Jayatissa, M. L. Avila, E. Bravo, C. Angus, C. Badenes, S. Chakraborty, C. Diget, N. de Sereville, A. Hall-Smith, R. Longland, W. -J. Ong, K. E. Rehm, D. Santiago-Gonzalez
Earth and Planetary Astrophysics
Motional induction in Ganymede's ocean
Simon Cabanes, Thomas Gastine and Alexandre Fournier
We investigate the
magnetic signature of oceanic circulation in Ganymede's subsurface ocean using kinematic induction modeling. Our approach couples zonal jet flows from rotating thermal convection simulations with
magnetic field models incorporating Ganymede's internal dynamo and external contributions from Jupiter. We solve the induction equation in spherical geometry for deep-ocean (493 km) and shallow-ocean (287 km) scenarios with varying
magnetic Reynolds numbers. Ocean flows generate a predominantly toroidal
magnetic field through the omega-effect, with a weaker poloidal component pervading beyond the conductive ocean layer. For some, but not all, induction configurations, analysis of the time-averaged Lowes-Mauersberger spectra reveals that ocean-induced signals dominate at spherical harmonic degrees $\ell \geq 4$. Deep ocean scenarios with
magnetic Reynolds numbers above unity produce surface
magnetic signals up to 9 nT. Our results demonstrate that Ganymede's intrinsic
magnetic field creates favorable conditions for detecting subsurface ocean dynamics, thus emphasizing the need for low-altitude orbits for the Juice probe.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Revisiting unitarity of single scalar field with non-minimal coupling
Minxi He, Muzi Hong, Kyohei Mukaida et al. (+1 more)
We have investigated the unitarity violation scale of a non-minimally coupled scalar field with quartic self-coupling. This model is widely studied in the literature but the estimation of the unitarity violation scale has not been consistently discussed, especially in the Jordan frame. We have calculated the six-point scattering amplitudes of the scalar particles in both the Jordan frame and the Einstein frame, and explicitly shown the frame-independence of the results. Since the extended target space with the conformal mode is trivial in the single-field case, the dominant contribution comes from the potential of the scalar field. The results in both frames become trivial in the vanishing self-coupling limit as expected.
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All authors Minxi He, Muzi Hong, Kyohei Mukaida, Tomoya Nishiki
High Energy Astrophysical Phenomena
Polarized quasi-periodic oscillations reveal kink instability in magnetized jets of black holes
Jiashi Chen, Pengfu Tian and Wei Wang
The dynamics and instability of the magnetized jets connected to jet acceleration are complicated and are not yet well understood. Quasi-periodic oscillations (QPOs) as special timing features in black hole systems can directly probe dynamics and structure of accreting and
outflow materials. Recently, GHz-band
radio polarization oscillations in a
stellar-mass black hole are reported, and the physical origin is unclear. We propose that the QPOs in both
radio flux and linear polarization will be connected to kink instability in relativistic magnetized jets. The simulations are performed to fit the observed curves of
radio flux and linear polarization modulations, in addition, the kink instability model well explains the anti-correlation between flux and linear polarization. These polarized QPOs provide evidence for kink stability in relativistic jets, a phenomenon of significant theoretical importance for understanding the
magnetic field configuration near the black hole, as well as for particle acceleration in jets.
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