Astrophysics of Galaxies
A Deep Look at the Ultra-Faint Milky Way Satellite Virgo III with Rubin Observatory Data Preview 2
Aashay Pai, Alex Drlica-Wagner, Peter S. Ferguson et al. (+10 more)
We analyze the ultra-faint Milky Way satellite Virgo III using data from the Vera C. Rubin Observatory Data Preview 2 (DP2). Virgo III was observed in the Rubin "
Cosmic Treasure Chest" (M49) First Look field, which contains 924 visits in the u,g,r,i bands comprising ~10.5hrs of exposure time with LSSTCam. These data are considerably deeper than the majority of DP2, with a $5\sigma$ limiting magnitude that approaches the expected 10-year depth of LSST (~25.2-26.5mag, depending on band). We report the morphological and
stellar population parameters of Virgo III measured with the maximum-likelihood-based package ugali. The depth of the Rubin imaging yields more than a factor of four increase in the number of candidate member
stars ($N_* = 114^{+11}_{-11}$) relative to the Virgo III discovery results ($N_* = 25^{+5}_{-4}$), enabling significantly more precise morphological constraints. Our best-fit parameters broadly agree with previous measurements, further confirming that Virgo III has properties that are consistent with an ultra-faint
dwarf galaxy ($M_V = -2.72^{+0.49}_{-0.70}$; $r_{1/2} = 53^{+10}_{-8}$) located at a heliocentric distance of $D_\odot = 151^{+8}_{-8}$. We also demonstrate that the depth and photometric quality of the DP2 data are sufficient to separate metal-poor and metal-rich
stars in color-color space. We further present period estimates for the three known RR Lyrae member
stars derived from the DP2 forced photometry; we use theoretical Period-Luminosity-
Metallicity (PLZ) and Period-Wesenheit-
Metallicity (PWZ) relations to obtain independent distance estimates. We find that our period and distance estimates are broadly consistent with previous measurements for these RR Lyrae. These results demonstrate the power of LSST data for the discovery and characterization of ultra-faint
dwarf galaxies and motivate future searches for new satellites across the southern sky.
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All authors Aashay Pai, Alex Drlica-Wagner, Peter S. Ferguson, William Cerny, Chin Yi Tan, Jeffrey L. Carlin, Yumi Choi, Željko Ivezić, Andrés A. Plazas Malagón, Lauren A. MacArthur, Colin T. Slater, Dan S. Taranu, Brian Yanny
Astrophysics of Galaxies
How massive and clumpy must a quasar wind be to create emission line blueshifts?
James H. Matthews
Blue asymmetries (“Blueshifts”) in the C IV 1550A emission line are common in luminous
quasars. If they are formed in winds, how much energy, momentum and mass do those winds transport? We address this question by considering how much mass must be supplied through the line-forming region to maintain a given density and ionization state. Using a combination of 1D analytic and 2D numerical models, we find that for blueshifted C IV lines to form in a wind, the wind must have mass
outflow rates of $\sim 50 f_V$ times the
accretion rate, where $f_V \leq 1$ is the volume filling factor accounting for clumping. Our results therefore disfavour line formation in a smooth disc wind and point towards one of two scenarios: either the wind is clumpy, with required clumping factors suggestively close to those in hot
star winds; alternatively, if the mass is instead swept up from the ambient medium, the wind need not be clumpy and MHD and radiative winds can provide the original source of momentum and energy. The power of the
outflow depends on the square of the terminal velocity of the flow, $v_\infty$. If the wind is also the BAL
outflow, with $v_\infty \sim10,000~{\rm km~s}^{-1}$, the wind power is significant and important for feedback. There are various caveats which moderate our conclusions, motivating i) a better theoretical understanding of wind driving and clump formation physics and ii) improved observational constraints on the physical conditions where the lines are formed.
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Cosmology and Nongalactic Astrophysics
CosmoLattice 2.0
Jorge Baeza-Ballesteros, Daniel G. Figueroa, Adrien Florio et al. (+4 more)
This paper introduces $\tt {\mathcal C}osmo{\mathcal L}attice$ $\tt v2.0$, a major upgrade that substantially broadens the physical scope and computational capabilities of the code. It introduces
lattice implementations of scalar fields non-minimally coupled to
gravity through $\phi^2R$, as well as
axion-like fields coupled to Abelian gauge sectors as $\phi F_{\mu\nu}\widetilde F^{\mu\nu}$. It also provides new procedures for generating specialized initial conditions, including scaling networks of
cosmic defects ($\it e.g.$ strings and domain walls), and fields with arbitrary power spectra. The release also incorporates low-storage Runge-Kutta integrators for non-
symplectic systems (suitable $\it e.g.$ for non-minimal scalar kinetic terms as $\mathcal{G}_{ab}\partial_\mu\phi^a\partial^\mu\phi^b$), scalar-field simulations on reduced $(1+1)$- and $(2+1)$-dimensional
lattices, new optimized gravitational-wave
evolution, more flexible field and energy-density outputs, and GPU support that can accelerate simulations by a factor $\mathcal{O}(10)$ relative to CPU execution. Extensive documentation on the use of the code is provided on https://www.cosmolattice.com
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All authors Jorge Baeza-Ballesteros, Daniel G. Figueroa, Adrien Florio, Nicolás Loayza, Franz R. Sattler, Francisco Torrentí, Ander Urio
Astrophysics of Galaxies
The $\sigma_s^2-\mathcal{M}$ relation in the multi-phase ISM: Exploring the density PDF with the Cloud Factory simulations
Mairi Nonhebel, Rowan J. Smith and Ralf S. Klessen
The density probability distribution (PDF) of molecular clouds is a crucial component of analytical theories of
star formation. In idealised simulations of isothermal
turbulence, the width of the density PDF, $\sigma_s^2$, is dependent on the sonic Mach number of the medium, $\mathcal{M}$. The $\sigma_s^2-\mathcal{M}$ relation is widely used to connect cloud-scale
turbulence to the density PDF, and further to
star formation activity, yet its validity within individual phases of the multi-phase interstellar medium (ISM) remains untested. In this study, we evaluate whether the $\sigma_s^2-\mathcal{M}$ relation is applicable to individual phases of the ISM. We study the density PDFs of molecular cloud complexes in the Cloud Factory simulations; a suite of detailed zoom-in simulations that self-consistently generate a turbulent, multi-phase ISM. We test whether the $\sigma_s^2-\mathcal{M}$ relation holds in the hot ionised medium (HIM), warm ionised medium (WIM), warm neutral medium (WNM), cold neutral medium (CNM), the molecular phase, and the highly-shielded molecular phase traced by CO. We find the applicability of the classical $\sigma_s^2-\mathcal{M}$ relation to vary between phases and depend strongly on how $\sigma_s^2$ and $\mathcal{M}$ are measured. The relation fails to capture the widths of the WNM and CNM density distributions, with possible contributing factors including non-isothermality and large-scale coherent motions. In contrast, we find the $\sigma_s^2-\mathcal{M}$ relation to tentatively hold for the log-normal portion of the H$_2$ distribution. The width of the CO density PDF is systematically overpredicted by the classical relation, resulting from the selective nature of CO as a molecular gas tracer.
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High Energy Astrophysical Phenomena
A radio view on Gamma-Loud Protostars: Derivation of jet mechanical luminosity
Javier Méndez-Gallego, Carlos Carrasco-González, Rubén López-Coto et al. (+5 more)
Context. Gamma-Loud Protostars (GLPs) have been recently reported as
Galactic hadronic accelerators whose acceleration site is situated in their protostellar jets. Theoretical and observational analysis situate
radio cm luminosity as a thermal tracer of jet activity, presenting an unique opportunity to study jet properties as accelerators. Aims. We aim to develop a way to estimate the kinetic power of protostellar jets and compare their energetics with those extracted from the non-thermal gamma-ray side of GLPs. Methods. We combine theoretical and phenomenological relations to estimate the jet mechanical luminosity based on the
radio cm luminosity. We relate the resulting values to the non-thermal contribution of GLPs, studying its behaviour and efficiency. Results. The derivation of the jet power successfully reproduces infrared and
radio observations. The
cosmic-ray energy correlates to the injected mechanical energy, implying an acceleration efficiency of 1–10%. Future
radio observations are needed to find the definite accelerators and obtain reliable efficiencies.
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All authors Javier Méndez-Gallego, Carlos Carrasco-González, Rubén López-Coto, Iván Agudo, Stefano Menchiari, Rubén Fedriani, Emma de Oña Wilhelmi, Guillem Anglada
Astrophysics of Galaxies
Observational Tests of Sgr A*'s State of the Accretion Flow
F. Yusef-Zadeh, R. G. Arendt, H. Bushouse et al. (+4 more)
General relativistic magneto-hydrodynamic (GRMHD) simulations of the possibly magnetically arrested disk (MAD) of the
accretion flow of Sgr A* predict short and long time variability, lumpiness in the flow, strong
magnetic fields, reconnection driving flux eruptions and a jet aligned with its
spin angular momentum. We carried out simultaneous multi-wavelength observations with the objective of placing some constraints on these predictions. Our analysis supports most of the predictions of the MAD picture of the flow. It is not clear if there is evidence for a jet, but this could be the result of confusion in the complex region surrounding Sgr A*. Also, the geometry of the
magnetic fields, which accelerate particles to produce X-ray emission via inverse Compton Scattering (ICS), appears to be consistent with a hybrid state where the
accretion flow is represented by MAD-like
magnetic field strength and with Standard and Normal
Evolution-like (SANE-like)
magnetic field geometry.
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All authors F. Yusef-Zadeh, R. G. Arendt, H. Bushouse, C. J. Chandler, D. Kunneriath, S. M. Ressler, M. Wardle
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Fast, accurate, and differentiable: a neural-network surrogate for NRSur7dq4 precessing binary black hole waveforms
Michael Pürrer, Ashwin Girish, Lucy M. Thomas et al. (+2 more)
We present a neural network surrogate model that emulates the NRSur7dq4 gravitational waveform model for precessing binary black hole mergers. The surrogate decomposes the waveform into constituent quantities and trains an independent multilayer perceptron (MLP) for each. We validate the surrogate against NRSur7dq4 on 10,000 waveforms spanning its full parameter space ($1 \leq q \leq 4$, $|\chi_{A,B}| \leq 0.8$). For representative total masses between 60 and 300 $M_\odot$, median sky-averaged frequency-domain mismatches range from $8.0 \times 10^{-5}$ to $1.7 \times 10^{-4}$, with 95th percentiles below $10^{-3}$. On an NVIDIA L40S GPU the JAX surrogate evaluates a single waveform in about 1 ms end-to-end, roughly 10 times faster than the LALSimulation C implementation of NRSur7dq4, and sustains about 140 times the LALSimulation throughput at batch size 64, making it well suited for both low-latency parameter-estimation samplers and large-scale waveform generation. The full NRSur7dq4 NN waveform-to-likelihood pipeline is implemented in JAX and is differentiable. This is the first neural-network surrogate of a precessing numerical-relativity waveform model to combine validated NR-faithful accuracy with a fully differentiable, GPU-accelerated inference pipeline, enabling gradient-based inference approaches via automatic differentiation including Fisher information
matrices, GPU-accelerated nested sampling, gradient-based MCMC and importance sampling.
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All authors Michael Pürrer, Ashwin Girish, Lucy M. Thomas, Scott E. Field, Vijay Varma
Solar and Stellar Astrophysics
Empirical H- and K-band Limb Darkening for 31 CHARA Stars: A Near-Infrared Benchmark for Stellar-Atmosphere Models
Narsireddy Anugu, John D. Monnier, Antoine Mérand et al. (+9 more)
Limb darkening, the decrease in
stellar intensity from the disk center to the limb, encodes the temperature structure and opacity of
stellar atmospheres. Direct spatially resolved measurements of this center-to-limb variation remain scarce, especially in the near-infrared. We present interferometric limb-darkening measurements for 31
stars observed simultaneously in the $H$ and $K$ bands with the CHARA Array. The sample spans spectral types F–M and luminosity classes IV–I. The targets are well resolved in $H$ and, for most targets, also in $K$. This coverage constrains the visibility
curvature associated with limb darkening in joint $H+K$ fits. We fit the combined $H{+}K$ squared visibilities with four analytic limb-darkening laws and compare the resulting coefficients with bandpass-matched predictions from five
stellar-atmosphere grids (Kurucz, MPS1, MPS2, Stagger, and spherical SATLAS, with reported coefficients placed on the Rosseland-radius convention) spanning one-dimensional plane-parallel, three-dimensional radiation–hydrodynamic, and spherical low-
gravity models. The associated limb-darkened angular diameters are measured with median formal precisions of $\simeq 0.2$–0.3%. The CHARA results show expected weaker limb darkening at longer wavelengths and also with increasing $T_{\rm eff}$. The clearest discrepancy with the atmosphere grids is in the wavelength dependence: the median fractional decrease in the power-law coefficient from $H$ to $K$ is $\simeq 39\%$ in the CHARA sample, compared with only $\simeq 17$–$22\%$ with model predictions. Relative to the MPS2 comparison, the empirical coefficients are higher by $\simeq 21\%$ in $H$ and lower by $\simeq 5\%$ in $K$. These results provide multi-band interferometric limb darkening as a near-infrared
benchmark for
stellar-atmosphere models.
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All authors Narsireddy Anugu, John D. Monnier, Antoine Mérand, Becky Flores, Alexandre Gallenne, Douglas R. Gies, Mayra Gutierrez, Robert Klement, Stefan Kraus, Jayadev Rajagopal, Rachael M. Roettenbacher, Gail H. Schaefer
High Energy Astrophysical Phenomena
Simulation of combined radio and radar signals at the Radar Echo Telescope for Cosmic Rays
K. Nivedita, I. Loudon, J. Loonen et al. (+29 more)
To explore
neutrino astronomy at high energies (> 10 PeV), the Radar Echo
Telescope for
Cosmic Rays (RET-CR) was developed to assess the feasibility of a radar technique for detecting particle cascades in ice, serving as a precursor to the Radar Echo
Telescope for
Neutrinos (RET-N). The main concept of RET-CR is that, as a high-energy
cosmic-ray air-shower core propagates into the high-altitude ice sheet, a dense secondary-particle cascade is created, which is very similar to that of an in-ice high-energy
neutrino-induced cascade. At RET-CR, the expected signal consists of three distinct components:
radio emission from the in-air particle shower, Askaryan
radio emission from the secondary in-ice cascade, and the radar signal itself arising from the reflection of the transmitted
radio signal from the ionisation trail of the in-ice secondary cascade. In this work, we present the first combined simulation-based package and study aimed at characterising the combined
radio and radar signals at the in-ice receivers at RET-CR. We describe the simulation framework and provide a detailed discussion of the salient features of the
radio and radar signals, including their spatial footprints and temporal characteristics, as predicted for the shallow in-ice detectors.
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All authors K. Nivedita, I. Loudon, J. Loonen, P. Allison, J. J. Beatty, D. Z. Besson, A. Connolly, A. Cummings, C. Deaconu, S. de Kockere, K. D. de Vries, I. Esteban, D. Frikken, C. Hast, E. Huesca Santiago, C.-Y. Kuo, A. Kyriacou, U. A. Latif, V. Lukic, C. McLennan, K. Mulrey, J. Nam, S. Prohira, J. P. Ralston, M. F. H. Seikh, N. Shahid, R. S. Stanley, J. Stoffels, S. Toscano, D. van den Broeck, N. van Eijndhoven, S. Wissel
Astrophysics of Galaxies
Reaching the Metallicity Floor at $z\sim 10$: Lensed Star Clusters at Cosmic Dawn and Cosmic Noon
Raul Jimenez, Elena Tomasetti, Carmela Lardo et al. (+1 more)
Origins of globular clusters (GCs) are linked to the assembly of their host
galaxies. We analyze
star-cluster populations in two strongly lensed systems that bracket
Cosmic Dawn and
Cosmic Noon: the
Cosmic Gems arc (GEMS) at z=9.625, among the first
galaxies, and the Sparkler at z=1.378. New STARRED deconvolution photometry of GEMS provides SEDs for ten unique, doubly imaged cluster candidates, while a homogeneous
Bayesian analysis places both populations on a common cosmological timeline. The GEMS clusters formed at $z_{\rm form}\approx 10$–$11$ (median $\simeq10.2$), consistent with
halo assembly at or above the atomic-cooling scale. Their photometry requires low
metallicities: individual clusters are consistent with $[Z/{\rm H}] \lesssim -1.2$, and the data exclude $[Z/{\rm H}]\geq-0.5$, though they cannot distinguish reliably below $[Z/{\rm H}] \simeq -1.5$. This conclusion is unchanged when using
stellar-population models including binary
evolution—important for ultraviolet emission at this age—yielding similarly low
metallicities, $[Z/{\rm H}]=-2.2$ to $-2.7$. The formal estimate, $[Z/{\rm H}] = -2.3\pm0.3$, is consistent with the Milky Way GC
metallicity floor, though its value remains prior-dependent. The Sparkler clusters formed $\sim2.5$ Gyr later, at $z_{\rm form}\approx 2$–$3.5$ in a
Cosmic Noon
dwarf galaxy, and are more enriched ($[Z/{\rm H}] \approx -0.5$). Comparison with Milky Way GCs places GEMS in an exceptionally early, metal-poor regime and the Sparkler among later, more enriched populations, though neither association uniquely determines an in-situ or ex-situ origin. Closed-box and gas-regulator calculations show both systems are compatible with limited pre-enrichment followed by rapid enrichment and
accretion-regulated growth. Together, they probe distinct cluster-forming environments from
Cosmic Dawn to
Cosmic Noon.
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All authors Raul Jimenez, Elena Tomasetti, Carmela Lardo, Licia Verde
High Energy Astrophysical Phenomena
Gravitational Wave Modeling of White-Dwarf–Compact-Object Binaries and Observational Outlook
Tristan S. Weaver, David Radice, Donghui Jeong et al. (+1 more)
We investigate the end stages of circular white-
dwarf–compact-object binaries by developing a novel integrator implementing mass transfer and 2.5-order Post-Newtonian kinematics. White-
dwarf–compact-object binaries are subject to two phases: a slow inspiral during which binary
evolution is dominated by weak-
gravity radiation reaction and a quicker “outspiral" dominated by mass transfer. These systems have unique gravitational waveforms with several characteristic features including an accumulation of signal near the maximum cutoff frequency set by the transition between in- and outspiral. We investigate trends in gravitational wave parameters based on component masses. In particular, maximum cutoff frequency depends strongly on white
dwarf mass and compactness. It is unlikely that extragalactic binaries will be measured by LISA or current or future terrestrial detectors. However, white-
dwarf–compact-object binary end stages will be an important source for future decihertz detectors such as DECIGO and LGWA: The final inspiral of tens of white-
dwarf–
neutron-
star binaries will be detected annually by LGWA, and millions of inspirals along with thousands of outspirals will be detected by DECIGO. The ultimate fates of these binaries are diverse and dependent upon the intricacies of angular momentum loss. In particular, we show that white
dwarfs with partners of sufficiently low/high mass can end their lives in common envelopes/mergers, while white
dwarfs do not enter contact with partners of intermediate mass. The highest frequencies produced by white-
dwarf–compact-object binaries in our tests are 10–20 Hz—incapable of mimicking sub-
solar-mass compact object signals in terrestrial detectors or explaining S251112cm-like signals.
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All authors Tristan S. Weaver, David Radice, Donghui Jeong, Victor Liu
Solar and Stellar Astrophysics
A Test of FeH Line Parameters using DR19 APOGEE spectra of Benchmark M Dwarfs
Anderson Silva-Andrade, Diogo Souto, Katia Cunha et al. (+9 more)
Recent studies have suggested a mismatch of up to 0.20 dex between iron abundances derived from Fe I and FeH lines in the H-band spectra of M
dwarfs, and in this work we investigate the nature of this possible offset. We analyze near-infrared H-band APOGEE spectra of
stars in 18 binaries composed of a G-
dwarf primary and an M-
dwarf secondary, together with four M-
dwarf stars having measured angular diameters from the literature, and six M-
dwarf members of the Hyades and Coma Berenices open clusters. These three families of
benchmarks were used to evaluate the FeH line list and check for possible systematic uncertainties in the FeH $gf$-values. Our tests used 1-D LTE plane-parallel model atmospheres, a radiative transfer code, and the baseline APOGEE spectral line list to derive
metallicities for the binary G-
dwarf primaries using Fe I lines, while
stellar parameters and
metallicities for the M
dwarfs used both FeH and Fe I lines. The mean
metallicity obtained for the Hyades M-
dwarfs was $\langle$[Fe/H]$\rangle$=+0.08$\pm$0.04, and for Coma Berenices $\langle$[Fe/H]$\rangle$=+0.02$\pm$0.08. The
metallicities of the G- and M-
dwarfs in binary systems showed excellent agreement (0.06 dex), and the mean
metallicities for the open clusters were also consistent with literature values from high-resolution optical analyses. We investigated the consistency between the spectroscopic and interferometric $T_{\rm eff}$ scales, finding agreement within the uncertainties. Forcing full agreement between the spectroscopic and interferometric $T_{\rm eff}$ scales resulted in a poorer match for the
metallicities in the binaries and the open clusters. We conclude that the best overall concordance is obtained when no adjustments are made to the FeH $gf$-values, which are based on the Hargreaves et al. (2010) line list.
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All authors Anderson Silva-Andrade, Diogo Souto, Katia Cunha, Verne V. Smith, Carlos Allende Prieto, Ricardo P. Schiavon, Verónica Loaiza-Tacuri, Aida Behmard, Dmitry Bizyaev, Ilija Medan, Dan Qiu, Bárbara Rojas-Ayala
Astrophysics of Galaxies · Cross-listed from cs.LG
Multiclass Classification without Labels via Posterior Simplex Geometry
Raphaël Bonnet-Guerrini, Johann Ioannou-Nikolaides, Troels Petersen et al. (+1 more)
In many classification problems, reliable instance-level labels are unavailable. However, it is often possible to construct weakly enriched unlabeled samples:
datasets selected by different cuts, sources, populations, or experimental conditions that change latent class proportions without revealing them. Classification without Labels (CWoLa) shows that, in the binary case ($K=2$), a classifier trained to distinguish two impure mixtures with different class proportions can recover an optimal class discriminator without knowing the mixture proportions. We extend this principle to multiclass learning from several unlabeled mixtures ($K>2$), where the learner observes only mixture identity and neither latent class labels nor class-prior
matrices. We prove that, for a multiclass mixture model, the Bayes-optimal mixture classifier $g^\star$ maps data points into a $(K-1)$-simplex embedded in mixture-posterior space. The $K$ vertices of this simplex are induced by the latent classes through the unknown mixing
matrix. Leveraging this geometry, we propose prior-free procedures that train a standard classifier to distinguish mixture identities and then extract latent class structure using either post-hoc simplex fitting or a bottleneck architecture. Experiments on MNIST, CIFAR-10, and
Galaxy10 DECaLS show that mixture identity alone can recover latent classes and their fractions in the mixture. By narrowing the gap between weakly supervised and fully supervised performance, we provide a mathematically grounded, scalable tool for multiclass discovery in label-scarce domains.
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All authors Raphaël Bonnet-Guerrini, Johann Ioannou-Nikolaides, Troels Petersen, Vincenzo Piuri
Solar and Stellar Astrophysics
Investigating the Observational Progenitor Mass Gap in the White Dwarf Initial-Final Mass Relation. I. Cluster Census and Characterization of the First White Dwarfs in the Gap
David R. Miller, Jeremy Heyl and Pier-Emmanuel Tremblay
In recent years,
Gaia has been the primary driver of the expansion of the white
dwarf (WD) initial-final mass relation (IFMR) in open clusters. The increased sample size has highlighted a pronounced observational gap at progenitor masses of $\simeq2$–$2.7\,M_\odot$, with no spectroscopically confirmed cluster-member WDs in this range. Analysis of the Milky Way open cluster census shows that this absence is primarily driven by the scarcity of appropriately aged, nearby clusters capable of hosting
Gaia-detectable WDs, implying that deeper, targeted photometry will be required to build a substantial sample in this progenitor mass range. We further searched for previously unexamined
Gaia WD candidates in clusters with ages consistent with producing gap progenitors and identified two viable targets, which we observed spectroscopically with Gemini GMOS-N. Both targets yield inferred progenitor masses within the observational gap, making them the first spectroscopically confirmed cluster-member WDs in this progenitor mass range. The NGC 6991 candidate, in particular, is confirmed as a DA WD with an inferred progenitor mass of $2.12^{+0.04}_{-0.15}\,M_\odot$, providing further support for a non-monotonic trend in the IFMR.
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Cosmology and Nongalactic Astrophysics
EFT-Ramses: a code to simulate the effective field theory of dark energy
Nathaniel Ota Woodcock, Sownak Bose, Yunhao Gao et al. (+1 more)
While the standard $\Lambda$CDM paradigm is in excellent agreement with most current cosmological observations, theoretical challenges surrounding the cosmological constant ($\Lambda$) have strongly motivated the exploration of dynamical dark energy (DE) and modified
gravity (MG) models. Investigating the physical nature of the
cosmic acceleration requires N-body simulations to probe the non-linear growth of
cosmic structure and prepare for the high-precision data from Stage-IV surveys. In this paper, we present EFT-RAMSES, a comprehensive extension of the ECOSMOG cosmological simulation code designed to explore non-linear structure formation in DE and MG scenarios. We embed the effective field theory of dark energy (EFTofDE) framework into this new numerical pipeline, utilising the $\alpha$-basis parameterisation to provide a versatile, model-agnostic, computational engine. By consolidating diverse scalar and vector-tensor theories—including the normal and self-accelerating Dvali-Gabadadze-Porrati (DGP) models, cubic Galileons (cubic scalar Galileon (csG), cubic vector Galileon (cvG) and generalised cubic covariant Galileon (GCCG)), and generic effective field theory (EFT) parameterisation—into a single "master" Vainshtein equation, this pipeline bypasses the need for model-specific solvers and easily specialises to any particular model. As validations, we perform high-resolution N-body simulations for the normal-branch DGP (nDGP), csG, GCCG, and EFT models, comparing the resulting matter power spectra against dependent and independent codes such as legacy ECOSMOG and HiCOLA, as well as linear theory, and find excellent agreement. EFT-RAMSES provides a robust and versatile computational tool for precision cosmological tests of DE and MG using upcoming cosmological surveys. The code is available for download from the GitHub EFT-RAMSES repository.
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All authors Nathaniel Ota Woodcock, Sownak Bose, Yunhao Gao, Baojiu Li
Cosmology and Nongalactic Astrophysics
Primordial Physics in the Nonlinear Universe: Revealing the oscillating halo bias from cosmological collider models
Dhayaa Anbajagane and Neal Dalal
The initial conditions of our Universe contain a wealth of information about the particle physics of very high energies. One such class of signatures, called cosmological
colliders, generates oscillations in the three-point correlations (or bispectra) of the
primordial density field, and these imprint scale-dependent oscillations in the
halo bias. We develop a new method for simulating cosmological
collider models that foregoes traditional template-based basis-decomposition methods and can reproduce the scale-dependent signals of the input template at percent-level accuracy. Using this method, we produce simulations for one class of
collider models and present the first measurements of oscillating
halo bias in simulations. The amplitude and phase of the oscillations show a clear dependence on
halo mass, with a factor of ten shift in
halo mass causing a factor of two shift in the location of the oscillations. Increasing the frequency of the
primordial bispectra model suppresses the signal in the
halo bias, as the oscillations average down over the window function of the
halo. The phase of the signal is also sensitive to assembly bias. In all cases, the scale-dependent
halo bias can be accurately modeled using a simple peak background-split theory. The oscillations and their mass/selection-dependent phase offsets are a unique signature that is not easily mimicked by known observational systematics and is therefore a more robust target. Our simulations and underlying initial conditions code are both made publicly available.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Tidal deformation of an accreting compact object
Avijit Chowdhury, Chiranjeeb Singha, Kazuharu Bamba et al. (+1 more)
Tidal deformation of a compact object serves as a sensitive probe of the strong-
gravity regime and nature of the compact object. It captures how a compact object responds to the external perturbing field of a companion. In realistic astrophysical settings, compact objects are typically immersed in matter-rich environments, which can significantly alter the response. In this work, we investigate the static deformability of Schwarzschild-like exotic compact objects (ECOs) embedded in a quasi-stationary, self-gravitating thin
accretion disk. By modelling the external spacetime with a relativistic thin-disk solution, we isolate environmental contributions to the scalar and
spin-1 response while maintaining analytical control. We show that, for perfectly reflecting ECOs, the characteristic logarithmic dependence of the scalar and
spin-1 response on compactness, set by near-horizon physics, remains intact even in the presence of
accretion. The disk primarily amplifies the overall magnitude of the response significantly. These findings highlight that environmental effects can seriously impact
tidal signatures, while still permitting, under suitable conditions, the distinguishability of horizonless compact objects from black holes in gravitational-wave observations.
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All authors Avijit Chowdhury, Chiranjeeb Singha, Kazuharu Bamba, Sumanta Chakraborty
Astrophysics of Galaxies
Using Scattered Near-Infrared Light to Map Water Ice in Prestellar Cores with SPHEREx
Tamojeet Roychowdhury, Jennifer B. Bergner, Jens Kauffmann et al. (+2 more)
We present the first coreshine-derived, spatially-resolved maps of the 3 $\mu$m H$_2$O ice absorption feature in four prestellar cores, using SPHEREx spectra. Ices are a key component of dense cores in molecular clouds, playing a central role in the chemistry of
planet formation around young
stars. However, spatially resolved abundance studies remain limited, typically relying on unevenly distributed background
star sightlines. Here, we take advantage of the all-sky spectrophotometric capabilities of SPHEREx to construct ice absorption maps with uniform spatial resolution using the illumination of dense cores by scattered
Galactic radiation, or coreshine. To demonstrate proof of concept, we analyse the spatially varying H$_2$O ice absorption in four nearby (~140 pc) prestellar cores - L1544, CrA 151, L260 and L1512. Two cores follow the expected spatial trend of ice absorption peaking at the centre, but the two densest cores show a surprising drop in observed ice absorption in the innermost regions. To interpret the absorption maps, we construct analytical and simulated models of a Bonnor-Ebert sphere illuminated by scattering. We study the effects of different
geometric configurations, ice mass fractions, and spatial differences in ice composition. None of these can explain the reduced central absorption, pointing to an unexplained physical or chemical effect operating in the densest prestellar regions. Our simulations further show that spectra derived from coreshine provide a robust tracer of spatially varying ice density and composition, establishing SPHEREx scattered-light spectroscopy as a powerful new probe of ice in dense cores.
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All authors Tamojeet Roychowdhury, Jennifer B. Bergner, Jens Kauffmann, Thushara G.S. Pillai, Silvia Spezzano
Astrophysics of Galaxies
S301 and friends: Measuring the spin of Sgr A*
T. Piran, P. Amaro-Seoane, B. Aytac et al. (+15 more)
The discovery of S301 (
GRAVITY Collaboration et al., 2026) with pericenter distance rp= 280rg and eccentricity e=0.9825, opens the prospect of measuring the
spin parameter of Sgr A* through Lense–Thirring (LT) nodal precession. A major obstacle is Newtonian confusion: any non-spherical extended mass distribution can also induce nodal precession. We aim to separate the LT
spin signal of S301 from the Newtonian nodal precession. We compare the secular Newtonian torque exerted by a disk or flattened mass distribution on the orbits of S301 and of the apocenter-matched reference
stars S2, S55, and S38, using analytic estimates validated by numerical orbit-averaged torque calculations. For a disk or flattened distribution extending beyond the
stellar pericenters, the secular Newtonian torque on a highly eccentric orbit is controlled mainly by the apocenter, whereas the LT signal is controlled mainly by the pericenter. Thus
stars with apocenters comparable to S301's but much larger pericenters, in particular S2, but also S55, and S38, experience comparable Newtonian torques while having ~ 30 times smaller LT signals (for S2). Their measured precessions, or upper limits on them, can therefore calibrate the mass and orientation of the Newtonian background for subtraction from S301's precession. The Schwarzschild apsidal advance of S301 further rotates the orbit's pericenter relative to any disk, producing a systematic time dependence in the Newtonian contribution, while the LT signal remains fixed by the
spin vector. Granularity of the perturber population sets a
stochastic floor on this subtraction, which orbit- and
star-averaging suppress. With continued
GRAVITY+ astrometry and Extremely Large
Telescope (ELT) spectroscopy, the in-plane
spin projection may be within near-term reach; the full
spin vector requires a much longer-term accumulation of the LT apsidal signal.
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All authors T. Piran, P. Amaro-Seoane, B. Aytac, G. Bourdarot, A. Burkert, D. Calderon, J. Cuadra, F. Eisenhauer, R. Genzel, S. Gillessen, S. Joharle, F. Mang, T. Naab, T. Ott, H.B. Perets, D.C. Ribeiro, M. Sadun Bordoni, R. Sari
Astrophysics of Galaxies
Observational Evidence for Anisotropic Metal Excess around Galaxies
Cheqiu Lyu, Enci Wang, Zeyu Chen et al. (+4 more)
The exchange of matter and energy between
galaxies and their surroundings drives the
cosmic baryon cycle, yet mapping metal transport remains an observational challenge. While simulations predict that
galactic winds escape anisotropically along minor axes, evidence for chemical enrichment in neighboring
galaxies is limited. We analyze 1,433
galaxy pairs from the Dark Energy Spectroscopic Instrument survey and detect a gas-phase
metallicity excess of 14.6% $\pm$ 3.7% to 24.2% $\pm$ 2.6% in neighbors aligned with the minor axis of massive primary at projected separations of 15–60 kpc, qualitatively consistent with IllustrisTNG simulation. Permutation tests indicate that this excess varies from a marginal detection ($>$92% confidence) at closer separations (15–30 kpc) to a significant signal ($>$98% confidence) at intermediate separations (30–60 kpc). Here, we show that these results provide empirical constraints on
galactic feedback models and are consistent with a scenario where anisotropic
outflows can enrich nearby
galaxies, a mechanism that complements other environmental processes.
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All authors Cheqiu Lyu, Enci Wang, Zeyu Chen, Chengyu Ma, Yangyao Chen, Haoran Yu, Xu Kong
Solar and Stellar Astrophysics
Syntriod: A Robust Initial Parameter Estimator for Radial Velocity Curve Solutions Beyond Conventional Sampling Limits
Emre Barbaros, Hasan Ak and N. Filiz Ak
We present Syntriod, an orbital-phase domain radial velocity (RV) template-based
algorithm designed to provide robust initial orbital parameter estimates for spectroscopic binaries across diverse observational sampling conditions. Rather than performing full orbital inference, Syntriod constrains the parameter space with physically consistent solutions to guide subsequent optimization procedures. We evaluate its performance using 10,000 synthetic Keplerian orbits spanning diverse configurations and sampling regimes. For well-sampled
datasets ($N_{obs} \ge 8$), Syntriod recovers orbital periods with relative accuracies of order $10^{-3}$. At the theoretical sampling limit ($N_{obs} = 6$), the method maintains a ~94% success rate, while classical period-search techniques like Lomb-Scargle become increasingly affected by aliasing. Even below this limit ($N_{obs} = 5$), Syntriod recovers the correct orbital solution in ~83% of cases, showing gradual degradation rather than catastrophic failure. We further evaluate the method on 12 real spectroscopic binary systems (HD 160934, Phi Cyg, Capella A, Kepler 16, KIC 3858884, KIC 6867766, KIC 2445134, KIC 3003991, DU Boo, HL Dra, FP Boo, and AK Her) spanning broad orbital periods and eccentricities. Syntriod consistently reproduces literature solutions even when
datasets are randomly subsampled to sparse regimes. Where a full Keplerian solution becomes underconstrained ($N_{obs} \le 4$), the
algorithm transitions to linear dynamical relations, recovering parameters such as mass ratio ($q$) and systemic velocity ($\gamma$) with success rates exceeding 99%. These results demonstrate that Syntriod provides reliable, computationally efficient initial parameter estimates across well-sampled and sparse regimes, making it a practical pre-solver for modern orbit-fitting pipelines and large spectroscopic surveys.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing long-range $L_e-L_\mu$ forces with supernova neutronization burst neutrinos
Amol Dighe, Sadashiv Sahoo and Manibrata Sen
Ultralight gauge
bosons associated with flavour-dependent leptonic
symmetries generate long-range potentials that can modify
neutrino flavour
evolution over astrophysical distances. We investigate the sensitivity of neutronization-burst
neutrinos from core-collapse
supernovae for such interactions in the anomaly-free $U(1)'_{L_e-L_\mu}$ framework. Incorporating the long-range potential into
supernova neutrino oscillations, we simulate the corresponding signal in the Deep Underground
Neutrino Experiment (DUNE) using a realistic detector response of its 40 kt
Liquid Argon Time Projection Chamber. We show that in the range where the long-range potential dominates over or is comparable to the
vacuum oscillation term, the electron-
neutrino survival probability can be significantly modified. This would produce observable distortions in the time and energy distributions of the neutronization burst
neutrino spectra. Our results demonstrate that future observations of
galactic supernova neutrinos, particularly from a nearby event such as Betelgeuse, can provide a sensitive and complementary probe of flavour-dependent long-range leptonic interactions.
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Cosmology and Nongalactic Astrophysics
Interlopers as Signal in Line Intensity Mapping
Anirban Roy
Line intensity mapping measures the combined emission of atomic and molecular lines from unresolved
galaxies, offering a way to map
cosmic structure across enormous volumes. A single observed frequency, however, contains emission from several spectral lines at different
redshifts. These interlopers are usually removed before cosmological inference. We show that this removal is not always optimal. Once the possible emitting lines and their
redshifts are included in the model, interlopers become additional tracers of large-scale structure at other epochs, projected into the coordinate system of the target line. We formulate interloper treatment as a Fisher decision problem, requiring both improved precision and parameter bias below a chosen tolerance. In SPHEREx forecasts for H$\alpha$ with [O III], H$\beta$, and [O II] interlopers, and in FYST forecasts for [C II] with CO interlopers, $\Omega_m h^2$ and
baryon acoustic oscillation (BAO) distance measurements are comparatively robust to astrophysical calibration errors, whereas the clustering amplitude $\sigma_8$ and the dark energy parameters $w_0$ and $w_a$ are more sensitive to the adopted line model and priors. The BAO distance measurement gives a simple physical picture: modeling interlopers turns two observed bands into a transverse BAO distance ladder over $0.7\lesssim z\lesssim5.8$. Interlopers are therefore not only contaminants to remove, but a calibrated component of the cosmological signal model for future LIM surveys.
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Cosmology and Nongalactic Astrophysics
Correlated signals of ultralight scalar dark matter in pulsar timing
Joshua W. Foster, Kimberly K. Boddy, Jeff A. Dror et al. (+5 more)
Pulsar timing arrays (PTAs) are sensitive to ultralight dark matter (ULDM) in the $10^{-24}$-$10^{-20}\,\mathrm{eV}$ mass range, with existing
datasets already probing otherwise open parameter space and future PTAs promising substantial improvements in reach. Thus far, however, PTA searches for ULDM have typically been formulated using limiting descriptions. Analyses are performed in either the fully correlated limit, in which the local ULDM amplitude is shared across the array, or the fully uncorrelated limit, in which each
pulsar has an independent local amplitude. Because the transition between these regimes occurs within the PTA-sensitive mass range, projected sensitivities and data-derived constraints can depend on which limiting description is assumed. For the first time, we develop a self-consistent analysis that treats the ULDM field as a Gaussian random field with finite spatial correlations, allowing the amplitude prior used in PTA signal models to interpolate continuously between the fully correlated and fully uncorrelated limits. We apply the framework to both linearly and quadratically coupled scalar ULDM, the latter including the universal gravitational signal sourced by the oscillating ULDM pressure.
Pulsar-distance uncertainties are incorporated through an augmented latent-field prior, and the resulting distance-marginalized latent-amplitude distribution is represented with a normalizing-flow surrogate. We validate the method on mock PTA
datasets, including blinded signal injection tests.
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All authors Joshua W. Foster, Kimberly K. Boddy, Jeff A. Dror, Vincent S.H. Lee, Andrea Mitridate, Tristan L. Smith, Kelsie Taylor, Tanner Trickle
Astrophysics of Galaxies
Vigorous turbulence driven by quasar-mode feedback in a cluster core
Satoshi Yamada, Shutaro Ueda, Hirofumi Noda et al. (+9 more)
Quasars are among the most luminous objects. They are powered by
accretion onto supermassive black holes. They are thought to impact cosmological
evolution primarily through energetic winds, known as
quasar-mode feedback, yet the efficiency and spatial extent of this process remain poorly constrained. Here we present X-Ray Imaging and Spectroscopy Mission (XRISM) observations of H1821+643—the nearest
galaxy cluster with a central
quasar (
redshift z = 0.297)—which was a rare opportunity to directly probe
quasar-mode feedback in the intracluster medium. High-resolution spectroscopy reveals exceptionally broadened Fe XXV emission lines from the intracluster medium, with a velocity dispersion of approximately 300 km/s, far exceeding values observed in nearby cluster cores. These lines originate predominantly at radii of 20-100 kpc from the centre. Assuming that
turbulence from a
quasar-driven shock led to the broadening of the lines, the energy injected by the
quasar beyond
galactic scales ($\gtrsim$20 kpc) is estimated to be $\gtrsim$1-10% of its radiative energy. Notably, this feedback efficiency exceeds previous multiwavelength estimates by orders of magnitude ($\lesssim$0.01%) and reaches the levels required by the latest cosmological hydrodynamical simulations. This finding of vigorous
turbulence indicates that
quasar-mode feedback plays a central role in regulating
galaxy and cluster
evolution at high
redshift.
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All authors Satoshi Yamada, Shutaro Ueda, Hirofumi Noda, Yutaka Fujita, Misaki Mizumoto, Kentaro Nagamine, Claudio Ricci, Shoji Ogawa, Taiki Kawamuro, Shinya Yamada, Yuichi Terashima, Yoshihiro Ueda
Cosmology and Nongalactic Astrophysics
Cosmological evolution with decaying dark matter: an integral-equation approach
Nanoom Lee, Anna Bencke, Marc Kamionkowski et al. (+1 more)
We present CLASSIER-DDM, an extension of the Boltzmann solver CLASSIER that implements the decaying dark matter (DDM) model via its integral-equation approach. The code handles generic two-body decays of a dark matter particle into two lighter decay products with arbitrary masses, naturally encompassing both massless (dark radiation) and massive (warm) decay products, with their perturbations evaluated via integral equations solved iteratively. We describe the numerical implementation in detail, including the background
evolution, the iterative perturbation
evolution, and a small-scale analytic approximation. A modest number of iterations is sufficient to achieve sub-$0.1\%$ convergence in the matter power spectrum and the CMB
lensing power spectrum across the observationally relevant parameter space. We find that a hundred momentum bins for the decay product perturbations are sufficient to achieve $\mathcal{O}(0.1\%)$ accuracy in the matter power spectrum today up to $k \sim 3\,{\rm Mpc}^{-1}$. The code achieves $\mathcal{O}(1\,{\rm min})$ runtimes per evaluation, requiring neither a Boltzmann hierarchy nor any fluid approximation, making parameter estimation with the DDM model numerically tractable. We also discuss the impact of DDM on cosmological observables, focusing on the case of two massive decay products. This work further establishes the integral-equation approach as a versatile and efficient framework for modeling non-cold relics in cosmological perturbation theory.
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All authors Nanoom Lee, Anna Bencke, Marc Kamionkowski, José Luis Bernal
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-lat
TempLat: a versatile C++ engine for lattice field theories
Adrien Florio and Franz R. Sattler
We present TempLat, a C++ framework for
lattice field theory simulations in arbitrary dimensions. Its symbolic
language, built on expression templates, translates mathematical expressions almost verbatim into C++ while compiling to highly optimized kernels, in contexts ranging from classical-statistical to Monte Carlo simulations. TempLat is performance-portable: building on Kokkos, it supports large CPU clusters, as well as NVIDIA and AMD GPUs. Its abstraction of hardware into a device concept makes TempLat extensible to future architectures. We demonstrate excellent strong and weak scaling on both CPUs and GPUs. We also present ParaFaFT, a standalone parallel discrete
Fourier transform library supporting arbitrary dimensions on all of the above hardware, and
benchmark its scaling. Both are open source and available on GitHub, and power a new release of CosmoLattice, a widely used early-universe simulation library now available on GPUs.
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Astrophysics of Galaxies
CHORD HI-Galaxy Survey Forecasts: Searching for nearby dark galaxies and high redshift giants
Akanksha Bij, Kristine Spekkens, Hans S. Hopkins et al. (+6 more)
Population studies of gas-rich
galaxies across the full range of Neutral Hydrogen (HI) masses that
galaxies are known to exhibit ($10^5 \lesssim M_{\mathrm{HI}} \lesssim 10^{11} M_{\odot}$) remain limited by the need to conduct high-sensitivity, wide-band surveys across significant sky areas. The Canadian Hydrogen Observatory and
Radio-transient Detector (CHORD) is a next-generation
radio telescope that will significantly expand the census of HI-
galaxies to date from untargeted drift-scan surveys at declinations $+20^{\circ} < \delta < +80^{\circ}$. We draw survey realizations from a known HI mass function (HIMF) to forecast HI detections in fiducial 1-year and 5-year CHORD surveys. The 5-year survey source counts is expected exceed currently available catalogs by roughly an order of magnitude, notwithstanding the potential impacts of
radio frequency interference (RFI) and spectroscopic source confusion that we also estimate. We predict that CHORD will push the low-mass HI
galaxy census to $M_{\mathrm{HI}} \sim 10^{5.5} M_{\odot}$, over an order of magnitude lower than has been previously achieved. At the high mass end of the HIMF, CHORD is expected to detect $\sim10^{3}$ massive gas-rich
giants ($M_{\mathrm{HI}} \gtrsim 10^{10.5}\, M_{\odot}$) at $0.3 \lesssim z \lesssim 0.5$, which will explore the
evolution of this population relative to local universe estimates. CHORD HI surveys will therefore improve our understanding of the neutral gas reservoirs at the low-mass and high-mass extremes of the
galaxy population.
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All authors Akanksha Bij, Kristine Spekkens, Hans S. Hopkins, Michael G. Jones, Arnab Chakraborty, Simon Foreman, Alex S. Hill, Dustin Lang, Adrian Liu
Earth and Planetary Astrophysics
Disk-averaged spectrum generation for spherically symmetric planets and moons
Nicholas A. Teanby
Here I present a simple and efficient method for generating a disk-averaged planetary spectrum. The technique uses a weighted average of component spectra generated on an irregular grid of offsets from the
planet center. This accounts for variations in center to limb brightness and emission from beyond the limb, which is important for bodies with extended atmospheres such as Saturn's moon Titan. The method assumes spherically symmetric emission and requires a grid of component spectra fine enough to faithfully capture radial radiance variations. An example application to Titan's 7.7 $\mu$m methane emission demonstrates the method.
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Cosmology and Nongalactic Astrophysics
Measuring Cosmic Neutrino Masses Independently of Dark Energy
Frank J. Qu, Fei Ge, Hanyue Wang et al. (+4 more)
Neutrino oscillations establish that
neutrinos are massive, providing the only laboratory detection of physics beyond the Standard Model. Direct kinematic experiments bound the electron-
neutrino mass to $m_{\nu_e} < 0.45$ eV (KATRIN, 90% CL), implying $\sum m_\nu \lesssim 1.3$ eV. Conversely, cosmology within $\Lambda$CDM is highly constraining: Planck CMB, CMB
lensing, and DESI DR2 BAO yield $\sum m_\nu < 0.056$ eV (95% CL), in 2-3$\sigma$ tension with the inverted-ordering floor (0.10 eV). However, this bound relies on $\Lambda$CDM, while data hint at an evolving dark energy. To determine the model dependence of
cosmic neutrino mass bounds, we deconstruct each probe's sensitivity to late-time physics and pursue two robust routes to a $\sum m_\nu$ bound: (i) The existing dark-energy-marginalized route, retaining all data and marginalizing over $(w_0, w_a)$, is shown to also be immune to flexible binned and cubic $w(a)$ histories, yielding $\sum m_\nu < 0.152$ eV, sharpening to $\sigma(\sum m_\nu) \approx 0.043$ eV with Simons Observatory
lensing and Spec-S5 BAO. (ii) A new late-Universe-free route combines primary CMB, marginalizing over acoustic-peak smoothing via $A_{\rm lens}$, with the reconstructed
lensing spectrum $C_L^{\kappa\kappa}$, removing late-time expansion dependence by construction. This yields $\sum m_\nu < 0.41$ eV today, tightening to 0.31 eV (Simons Observatory) and 0.28 eV (
cosmic-variance limit) across all tested dark-energy models. These relaxed bounds trade statistical power for model independence. Interestingly, they land in the sensitivity range targeted by next-generation laboratory experiments like Project 8 ($m_{\nu_e} \sim 0.1$ eV), motivating vital synergies between future cosmological and terrestrial
neutrino measurements.
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All authors Frank J. Qu, Fei Ge, Hanyue Wang, Emmanuel Schaan, W.L. Kimmy Wu, Alexander Friedland, Blake D. Sherwin