Astrophysics of Galaxies
Single Parameter Model for Galaxy Rotation Curves
Sophia N. Cisneros, Rich Ott, Meagan Crowley et al. (+2 more)
One key piece of evidence for dark matter is the rotation-curve problem: the disagreement between measured
galactic rotation curves and their luminous mass. A novel solution to this problem is presented here, in a model that predicts observed Doppler-shifted spectra based only on the luminous matter estimates and one free model parameter. This model is applied to fit the rotation curves of the SPARC sample of 175
galaxies, yielding mass-to-light ratios, goodness of fit measurements, and the free parameter. The model's average reduced chi square compares favorably with the dark matter model for the same data, and more
galaxies are successfully fit by this model. The model provides a useful formulation linking luminous matter to the observed rotation curves, with the dark matter contribution to
galaxies encoded in two transformation terms of the luminous mass. It also offers a lower-parameter characterization of the rotation curve problem, and a power law relationship between the model's free parameter and
galactic photometric quantities is observed, potentially removing the need for the free parameter.
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All authors Sophia N. Cisneros, Rich Ott, Meagan Crowley, Amy Roberts, Marcus Paz
Cosmology and Nongalactic Astrophysics
Discovery of a nearby radio relic in the low-mass, merging cluster Abell 4067
Isaac Magolego, Roger P. Deane, Kshitij Thorat et al. (+9 more)
Shock waves generated during cluster mergers offer a powerful probe of how large-scale structure grows and evolves in the Universe. As part of the MeerKAT-South Pole
Telescope (SPT) survey, we report the discovery of a single arc-like
radio relic in the
galaxy cluster Abell 4067 ($z=0.099$), one of the lowest-mass clusters known to host such a structure. MeerKAT UHF-band (0.58–1.09 GHz) observations reveal a relic with a largest linear size of $\sim 1.48 \pm 0.02$ Mpc, located at a projected distance of 0.95 Mpc from the cluster centre. XMM-Newton X-ray data show that the relic's position and orientation relative to the intracluster medium (ICM) elongation are consistent with a merger-driven shock-wave scenario. The relic has an estimated
radio power of $3.10 \pm 0.03 \times 10^{24}$ W Hz$^{-1}$ at 150 MHz. When placed in the $P_{150\,\mathrm{MHz}}$–$M_{500}$ scaling relation, the Abell 4067 relic appears less luminous compared to relics in more massive clusters, suggesting an association with weak merger shocks. This finding supports the idea that relics in low-mass clusters may form through less energetic merger events, leading to weak merger shocks. This is further supported by the absence of a detectable central
radio halo in Abell 4067, reinforcing the idea that luminous
radio halos are not a universal outcome of cluster mergers and highlighting the role of cluster mass, merger energetics, and evolutionary stage in shaping diffuse
radio emission in the intracluster medium.
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All authors Isaac Magolego, Roger P. Deane, Kshitij Thorat, Ian Heywood, Justin Spilker, Taweewat Somboonpanyakul, Dazhi Zhou, Manuel Aravena, Joaquin D. Vieira, Kedar A. Phadke, Lindsey E. Bleem, Scott C. Chapman
Astrophysics of Galaxies
Forecasting the cross correlation of Terahertz Intensity Mapper [CII] line intensity maps with Euclid galaxies
Justin S. Bracks, Ryan P. Keenan, Shubh Agrawal et al. (+24 more)
We forecast that the Terahertz Intensity Mapper (TIM) cross-correlated with Euclid's Fornax deep field (EDF-F), TIM$\times$EDF-F, will detect the [CII]-
galaxy cross-power spectrum at a median
redshift of 1.1 with $\gtrsim 7 \sigma$ confidence. The Poisson component of the cross-power spectrum at $0.1 \leq k \leq 10$ hMpc$^{-1}$ (i.e. cross-shot noise) will be detected at $\gtrsim 3 \sigma$ in 4 bins spanning $0.5 < z< 1.7$. This measurement will constrain the mean [CII] specific intensity over half of
cosmic history and assess the degree to which Euclid-selected
galaxies account for the [CII] intensity observed by TIM. We find that TIM can detect the cross-power spectrum across a wide range of [CII] intensity models.
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All authors Justin S. Bracks, Ryan P. Keenan, Shubh Agrawal, Garrett K. Keating, James E. Aguirre, Adam Lidz, Charles M. Bradford, Brockton Brendal, Jeffrey Filippini, Jianyang Fu, Karolina Garcia, Christopher Groppi, Steven Hailey-Dunsheath, Reinier M.J. Janssen, Wooseok Kang, Lun-Jun Liu, Ian Lowe, Alex Manduca, Daniel P. Marrone, Philip Mauskopf, Evan C. Mayer, Sydnee O'Donnell, Talia Saeid, Simon Tartakovsky, Mathilde Cuyck, Joaquin D. Vieira, Jessica A. Zebrowski
Earth and Planetary Astrophysics
Linear Polarization Variations and Circular Polarization are Common Among Airless Bodies
Sloane J. Wiktorowicz, Amanda J. Bayless and Larissa A. Nofi
Using the POLISH2 polarimeter at the Lick Observatory Shane 3-m and Nickel 1-m
telescopes, we discover rotation phase-locked variations in linear polarization to be common among asteroids and a NEO in a clear, 383 to 720 nm bandpass. Essentially all bodies in our eight-year study harbor statistically significant, repeatable linear polarization variations at the $0.01\% = 100$ ppm level or above (1 Ceres, 2 Pallas, 3 Juno, 4 Vesta, 6 Hebe, 7 Iris, 12 Victoria, 15 Eunomia, 16 Psyche, 132 Aethra, 216 Kleopatra, and 65803 Didymos). Since polarimetry is a differential technique, such variations cannot be due to shape changes and must be caused by heterogeneity in surface albedo and/or composition. While (4) Vesta has long been known to exhibit large, repeatable polarization variations across its surface, we discover the variations on (6) Hebe, (12) Victoria, and (65803) Didymos to be 1.5 to 3.5 times as large. We hypothesize that the DART impact with Dimorphos blanketed Didymos with depolarizing ejecta, which suggests pristine variations across Didymos to have been even larger. As the only NEO in this study with data quality sufficient to investigate polarization variations, Didymos' huge variations suggest they may be common among NEOs. We also discover optical circular polarization to be enhanced for low-albedo, M type asteroids, which is correlated with their large radar albedos. Thus, we present optical circular polarimetry as an alternative method for the identification of metalliferous bodies.
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Solar and Stellar Astrophysics
Few Made It Out: A Multi-Messenger Study of an In Situ Solar Energetic Electron Event Driven by a Solar Jet
Meiqi Wang, Bin Chen, Mallory Wickline et al. (+4 more)
When in situ
solar energetic electron (SEE) events are closely associated with nonthermal
flares, the escaping electron population is frequently observed to be much smaller than the nonthermal-radiation-emitting population near the
solar surface. If a single accelerated population drives both signatures, the physical mechanism causing this severe deficit of upward-propagating electrons remains poorly understood.Focusing on one of the 2022 November 10–12 SEE events associated with recurrent
solar jets and interplanetary type III
radio bursts, we present a new, combined microwave–X-ray analysis using the Expanded Owens Valley
Solar Array (EOVSA) and the Spectrometer/
Telescope for Imaging X-rays (STIX) aboard
Solar Orbiter. This synergy enables, for the first time for such an event, spatially resolved diagnostics over a broad energy spectrum of the near-Sun energetic electrons, complemented by in situ measurements made by spacecraft at multiple heliocentric longitudes and distances. Consistent with earlier results based on in situ and X-ray data, our results show that only 0.1–1% of energetic electrons escape into interplanetary space. Crucially, the new microwave spectral imaging analysis suggests that energetic electrons are strongly concentrated in a compact region just above a mini-
flare arcade at the base of the jet spire, and that their number density decreases by at least two orders of magnitude in the direction of the jet spire away from this region. This steep gradient, revealed by the microwave diagnostics, points to efficient local acceleration and trapping in the region analogous to the above-the-looptop “
magnetic bottle” region in major eruptive
flares, allowing only a small fraction of electrons to access open
magnetic field lines and enter interplanetary space.
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All authors Meiqi Wang, Bin Chen, Mallory Wickline, Sijie Yu, Sam Krucker, Jeongwoo Lee, Haimin Wang
Astrophysics of Galaxies
Filling the Gap in Cluster Evolution: JWST's Glimpse into a Young, Star-Forming Cluster at Cosmic Noon
Pierluigi Rinaldi, Stacey Alberts, Christopher N. A. Willmer et al. (+12 more)
We present a detailed study of HUDFJ0332.4-2746.6 (HUDF46), a $z \approx 1.84$ overdensity in the Hubble Ultra Deep Field, previously identified with HST as a proto-cluster. JWST/NIRISS spectroscopy expands its confirmed membership from 18 to 37
galaxies, while deep HST/ACS, JWST/NIRCam, and JWST/MIRI imaging provide a comprehensive multiwavelength view from the rest-frame UV to the mid-infrared. This
dataset probes the population across three dex in
stellar mass ($M_\bigstar \approx 10^{7.5\text{--}10.5}\,M_\odot$), delivering the first direct view of a young cluster down to such low-$M_\bigstar$ at $z\gtrsim1$. Assuming virialization, we derive a velocity dispersion of $\sigma \approx 670\pm 91\,\mathrm{km\,s^{-1}}$ and a
halo mass of $M_{200} \approx (1.2\pm0.2) \times 10^{14}\,M_\odot$, in agreement with X-ray constraints from deep Chandra data. Despite residing in a massive
halo likely in the hot-
halo regime, the population is overwhelmingly
star-forming, with no established red sequence and no extended X-ray emission from a hot intracluster medium. HUDF46 members have
stellar and structural properties nearly indistinguishable from coeval field
galaxies, and the structure hosts only one AGN candidate, found in its brightest
galaxy, which lies at the cluster center. Overall, HUDF46 appears to be in a transitional phase prior to the onset of environmental quenching, making its
galaxy population a key
benchmark for tracing the processes that will later build a passive population and shape the assembly of massive clusters at later
cosmic times.
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All authors Pierluigi Rinaldi, Stacey Alberts, Christopher N. A. Willmer, Courtney Carreira, Christina C. Williams, Gaël Noirot, Carys J. E. Gilbert, Andrew J. Bunker, William M. Baker, Luigi Barchiesi, Zhiyuan Ji, Jianwei Lyu, Sandro Tacchella, Zihao Wu, Yongda Zhu
Cosmology and Nongalactic Astrophysics
Weak lensing higher-order statistics to disentangle modified gravity and massive neutrinos
Alessandro Vadalà, Vincenzo Fabrizio Cardone, Simone Vinciguerra et al. (+3 more)
Going beyond second order in weak
lensing (WL) statistics is known to break degeneracies among cosmological parameters. We take a step further here, investigating whether higher-order statistics (HOS) in weak
lensing can disentangle among General Relativity (GR) and modified
gravity (MG), also taking into account the presence of massive
neutrinos. To this end, we rely on mock convergence maps obtained from GR and $f(R)$
gravity N - body simulations, and we look for MG signatures in a wide set of higher-order WL probes. We rely on different metrics to quantify the discriminatory power of each probe, also varying the measurement setup. We find out that WL HOS can indeed disentangle MG and GR also in the presence of massive
neutrinos.
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All authors Alessandro Vadalà, Vincenzo Fabrizio Cardone, Simone Vinciguerra, Filippo Bouchè, Marco Baldi, Carlo Giocoli
Cosmology and Nongalactic Astrophysics
A New Window into the Baryon Cycle at Cosmic Noon with Line Intensity Mapping: Forecasts for auto- and cross-correlations in [CII]-158$\mu$m, HI 21 cm, CO$_{J+1\rightarrow J}$, and H$\alpha$ galaxies
Shubh Agrawal, James E. Aguirre, Justin S. Bracks et al. (+24 more)
Across the peak of
cosmic star formation at $z\sim1-2$, inflow, processing, and feedback drive rapid changes in the spatial distribution and chemical composition of
baryons in
galaxies and surrounding reservoirs; this
baryon cycle can be tomographically mapped by line intensity mapping (LIM) of atomic hydrogen, ionized carbon, and carbon monoxide. We present a simulation-based
forecasting framework for detecting auto- and cross-power spectra between spectroscopic surveys of four such tracers at $z\sim0.5-1.7$ mapping the same deep field - TIM, EoRSpec/FYST, MeerKAT, & Euclid. We forward-model 3-D distributions for these tracers from magnetohydrodynamic simulations, directly capturing the two-
halo, one-
halo, and shot statistics without relying on analytical decompositions. We further detail a signal-to-noise formalism, tailored to LIM surveys with highly anisotropic geometries and
Fourier-space coverage. We demonstrate that
galaxy cross-correlations will be the dominant discovery channel for current-generation surveys. These instruments will detect the auto-spectra for CO and HI 21 cm and the CO $\times$ 21 cm cross-spectrum at modest S/N $\sim 1-10$, while placing upper limits on the [CII]-158$\mu$m signals. [CII], CO, and HI LIM will be $\sim3-30\times$ ($0.5-1.5$ dex) more sensitive to cross-correlation with the Euclid survey, however, than their respective auto-correlations, constraining all three models of line emission at high significance (S/N $\sim 10-40$) within this decade. Finally, we formulate a staged instrumental trajectory with planned or reasonable improvements, including the as-proposed SKA-Mid. We forecast advancing the per-$k$-mode sensitivities of each auto-,
galaxy-line, and line-line spectrum by several orders of magnitude, enabling new percent- and sub-percent level constraints on cosmology and the
redshift evolution of
star formation and the
baryon cycle.
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All authors Shubh Agrawal, James E. Aguirre, Justin S. Bracks, Ryan P. Keenan, Charles M. Bradford, Brockton S. Brendal, Peter Dow, Jeffrey P. Filippini, Jianyang Fu, Karolina Garcia, Reinier M.J. Janssen, Bradley R. Johnson, Wooseok Kang, Christos Karoumpis, Garrett K. Keating, Adam Lidz, Lun-Jun Liu, Ian Lowe, Alexander Manduca, Aashrita Mangu, Daniel P. Marrone, Evan C. Mayer, Sydnee O'Donnell, Talia Saeid, Mathilde Van Cuyck, Joaquin Vieira, Jessica A. Zebrowski
Solar and Stellar Astrophysics
Temporal Evolution of Sunspot Groups and Increase in the Open flux During Solar Maximum in Cycle 24
Minami Yoshida, Toshifumi Shimizu, Shin Toriumi et al. (+1 more)
The
evolution of the global
solar magnetic field directly impacts the interplanetary
magnetic field (IMF). During the
solar maximum of Cycle 24, the monthly averaged IMF strength doubled over five Carrington rotations in late 2014. To understand the physical origin of this increase, we investigate the temporal
evolution of open
magnetic flux resulting from the emergence and decay of bipolar
magnetic regions (BMRs). Using surface flux transport and potential field source surface models, we simulated how BMR characteristics, spatial distributions, and interaction with background
magnetic fields affect open flux
evolution. Our simulation confirmed that the relative configuration of BMRs can either inhibit open flux expansion via closed loops or promote it through favorable connections. The increase in open flux is primarily driven by the equatorial dipole component, which is enhanced by differential rotation acting on tilted BMRs. These behaviors suggest that large open field structures develop from equatorial dipole components formed by these stretched BMRs. We attribute the rapid IMF increase in 2014 (Carrington rotations 2152-2157) to the combination of the following three factors: (1) a specific sunspot configuration that facilitated the expansion of the southern coronal hole; (2) the emergence of a
giant sunspot group (active region 12192) with high
magnetic intensity; and (3) the
diffusion of these regions, which reinforced the global
magnetic field. These results imply that rapid open flux variations during
solar maximum are governed not only by the characteristics of emerging BMRs but also by their interaction with pre-existing large coronal holes.
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All authors Minami Yoshida, Toshifumi Shimizu, Shin Toriumi, Haruhisa Iijima
Cosmology and Nongalactic Astrophysics
Probing power spectrum enhancement at small scales with the SKA
Hourui Zhu, Bin Yue, Yidong Xu et al. (+2 more)
The reionization process is driven by ionizing
photons from
dwarf galaxies in
halos with virial temperature $T_{\rm vir} \gtrsim 10^4$ K, while minihalos whose $T_{\rm vir}\lesssim 10^4$ K consume ionizing
photons and have negative contributions to reionization. Since ionizing sources and minihalos have different clustering characteristics, not only the reionization history, but also the morphology of the ionization field, is sensitive to the small-scale power spectrum. If the power spectrum at small scales is enhanced compared with the standard six-parameter $\Lambda$CDM model, then both the sources and sinks of ionizing
photons would be boosted and the net impact depends on the competition between them. Therefore, the 21 cm signal that can probe the morphology of the ionization field will be a useful tool for detecting the small-scale power spectrum. Using the power spectrum proposed by Cielo et al. (2025) (C25) as a demonstration, we investigate the influence of small-scale power spectrum enhancement on the ionization field and the 21 cm signal. We find that for the C25 model, even under the constraints of observed UV luminosity functions for high-$z$
galaxies and reionization history, the 21~cm power spectrum and the bubble size distribution could be still significantly different from the regular $\Lambda$CDM model. The upcoming SKA-low AA*
telescope, and a further imaging
telescope, have the potential to detect the small-scale power spectrum more deeply.
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All authors Hourui Zhu, Bin Yue, Yidong Xu, Xuelei Chen, Zhiqi Huang
High Energy Astrophysical Phenomena
Multi-messenger emission derived from relativistic magnetized jet dynamics using a multi-zone framework
Harshita Bhuyan, Bhargav Vaidya, Christian Fendt et al. (+1 more)
Relativistic jets from Active
Galactic Nuclei (AGN) are highly energetic and emit radiation across a wide range of frequencies. Despite several observational studies, their particle composition still remains a key open question. The detection of high-energy
neutrinos from blazar sources such as TXS 0506+056 has highlighted the plausibility of hadronic/lepto-hadronic models for AGN jets. To understand the origin of high-energy
neutrinos from such sources, it is imperative to capture the complex interplay between the jet dynamics, their composition, and the mechanism of particle acceleration and cooling in relativistic jets. In this pilot study, we have coupled a numerical multi-zone framework for lepto-hadronic modeling, with 3D relativistic magneto-hydrodynamic simulations of AGN jets, including external
photon fields. Our framework provides synthetic multi-wavelength and
neutrino flux by spatially sampling the simulated jet into multiple zones. We investigate the implications of such a framework in exploring the different intrinsic and extrinsic pathways for
proton-enrichment in jets. Essentially, we find that for low
proton-to-electron number density ratios, producing a substantial jet
neutrino flux, requires the underlying
proton energy distribution to have a relatively flat spectrum with a power-law index of $\simeq 2.0$. We further find that while intrinsic shocks triggered by kink-instabilities in the jet can accelerate electrons to high energies, they may not be sufficient to produce such flat particle energy distributions for the chosen set of parsec-scale jet parameters. Finally, to produce a significant jet
neutrino emission, our simulations suggest the need to consider particle acceleration mechanisms through alternative pathways, either internal or external.
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All authors Harshita Bhuyan, Bhargav Vaidya, Christian Fendt, Aditya Sharma
Instrumentation and Methods for Astrophysics · Cross-listed from physics.comp-ph
Shaping the Digital Future of ErUM Research: Sustainability & Ethics
Luca Di Bella, Jan Bürger, Markus Demleitner et al. (+36 more)
This workshop report from "Shaping the Digital Future of ErUM Research: Sustainability & Ethics" (Aachen, 2025) reviews progress on sustainability measures in data-intensive ErUM-Data research since the 2023 call-to-action on resource-aware research. It evaluates short-, medium-, and long-term actions around monitoring and reducing CO2 emissions, improving data and software
FAIRness, optimizing workflows and computing infrastructures, and aligning operations with low-carbon energy availability, including concepts such as "breathing" computing centers, long-term data storage strategies, and software efficiency certification. The report stresses the need for systematic teaching, training, mentoring, and new support formats to establish sustainable coding and computing practices, particularly among students and early-career researchers, and highlights the importance of dedicated steering and funding instruments to embed sustainability in project planning. Ethical discussions focus on the transformative use of AI in ErUM-Data, addressing autonomy, bias, transparency, explainability, attribution of responsibility, and the risk of deskilling, while reaffirming that accountability for scientific outcomes remains with human researchers. Finally, the report emphasizes that sustainable transformation requires not only technical measures but also targeted awareness-building, communication strategies, incentives, and community-driven initiatives to move from awareness to action and to integrate sustainability and ethics into everyday scientific practice.
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All authors Luca Di Bella, Jan Bürger, Markus Demleitner, Torsten Enßlin, Johannes Erdmann, Martin Erdmann, Benjamin Fischer, Martin Gasthuber, Gabriele Gramelsberger, Wolfgang Gründinger, Prateek Gupta, Johannes Hartl, Maximilian Horzela, Vijay Kartik, Stefan Krischer, Eva Kröll, Thomas Kuhr, Katharina Kürschner, Inga Lakomiec, Valerie Lang, Kristin Lohwasser, Thomas Metcalf, Martin Möller, Saskia Nagel, Susanne Pfalzner, Rebecca Redlin, Christopher Schrader, Kathrin Schulz, Markus Schumacher, Kilian Schwarz, Fabian Sigler, Dwayne Spiteri, Achim Stahl, Judith Steinfeld, Wim Vanderbauwhede, Cyrus Walther, Angela Warkentin, Peter Wissmann, Eoin Woods
High Energy Astrophysical Phenomena
The hydrodynamics of stratified ultra-relativistic outflows and the origin of GRB X-ray plateaus
Gilad Sadeh, Kenta Hotokezaka and Masaru Shibata
The origin of the X-ray plateau phase observed in a large fraction of gamma-ray burst afterglows remains debated. We present a novel analytic framework for the hydrodynamics of ultra-relativistic, radially stratified
outflows interacting with an external medium. By explicitly accounting for a continuous distribution of Lorentz factors within the ejecta, we derive analytic expressions describing the
evolution of a long-lived, mildly relativistic reverse shock and determine its crossing time. Then, we compute the resulting synchrotron emission from both the forward and reverse shocks. The forward shock naturally produces a shallow, long-lasting X-ray decay consistent with the observed properties of X-ray plateaus, including the Dainotti relation, without requiring prolonged central-engine activity or an additional high-energy emission component. We further show that reproducing the observed plateau durations requires a broad distribution of ejecta Lorentz factors, extending down to $\gamma_\text{min}\sim70-100$, consistent with the ultra-relativistic
outflow that powers the
prompt $\gamma$-ray emission. The reverse shock generates a long-lived millimeter emission component that outshines the forward shock emission at these wavelengths. Both the plateau and reverse shock emission terminate smoothly once the slowest ejecta are processed, marking a transition to the standard Blandford-McKee self-similar
evolution. Such stratified
outflows are expected on physical grounds, as the ultra-relativistic ejecta responsible for the
prompt $\gamma$-ray emission are unlikely to be launched with a single Lorentz factor. This model provides a unified picture in which the same
outflow powers the
prompt emission, the X-ray plateau, and the subsequent afterglow
evolution.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The Shape of Eccentricity: Rapid Classification of Eccentric Binaries with the Wavelet Scattering Transform
Priscilla Canizares, Seppe J. Staelens and Isobel Romero-Shaw
The gravitational-wave (GW) detections reported by the LIGO-Virgo-KAGRA (LVK) collaboration have so far been consistent with quasi-circular compact binary coalescences (CBCs). Nevertheless, a small fraction of binaries driven to merge through dynamical interactions in dense
stellar environments or in field triples may retain measurable orbital eccentricity when entering the sensitive frequency band of LVK detectors. Confident measurement of eccentricity in the LVK band would provide strong evidence for such dynamically driven mergers; however, eccentric gravitational-waveform models are computationally expensive, and performing production-level inference on all detected signals is not an efficient use of resources when eccentric signals are expected to be rare. An intermediate step between detection and analysis, in which the signal is assessed for the potential presence of eccentricity, could provide quick recommendations for which signals should undergo full eccentric inference. We apply the wavelet scattering transform (WST) to a large set of synthetic waveforms in realistic noise and assess its discriminatory power using simple linear and shallow neural-network classifiers. We find that the WST representation enables effective discrimination between eccentric and quasi-circular binaries and provides a compact multi-scale representation of GW signals. Our approach achieves ~64% percent detection accuracy at a false alarm rate of 10%, with an AUC of 0.844 and an average precision of 0.876. We also examine the ability of our classifiers to distinguish eccentricity from
spin-induced precession and find robust performance across a range of
spin-precession magnitudes.
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Solar and Stellar Astrophysics
Monitoring the magnetospheric accretion of the classical T Tauri star DO Tau with SPIRou
J.-F. Donati, P.I. Cristofari, A. Carmona et al. (+11 more)
We present observations of the classical T Tauri
star DO Tau collected with the near-infrared SPIRou spectropolarimeter and precision velocimeter at the Canada-France-Hawaii
Telescope from early 2020 to late 2025. Circularly polarized Zeeman signatures were clearly detected at most epochs in the atomic spectral lines of DO Tau, yielding longitudinal
magnetic fields of up to 280 G modulated with a period of 5.128+-0.002 d which we identified as the rotation period of DO Tau. Applying Zeeman-Doppler imaging to the SPIRou data recorded in 2021, 2024 and 2025, we found that DO Tau hosts an unusual large-scale
magnetic field that is weaker, less poloidal, more inclined to the rotation axis, and varies more rapidly with time than those of previously studied T Tauri
stars, possibly as a result of intense
accretion between the inner disk and the
stellar surface. The dipole component of this large-scale field of about 0.2-0.3 kG even flipped polarity toward the end of our observing campaign, making DO Tau the first T Tauri
star for which a
magnetic polarity reversal is reported. The magnetospheric gap surrounding the central
star was quite compact, extending to ~1.6 Rstar (0.014 au) as a result of the strong
accretion rate (log Mdot = -7.7 Msun/yr), with the inner
accretion disk being warped by the tilted
stellar magnetic field. Radial velocity variations suggest the presence of a close-in
planet of a few Mjup or a density structure in the inner
accretion disk at an orbital period of 21 d (corresponding to 0.12 au), which might be linked to the wiggle in the jet axis of DO Tau.
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All authors J.-F. Donati, P.I. Cristofari, A. Carmona, A. Lavail, C. Moutou, J. Bouvier, K. Perraut, S.H.P. Alencar, F. Ménard, M. Audard, P. Petit, E. Alecian, T. Ray, the SPIRou science team
Cosmology and Nongalactic Astrophysics
A Unified Origin of Primordial Black Hole Dark Matter and Nanohertz Gravitational Waves
Guillem Domènech, Shi Pi and Ao Wang
Recent high-cadence observations by Subaru-HSC have identified a population of ultrashort-timescale microlensing events, providing a compelling window for
planet-mass
primordial black holes (PBHs) to constitute the entirety of dark matter. In this Letter, we demonstrate that this PBH population and the nanohertz
stochastic gravitational-wave (GW) background reported by
pulsar timing arrays (PTAs) can be naturally unified by a single
primordial origin: a broad, nearly-flat enhancement of the
curvature power spectrum with an amplitude of $O(10^{-2})$. The resulting PBH mass function spans the
planet-to-
solar mass range, while remaining consistent with all current observational constraints. This unified PBH–induced-GW framework makes concrete multi-messenger predictions, which can be decisively scrutinized by forthcoming microlensing surveys, next-generation PTAs, space-borne interferometers, precision astrometry, and
laser ranging experiments.
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Astrophysics of Galaxies
A Quality Framework for Testing Gravity with Wide Binaries: No Evidence for MOND
Stephen A. Cookson, Indranil Banik, Kareem El-Badry et al. (+4 more)
Wide binaries (WBs) offer a unique opportunity to test
gravity in the low-acceleration regime, where modifications such as Milgromian dynamics (MOND) predict measurable deviations from Newtonian
gravity. We construct a rigorous framework for conducting the wide binary test (WBT), emphasizing high quality sample selection, filtering of poor astrometric solutions, contamination mitigation, and uncertainty propagation. We show that undetected close binaries, chance
alignments, and improper treatment of projection effects can mimic MOND-like signals. We introduce a checklist of best practices to identify and avoid these pitfalls. Applying this framework to
Gaia DR3 data, we compile a high-purity sample of WBs within 130 pc with projected separations of 1 - 30 kAU, spanning the transition between the Newtonian and MOND regimes. We find that the scaled relative velocity distribution of wide binaries does not exhibit the 20% enhancement expected from MOND and is consistent with Newtonian
gravity across all separations. A meta-analysis of previous WBTs shows that apparent MOND signals diminish as methodological rigour improves. We conclude that when stringent quality controls are applied, there is no observational evidence for MOND-induced velocity boosts in wide binaries. Our results place strong empirical constraints on modified
gravity theories operating between a0/10 and 200 a0, where a0 is the MOND acceleration scale. Across this range of internal accelerations, Newtonian
gravity is up to 1500x more likely than MOND for our cleanest sample.
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All authors Stephen A. Cookson, Indranil Banik, Kareem El-Badry, Will Sutherland, Zephyr Penoyre, Charalambos Pittordis, Cathie J. Clarke
Instrumentation and Methods for Astrophysics
Rachit Deshpande and Shantanu Desai
This work investigates symbolic regression (SR) as an interpretable alternative to black-box machine learning for the classification of
stars,
galaxies, and
quasars in the Sloan Digital Sky Survey Data Release 17 (SDSS DR17). We conduct a systematic comparative study of four state-of-the-art SR frameworks: PySR, Exhaustive Symbolic Regression (ESR) with MDL-based selection, Physical Symbolic Optimization (PhySO) using deep reinforcement learning, and Multi-View Symbolic Regression (MvSR). By deriving compact analytic functions (complexity $\leq$ 10) on a representative training subset and subsequently evaluating them via an 80,000-sample 5-fold cross-validation threshold optimization phase and a subsequent 10,000-sample unseen hold-out test set, we map spectroscopic
redshift ($z$) to continuous classification scores. Our results demonstrate that these low-complexity expressions achieve high predictive reliability, with MvSR reaching a cross-validation Cohen's Kappa of 0.8956 (0.8876 on the hold-out set) and PhySO achieving exceptional parametric stability ($\sigma < 0.002$). We note however that the resulting equations returned by Symbolic regression are purely empirical and no physical significance should be ascribed to these equations.
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Astrophysics of Galaxies
Ruling out conventional photoionization models in the closest LINER M31 with CFHT/SITELLE observations
Zongnan Li, Zhiyuan Li, Sumin Wang et al. (+2 more)
The ionization mechanisms of low-ionization
nuclear emission-line regions (LINERs), which are common in the local Universe, have been debated for decades. Our nearest large neighbor, M31, is classified as a LINER based on its optical emission line properties within the central kpc. In this work, we present a detailed photoionization modeling of the circumnuclear ionized gas in M31, explicitly tailored to its well-constrained physical conditions, including the absence of ongoing
star formation and a currently inactive active
galactic nucleus (AGN). Using spatially resolved CFHT/SITELLE observations, we find that photoionization by hot, evolved low-mass
stars distributed throughout the bulge can roughly reproduce the observed radial intensity profiles of H{\alpha}, He̱ta}, and [NII]. However, these models fail to match the observed [OIII] emission, producing radial profiles and [O III]/He̱ta} ratios that are significantly steeper than observed. This discrepancy indicates a deficit of high-energy ionizing
photons in standard
stellar photoionization models, even with extended ionizing sources. We explore whether this tension can be alleviated by invoking either a bulge-filling, low-density ionized medium surrounding a denser H{\alpha}-emitting disk, or enhanced AGN activity in the recent past. While both scenarios can partially increase the [O III] emission, neither provides a fully satisfactory explanation under physically plausible conditions. Together with our earlier results for M81, these findings underscore persistent challenges in explaining LINER-like emission solely through conventional photoionization mechanisms.
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All authors Zongnan Li, Zhiyuan Li, Sumin Wang, Ruben Garcia-Benito, Yifei Jin
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Impact of non-standard neutrino-electron interactions on Big Bang Nucleosynthesis
Julien Froustey, Stefano Gariazzo, Jaume Moncho et al. (+2 more)
Neutrino non-standard interactions (NSI) with electrons, predicted in many extended theoretical models of particle physics, are known to alter the picture of
neutrino decoupling from the
cosmic plasma. We update previous analyses of
neutrino decoupling in the presence of NSI with electrons, extending the parameter space and assessing their impact on the
primordial light-element abundances produced during Big Bang Nucleosynthesis (BBN). We show that tracking the NSI-induced modifications of the
neutrino distributions is necessary to accurately predict the helium-4 abundance, which cannot be derived from a pure $N_{\rm eff}$-driven change. BBN therefore provides additional observables that are complementary to $N_{\rm eff}$. We then derive cosmological constraints on non-universal and flavour-changing NSI parameters, using different
dataset combinations, and compare them with bounds from terrestrial experiments. We find that the cosmological limits are significantly less stringent than the terrestrial ones, but they provide an independent probe of
neutrino interactions in the early universe.
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All authors Julien Froustey, Stefano Gariazzo, Jaume Moncho, Sergio Pastor, Ofelia Pisanti
Cosmology and Nongalactic Astrophysics
Probing inflationary features with galaxy ultraviolet luminosity function observables
Sandeep Kumar Acharya
We use the
galaxy ultraviolet luminosity function measurements at $z=4-8$ to constrain modification to standard inflationary power spectrum. These observables are sensitive to the matter power spectrum which itself depends on inflationary initial conditions. We consider a specific model where a bump feature is introduced to the standard power law inflation spectrum. We find that the
galaxy luminosity observables can probe such modifications at wavenumbers $0.5\lesssim k \lesssim 50$ Mpc$^{-1}$. We obtain upper limits on the amplitude of bump-like features at the mentioned wavenumbers. We obtain constraints which are similar to previous constraints on these models using measurements of optical depth of reionization. However, the
galaxy luminosity functions are a more direct probe for these type of models and, therefore, can complement indirect constraints coming from measurements of IGM properties.
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Astrophysics of Galaxies
Age and metallicity of the Milky Way's nuclear star cluster studied at 3 pc from Sagittarius A*
E. Gallego-Cano, R. Schödel, T. K. Fritz et al. (+5 more)
The Milky Way's
nuclear star cluster (NSC) is a unique laboratory to study the formation and
evolution of dense
stellar systems around a supermassive black hole. Previous work suggests that most
stars in the NSC are old; however, the detailed age and
metallicity distributions remain uncertain. We constrain the
star formation history (SFH) and
metallicity of a poorly explored region located $\sim$3 pc from SagittariusA*. We analyse VLT/NACO imaging in an intermediate-band filter centred at 2.24 $\mu$m, complemented by $H$-band data. We construct completeness-corrected $K$-band luminosity functions (LFs), clearly identifying the Red Clump and Red
Giant Branch Bumps. The SFH is derived by fitting cumulative LFs with MIST, PARSEC, and BaSTI models spanning a wide range of ages and
metallicities, using Monte Carlo sampling to estimate uncertainties.
Metallicity constraints are refined using spectroscopic measurements from the literature. The
stellar population is predominantly old and metal-rich: $75.6 \pm 9.5$% of the
stellar mass formed $\gtrsim 10$ Gyr ago, with median [M/H] $\sim +0.35$. An intermediate-age component at 2-3 Gyr contributes $20.8 \pm 8.7$%, while minor populations are present at $\sim$400 Myr ($0.9 \pm 0.8$%) and 20 Myr ($3.6 \pm 1.4$%), the latter representing a small but non-negligible young population. Systematic uncertainties from
stellar models, binning, photometric range, unresolved binaries, and filter choice are assessed. These results indicate early dominant formation, a significant 2-3 Gyr episode, and minor recent activity, consistent with spectroscopic measurements and with properties of the inner NSC and
nuclear stellar disc.
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All authors E. Gallego-Cano, R. Schödel, T. K. Fritz, M. W. Hosek Jr., K. Muzic, A. Feldmeier-Krause, Á. Martínez-Arranz, F. Nogueras-Lara
Solar and Stellar Astrophysics
Discovery of a runaway star likely ejected by a Type Iax Supernova
A. Bhat, M. Hollands, M. Dorsch et al. (+5 more)
Over the past decade, runaway
stars have been identified, believed to originate either as surviving donors of Type Ia
supernovae or as partially deflagrated accretors producing Type Iax
supernovae. While the former have been extensively studied recently, the origins of the latter (also called LP 40-365 type
stars) remain under-explored and therefore less well understood. So far seven such objects are known. In this paper, we report the discovery of a new LP 40-365 type runaway
star, notably hotter than previously studied members of this class. Spectral analysis confirms that its atmosphere is neon- and oxygen-dominated, consistent with earlier analyses of other LP 40-365 type
stars. Kinematic analysis indicates that the
star has a high probability of being unbound from the
Galaxy and was most likely ejected from the
Galactic disk approximately 2.8 Myr ago with an ejection velocity exceeding 600 km/s. This result further emphasizes the discrepancy between the abundance yields and kick velocities predicted by white
dwarf deflagration models and those observed in
stars of LP 40-365 type, underscoring the need for a reassessment of such systems.
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All authors A. Bhat, M. Hollands, M. Dorsch, S. Geier, U. Heber, D. Koester, R. Pakmor, Ken J. Shen
Cosmology and Nongalactic Astrophysics
Dark Acoustic Oscillations and the Hubble Tension
Mathias Garny, Florian Niedermann and Martin S. Sloth
The Hubble tension and the recently reported anomaly in data from the Dark Energy Spectroscopic Instrument (DESI) are considered to pose serious challenges to the standard $\Lambda$CDM model of cosmology. In this work, we show that resolving the Hubble tension with a scenario featuring dark radiation-matter decoupling (DRMD) predicts the presence of dark acoustic oscillations (DAO) similar in scale to
baryon acoustic oscillations (BAO). Using an inference independent of large-scale structure data, relying only on Planck measurements of the
cosmic microwave background and SH$0$ES-calibrated
supernova data, we find evidence for a DAO signal with drag-horizon scale $r_{d,\mathrm{DAO}} \in[54,65]\,\mathrm{Mpc}/h$ ($68\%\,\mathrm{C.I.}$) and amplitude $A_\mathrm{DAO} \in [0.02,0.05]$ ($68\%\,\mathrm{C.I.}$). These predictions provide a concrete target for current and upcoming large-scale structure surveys, including DESI, Euclid, and the Roman Space
Telescope. Remarkably, the predicted DAO properties are consistent with those required to explain the DESI anomaly, offering both an alternative to evolving dark energy and a preliminary validation of the relevance of a dark radiation-matter decoupling scenario for addressing the Hubble tension.
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Astrophysics of Galaxies
Timing and scintillation of a young Galactic halo pulsar
J. M. Yao, F. F. Kou, J. P. Yuan et al. (+6 more)
We present a timing and scintillation study of the young
Galactic halo pulsar PSR J1740+1000 using observations from the Nanshan, FAST, and Parkes
radio telescopes. From timing analysis, we measure the
pulsar's proper motion for the first time, indicating motion away from the
Galactic plane at a position angle of 16.7 +/- 4.8 degrees (
Galactic coordinates), with a total proper motion of 56.9 +/- 8.0 mas/yr and a corresponding transverse velocity of 329 +/- 80 km/s. This velocity suggests that PSR J1740+1000 is a typical-velocity young
pulsar born within the
Galactic halo. In scintillation studies, we detect scintillation arcs, arclets, and double-layered adjacent arcs in the secondary spectra. Under isotropic and anisotropic scattering assumptions, the screen-to-
pulsar distance is 370 +/- 72 pc and 1 +/- 12 pc, respectively. The latter closely matches the scale of the
pulsar wind nebula associated with PSR J1740+1000 and provides a better fit, suggesting that scattering is likely dominated by the PWN. The double-layered adjacent arcs observed on MJD 60180 imply that the
pulsar's scattered image consists of two dominant components (A and B) and multiple weaker components. Component A is located at the
pulsar's
geometric position (0 uas), while Component B is located 112 +/- 16 uas and 23 +/- 17 uas from the central component under isotropic and anisotropic scattering, respectively. The frequency-independent angular position of Component B hints at refraction by an AU-scale structure within the scattering region, possibly originating from the PWN.
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All authors J. M. Yao, F. F. Kou, J. P. Yuan, Y. Wei, William A. Coles, Richard N. Manchester, N. Wang, S. Q. Wang, W. M. Yan
High Energy Astrophysical Phenomena
Magnetic Flux Tubes Illuminated by Pulsar Winds
Yifan Sun, C.-Y. Ng and Siming Liu
Observations of linear structure connecting
pulsars to gamma-ray
halos reveal injection of TeV electrons into the interstellar medium (ISM). In some cases, this could be attributed to nearly scattering-free electron transport along large-scale
magnetic fields connected to
pulsar winds with very slow
diffusion across the field lines. In this work we model this process with a
magnetic flux tube emerging from the
pulsar and attached to the ISM
magnetic field. We show that particles in this case have an anisotropic distribution of
magnetic pitch angle, such that the overall emission is highly beamed. We apply this model to
pulsar tails and filaments, including the extended X-ray and TeV emission associated with PSR J1740+1000 and the misaligned X-ray jet in the Guitar Nebula, to constrain their particle population and
magnetic fields.
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Instrumentation and Methods for Astrophysics
Eigenmode initialisation of 2D (magneto)hydrodynamic simulations
Jordi De Jonghe and Alexander J. B. Russell
The early
evolution of unstable hydrodynamic and magnetohydrodynamic
equilibria is often governed by a few dominant linear eigenmodes. We investigate whether initialising a simulation with a superposition of linear eigenmodes that contains the most unstable mode saves computation time, and how the selection of the included modes affects the non-linear
evolution. Using the non-linear (magneto)hydrodynamic simulation code MPI-AMRVAC, the evolutions of a flow-sheared fluid interface, a Harris current sheet, and a flow-sheared
plasma interface were simulated for various initial perturbations. The novel initial perturbations were linear eigenmodes of the
equilibrium, or superpositions thereof, and calculated with the Legolas code. We benchmarked to initialisation with velocity noise and, in the case of the Harris sheet, initialisation with an analytic
magnetic field perturbation. By perturbing an unstable
equilibrium with a superposition of linear eigenmodes that contains the most unstable mode, significantly less computation time is spent on the linear stage of the
evolution compared to traditional perturbation methods. In the best case, the simulation time needed to reach the non-linear stage is reduced by an order of magnitude. The inclusion or omission of certain modes in the initial perturbation is observed to affect the non-linear
evolution to various degrees. The perturbation of
equilibria with a superposition of linear eigenmodes that contains the most unstable mode allows simulations to reach a late-
evolution stage faster, thus saving computation time. Additional eigenmodes can be included alongside the fastest growing mode to obtain further benefits, for example, to accelerate
symmetry breaking in the non-linear stage, or to delay their effect on the non-linear
evolution. Coupling spectroscopic codes with (magneto)hydrodynamic codes therefore offers significant advantages.
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Astrophysics of Galaxies
The capture of halo material by orbiting subhaloes
Hang Yang, Simon D.M. White and Liang Gao
When a dark matter
halo falls into a more massive object and becomes a subhalo, it typically loses much of its mass through
tidal stripping. The reverse process is also possible in principle. The subhalo may gravitationally capture material from its host. If sufficiently efficient, this process could make an initially starless subhalo visible. We use high-resolution N-body simulations to estimate the efficiency of capture. We find that after an extended period orbiting within its host, at most $\sim 10^{-4}$ of a subhalo's remaining mass has been acquired since infall. This captured material is less concentrated to subhalo centre than material retained from before infall. It is also very much less abundant than host material that is instantaneously passing through the subhalo on almost unperturbed orbits. Captured
stars are not sufficiently spatially concentrated to be distinguished from the dominant background of "field"
stars, and their concentration in velocity space is no greater than that of typical
stellar streams in the
halo. Unfortunately,
stellar capture is not efficient enough to allow initially starless low-mass subhaloes to be detected.
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Solar and Stellar Astrophysics
New possible way to determine stellar wind terminal velocity from analysis of Lyman-$\alpha$ absorption spectra
Sergey D. Korolkov and Vladislav V. Izmodenov
Stellar winds interact with the partially ionized interstellar medium (ISM), forming astrospheres. A key feature of this interaction is the hydrogen wall - secondary interstellar atoms produced via charge exchange near the tangential discontinuity separating the
stellar wind from the ionized ISM component. This secondary component is decelerated and heated compared to primary interstellar hydrogen, making the hydrogen wall detectable through Lyman-$\alpha$ absorption spectra toward nearby
stars. Such structures have been observed by the Hubble Space
Telescope around the Sun and other
stars. In this paper, we propose that another feature of the
stellar wind/partially ionized ISM interaction may also be detectable in Lyman-$\alpha$ spectra: the neutral
stellar wind. It forms via charge exchange between supersonic
stellar wind
protons and interstellar atoms penetrating deep into the astrosphere due to their long mean free paths. We present a parametric numerical analysis of astrospheric structures and their synthetic Lyman-$\alpha$ absorption spectra. Using a 2D kinetic-hydrodynamic model, we vary the terminal wind velocity while maintaining constant dynamic pressure to keep the astrosphere size consistent. For winds slower than the
solar wind (terminal velocities $V_0 \lesssim 200$ km/s), charge exchange efficiency in the supersonic region increases dramatically, producing a distinct and observable absorption feature from the neutral wind. This signature is negligible for
solar-like winds ($V_0 \approx 400$ km/s) but emerges as a direct spectroscopic diagnostic for winds up to $\sim 200$ km/s. Detecting this neutral wind absorption offers a novel method to directly constrain
stellar wind velocities.
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Astrophysics of Galaxies · Cross-listed from nucl-ex
High-Precision Mass Measurements of Proton-Rich Rh, Pd, Cd isotopes in the vicinity of 100Sn and Impact on X-Ray Burst and Supernova Nucleosynthesis
D. S. Hou, W. D. Xian, M. Rosenbusch et al. (+55 more)
Using the ZeroDegree multi-reflection time-of-flight mass spectrograph of the CRISMASS project at RIKEN Radioactive Isotope Beam Factory, we performed high-precision mass measurements of
proton-rich
nuclei near the doubly magic
nucleus 100Sn, achieving uncertainties on the order of 10 keV. The masses of 91Rh, 92Pd, and 96Cd were determined for the first time with high precision, and the accuracy of several additional masses was substantially improved. Incorporating the new data into X-ray burst simulations significantly reduces the abundance uncertainties in the $A$ = 90-100 region, shifting the reaction flow toward $A$ = 90 production and suppressing the synthesis of heavier
nuclei. Further investigation of the $\nu p$-process indicates that 99Rh plays a significant role in the reaction flow within the mass region studied. These high-precision mass measurements refine the mass surface near 100Sn and provide critical constraints on models of
proton-rich nucleosynthesis.
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All authors D. S. Hou, W. D. Xian, M. Rosenbusch, M. Wada, P. Schury, A. Takamine, Y. Luo, J. Lee, H. Ishiyama, S. Nishimura, C. Y. Fu, A. Dohi, H. Feng, Z. He, S. Kimura, T. Niwase, V. H. Phong, T.T. Yeung, Q. B. Zeng, S. X. Zha, Y. Hirayama, Y. Ito, S. Iimura, T. Gao, J. M. Yap, M. Zhang, T. Kajino, Y. X. Watanabe, F. Browne, S. D. Chen, M. L. Cortes, P. Doornenbal, N. Fukuda, H. Haba, K. Kusaka, T. M. Kojima, S. Kubono, X. Y. Liu, Z. Liu, W. Marshall, S. Michimasa, J. Y. Moon, H. Miyatake, M. Mukai, M. Ohtake, S. Paschalis, M. Petri, Y. Shimizu, T. Sonoda, H. Suzuki, H.Takeda, R. Taniuchi, Y. Togano, L. Tetly, H. Ueno, H. Wollnik, Y. Yanagisawa, M. Yoshimoto