Astrophysics of Galaxies
Galactic Outflows and Star-Formation Quenching: A JWST Perspective
Rebecca L. Davies and Sirio Belli
Outflows driven by active galactic
nuclei (AGN) are widely considered a key mechanism for regulating and quenching
star formation in massive
galaxies. However, direct observational evidence linking outflows to quenching has remained elusive for decades. This article reviews recent findings for massive
galaxies at
cosmic noon ($z\sim 2$), based on sensitive James Webb Space
Telescope (JWST) observations tracing both
star formation histories (through Balmer absorption lines) and neutral outflows (through blueshifted NaID absorption). Neutral outflows are found in $\sim$ 25 - 50% of massive ($\log(M_*/M_\odot)>$ 10)
galaxies, independent of
star formation rate. Outflows from
star-forming
galaxies are consistent with being powered by
star-formation and/or AGN activity, whereas outflows from quiescent systems are generally attributed to current or previous AGN activity. There is growing evidence that recent rapid quenching of
star-formation is associated with powerful AGN-driven outflows with mass loading factors $\eta \gtrsim$ 1 - 10. The neutral gas dominates the outflow mass budget but in most cases its velocity is below the
halo escape velocity, indicating that this gas may form part of a galactic fountain. Detections of neutral gas inflows and residual cold gas reservoirs in quiescent
galaxies suggest that other feedback mechanisms such as AGN heating are required to keep
galaxies quenched over long timescales. We highlight the potential of multiphase outflow measurements to constrain feedback models, describe the main systematic uncertainties in mass outflow rate measurements, and discuss how the $z\sim 2$ results inform our understanding of the formation of the earliest massive quiescent
galaxies.
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Astrophysics of Galaxies
Emergence of high-mass stars in complex fiber networks (EMERGE) VII. Multi-Tracer Column Density Synthesis
Alvaro Hacar, Andrea Socci, Mario Tafalla et al. (+1 more)
Obtaining accurate estimates of the gas column density $\mathrm{N(H_2)}$ is crucial to determine the physical conditions of the molecular gas in the Interstellar Medium. This paper introduces the "Multi-Tracer Column Density Synthesis" (MT-CDS) technique, a new empirical approach to derive high dynamic-range column density maps with interferometers such as ALMA. We have compared the integrated intensity maps of two density selective tracers, namely HNC (1-0) and $\mathrm{N_2H^+}$ (1-0), obtained with IRAM-30m with ancillary Herschel column density estimates in seven
star-forming regions in Orion and derived individual temperature-corrected conversion factors for each of these tracers. We applied these conversion factors obtained at low-resolution into similar high sensitivity ALMA observations to derive independent column density maps describing both the low $N_\mathrm{HNC}\mathrm{(H_2)}$ and high $N_\mathrm{N_2H^+}\mathrm{(H_2)}$ column density components at high spatial resolution (4.5"). We also combined these independent maps into estimates for the total gas column density gas $N_\mathrm{tot}\mathrm{(H_2)}$ sampling more than two orders of magnitude in column density between $\sim 10^{21.5}-10^{23.5}$ cm$^{-2}$. A comparison with independent ArTeMiS column density maps at intermediate resolution (8") shows typical deviations of $\lesssim$0.2 dex from our MT-CDS gas column density estimates. We obtained individual column density maps in five of our targets at $\sim$2000 au resolution in which ALMA observations were available, that is a factor of $\sim$5 better than originally calibrated. These results demonstrate the potential of this MT-CDS technique to retrieve accurate, high dynamic range $N\mathrm{(H_2)}$ total gas column density estimates at interferometric resolution combining multiple molecular line tracers.
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All authors Alvaro Hacar, Andrea Socci, Mario Tafalla, Francesca Bonanomi
Astrophysics of Galaxies
SQuIGGLE: Radio AGN Found Predominantly in Young, Gas-rich Post-starburst Galaxies at z ~ 0.7
Vincenzo R. D'Onofrio, Justin S. Spilker, Krista L. Smith et al. (+13 more)
The processes that rapidly quench massive
galaxies and maintain their quiescence remain poorly understood. Substantial molecular gas reservoirs can survive this shutdown in post-starburst
galaxies, raising the question of what prevents the remaining gas from efficiently forming
stars. We present deep, subarcsecond VLA 6 GHz observations of 52 massive SQuIGGLE post-starburst
galaxies at $z\sim0.7$ to test the prevalence and mechanical impact of
radio activity during the gas-rich post-burst phase. We detect 6 GHz continuum emission in 18/52
galaxies ($\approx$35%), spanning $\log(L_{1.4\,{\rm GHz}}/{\rm W\,Hz^{-1}})\simeq23.0$–$25.0$ and generally exceeding the contributions expected from ongoing
star formation and the fading starburst, favoring an AGN origin. Ancillary data at other wavelengths provide little evidence for a population of luminous, radiatively efficient AGN, suggesting that these sources are instead dominated by comparatively weak, mechanically powered
radio AGN.
Radio activity is strongly concentrated within the first $\sim$200 Myr post-burst and is predominantly associated with
galaxies retaining substantial gas reservoirs. Above a common
radio luminosity threshold, the
radio detection fraction is enhanced by a factor of $\approx$2.5 relative to the
radio AGN candidate fraction in mass- and
redshift-matched quiescent LEGA-C
galaxies, primarily due to lower power sources. For efficient jet–ISM coupling, the inferred mechanical power could supply the approximate energy required to unbind the molecular gas on timescales comparable to its observed decline. Together, these results identify a population of radiatively inefficient AGN hosted predominantly by young, gas-rich post-starburst
galaxies at $z\sim0.7$ and suggest that they may have a role in maintaining inefficient
star formation.
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All authors Vincenzo R. D'Onofrio, Justin S. Spilker, Krista L. Smith, Rachel Bezanson, Robert Feldmann, Alex J. Geiger, Andy D. Goulding, Jenny E. Greene, Mariska Kriek, Anika Kumar, Yuanze Luo, Desika Narayanan, David J. Setton, Katherine A. Suess, Margaret E. Verrico, Pengpei Zhu
Astrophysics of Galaxies
Are Broad Mg II Galaxies Fading AGN?
Stephanie M. LaMassa, Michael Eracleous, Jessie Runnoe et al. (+2 more)
We analyzed a sample of 494
galaxies from the Sloan Digital Sky Survey (SDSS) I-IV that have unusual properties. They display broadened Mg II $\lambda$2798 line emission, as would be expected of Type 1 active galactic
nuclei (AGN). However, they have weak or absent broad Balmer lines though broadened Balmer lines often accompany broadened ultraviolet lines in Type 1 AGN spectra. We performed a spectral decomposition of these "broad Mg II
galaxies” to assess whether they can be considered fading AGN. The Balmer lines are more responsive to changes in the AGN continuum than the Mg II line. As the AGN power source fades, broad H$\beta$ and then H$\alpha$ will weaken and eventually disappear, leaving broad Mg II as a signpost of a more active past. In support of this interpretation, we found that broad Mg II
galaxies have weaker AGN luminosities and lower
accretion rates (parameterized by the Eddington ratio) than typical Type 1
quasars from SDSS. The Eddington ratio of broad Mg II
galaxies are similar to dim-state changing-look AGN, with an average value $\lesssim$1%, which is the threshold at which the inner region of a geometrically thin
accretion disk is thought to evaporate and be replaced by a geometrically thick radiatively inefficient
accretion flow in stellar-mass black holes. Broad Mg II
galaxies may represent the penultimate stage in a changing-look AGN sequence prior to the complete disappearance of all broad lines.
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All authors Stephanie M. LaMassa, Michael Eracleous, Jessie Runnoe, Benny Trakhtenbrot, Gisella de Rosa
Solar and Stellar Astrophysics
A Distinct Type of Standstill in Ultra-Compact White Dwarf Binaries
Jan Kára, Liliana Rivera Sandoval, Iwona Kotko et al. (+3 more)
AM CVn
stars are ultra-compact, semi-detached binaries consisting of a white dwarf primary and a hydrogen-poor secondary. In this work, we analyse the AM CVn-type systems MGAB-V270, ZTF18aaxuusk and ASASSN-19ct, which have similar properties and show unusual post-superoutburst behaviour. We focus on the occurrence of standstill-like phases. In MGAB-V270, superoutbursts are followed by a series of echo outbursts that evolves into a standstill-like phase before the system returns to quiescence. ZTF18aaxuus shows similar post-superoutburst activity, with one echo-outburst series also developing into a standstill-like phase. ASASSN-19ct exhibits comparable echo outbursts but no standstill-like phases. Periodicity analysis using TESS data shows that superhumps can persist during both echo outbursts and standstill-like phases. Although standstills have previously been observed in AM CVn
stars, the standstill-like phases we observe appear to represent a distinct phenomenon associated with post-superoutburst activity. We compare our results to other AM CVns that may exhibit similar behaviour.
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All authors Jan Kára, Liliana Rivera Sandoval, Iwona Kotko, Jean-Marie Hameury, Luis E. Salazar Manzano, Ryan J. Oelkers
Solar and Stellar Astrophysics
Understanding the Complex Morphology of a Coronal Mass Ejection. III: How to Create a Severe Geomagnetic Storm
Cecilia Mac Cormack, Abril Sahade, Erika Palmerio et al. (+4 more)
On April 21, 2023, a complex filament eruption produced an Earth-directed coronal mass ejection (CME) that triggered the first severe geomagnetic storm of solar cycle 25. The primary objective of this work is to understand the physical origin of the severe impact of this CME on Earth. We explore the CME's complex morphology by simulating the eruption using the thermodynamic magnetohydrodynamic (MHD) model CORHEL-CME. We model the pre-eruptive structure as two intertwined
magnetic flux ropes and validate the early
evolution of the event by comparing synthetic observables generated from the model with extreme-ultraviolet and white-light observations. We then compare the simulated CME structure with in situ measurements. From our analysis, we conclude that the CME merged with a stream interaction region (SIR) before reaching Earth. This interaction compressed the CME sheath, producing a sustained negative $B_n$ component that, together with the associated enhancement in solar wind density and velocity, triggered the geomagnetic storm. The internal configuration of the
magnetic flux rope, which also maintained a sustained southward component during its propagation toward Earth, intensified the storm to severe levels. This model-data comparison underscores the power of using MHD simulations, when validated by multi-viewpoint observations, to reveal hidden dynamical processes and improve the understanding and prediction of space weather impacts.
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All authors Cecilia Mac Cormack, Abril Sahade, Erika Palmerio, Evangelia Samara, Phillip Hess, Robin C. Colaninno, Teresa Nieves-Chinchilla
Earth and Planetary Astrophysics
Science-Driven Performance Requirements for UV Coronagraph Design: Implications for O$_3$ Detection in Earth-like Atmospheres
Amber V. Young, Giada Arney, Shawn Domagal-Goldman et al. (+6 more)
Detecting biosignatures on Earth-like
exoplanets from the Proterozoic era requires instrumentation capable of probing near-ultraviolet (NUV) spectral features, particularly ozone (\ce{O3}), which serves as an indirect proxy for molecular oxygen (\ce{O2}) when direct detection is challenging. Using a combination of photochemical-
climate modeling and atmospheric
retrieval simulations, we quantify fiducial instrument performance requirements for robust \ce{O3} detection and assess the risk of spectral false positives from sulfur dioxide (\ce{SO2}). Our analysis demonstrates the \ce{O3} abundances for Proterozoic Earth-like
planets with \ce{O2} as low as 0.1% the present atmospheric level, can be constrained to within an order of magnitude at 1\,$\sigma$ confidence using three adjacent photometric bandpasses at a signal-to-noise ratio of 10 at 0.366\,$\upmu$m, each with a 15% width, and a short wavelength cutoff for those observations near 0.26\,$\upmu$m. The self-consistent steady state atmospheric modeling results show that \ce{SO2} buildup is difficult in a habitable environment with appreciable amounts of water vapor in its atmosphere and would require volcanic outgassing rates at least two orders of magnitude above present-day Earth to reach surface abundance levels comparable to Proterozoic Earth-like abundances of \ce{O3}. Even under these high \ce{SO2} flux scenarios, \ce{SO2} remains largely unconstrained with the recommended observational configuration, reinforcing the need for NUV coverage in coronagraphic instruments. Our findings support the inclusion of UV-optimized optics and detectors on the Habitable Worlds Observatory (HWO) to enable biosignature detection strategies sensitive to atmospheric conditions across key phases of Earth's geological history.
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All authors Amber V. Young, Giada Arney, Shawn Domagal-Goldman, Tyler D. Robinson, Roser Juanola-Parramon, Christopher Stark, Renyu Hu, Armen Tokadjian, Mario Damiano
Astrophysics of Galaxies
MOSS III: MeerKATs view on the galaxy populations in two massive galaxy clusters
Robert Kincaid, Mark Sargent, Pascale Jablonka et al. (+5 more)
The MeerKAT Observations of the Saraswati Supercluster (MOSS) is an ongoing project attempting to study the
radio and optical properties of the core region of the Saraswati supercluster (z = 0.28) and will eventually entail a full survey of the entire supercluster region. Here we use
radio catalogs from previous deep pilot MeerKAT L-band (1.28 GHz) observations (angular resolution of 8 arcsec) of the core region of the Saraswati supercluster. The region hosts two
galaxy clusters representing distinct environments: The most massive cluster Abell 2631, and the second most massive cluster ZwCl2341, that is significantly more dynamically active. The deep
radio catalogs of these clusters were combined with spectroscopic
redshifts (mainly from DESI DR1 and SDSS DR16) and optical photometry catalogs of the cluster member
galaxy source population. We use these
redshifts together with the 1.4GHz MeerKAT flux densities to derive the dust-free
star-formation rate (SFR) and evaluate various trends in the
radio SFG and AGN
galaxy populations. We find that the actively merging cluster ZwCL2341 has an increased
star-forming
galaxy population compared to A2631 with up to 4 times more
star-forming
galaxies. When looking at SFG-related
radio processes we see s enhanced SF-related activity in ZwCL2341 with SF-related
radio processes dominates entirely over AGN-related
radio processes. This suggests that dynamically active environments associated with cluster assembly, such as mergers, have enhanced SF
radio-activity and increased SFG (both
radio and non-
radio)
galaxy population compared to lesser active systems.
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All authors Robert Kincaid, Mark Sargent, Pascale Jablonka, Bruno Slaus, Viral Parekh, Shishir Sankhayan, Sameer Salunke, Jean-Paul Kneib
High Energy Astrophysical Phenomena · Cross-listed from hep-th
Coherent states of neutrinos in rotating matter
Alexander Breev and Maxim Dvornikov
We study coherent states of
neutrinos electroweakly interacting with rotating matter. We start with the Dirac equation for a massive
neutrino propagating in background matter with a coordinate dependent effective potential. Then, we consider the limit of massless particles and the specific matter velocity profile. It allows us to reduce the
neutrino Hamiltonian to the harmonic oscillator form. We find the exact solutions of the Dirac equation and construct the creation and annihilation operators. Using these results, we build the generalized coherent states of
neutrinos. We provide the interpretation of these coherent states in terms of the classical physics. In particular, we demonstrate that the coherent states constructed approach plane waves in the limit of slow matter rotation. We also define the effective
neutrino mass owing to the interaction of a massless
neutrino with rotating matter. Then, we consider a special case of the generalized coherent states which are called the
neutrino coherent states. The situation of the degenerate parameters of the system is also studied. Finally, we apply our results for astrophysical
neutrinos propagating in dense matter of a rapidly rotating
neutron star (NS). We calculate the effective
neutrino masses for different
neutrino energies for realistic parameters of NS.
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Instrumentation and Methods for Astrophysics
Neural networks applied to forecasting the astroclimatic and meteorological parameters in an operational context
C. Weinberger, E. Masciadri, M. De Sepibus et al. (+4 more)
Forecasting optical
turbulence and atmospheric parameters is crucial for science operations of present and new generation ground-based
telescopes (ELT) as well as for free-space optical communication (FSOC). These forecasts are also useful to optimize the AO use, particularly in the ELT framework too. Recent research has demonstrated that the AR technique currently provides the best performances in predicting atmospheric and astroclimatic parameters on a time scale of 1 hour (e.g., RMSE 0.1" for the seeing), however deep learning offers some intriguing features that include the high adaptability, the correlation that can be found between different parameters treated simultaneously and different architectures can explore the capability for possible improvements. For this reason, it is important to investigate on the possibility to improve forecast performances beyond the score achieved by AR or simply to apply deep learning in those context in which it is not possible to apply the AR. In this contribution we investigate a set of
algorithms belonging to the family of the neural networks that in principle are more suitable than the Random Forest (RF) model for this kind of application. We address specific questions related to the forecast performances in operational configurations. Besides that, we also investigate the impacts on gaps on the trained data set due to the lack of measurements of the optical
turbulence during the day time. We show evidences that with measurements covering the whole 24-hours forecast performances might improve. Our test has been done on the wind speed in this contribution. This work is done in the framework of the operational forecast system for LBT (ALTA Center) and for the VLT (FATE project) that are leaded by our team.
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All authors C. Weinberger, E. Masciadri, M. De Sepibus, A. Otarola, S. Miesske, C. Veillet, S. Ragland
Cosmology and Nongalactic Astrophysics
The Atacama Cosmology Telescope: DR6 Constraints on Isotropic Time-Dependent Cosmic Birefringence from Axion-like Particles
Zachary B. Huber, Huajian Yang, Steve K. Choi et al. (+7 more)
Axion-like particles (ALPs) with sufficiently low masses are dark matter candidates because they could account for much or all of the observed dark matter energy density and help explain observations of galactic substructure. Such pseudoscalar fields could couple to
photons, causing a time-dependent rotation of the polarization of the light with an oscillation frequency equal to the ALP mass. We use measurements of the polarization of the
cosmic microwave background (CMB) by the Atacama Cosmology
Telescope (ACT) between 2017 and 2022 to search for this effect using an EB power spectrum
estimator. By probing oscillation periods from days to years, the data constrain the coupling between ALPs and
photons for ALP masses between $2.5\times 10^{-23}$ eV and $4.8\times 10^{-20}$ eV. We find no evidence for such a signal and set a 95% upper bound on the
axion-
photon coupling constant, $g_{\phi\gamma} < 1.1\times10^{-11}\left({m_\phi}/{10^{-21}\,\mathrm{eV}}\right)\,\mathrm{GeV}^{-1} .$ This limit assumes that ALPs make up all of the dark matter and that the ALP field amplitude is stochastically distributed, which leads to more conservative bounds than the deterministic-field assumption used in some previous CMB polarization analyses. Among searches for ALP-
photon coupling using CMB polarization, we set the strongest bounds to date under the
stochastic-field assumption. This work develops a methodology to analyze over 10,000 time-sliced "depth-1" polarization maps from ACT, a data product that will be standard for time-domain astrophysics with the Simons Observatory, enabling searches with a higher sensitivity and observing span.
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All authors Zachary B. Huber, Huajian Yang, Steve K. Choi, Erminia Calabrese, Vera Gluscevic, Sigurd Naess, Michael D. Niemack, Lyman A. Page, Alexander van Engelen, Edward J. Wollack
Solar and Stellar Astrophysics
Velocity-field estimation techniques for on-disk solar coronal bright fronts (CBFs) and shock-wave propagation
Oleg Stepanyuk and Kamen Kozarev
Coronal mass ejections (CMEs) are large expulsions of
plasma and
magnetic fields from the solar corona into the heliosphere. Coronal shock waves are driven by CMEs, and accurate Solar Energetic Particles (SEP) forecasting requires knowing when and where shocks form, how fast they propagate, and how they interact with the coronal
magnetic field. By measuring the speed, geometry and temporal
evolution of coronal bright fronts (CBFs), one can create more realistic predictions of SEP onset and intensity at Earth, thus velocity-field estimation techniques supply these critical parameters. High-resolution velocity field maps can provide even deeper insight. Instead of yielding only an overall speed of the front, techniques like FLCT and optical flow can show the spatial distribution of velocities across the entire wave dome or front. These analyses reveal which parts of the front are moving fastest and how the front might be deforming as it expands. Here we discuss a set of practical parameters for Lucas–Kanade, Horn–Schunck, FLCT, and Farneback
algorithms, arrived at by combining analytic
reasoning with empirical measurements on a single event—and demonstrate the potential of these techniques for on-disk shock-wave propagation during the X1.5-class event that took place 10 May 2022, processed by the wavelet-based Wavetrack technique. A better understanding of how to fine-tune these parameters could improve the precision of
algorithms running in pipelines, and is especially valuable where per-event hand-tuning is impractical.
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Astrophysics of Galaxies
The connection between massive galaxies and their dark matter haloes from $z=0.25$ to $z \sim 4$ from the combined COSMOS, XMM-LSS and ECDF-S fields
Natalia Stylianou, Matt J. Jarvis, Rohan G. Varadaraj et al. (+4 more)
Understanding how
galaxies populate and grow within dark matter
haloes is essential for linking the observed
evolution of
galaxies to the hierarchical growth of structure. We present a
galaxy clustering analysis using optical and near-infrared data from the UltraVISTA and
VIDEO surveys covering $9.3$ deg$^2$ across the COSMOS, XMM-LSS and ECDF-S fields, $\sim 5\times$ larger than previous comparable studies, providing sufficient volume to determine the
halo occupation of the most massive
galaxies to $z\sim 4$. We measure the angular two-point correlation function for stellar-mass-selected
galaxies over $0.25<z<4$ and by combining the three fields, we reduce the
cosmic variance by a factor of $\sim2$ compared to the individual fields. The stellar-to-
halo mass ratio peaks at a
halo mass of $M_{h}\approx10^{12} {\rm M}_{\odot}$ and is a maximum at $z\sim 1$. For the most massive
galaxies, the peak
halo mass ($M_{h}^{\rm peak}$) increases from $z=1\rightarrow 0$, while the peak stellar mass in such
haloes remains approximately constant, indicating that at $z<1$ massive
galaxy formation becomes less efficient. We also find a steady increase in the satellite fraction since $z\sim 1$, from which we infer that massive
halos continue to grow hierarchically while their central
galaxies experience suppressed stellar-mass growth. We suggest this is due to the central massive
galaxies having their growth controlled by feedback from active galactic
nuclei feedback, likely from low-power
stochastic radio emission.
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All authors Natalia Stylianou, Matt J. Jarvis, Rohan G. Varadaraj, Peter W. Hatfield, Joel Hamlett, Catherine L. Hale, Tariq Yasin
Solar and Stellar Astrophysics
SPICY 30021: an embedded bona fide FUor with a mid-infrared precursor
Zhen Guo, Calum Morris, Vitor Fermiano et al. (+37 more)
Unstable mass
accretion in young stellar objects (YSOs) often leads to observable outbursts, which play a key role in stellar mass assembly during pre-main-sequence
evolution. The highest-amplitude, longest-duration events are classified as FUors. Until recently, only 50 FUor events had been confirmed. Many occur in embedded protostars, which are difficult to monitor in optical surveys. We present photometric and spectroscopic observations of SPICY 30021, an eruptive young
star discovered in the mid-infrared (MIR) NEOWISE time series. We aim to construct its spectral energy distribution and characterise its eruptive nature. We compiled multi-wavelength photometric time series from NEOWISE, VVV and VVV-RENEW, and obtained photometric and spectroscopic observations during the outburst with SOAR, Magellan and VLT, including data from the ESO public survey VVVX-GalCen. We identified the outbursting source, separated it from nearby companions, and estimated the line-of-sight extinction from spectroscopic features. Stellar parameters were constrained using radial velocity, proper motions and stellar
evolution models. SPICY 30021 is an optically obscured FUor with a total interstellar and circumstellar extinction of Av = 12.5 mag. Its spectrum closely resembles those of classical FUors. Multiple methods yield a distance of 1.7+_0.4 kpc. Its
accretion luminosity is Lacc = 32 L_sol, moderate among FUors. Quiescent near-infrared photometry is consistent with a young 0.9 M_sol progenitor, although the mass depends on the adopted model and distance. We confirm SPICY 30021 as a bona fide FUor event. Its MIR precursor suggests an outside-in triggering mechanism.
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All authors Zhen Guo, Calum Morris, Vitor Fermiano, Carolina Lizana-Vidal, Aldo Aliaga, Javier Osses, Felipe Navarete, Philip Lucas, Roberto K. Saito, Adolfo Carvalho, Vardan Elbakyan, Carlos Contreras Peña, Koshvendra Singh, Min Fang, Philipp Weber, He Zhao, Tigran Yu. Magakian, Tigran A. Movsessian, Matias Gomez, Dante Minniti, Valentin Ivanov, Maria Gabriela Navarro, Sara Federle, Ilaria Petralia, Alonso Luna, Jesus Corral-Santana, Elisa R. Garro, Sean D. Points, Cesar Briceño, Zenghua Zhang, Radostin Kurtev, Jura Borissova, Jose G. Fernández-Trincado, Javier Alonso-García, Claudio Cáceres, Casmir O. Obasi, Daniela Galdeano, Laura Baravalle, Teresa Giannini, Zhikai Zhu
Solar and Stellar Astrophysics
First L-type substellar object discovered in the vicinity of the embedded cluster NGC 2023
Styliani Tsilia, Carlos Dominguez-Tagle, Maruša Žerjal et al. (+8 more)
We present the first substellar object in a
star-forming region spectroscopically confirmed with Euclid, namely J054158.70-021031.4. This young and faint source is located close to the embedded open cluster NGC 2023. It has a spectral type of L3, a reddening of Av = 3 mag, proper motion consistent with the nearby cluster NGC 2024, and a magnitude of $\sim24.5$ in the Euclid optical band. At the distance of 403 pc, its inferred mass lies close to the planetary-mass boundary. We discovered the object by searching for ultracool dwarf candidates in the Euclid Early Release Observations. The search was based on photometric criteria, followed by the analysis of slitless 2D spectro-images in order to distinguish features that indicate the nature of these objects. This work demonstrates the potential of Euclid to unveil previously hidden populations of very low-mass objects, located in obscured regions where
star formation is ongoing.
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All authors Styliani Tsilia, Carlos Dominguez-Tagle, Maruša Žerjal, Eduardo L. Martín, Hervé Bouy, Nafise Sedighi, Sara Muñoz Torres, Nikola Vitas, Khalid Barkaoui, Nicolas Lodieu, Jerry J.-Y. Zhang
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The WDM time-frequency transform in gravitational-wave data analysis II: Evolutionary spectrum and noise covariance
Aaron D. Johnson, Katerina Chatziioannou and Robert Rosati
Noise cannot be treated as stationary over the timescales required for upcoming gravitational-wave detectors, minutes for ground-based and months for space-based detectors. Nonstationarity leads to a non-diagonal frequency-domain noise covariance
matrix, thus motivating a shift to the time-frequency domain. We introduce evolutionary power spectra for describing nonstationary noise in the Wilson-Daubechies-Meyer time-frequency basis. Under the framework of oscillatory processes, we show that, to leading order in the ratio of the Meyer filter and the nonstationarity timescales, the evolutionary spectrum is a power-frequency distribution that can be estimated from a single noise realization. We derive the corresponding noise covariance
matrix and show that it is band tri-diagonal, like its stationary counterpart. The exact covariance to all orders is positive semi-definite by construction and dense depending on the noise. We further derive the optimal tiling of the time-frequency plane that minimizes the error of a diagonal covariance approximation and show that coarse-graining the plane suppresses correlations quadratically. Using simulated data with a LISA Galactic foreground and a drifting powerlaw spectrum, we show that the stationarity approximation leads to signal-to-noise ratio loss and severely biases inference. For realistic LISA data, approximating the covariance as diagonal in the Wilson-Daubechies-Meyer domain is accurate for the narrow-band analysis of a single resolved Galactic binary, but insufficient for a broad-band analysis. Finally, we provide mitigation strategies for the wraparound correlations induced across the data time edges whenever the spectrum differs between the start and the end of the data.
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Cosmology and Nongalactic Astrophysics
Kinetic Theory of the EFTofLSS : A Halo-Based Approach
Om Kishor Hebbar, Caio B. de S. Nascimento and Arka Banerjee
The Effective Field Theory of Large Scale Structure (EFTofLSS) provides a coarse-grained description of the non-linear gravitational clustering of dark matter, in which the effects of short-scale physics are encoded in an effective stress tensor and a set of counterterms. In this work, we develop a framework to investigate the physical origin of these counterterms by relating the effective stress tensor to the dynamics of individual dark matter
halos in cosmological N-body simulations. We find that
halo accretion contributes to the trace of the
halo-based effective stress tensor, contributing to the background pressure and effective sound speed, while anisotropic
accretion generates the traceless part, consequently contributing to the shear viscosity. For the
halo population with $M_\mathrm{vir}>10^{12}\,M_\odot/h$, we find that
halos account for $\sim\!95\%$, $\sim\!85\%$, and $\sim\!70\%$ of the full box background pressure, effective sound speed, and shear viscosity, respectively, depending on the EFT cutoff scale. The contributions to the counterterms are dominated by cluster-scale
halos, $M_\mathrm{vir} \sim 10^{14} - 10^{15}\,M_\odot/h$ and
halos with larger inflow rates, supporting an interpretation in terms of
accretion-driven, out-of-
equilibrium dynamics. Our results provide a short-scale, kinetic-theory interpretation of the EFTofLSS counterterms and establish a framework for connecting the properties and dynamics of short-scale structures to physics-informed priors for large-scale cosmological observables.
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Instrumentation and Methods for Astrophysics
jax-SNANA: A GPU-accelerated Supernova Framework for the SBI Era
Matthew Grayling
We present jax-SNANA, a JAX reimplementation of the
supernova analysis framework SNANA. jax-SNANA enables GPU-accelerated transient simulations and light curve fitting,
supernova standardisation and cosmological inference. Running in single precision on an NVIDIA A100 GPU, jax-SNANA simulates more than 100,000 LSST-observed
supernovae per second and fits 5,000 light curves per second after JIT compilation, a two orders-of-magnitude increase over current tools, essential for analysing samples at the scale expected from LSST. jax-SNANA currently supports the SALT and BayeSN spectral energy distribution (SED) models as well as physical models from redback-jax and a variety of SN SED templates; light curve fitting is supported with both photometric and spectroscopic
redshifts. We fully validate the accuracy of jax-SNANA by comparing to SNANA, finding excellent consistency between the two across a variety of tasks. The code provides a modular JAX end-to-end
supernova cosmology pipeline, user-extensible to support new features including different SED templates and photometric classification
algorithms. jax-SNANA has been designed with future applications of simulation-based inference in mind, providing fast simulations and enabling fully compiled on-the-fly simulations to be generated within the training loop of downstream SBI tasks. jax-SNANA extends beyond SNANA by supporting simulations of generic SN-host
galaxy relationships and multiple sub-populations of events, for example originating from young and old progenitors. jax-SNANA is publicly available at https://github.com/mattgrayling/jax-snana and installable through pip.
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Astrophysics of Galaxies
The convective-transition gap in 47 Tucanae with JWST
M. Scalco, L. R. Bedin, M. Libralato et al. (+3 more)
We report the detection of the convective-transition gap along the lower main sequence (MS) of the Galactic globular cluster (GC) 47 Tucanae using deep James Webb Space
Telescope (JWST) observations. We analyse the stellar luminosity function (LF) in the vicinity of the gap location using two independent colour-magnitude diagrams (CMDs). In both cases, the LF is characterised by a narrow gap followed by a discontinuous increase in the stellar number counts, and presents an overall morphology qualitatively consistent with that reported in previous studies. By modelling the observed LFs with an empirical likelihood model, we estimate the statistical significance of the observed feature. Additional JWST passbands exhibit similar signatures, providing further evidence for the presence of a discontinuity.
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All authors M. Scalco, L. R. Bedin, M. Libralato, M. Griggio, E. Vesperini, R. Gerasimov
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
The Forgetful Black Hole: Memory Burden and Hysteresis in Hawking Evaporation
Yen Chin Ong
The
memory-burden scenario of black hole evaporation proposes that Hawking emission may become increasingly suppressed as maintaining stored
quantum information becomes dynamically costly. In this work, we revisit this scenario and investigate the conditions under which information retention can produce a genuine dynamical burden. We derive general scaling conditions for incremental
memory accumulation at a fixed fractional mass loss and establish a conditional no-go result:
entropy-suppressed, zero-mean deposits with subextensive integrated correlations cannot produce an order-one luminosity modification through unamplified accumulation and bounded feedback. We identify three essential requirements for dynamical
memory: a record of the past must be written, retained, and coupled back to subsequent evaporation. We illustrate these requirements with concrete toy models that exhibit either a prolonged but finite black hole lifetime or an asymptotically approached finite-mass state (an effective remnant). We further distinguish kinetic-
memory, thermodynamic-
memory, and spectral-
memory sub-categories of possible
memory-burden mechanisms. In particular, we demonstrate that an independently evolving
memory variable can generate evaporation-
accretion hysteresis, such that a black hole returning to the same mass may possess a different retained
memory and consequently a different luminosity. This history dependence may have implications for primordial black hole phenomenology. Finally, we briefly discuss the possibility of "merger rejuvenation", in which black hole mergers reorganize or reset the effective
memory state.
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Solar and Stellar Astrophysics
The mass functions of multiple stellar populations in 47 Tucanae
M. Scalco, J. Bruce, E. Vesperini et al. (+1 more)
We used a combination of James Webb Space
Telescope (JWST) and Hubble Space
Telescope (HST) observations to investigate the mass functions (MFs) of the different stellar populations in the globular cluster (GC) 47 Tucanae (NGC 104) over a wide stellar-mass interval. We identified the multiple populations along the lower main sequence using only JWST photometry and, in particular, colour combinations sensitive to variations in oxygen abundance. We derived the MFs of the first- and second-population (1P and 2P)
stars separately and found that in the low-mass regime, the present-day MF of the 1P population is significantly steeper than that of the 2P population, which appears nearly flat. We also present the results of a dynamical model showing that this behaviour requires a different initial mass function (IMF) for the 2P and the 1P populations in the 0.1-0.4 solar masses mass range, thus providing a new fundamental constraint for the study of the
star formation of multiple populations in GCs.
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All authors M. Scalco, J. Bruce, E. Vesperini, L. R. Bedin
Solar and Stellar Astrophysics
JWST observations of 47 Tucanae: I. The low-mass main sequence down to the hydrogen-burning limit
M. Scalco, R. Gerasimov, L. R. Bedin et al. (+4 more)
We present the first results of a series of studies based on JWST observations of the globular cluster 47 Tucanae (47 Tuc, or NGC 104) obtained with NIRCam. By combining new data with earlier JWST observations, we derive high-precision proper motions (PMs) over a multi-year baseline (of ~3 years) and construct a clean sample of cluster members extending to very faint magnitudes (F444W~24.25 mag, corresponding to ~0.077 solar masses, slightly above the estimated hydrogen-burning limit of 47 Tuc, ~0.074 solar masses) along the main sequence (MS). We investigated the presence of the low-mass MS kink previously identified in 47 Tuc using the new F090W and F444W photometry. No significant signature of the feature is found using these filters, consistent with its proposed physical interpretation as a consequence of the transition in carbon chemistry toward a methane-dominated
equilibrium in very low-mass
stars. A comparison with theoretical isochrones indicates that the stellar population near the bottom of the MS is likely dominated by oxygen-poor
stars, in agreement with previous findings. Using artificial-
star tests, we quantify the completeness of our sample and show that the requirement of PM-based membership significantly limits the detection of the faintest objects, indicating that current JWST observations of 47 Tuc are not sufficiently deep to reliably trace the cluster's brown dwarf cooling sequence. The mass function (MF) of 47 Tuc shows a structured behaviour, with a break at ~0.15 solar masses not associated with the onset of convection, and a mild but systematic radial variation consistent with mass segregation. Our analysis indicates that the MF shape in this mass regime is more complex than a simple power-law description. This feature in the MF may point to a presently unrecognised mechanism affecting the formation or dynamical
evolution of low-mass
stars in globular clusters.
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All authors M. Scalco, R. Gerasimov, L. R. Bedin, E. Vesperini, M. Griggio, D. Nardiello, J. Anderson
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Black Hole Fine Structure
Adrian Ka-Wai Chung, Richard Dyer, Tomasz Kinowski et al. (+1 more)
In General Relativity, axial and polar black-hole perturbations share identical quasinormal-mode spectra, a property known as isospectrality. New physics can break this degeneracy, producing a spectral splitting analogous to atomic fine structure. We perform a theory-agnostic search for such splitting in gravitational-wave observations. We find no evidence for isospectrality breaking and place a combined $90\%$ upper limit of $<28.5\%$ on the relative frequency splitting. We map these constraints onto several modified-
gravity theories, constraining the coupling-lengths to be $\lesssim 28\,\mathrm{km}$.
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All authors Adrian Ka-Wai Chung, Richard Dyer, Tomasz Kinowski, Christopher J. Moore
Cosmology and Nongalactic Astrophysics
Scalar-Assisted Growth of Supermassive Black Holes: Boson-Mass Windows and Observational Constraints
Jorge Castelo Mourelle, Darío Núñez Zúñiga, Saeed Fakhry et al. (+1 more)
We study a phenomenological cosmological model of black-hole growth in which a finite baryonic reservoir and a bosonic scalar cloud feed the black hole simultaneously. The baryonic component accretes through an Eddington-like channel, while the scalar cloud transfers mass through an effective quasibound-state decay rate. Evolving the system directly in
redshift within a flat $\Lambda$CDM background, we scan over $\mu$, $M_0$, $M_{c,0}$, and $M_{b,0}$ to assess whether scalar-assisted
accretion can accelerate the formation of $10^9M_\odot$ supermassive black holes. We find that the scalar contribution is highly selective in parameter space. For the mass scales explored here, scalar transfer is most efficient for $\mu\sim10^{-19}-10^{-16} \mathrm{eV}$, producing rapid cloud depletion and significantly earlier black-hole growth, while outside this interval the
evolution remains mainly baryonic. More generally, this efficient window reflects a preferred range of the dimensionless coupling $\alpha=\mu M_{\rm BH}$ and therefore shifts approximately as $\mu\propto M_{\rm BH}^{-1}$. Comparison with observed
quasar masses and luminosities instead favors lower
boson masses, broadly around $\mu\sim10^{-21}-10^{-20}\mathrm{eV}$. These results are not necessarily in tension, since the
boson mass that maximizes early growth depends on the characteristic black-hole mass and evolutionary stage. This separation between dynamical efficiency and observational compatibility leaves open complementary roles for different bosonic mass scales in supermassive black hole growth and dark-matter phenomenology.
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All authors Jorge Castelo Mourelle, Darío Núñez Zúñiga, Saeed Fakhry, Nicolas Sanchis-Gual
Astrophysics of Galaxies
Substructure-enhanced Collisional Relaxation in Stellar Systems
Jian-Yu Gu, Xiao-Bo Dong and Run-Yu Meng
Two-body collisional relaxation in stellar systems is conventionally estimated using the classical Chandrasekhar theory, in which a subject
star is assumed to be embedded in a homogeneous medium of field
stars and their velocity distribution taken to be isotropic and Gaussian. Real stellar systems, however, can exhibit pronounced spatial and kinematic substructures. We investigate how such substructures – particularly the non-classical spatial inhomogeneity – modify the two-body
diffusion coefficient. We retain
hyperbolic two-body encounters but generalize the encounter calculation by integrating explicitly over the spatial distribution $n(\mathbf{r})$, while evaluating the velocity contribution from the full distribution $f_v(\mathbf{v})$. This yields a separable tensor expression for the
diffusion coefficient. We find that spatial substructure produces the dominant enhancement. The enhancement of the
diffusion coefficient increases systematically as the effective fractal dimension $D_{\rm frac}$ decreases, $\log \zeta_r(D_\text{frac}) \sim \left(1-D_\text{frac}/3\right)^q$ with $q \approx 4.28$. For the observationally motivated case with $D_{\rm frac}\approx 1.5$, the enhancement is moderate, whereas substantially lower fractal dimensions produce much larger enhancements. In contrast, the anisotropic, power-law-tailed, and fractal-like velocity distributions modify the
diffusion coefficient only by factors of order unity. Our representative substructured model yields enhancement ratios $\zeta_r\simeq3.45$ and $\zeta_v\simeq1.33$ when the measured particle-number trends are extrapolated to $N=10^{11}$, corresponding to an overall enhancement of $\zeta\simeq4.6$. Therefore, within the two-body encounter framework and the commonly used separable distribution functions, the enhanced collisional relaxation still has little impact on the mean-field nature of typical galactic systems.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Strong-Field Gravitational-Wave Lensing from Ray-Traced Arrival-Time Surfaces
Luka Vujeva, João S. Santos and Brian C. Seymour
The diffraction integral formalism has been greatly successful in describing gravitational wave
lensing effects in scenarios where the wavelength of the signal is comparable to the characteristic length scale of the lens, known as the wave optics regime. However, the assumptions required to construct its integrand break down as the source approaches the strong
gravity region of a black hole lens. In particular, we are interested in the lensed signal from a binary (the source) near a massive black hole (the lens). We present a new formalism for obtaining low frequency corrections to sources being lensed in the strong field regime of
gravity by leveraging the fact that null geodesics obey the Hamilton–Jacobi equations. In doing so, we are able to construct a time delay surface without relying on the thin lens approximation, and solve the diffraction integral for the resulting surface directly. For a stationary source at $10M$, deep in the strong field regime, when comparing the results with a relativistic wave scattering model, we find $6.5\%$ and $0.3\%$ agreement in the peak amplification and first diffractive fringe, respectively. Furthermore, we find a $< 1\%$ agreement with the amplitude of the point mass lens with a source at $10^4 M$ in the weak field, but noticeable dephasing between the peaks of the amplification function at higher frequencies. This work allows for clean interpolation between otherwise separate regimes, valid for sources from $\sim 6M \to \infty$. It provides a transparent, physically motivated framework for computing beyond-
geometric optics
lensing effects in the strong field regime.
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Earth and Planetary Astrophysics
Thermodynamically consistent equation of state tables for use in giant planet and brown dwarf interior modeling
Emily Sandford and Yamila Miguel
Equation of state (EOS) tables used in giant
planet modeling exhibit regions of strong thermodynamic inconsistency, or disobedience to the first law of thermodynamics. These generally result from smooth interpolation over physical discontinuities or between thermodynamic sub-domains governed by different physical models. The effect of thermodynamic inconsistency on structure models of
planets evolved with these EOS has never been studied in detail, although it is understood to introduce spurious sources or sinks of energy or
entropy in the models, leading to inaccuracies. Here, we present a method for improving the thermodynamic consistency of an existing EOS table, based on constructing a Helmholtz free energy $F(\rho,T)$ covering the EOS domain and deriving all the other necessary EOS quantities from it. This method produces EOS tables with roughly thousandfold better thermodynamic consistency across the EOS domain of interest, as quantified by three thermodynamic consistency metrics derived from the first law. We also present a controlled experiment comparing giant
planet models evolved with MESA using the original EOS and the $F$-derived, thermodynamically consistent versions, and find that the models can differ by up to $5\%$ in radius at an age of 5 Gyr, and by up to $25\%$ in luminosity at earlier stages of
evolution; thermodynamic consistency is thus an especially important consideration for characterising young directly imaged
planets. We present the $F$-derived, thermodynamically consistent versions of the tables for download at \href{https://doi.org/10.5281/zenodo.21103561}{https://doi.org/10.5281/zenodo.21103561}, along with example MESA inlists to reproduce our
evolution models.
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Cosmology and Nongalactic Astrophysics
Forecasting a Cosmological 21 cm Stacking Detection with Early HIRAX Data
Pascal Hitz, Devin Crichton and Alexandre Refregier
Post-reionization 21 cm intensity mapping provides a powerful technique for efficiently mapping the Universe on large scales. The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a compact and highly redundant
radio interferometer designed to exploit this technique. We present a forward modelling pipeline for forecasting a statistical detection of the cosmological 21 cm signal with HIRAX through cross-correlation with an external source catalogue. We simulate the cosmological signal using the
halo model and propagate it, together with Galactic and extragalactic foreground emission and instrumental noise, through a model of an early-stage 36-dish HIRAX array configuration. We generate simulated visibilities, apply delay-domain foreground filtering, and construct cross-correlation-ready ringmaps for an observing time of 120 days with a single zenith pointing over the frequency range from 700 to 800 MHz, covering approximately 3547 deg$^2$ of the sky. We investigate the prospects for an early statistical signal detection by stacking these ringmaps at the known three-dimensional positions of sources from an overlapping external survey. Specifically, we quantify how delay-domain foreground filtering, the number of stacking sources, catalogue completeness, and source
redshift uncertainties affect the detection significance. We find that
redshift precision is the most critical requirement: while spectroscopic
redshifts with $\sigma_z / (1+z) \sim 0.001$ preserve a significant stacking signal even under realistic foreground filtering and substantial catalogue incompleteness, photometric
redshift uncertainties of $\sigma_z / (1+z) \sim 0.01$ strongly suppress the signal for realistic delay cutoffs. Applying the framework to a Euclid-like spectroscopic
galaxy sample, we recover a minimum signal-to-noise ratio of 11 for our most conservative delay cutoff of 100 ns.
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Astrophysics of Galaxies
A Nonlinear General Implicit Runge-Kutta Integrator for Multifluid Charged Dust and Gas
Mengxuan Chen, Hui Li, Chong-Chong He et al. (+3 more)
Charged dust in magnetized gas is subject to aerodynamic drag and the Lorentz force, both of which can be difficult to model numerically in a fluid simulation where their characteristic timescales are shorter than the timestep set by the Courant condition. We present a two-stage general implicit Runge-Kutta (GIRK) source integrator for multifluid charged dust coupled to an ideal magnetohydrodynamic (MHD) gas, implemented in the open source GPU-accelerated quokka code. Drag and Lorentz forces are advanced together in one implicit source update, avoiding errors in the terminal drift that can arise when the two forces are advanced in separate substeps. The timestep is compared with a drag-Lorentz timescale to select between resolved and stiff branches. The resolved branch uses Gauss-Legendre coefficients, while the stiff branch uses a coefficient set designed to recover the terminal drift set by the drag-Lorentz balance. We also allow the dust stopping time and charge-to-mass ratio to depend on the evolving state, evaluating them separately at the two implicit stage states and solving the resulting nonlinear stage equations by Picard iteration. The source update conserves total gas-dust momentum, and its computational cost scales linearly with the number of dust species. Tests reproduce the expected drag damping and terminal drift, confirm the predicted gyromotion amplitude and phase errors, demonstrate accurate treatment of state-dependent source coefficients, and recover the expected wave, shock, and instability dynamics in dusty MHD flows.
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All authors Mengxuan Chen, Hui Li, Chong-Chong He, Benjamin D. Wibking, Mark R. Krumholz, Xue-Ning Bai
Astrophysics of Galaxies
GroArnold: A Framework for Constructing Action-based Models for Triaxial Galaxies and Dark Matter Halos
Jian-Yu Gu, Xiao-Bo Dong, Shi-Yan Zhong et al. (+1 more)
Action-based distribution functions $f(\mathbf{J})$ provide a powerful description of stellar systems. Consequently, the construction of physically accurate and dynamically stable $f(\mathbf{J})$ for galactic components has emerged as a key challenge in the field. In this study, we present GroArnold, a computational framework designed to construct analytical $f(\mathbf{J})$ expressions for axisymmetric and triaxial
galaxies and dark matter
halos. The framework integrates modules for $N$-body initial condition generation, $N$-body simulation, angle–action variable estimation, and distribution-function fitting into a unified workflow. It supports a wide range of density profiles and kinematic properties, and is uniquely designed to generate stable $N$-body models for user-specified galactic systems, with the aim of obtaining an $f(\mathbf{J})$ that approximates a dynamically stable and physically consistent state. To this end, we extend the triaxial Stäckel Fudge method of the TACT code, implemented in our Nbody-TACT module, to enable action estimation directly from $N$-body gravitational potentials. GroArnold provides a robust and flexible tool for deriving numerically empirical, explicitly analytical distribution functions for user-specified
galaxies or
halos, thereby facilitating a wide range of practical $f(\mathbf{J})$-based modeling applications. In addition, it serves as a powerful tool for investigating the dynamics of realistic triaxial
galaxies and
halos beyond the scope of traditional spherical or axisymmetric models. We assessed the accuracy of the output $f(\mathbf{J})$ by comparing its predicted spatial and velocity distributions with those of the input $N$-body snapshot, and confirmed that it provides a reasonably accurate representation of the input. The code is modular, publicly available, and designed to support future extensions and adaptations.
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All authors Jian-Yu Gu, Xiao-Bo Dong, Shi-Yan Zhong, Run-Yu Meng