Cosmology and Nongalactic Astrophysics
21 cm Cosmology Sensitivity to Small-Scale Structure: Warm vs Neutrino-Interacting Dark Matter
Virgile Dandoy, Christian Döring, Gaétan Facchinetti et al. (+2 more)
The $21\,$cm signal originating from
Cosmic Dawn to the Epoch of Reionisation is highly sensitive to the processes governing
star formation in the early universe as well as new physics. In this work, we focus on the imprint of non-cold dark matter (DM), which impacts the formation of the smallest
halos. Our goal in particular is to clarify whether near-future
radio telescopes such as the Hydrogen Epoch of Reionisation Array (HERA), will be able to distinguish between free-streaming dark matter, specifically in the form of thermal warm DM (WDM), and collisional damping due to
neutrino-DM ($\nu$DM) interactions giving rise to larger overdensities on small scales. For that purpose we first implement a mapping between the two models in terms of a cutoff scale and determine detection thresholds for the two DM models. Using Fisher
matrix forecasts, we show that $\nu$DM interaction strengths down to $\sigma_{\nu{\rm DM}}\sim 3\times10^{-35}$ cm$^2$ could be probed by $21\,$cm cosmology when considering two populations of
galaxies for a GeV mass DM. This would allow to either confirm or rule out a recent claimed preference for a non-zero $\nu$DM interaction in Lyman-$\alpha$ data. Furthermore, we find that HERA will not be able to distinguish between $\nu$DM and WDM. In the latter context, the threshold for detection of $\nu$DM interactions translates into WDM with mass up to $m_{\rm WDM}\sim 9$ keV that could be detected by HERA.
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All authors Virgile Dandoy, Christian Döring, Gaétan Facchinetti, Laura Lopez-Honorez, Justus Schwagereit
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A New Definition of Horndeski Theory and the Possibility of Multiple Scalar Field Extensions
Tomoki Katayama
In the single-field case, Horndeski provides the most general scalar-tensor theory with second-order field equations. By contrast, systematic multi-field extensions remain incomplete: while the general field equations for the bi-Horndeski case are known, a general action has not been established, and for cases with three or more fields, neither a general action nor general equations are available. We characterize Horndeski theory by three mild axioms: closure under invertible pure disformal transformations, the inclusion of a minimal Horndeski theory as an anchor, and the requirement that the coefficient functions of the Lagrangian be arbitrary up to relations required by the closure. Under this characterization, we recover the standard single-field action up to boundary terms and obtain a practical path to multi-field constructions. In particular, we show that antisymmetric structures, such as those identified by E. Allys, S. Akama, and T. Kobayashi, appear within this framework, and indicate that this viewpoint has the potential to account for features captured by known bi-Horndeski equations.
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Cosmology and Nongalactic Astrophysics
Viscous Dark Energy and Mass-Varying Dark Matter in Lyra Manifold: Cosmological Dynamics and Observational Constraints
Giridhari Deogharia, Madhurima Pandey and Ashadul Halder
We investigate the cosmological dynamics of a universe described by Lyra's geometry in the presence of dark energy (DE) and dark matter (DM). Dark energy is modeled as a quintessence scalar field with bulk viscosity, while dark matter is allowed to interact with the scalar sector. The displacement vector field, arising naturally in Lyra's
manifold, provides an additional
geometric contribution. By employing dynamical system techniques, we analyze stability properties and late-time attractors. Our results indicate that viscosity and DE–DM interaction enrich the phase space structure and can help address both the
cosmic acceleration and the coincidence problem. Furthermore, by performing a Markov Chain Monte Carlo (MCMC) analysis with recent observational
datasets, we derive best-fit values for the model parameters that exhibit good consistency with current data.
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Astrophysics of Galaxies
Elemental abundance ratios for the bulge of M31
F. La Barbera, A. Vazdekis, F. Matteucci et al. (+3 more)
We present radial trends of
metallicity ([Fe/H]) and abundance ratios ([X/Fe]) for several chemical elements – including C, N, Na, and the so-called alpha-elements (O, Mg, Si, Ca, and Ti) – in the bulge of M31, out to ~0.6kpc from the center. We estimated abundances using full-spectrum fitting, full-index fitting, and line-strength analysis, in combination with different
stellar population models. We first tested these techniques on mock spectra and SDSS stacked spectra of ETGs, and then applied them to high-quality long-slit spectroscopy of the M31 bulge obtained with the OSIRIS spectrograph at the GTC. We find that O, N, and Na are significantly enhanced relative to Fe across the bulge, with typical abundances >0.3~dex. In particular, N and Na show steep central enhancements, reaching ~0.5dex. C, Mg, and Si exhibit intermediate enhancements of [X/Fe]~0.2dex, with C and Mg decreasing toward the center to <~0.1dex; while Ca, and to a lesser extent Ti, closely follow Fe, with [X/Fe]<0.1dex. Applying the same analysis to SDSS stacked spectra of ETGs revealed that the abundance pattern of the M31 bulge closely resembles that of the most massive
galaxies, except for N, which is significantly more enhanced (by ~0.1dex) in the bulge. For the bulk of the bulge, chemical
evolution models assuming high
star-formation efficiency and a short gas infall timescale reproduce the overall trends in [Fe/H] and [X/Fe]. In the central region (<~100pc), the high
metallicity content of the bulge can be explained by either an IMF flatter than Salpeter at high mass, or a prolonged
star formation. Additional processes, such as differential
galactic winds, appear necessary to account for the observed decoupling among alpha elements and the strong central N enhancement. Our results support a scenario whereby the bulk of the M31 bulge formed during a fast and intense episode of
star formation.
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All authors F. La Barbera, A. Vazdekis, F. Matteucci, E. Spitoni, A. Pasquali, I. Martín-Navarro
High Energy Astrophysical Phenomena
Explosions in the Empty: A Survey of Transients in Local Void Galaxies
Suo-Ning Wang, Bin-Bin Zhang and Rubén García-Benito
We present a systematic analysis of transient astrophysical events – including
supernovae (SNe), gamma-ray bursts (GRBs), and fast
radio bursts (FRBs) – in void and non-void
galaxies within the local universe ($0.005 < z < 0.05$).
Cosmic voids, defined by low
galaxy densities and characterized by minimal environmental interactions, offer a natural laboratory for isolating the impact of large-scale underdensities on
stellar evolution and transient production. Using multi-wavelength data from the Sloan Digital Sky Survey, the Sternberg Astronomical Institute
Supernova Catalogue, and high-energy space observatories, we compare transient occurrence rates and host
galaxy properties across environments. We find that core-collapse
supernovae (CCSNe) are significantly more common in void
galaxies, indicating that massive
star formation remains active in underdense regions. In contrast, Type Ia
supernovae are less frequent in voids, consistent with a scarcity of older
stellar populations. Notably, we identify a short-duration GRB hosted by a void
galaxy, demonstrating that compact object mergers can occur in isolated environments. Additionally, we find no FRBs associated with void
galaxies. Taken together, these results show that
cosmic voids exert a measurable influence on the
star formation history of
galaxies and hence on the production of transients.
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Astrophysics of Galaxies
Insights on Gas Distribution and Dynamics in Massive Proto-cluster G358.46$-$0.39: Possible Multiplicity in G358.46$-$0.39 MM1a
Chukwuebuka J. Ugwua, James O. Chibuezea, Willice Obonyoa et al. (+1 more)
This work explored the spatial distribution of C$^{17}$O, SiO, HC$_{3}$N and SO$_{2}$ molecules, as well as the energetics of
outflows in G358.46$-$0.39 proto-cluster using ALMA band 7 archival data, with the aim of providing an improved understanding of its protostellar nature, gas kinematics and dynamics. G358.46$-$0.39 is previously known to consist of 4
dust continuum cores (MM1a, MM1b, MM1c and MM2). The integrated intensity map of C$^{17}$O reveals filamentary and dumbbell-shaped structures that are probably compressed gases from the expansion of the HII region MM2. The SiO emission reveals spatially overlapped blue and red
outflow lobes, likely driven by an unresolved young
stellar object (YSO) in MM1a. The spatial distribution of HC$_{3}$N and SO$_{2}$ molecules in MM1a shows a compact morphology, with no detectable HC$_{3}$N and SO$_{2}$ emissions in the other cores. The SO$_{2}$ emission reveals a clear velocity gradient in MM1a, as well as large velocity dispersion ($\sim$ 3\,\kms) within the inner core of MM1a, which are consistent with rotating structures. We estimated the mass, momentum and energy
outflow rate, as well as other
outflow parameters. The SiO
outflow exhibits a different morphology compared to the $^{12}$CO
outflow morphology previously observed in MM1a. The SiO and $^{12}$CO
outflows are probably associated with disks of separate cores with one face-on and the other edge-on, pointing to multiplicity of YSOs in MM1a. The properties of MM1a indicate that it is a massive protostar that is actively accreting and undergoing
star formation.
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All authors Chukwuebuka J. Ugwua, James O. Chibuezea, Willice Obonyoa, Mavis Seidu
Astrophysics of Galaxies
Simple relations from complex outflows: How the $M-\sigma$ relation emerges in a multi-phase environment
Matas Tartėnas, Kastytis Zubovas and Eimantas Skuodas
The tight empirical $M-\sigma$ relation between the mass of a SMBH) and the velocity dispersion of the host
galaxy bulge is often interpreted as the result of self-regulation by AGN feedback. This picture is motivated by analytical and semi-analytical models in which momentum-driven AGN winds can expel the gas once the SMBH reaches a critical mass. However, these models typically assume idealised conditions: smooth gas distributions, spherical
symmetry, and very efficient cooling of the shocked AGN wind. We checked whether AGN
outflows can establish the $M-\sigma$ relation in a multi-phase and turbulent
galactic bulge subject to realistic radiative cooling while conserving the shocked AGN wind energy. We calculated a suite of purpose-built hydrodynamical simulations of AGN
outflows in turbulent gas shells, covering a wide range of constant AGN luminosities. We tracked the
outflow evolution over the course of $\geq1$~Myr. We analysed the effect of AGN
outflow on the cold dense gas and SMBH feeding, estimating the luminosity threshold for removing most of the cold gas from the central regions. We find that AGNs with significantly sub-Eddington luminosities cannot suppress SMBH feeding, while luminosities exceeding $\sim 0.7$ times Eddington clear out both the diffuse hot gas and the cold clumps, consistent with the momentum-driven
outflow formalism. We also show that dense gas clusters are affected almost exclusively by the AGN wind momentum, while the shocked wind energy escapes through low-density channels and inflates large bubbles of diffuse gas. Therefore, AGN wind-driven energy-conserving feedback in a turbulent multi-phase medium affects the dense gas only via the wind momentum. Thus, the momentum-driven
outflow paradigm is applicable for explaining the $M-\sigma$ relation even in realistic systems.
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Astrophysics of Galaxies
Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. V. Dramatic Variability in High-Ionization Broad Emission Lines
Zhi-Qiang Chen, Jun-Jie Jin, Wei-Jian Guo et al. (+10 more)
We present a systematic search for changing-look (CL)
quasars at high
redshift z > 0.9 by cross-matching the spectroscopic
datasets from the Dark Energy Spectroscopic Instrument Data Release 1 and Sloan Digital Sky Survey Data Release 18. We identify 97 CL
quasars showing significant variability in high-ionization broad emission lines, including 45 turn-on and 52 turn-off events, corresponding to a detection rate of approximately 0.042%. This rate is lower than that found for low-ionization CL
quasars, likely due to both selection effects and physical differences in high-ionization lines. Based on the CL
quasar sample, we find that CL
quasars generally exhibit lower
accretion rates compared to typical
quasars, with average Eddington ratios of log lambda_Edd approximately -1.14 in the bright state and approximately -1.39 in the dim state, compared to approximately -0.65 for typical
quasars. While high-ionization lines in CL
quasars follow the Baldwin effect on a population level, some individual sources show inverse Baldwin trends. We also find a positive correlation between the variability of high-ionization lines such as Mg II and C III] and the change in bolometric luminosity. In addition, we estimate a characteristic rest-frame timescale of approximately 3 years for CL transitions, with no significant difference between turn-on and turn-off cases. Taken together, these results support an
accretion-driven origin for the CL phenomenon and provide new insights into the variability of high-ionization emission lines.
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All authors Zhi-Qiang Chen, Jun-Jie Jin, Wei-Jian Guo, Sheng-Xiu Sun, Zhi-Wei Pan, Chen-Xu Liu, Hua-Qing Cheng, Jing-Wei Hu, Zhen-Feng Sheng, Hu Zou, Zhao-Bin Chen, Qi Zheng, Qi-Rong Yuan
Cosmology and Nongalactic Astrophysics
Galaxy-Multiplet Clustering from DESI DR2
Hanyue Wang, Daniel J. Eisenstein, Jessica Nicole Aguilar et al. (+44 more)
We present an efficient
estimator for higher-order
galaxy clustering using small groups of nearby
galaxies, or multiplets. Using the Luminous Red
Galaxy (LRG) sample from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2, we identify
galaxy multiplets as discrete objects and measure their cross-correlations with the general
galaxy field. Our results show that the multiplets exhibit stronger clustering bias as they trace more massive dark matter
halos than individual
galaxies. When comparing the observed clustering statistics with the mock catalogs generated from the N-body simulation AbacusSummit, we find that the mocks underpredict multiplet clustering despite reproducing the
galaxy two-point auto-correlation reasonably well. This discrepancy indicates that the standard
Halo Occupation Distribution (HOD) model is insufficient to describe the properties of
galaxy multiplets, revealing the greater constraining power of this higher-order statistic on
galaxy-
halo connection and the possibility that multiplets are specific to additional assembly bias. We demonstrate that incorporating secondary biases into the HOD model improves agreement with the observed multiplet statistics, specifically by allowing
galaxies to preferentially occupy
halos in denser environments. Our results highlight the potential of utilizing multiplet clustering, beyond traditional two-point correlation measurements, to break degeneracies in models describing the
galaxy-dark matter connection.
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All authors Hanyue Wang, Daniel J. Eisenstein, Jessica Nicole Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Todd Claybaugh, Axel de la Macorra, Arjun Dey, Biprateep Dey, Peter Doel, Simone Ferraro, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztañaga, Gaston Gutierrez, Klaus Honscheid, Mustapha Ishak, Richard Joyce, Stephanie Juneau, David Kirkby, Theodore Kisner, Anthony Kremin, Ofer Lahav, Claire Lamman, Martin Landriau, Marc Manera, Aaron Meisner, Ramon Miquel, Eva-Maria Mueller, Seshadri Nadathur, Gustavo Niz, Nathalie Palanque-Delabrouille, Will J. Percival, Francisco Prada, Ignasi Pérez-Ràfols, Ashley J. Ross, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Joseph Harry Silber, David Sprayberry, Gregory Tarlé, Benjamin Alan Weaver, Rongpu Zhou, Hu Zou
Solar and Stellar Astrophysics
Type Iax supernovae as a source of iron-rich silicate dust
Aman Kumar and Arkaprabha Sarangi
We model the formation of
dust in the ejecta of Type Iax
supernovae (SNe), which is a low-luminosity subclass of Type Ia SNe. A non-
equilibrium chemical kinetic approach is adopted to trace the synthesis of molecules, molecular clusters, and
dust grains in the ejecta of thermonuclear SNe. We find that Type Iax SNe provide conditions conducive to the formation of several O-rich
dust species in the ejecta. Particularly, iron-rich silicates of chemical type FeSiO3, Fe2SiO4, and MgFeSiO4 are found to form in abundance, suggesting that the ejecta of low-luminosity thermonuclear SNe can be a site where a large fraction of iron is locked up in
dust, unlike other
stellar sources. The final mass of
dust formed in the ejecta ranges between 10^{-5} and 10^{-4} Msun, where most of the
dust forms between 1000 and 2000 days post-explosion. Apart from Fe-rich silicates, Mg-silicates, and silicon carbide are also formed in the ejecta of Type Iax SNe. When compared to the
dust budget of typical Type Ia SNe, we find that the expected
dust-to-ejecta mass ratio is 1 or 2 orders of magnitude larger in Type Iax SNe. We conclude that the ejecta of typical Type Ia SNe form a negligible amount of
dust, in agreement with observation, while the low-luminosity subclass Type Iax SNe are potential producers of iron-rich silicates.
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Solar and Stellar Astrophysics
Interacting binaries on the Main Sequence as in-situ tracers of mass transfer efficiency and stability
Koushik Sen, Mathieu Renzo, Harim Jin et al. (+8 more)
Understanding the transfer of mass and angular momentum in binary interactions is crucial for modelling the
evolution of any interacting binary after the first mass transfer phase. Mass transfer physics assumptions shape the predictions for later stages of binary
evolution, such as the immediate progenitors of stripped-envelope
supernovae and gravitational wave mergers. We constrain the efficiency and stability of thermal timescale mass transfer in massive binary
evolution using the observed population of 62 massive interacting binaries on the Main Sequence (`Algols') in the Milky Way, Large and Small Magellanic Clouds. We find that purely conservative or non-conservative mass transfer cannot explain the current mass ratio and orbital period of all massive Algols. Angular momentum conservation rules out conservative mass transfer in $\sim$28\,% of massive Algols in the SMC. About three-quarters of all massive Algols are consistent with having undergone inefficient mass transfer ($\lesssim$\,50\,%), while the remaining systems, mostly residing in the LMC and Milky Way, require mass transfer to have been more efficient than 25%. For our fiducial assumption on the extent of envelope stripping, the current sample of massive Algols does not require mass transfer to be efficient at the shortest orbital periods ($\sim$2\,d) at any
metallicity. We find evidence that mass transfer on the Main Sequence needs to be stable for initial accretor-to-donor mass ratios as unequal as $\sim 0.6$. Unless biased by observational selection effects, the massive Algols in the SMC seem to have undergone less efficient mass transfer than those in the LMC and Milky Way.
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All authors Koushik Sen, Mathieu Renzo, Harim Jin, Norbert Langer, Abel Schootemeijer, Jaime I. Villaseñor, Laurent Mahy, Aldana Grichener, Neev Shah, Chen Wang, Xiao-Tian Xu
Cosmology and Nongalactic Astrophysics
Nikolaos Samaras
Milgromian Dynamics (MOND) has been particularly successful in predicting scaling relations for
galactic systems, namely the baryonic Tully-Fisher for spirals, the Faber-Jackson for ellipticals and the Radial Acceleration Relation for late-type
galaxies. Its essential tenet is the modification of the
gravity law at low accelerations. Nevertheless, despite MOND's passed tests, the puzzle of the missing mass on
galaxy clusters' scales still persists. One proposed scenario to complete this deficit and apply it further to cosmology is the so-called $\nu$HDM model. It is composed of a sterile
neutrino and the MOND
gravity. In this Ph.D. thesis, I have put forward this cosmological idea, conducting hydrodynamical simulations to investigate the $\nu$HDM structure formation. In the debut attempt, the $\nu$HDM model was proven capable of reproducing the $\Lambda$CDM cosmology, imitating the same expansion history ($\Omega_m \approx$ 0.3 and $H_0 \approx$ 67.6 km/s/Mpc), reproducing the CMB phenomenology, while the
cosmic web is nicely formed. In the next step, I have optimized the $\nu$HDM model using
Bayesian statistics, re-branding it to opt-$\nu$HDM. I managed to optimally fit the angular power spectrum of the CMB calculated by Planck, except its fourth peak, but the opt-$\nu$HDM cosmological parameters changed significantly with respect to its precursor, resulting in a much heavier cosmos, with $\Omega_m \approx$ 0.5 and $H_0 \approx$ 55.6 km/s/Mpc. Next, I explore the opt-$\nu$HDM expansion history, its structure formation and the resulting mass function. The appearance of the early-time structures, firstly in the $\nu$HDM model, as well as in the opt-$\nu$HDM model occurs quiet late, at $z\approx4$ and at $z\approx 5.5$, respectively. Although the resolution has improved from previous studies, the $\nu$HDM variants cannot explain easily the high-
redshift galaxies, observed by JWST.
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Earth and Planetary Astrophysics
A JWST Transit of a Jupiter Analog: II. A Search for Exomoons
David Kipping, Ben Cassese, Quentin Changeat et al. (+3 more)
We present a search for exomoons around the Jupiter-like
exoplanet Kepler-167e using a NIRSpec JWST transit. Our 60 hour time series clearly reveals the enormous impact of long-term trends in NIRSpec data, specifically a gradual flux drift occurring over each of six 10 hour exposures. We weighed the evidence for exomoons by comparing a
planet-only model with a
planet+moon model for a grid of twelve different analysis choices. Our grid was comprised of three different reduction pipelines and four different models for the exposure-long trends - two using linear models and two using Gaussian processes. Seven grid realizations indicate a strong exomoon detection, typically favoring a Roche-skimming orbit roughly 10% the size of the
planet. We find that the only likely real astrophysical feature driving these fits is a syzygy-like event occurring almost exactly mid-transit, which is highly ambiguous with a spot-crossing event. Indeed, we show that a spot of the necessary size is compatible with the earlier Kepler data. Ironically, the fact that JWST is so superior to Kepler means that our fits are effectively driven by a single transit - a regime in which exomoons have enormous freedom to explain non-Gaussian behavior. We thus strongly urge the next transit be observed in October 2027 to break these degeneracies. Our pilot study to seek transiting exomoons with JWST reveals the profound impact exposure-long trends exert - a cautionary tale for future analyzes of this data - as well as the need for a deeper understanding of this systematic's cause and modeling best-practices.
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All authors David Kipping, Ben Cassese, Quentin Changeat, Daniel Yahalomi, Alex Teachey, Billy Edwards
High Energy Astrophysical Phenomena
A Method for Gamma-Ray Energy Spectrum Inversion and Correction
Zhi-Qiang Ding, Xin-Qiao Li, Da-Li Zhang et al. (+13 more)
Accurate spectral analysis of high-energy astrophysical sources often relies on comparing observed data to incident spectral models convolved with the instrument response. However, for Gamma-Ray Bursts and other high-energy transient events observed at high count rates, significant distortions (e.g., pile-up, dead time, and large signal trailing) are introduced, complicating this analysis. We present a method framework to address the model dependence problem, especially to solve the problem of energy spectrum distortion caused by instrument signal pile-up due to high counting rate and high-rate effects, applicable to X-ray, gamma-ray, and particle detectors. Our approach combines physics-based Monte Carlo (MC) simulations with a model-independent spectral inversion technique. The MC simulations quantify instrumental effects and enable correction of the distorted spectrum. Subsequently, the inversion step reconstructs the incident spectrum using an inverse response
matrix approach, conceptually equivalent to deconvolving the detector response. The inversion employs a Convolutional Neural Network, selected for its numerical stability and effective handling of complex detector responses. Validation using simulations across diverse input spectra demonstrates high fidelity. Specifically, for 27 different parameter sets of the brightest gamma-ray bursts, goodness-of-fit tests confirm the reconstructed spectra are in excellent statistical agreement with the input spectra, and residuals are typically within $\pm 2\sigma$. This method enables precise analysis of intense transients and other high-flux events, overcoming limitations imposed by instrumental effects in traditional analyses.
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All authors Zhi-Qiang Ding, Xin-Qiao Li, Da-Li Zhang, Zheng-Hua An, Zhen-Xia Zhang, Roberto Battiston, Roberto Iuppa, Zhuo Li, Yan-Qiu Zhang, Yan Huang, Chao Zheng, Yan-Bing Xu, Xiao-Yun Zhao, Lu Wang, Ping Wang, Hong Lu
Earth and Planetary Astrophysics
Refractive indices of photochemical haze analogs for Solar System and exoplanet applications : a cross-laboratory comparative study between the PAMPRE and COSmIC experimental set-ups
Thomas Drant, Ella Sciamma-O'Brien, Lora Jovanovic et al. (+9 more)
Previous observations of Titan, Pluto and
Solar System gas
giants along with recent observations of
exoplanet atmospheres with the James Webb Space
Telescope taught us that photochemical hazes are ubiquitous and form in a variety of temperature, gas composition and irradiation environments. Despite being crucial to understand their impact on observations and on the planetary radiative budget, the refractive indices of these haze particles are unknown and strongly influenced by changes in the gas phase chemistry. In this study, we perform a cross-laboratory investigation to assess the effect of the experimental set-up and gas composition on the refractive indices of Titan, Pluto and
exoplanet haze analogs. We report new data in a broad spectral range from UV to far-IR (up to 200 microns) for future use in
climate models and
retrieval frameworks.
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All authors Thomas Drant, Ella Sciamma-O'Brien, Lora Jovanovic, Zoé Perrin, Louis Maratrat, Ludovic Vettier, Enrique Garcia-Caurel, Jean-Blaise Brubach, Diane H. Wooden, Ted L. Roush, Claire L. Ricketts, Pascal Rannou
Astrophysics of Galaxies
The Rotation Dip in the Envelope-Disk Transition of HH 111: Evidence for Magnetic Braking
Jyun-Heng Lin, Chin-Fei Lee, Zhi-Yun Li et al. (+3 more)
Magnetic braking can drive angular momentum loss in
star formation and influence disk
evolution. A previous study of HH 111 VLA1 suggested a decrease in rotation velocity in a region between the infalling envelope and rotating disk. Using ALMA C$^{18}$O ($J = 2-1$) data, we analyzed the gas motion within 6000 au and found clear deviations from the simplest expectations of free-fall towards the central
star with conserved angular momentum in the transition region between the envelope and disk (from $\sim$5200 to 160 au). The region can be further divided into three zones: (1) outer region with a significant decrease in infall velocity, dropping to approximately 60% of the free-fall velocity and 70% of conservation of angular momentum and energy; (2) middle region with a sharp drop in angular momentum and thus rotation velocity and an increase in infall velocity; and (3) inner region with rotation velocity increasing inward to connect to that of the Keplerian disk and infall velocity decreasing to zero. Comparison with non-ideal MHD simulations suggests that the reduced infall velocity in the outer region can be due to
magnetic tension by the pinched
magnetic field lines, the sharp drop of angular momentum in the middle region can be due to
magnetic braking as the field lines pile up, and the rapid increase in rotation velocity in the inner region might result from weaker
magnetic braking due to ambipolar
diffusion of the field lines. The resulting dip in the rotation profile supports
magnetic braking.
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All authors Jyun-Heng Lin, Chin-Fei Lee, Zhi-Yun Li, Yueh-Ning Lee, Ya-Lin Wu, J. A. López-Vázquez
Astrophysics of Galaxies
Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. IV. Broad Emission Line Evolution Sequence Among H{\alpha}, Mg II, and H{\beta}
Wei-Jian Guo, Victoria A. Fawcett, Małgorzata Siudek et al. (+15 more)
From a parent catalog of 561 changing-look active
galactic nuclei (CL-AGNs) identified by Guo et al. (2025), we investigate the evolutionary sequence of broad emission lines using a
redshift-selected subset (0.35 < z < 0.45) of 54 CL-AGNs whose Dark Energy Spectroscopic Instrument (DESI) spectra simultaneously cover the H{\alpha}, He̱ta}, and Mg II emission lines. To provide a baseline for comparison, we construct a control sample of 19,897 normal Type 1 AGNs within the same
redshift range from the DESI Year 1 data. Through stacked spectral analysis and line-continuum luminosity correlations, we identify a clear evolutionary sequence in all AGN where broad He̱ta} fades first, followed by Mg II, and then H{\alpha}, as the AGN luminosity declines - consistent with expectations from reverberation mapping. This trend reflects a radially stratified broad line region (BLR), where each line's responsivity depends on its ionization potential and radial distance from the central engine. In addition, we find that more massive supermassive black holes (SMBHs) require lower Eddington ratios to fully suppress broad emission lines, suggesting that the critical
accretion threshold for the CL phenomenon is mass-dependent. Our results present the first statistical confirmation of a stratified broad line fading sequence in AGNs, reinforcing the central role of
accretion state in shaping BLR structure and visibility.
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All authors Wei-Jian Guo, Victoria A. Fawcett, Małgorzata Siudek, Yan-Rong Li, Cheng Cheng, Swayamtrupta Panda, Zhiwei Pan, Shengxiu Sun, Claire L. Greenwell, David M. Alexander, John Moustakas, Shuo Zhai, Jun-Jie Jin, Huaqing Cheng, Jingwei Hu, Yong-Jie Chen, Zhi-Xiang Zhang, Jian-Min Wang
Astrophysics of Galaxies
Evolution of action-space coherence in a Milky Way-like simulation
Arunima Arunima, Mark R. Krumholz, Michael J. Ireland et al. (+2 more)
Efforts to dynamically trace
stars back to the now-dissolved clusters in which they formed rely implicitly on the assumption that
stellar orbital actions are conserved. While this holds in a static, axisymmetric potential, it is unknown how strongly the time-varying, non-axisymmetric structure of a real
galactic disk drives action drift that inhibits cluster reconstruction. We answer this question using a high-resolution magnetohydrodynamic simulation of a Milky Way-like spiral disc
galaxy. We show that, while
stars experience significant action
evolution over $\lesssim 100$ Myr, they do so in a correlated fashion whereby
stars born in close proximity maintain very similar actions for up to 0.5 Gyr. The degree of coherence shows no significant dependence on galactocentric radius, but varies between action components: vertical actions decohere for
stars born more than a few hundred parsecs apart (likely due to
giant molecular clouds), while radial and azimuthal actions remain correlated on kiloparsec scales (likely influenced by spiral arms). We use our measurements of the rate of action decoherence to develop a probabilistic framework that lets us infer the initial sizes of the
star cluster progenitors of present-day
stellar streams from their measured action distributions, which we apply to 438 known moving groups. Our results suggest that most of these streams likely originated from compact clusters, but that a significant minority are instead likely to be resonant or dynamically induced structures. This method of classifying streams complements existing methods, optimises the use of expensive spectroscopic abundance measurements, and will be enhanced by the more precise kinematic data that will soon become available from
Gaia DR4.
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All authors Arunima Arunima, Mark R. Krumholz, Michael J. Ireland, Chuhan Zhang, Sven Buder
High Energy Astrophysical Phenomena
Gravitational Wave Phase shifts of black hole mergers in AGN Disks
Hiromichi Tagawa, Connar Rowan, János Takátsy et al. (+4 more)
Ground-based gravitational wave (GW) detectors have discovered about 200 compact object mergers. The astrophysical origins of these events are highly debated, and it is possible that at least a fraction of them originate from dynamical environments. Among these, the disks of active
galactic nuclei (AGN) are particularly interesting as promising environments, as some observed properties may be more readily produced there. When compact objects merge in these environments, acceleration from the central supermassive black hole (SMBH) or nearby companions is inevitable. Such acceleration induces a phase shift in the observed GW waveforms, which can serve as a useful tool to distinguish the underlying merging environments for each GW event. In this paper, we investigate the expected distribution of such acceleration-induced GW phase shifts, using a semi-analytical model combined with a one-dimensional AGN population synthesis code. We find significant contributions from three-body interactions involving a nearby third object. Our results indicate that the GW phase shift is likely to be larger compared to other channels, making it distinguishable by future GW facilities such as TianQin, DECIGO, Taiji, Einstein
Telescope, and
Cosmic Explorer. Interestingly, a notable fraction of mergers in fact exhibit a significant GW phase shift ($\gtrsim~{\rm 1\ rad}$) at frequencies above $10~{\rm Hz}$, which could even be detectable by current GW detectors such as LIGO/Virgo/KAGRA. Additionally, if gas-hardening during three-body interactions is taken into account, the GW frequency can be boosted to $\gtrsim 10~{\rm Hz}$, potentially further aiding in the detection of the phase shift.
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All authors Hiromichi Tagawa, Connar Rowan, János Takátsy, Lorenz Zwick, Kai Hendriks, Wen-Biao Han, Johan Samsing
Cosmology and Nongalactic Astrophysics
Non-thermal processes in standard big bang nucleosynthesis: III. Reactions with slow nuclei and the overall effect
Victor T. Voronchev
The present paper completes a series of our works on non-thermal
nuclear processes in big bang nucleosynthesis (BBN) started in JCAP05(2008)010 (Part I) and 05(2009)001 (Part II). The processes are triggered by non-Maxwellian particles naturally born in the main BBN reactions. Half of these reactions generate fast particles k^+ (= n,p,t,3He,alpha). The other half, being radiative capture processes, produce slow
nuclei k^- (= d,t,3He,7Li,7Be) which can undergo (k^-,n) reactions with
neutrons having large cross sections. The particle production rate R_k, thermalization time tau_k, and effective number density n_k are determined. It is shown that the values of n_k at the Universe temperatures T > 65 keV can exceed the number densities of Maxwellian 7Li and 7Be ions. To clarify the overall non-Maxwellian effect on BBN, both types of the non-Maxwellian particles are taken into account in the reaction network. Particular
attention is paid to two-step sequential processes like p(n,gamma)d^-(n,gamma)t, d(p,gamma)3He^-(n,p)t, t(alpha,gamma)7Li^-(n,gamma)8Li, 3He(alpha,gamma)7Be^-(n,p)7Li, d(t,alpha)n^+(A,n)a_1a_2, and d(3He,alpha)p^+(A,p)a_1a_2 with (A,a_1,a_2) = 7Li,t,alpha) and (7Be,3He,alpha. It is obtained that the non-Maxwellian particles can selectively affect the element abundances, e.g., improve the prediction on 7Li/H by ~1.5% and at the same time leave unchanged the 4He abundance. The main conclusion however is that these particles are unable to significantly change the standard picture of BBN in general, and provide a pathway toward a solution of the cosmological lithium problem in particular.
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High Energy Astrophysical Phenomena
Electron Cyclotron Maser Emission as the Driving Mechanism in Long-Period Radio Transients
Lilia Ferrario
Long-period
radio transients (LPRTs) are highly polarised, coherent
radio sources with periods of minutes to hours and bursts typically lasting 10 to 100 s. Here we consider the apparently isolated subclass of LPRTs and argue that electron cyclotron maser emission (ECME) explains their narrow duty cycles and polarisation properties. In particular, we show that intrinsically circular ECME can emerge as predominantly linear after undergoing Faraday conversion in an overlying magnetospheric
plasma layer, thus reconciling the observed high linear fractions with a circularly polarised maser. In this picture, a rotating oblique magnetosphere beams radiation into a thin, hollow emission cone whose surface lies almost perpendicular to the local
magnetic field. The observed very narrow pulses arise when the line of sight skims the cone, while broader profiles and weak leading or trailing components occur when multiple azimuths along the emission ring meet the maser resonance condition. The observed isotropic-equivalent luminosities of about 10^30 to 10^31 erg s^-1 correspond to modest intrinsic powers once strong ECME beaming is taken into account. We show that such power levels can be supplied by
accretion from the interstellar medium (ISM), and that detectability at kiloparsec distances favours slowly rotating
neutron stars with comparatively low surface
magnetic fields below about 10^10 Gauss and low space velocities.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Dynamical Evolution and Graceful Exit in Quartic Warm Inflation
Bhargabi Saha and Malay K. Nandy
In this study, we investigate the full nonlinear dynamics of warm inflation driven by the quartic inflaton potential, avoiding any simplifying approximations. The thermal backreaction is incorporated through a dissipation coefficient that depends linearly on the temperature, and the model parameters are chosen to remain consistent with Planck observational constraints. By numerically integrating the complete set of three coupled, nonlinear differential equations that describe the
evolution of the inflaton field, radiation energy density, and background expansion, we obtain an exact description of the system's dynamics. Our results reveal that, while transition to radiation domination is suppressed in the weak regime, the strong dissipative regime leads to a smooth and natural transition to a hot, radiation-dominated Universe, thereby confirming graceful-exit within warm inflation in the quartic scenario. The reheating temperature is extracted directly from the nonlinear
evolution of warm inflation, yielding a temperature of approximately 10^13 GeV at the end of inflation, which cools to about 10^12 GeV near radiation-inflaton equality, whence the Universe transitions into a radiation-dominated era.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Gravitational Bound State Perturbations Inside Black Holes and Isospectrality
Hassan Firouzjahi, Kazem Rezazadeh and Masoud Molaei
We study the bound state solutions for the polar perturbations in the interior of the Schwarzschild black hole. It is shown that for a given value of the spherical harmonic index $\ell$, there are a total of $\ell-1$ bound states for polar perturbations. We show both analytically and numerically that the spectrum of $\ell-2$ of these perturbations coincides exactly with the spectrum of axial perturbations. Consequently, the isospectrality between the bound states of axial and polar perturbations in the interior of the black hole is preserved. Furthermore, the additional mode found in the spectrum of polar perturbations is the algebraically special mode, which also furnishes the ground state of polar perturbations. It is shown that the spectrum of the highly excited states is equally spaced, which, in the semi-classical approximation, yields the black hole area quantization $\Delta A = 16 \pi l_{\mathrm{Pl}}^2$.
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High Energy Astrophysical Phenomena
Measuring the crust-superfluid coupling time-scale for 105 UTMOST pulsars with a Kalman filter
Wenhao Dong, Andrew Melatos, Nicholas J. O'Neill et al. (+2 more)
Crust-superfluid coupling plays an important role in
neutron star rotation, particularly with respect to timing noise and glitches. Here, we present new timing-noise-based estimates of the crust-superfluid coupling time-scale \(\tau\) for 105
radio pulsars in the UTMOST
dataset, by Kalman filtering the pulse times of arrival. The 105 objects are selected because they favor a two-component, crust-superfluid model over a one-component model with log Bayes factor \(\ln \mathfrak{B}_{\rm BF} \geq 5\). The median estimate of \(\tau\) ranges from \(10^{4.6\pm0.4}\)\,s for PSR J2241$-$5236 to \(10^{7.7^{+0.7}_{-0.4}}\)\,s for PSR J1644$-$4559 among 28 out of 105 objects with sharply peaked \(\tau\) posteriors. A hierarchical
Bayesian analysis is performed on 101 out of 105 objects that are canonical (i.e.\ neither recycled nor magnetars) and reside in the populous core of the \(\Omega_{\rm c}\)-\(\dot{\Omega}_{\rm c}\) plane. It returns the population-level scaling \(\tau \propto \Omega_{\rm c}^{0.19^{+0.50}_{-0.52}} |\dot{\Omega}_{\rm c}|^{0.18^{+0.18}_{-0.19}}\), where \(\Omega_{\rm c}\) and \(\dot{\Omega}_{\rm c}\) are the angular velocity and
spin-down rate of the crust respectively. The variances of the
stochastic crust and superfluid torques are also estimated hierarchically, with \(Q_{\rm c} \propto \Omega_{\rm c}^{1.23^{+0.80}_{-0.75}} |\dot{\Omega}_{\rm c}|^{0.49^{+0.27}_{-0.32}}\) and \(Q_{\rm s} \propto \Omega_{\rm c}^{0.71^{+0.76}_{-0.78}} |\dot{\Omega}_{\rm c}|^{1.27^{+0.30}_{-0.28}}\) respectively. Implications for the physical origin of crust-superfluid coupling, e.g.\ through mutual friction, are discussed briefly.
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All authors Wenhao Dong, Andrew Melatos, Nicholas J. O'Neill, Patrick M. Meyers, Daniel K. Boek
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Potential divergence in tracing $\mu$ and $\tau$ flavors of astrophysical neutrinos
Zhi-zhong Xing
We derive general formulas for three
flavor fractions $(\eta^{}_e , \eta^{}_\mu , \eta^{}_\tau)$ of the high-energy
neutrinos originating from a remote astrophysical source by using their
flavor ratios $(f^{}_e , f^{}_\mu , f^{}_\tau)$ observed at a
neutrino telescope, and diagnose a potential divergence associated with $\eta^{}_\mu$ and $\eta^{}_\tau$ as an unavoidable consequence of the $\mu$-$\tau$ interchange
symmetry exhibiting in the $3\times 3$
lepton flavor mixing
matrix $U$. We present a complete set of analytical expressions for $(\eta^{}_e , \eta^{}_\mu , \eta^{}_\tau)$ as functions of two typical $\mu$-$\tau$
symmetry breaking parameters in the standard parametrization of $U$, and apply it to the recent IceCube all-sky
neutrino flux data ranging from 5 TeV to 10 PeV in the assumption that the relevant sources have a common
flavor composition. We also explain why only $\eta^{}_e$ and $\eta^{}_\mu + \eta^{}_\tau$ can be extracted from a precision measurement of $f^{}_e$ and $f^{}_\mu = f^{}_\tau$ in the exact $\mu$-$\tau$
flavor symmetry limit.
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Earth and Planetary Astrophysics
Solar Periodic Companion and Random Stellar Flybys: Dynamical Perturbations of Highly Eccentric Comets in the Oort Cloud
Shahed Shayan Arani
The
Gaia space
telescope has transformed our understanding of random
stellar encounters with the
Solar System. This study examines how such perturbations influence the most eccentric comets in the Oort Cloud (OC), a thermalized reservoir of $\sim 10^{12}$ icy bodies extending from $10^{4}$ to $10^{5}$ AU. Recent
Gaia-based analyses indicate about 20
stellar passages within 1 pc of the Sun per Myr. Using analytical estimates and direct $N$-body simulations, we quantify how these encounters modify highly eccentric orbits: individual flybys enhance comet-shower rates by factors of about 2, producing a cumulative increase of roughly 40 over a Myr. In parallel, we perform a full dynamical search through all
stars with six-dimensional phase-space data in
Gaia DR3 and identify a compelling candidate for a long-period
stellar companion to the Sun. This
star exhibits recurrent $\sim 45$ Myr perihelion passages and, in simulations, can elevate comet-shower activity by an order of magnitude. Because a perturber of this kind could also be a dispersed
solar sibling, the companion hypothesis links the dynamical structure of the OC directly to the long-standing problem of identifying the Sun's birth-cluster relatives. The chemical-abundance pattern of such a
star therefore becomes a critical observational test. Together, these results clarify how both
stochastic encounters and potential long-period companions shape the dynamical
evolution and observable output of the outermost OC, while highlighting the possibility that the OC retains a dynamical
memory of the Sun's earliest
stellar environment.
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Solar and Stellar Astrophysics
PHR~J1724-3859: A Bipolar Planetary Nebula in Open Cluster Trumpler 25
Vasiliki Fragkou, Quentin A. Parker and Denise R. Gonçalves
Planetary nebulae (PNe) studies are essential for understanding late
stellar evolution of low-to-intermediate mass
stars. PNe in open clusters (OC) are rare but valuable since their study directly links their properties to those of their progenitors, something that cannot be achieved for field PNe. Here, we report the identification of one more OC-PN association to add to the small sample of, now, five pairs. The physical properties of the host cluster, PN and its central
star (CSPN) have been explored using high and intermediate-resolution spectral and deep photometric data. The close agreement of the radial velocities of the PN and host cluster, together with concordance of reddening and distance, show that the PN PHR~J1724-3859 is highly likely to be physically associated with the OC Trumpler~25. Deep photometric data allowed clear identification of the CSPN. We find a CSPN effective temperature of around 250 kK and a nebular kinematic age of 23 kyrs, both at the extreme end, like the other members of this small class. The progenitor and final CSPN masses have been estimated to be 5.12$_{-0.15}^{+0.16}$ $M_\odot$ and 0.95$\pm$0.12 $M_\odot$ respectively. These latest results agree with the emerging trend for our other OC-PNe, falling below, but approximately parallel to, the latest initial-to-final-mass relation estimates derived from cluster white
dwarfs and has important implications for
stellar evolution models. All OC-PNe also possess some other common properties (e.g. all are Type-I PNe and bipolars) to be explored in future studies.
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Cosmology and Nongalactic Astrophysics
Implications of the Two-Component Dark Energy Model for Hubble Tension
Lu Chen, Peiyuan Xu, Guohao Li et al. (+1 more)
Dark energy plays a crucial role in the
evolution of
cosmic expansion. In most studies, dark energy is considered a single dynamic component. In fact, multi-component dark energy models may theoretically explain the accelerated expansion of the universe as well. In our previous research, we constructed the $w_{\rm{n}}$CDM ($n=2, 3, 5$) models and conducted numerical research, finding strong observational support when the value of n is small. Based on our results, both the $\chi^2$ and Akaike information criterion (AIC) favor the $w_{\rm{2}}$CDM model more than the $w_0w_{\rm{a}}$CDM model. However, previous studies were limited to two equal-component dark energy models, failing to consider the component proportions as variables. Therefore, we will further explore the $w_{\rm{2}}$CDM model. To simplify the model, we fix $w = -1$ in one component and set the other component to $w_{\rm{de2}}$, varying the proportions of both components in the population. Under different $w_{\rm{de2}}$, we obtain the one-dimensional distribution of ${H}_{0}$ with respect to $f_{\rm{de2}}$. Further fitting reveals the
evolution of ${H}_{0}$ under varying $w_{\rm{de2}}$ and $f_{\rm{de2}}$. We also perform the same operation on $\chi^2$. To evaluate the error of fitting, we introduce two indicators, $\text{R}^{2}_{\text{adj}}$ and MAPE, to quantify the fitting ability of our models. We find that when $w_{\rm{de2}}$ is less than -1, ${H}_{0}$ increases with the decrease of $w_{\rm{de2}}$ and the increase of $f_{\rm{de2}}$, effectively alleviating ${H}_{0}$ tension. For $\chi^2$, it still prefers the $\Lambda$CDM model, and the $w_{\rm{2}}$CDM model will decrease significantly when it approaches the $\Lambda$CDM model. The excellent performance of $\text{R}^{2}_{\text{adj}}$ and MAPE further proves that our model has an outstanding fitting effect and extremely high reliability.
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All authors Lu Chen, Peiyuan Xu, Guohao Li, Yang Han
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Power-law Bianchi type I inflation with multiple vector fields
Duy H. Nguyen and Tuan Q. Do
We investigate an inflationary anisotropic universe in a supergravity-motivated model with one scalar field non-minimally coupled to multiple vector fields. We restrict ourselves to the Bianchi type I metric, which describes a homogeneous but anisotropic universe. For consistency, we consider a configuration consisting of one homogeneous scalar field and three mutually orthogonal vector fields. As a result, we find four types of power-law solutions, classified according to the number of non-vanishing vector fields. Moreover, we show that all these solutions are stable under certain conditions on the model parameters, thereby defining stability regions described both quantitatively and qualitatively. Interestingly, our analysis suggests that vector fields with significantly larger coupling constants tend to persist as the universe expands, while those with significantly smaller coupling constants are eventually diluted. On the other hand, we also find that the anisotropies depend on the number of persisting vector fields. Furthermore, our claims are confirmed by numerical calculations. This work may therefore shed light on how vector fields and anisotropies evolve in an inflationary universe.
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Astrophysics of Galaxies
The ALMA-QUARKS survey: Evidence of a candidate high-mass prestellar core aside a bright-rimmed cloud IRAS 18290-0924
Dongting Yang, Hong-Li Liu, Shengli Qin et al. (+32 more)
Although frequently reported in observations, the definitive confirmation of high-mass prestellar cores has remained elusive, presenting a persistent challenge in
star formation studies. Using two-band observational data from the 3mm ATOMS and 1.3mm
QUARKS surveys, we report a high-mass prestellar core candidate, C2, located on the side of the bright-rimmed cloud IRAS 18290-0924. The C2 core identified from the 3mm continuum data of the ATOMS survey ($\sim$2 arcsecond, $\rm\sim 10000~au$ at 5.3 kpc) has a mass ranging from 27-68 $M_{\odot}$ for temperatures 10-22K within a radius of $\sim$2800 au. The highest-resolution ($\sim$0.3 arcsecond, $\rm\sim 1500 au$) observations of this source presented to date from the
QUARKS survey reveal no evidence of further fragmentation. Further analysis of a total $\sim$10 GHz band width of molecular line survey does not find
star-formation activity (e.g.,
outflows, ionized gas) associated with the core, with a few molecular lines of cold gas detected only. Additionally, virial analysis indicates the C2 core is gravitationally bound ($\alpha_{\rm vir} \sim0.1-0.3$) and thus could be undergoing collapse toward
star formation. These results strongly establish a candidate for a high-mass prestellar core, contributing to the very limited number of such sources known to date.
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All authors Dongting Yang, Hong-Li Liu, Shengli Qin, Tie Liu, Anandmayee Tej, Siju Zhang, Xunchuan Liu, Fengwei Xu, Guido Garay, Lei Zhu, Patricio Sanhueza, Xiaofeng Mai, Wenyu Jiao, Paul F. Goldsmith, Sami Dib, Pablo Garc{\i}a, Di Li, Jinhua He, A.Y. Yang, Prasanta Gorai, Suinan Zhang, Yankun Zhang, Jianjun Zhou, Mika Juvela, James O. Chibueze, Chang Won Lee, Jihye Hwang, Leonardo Bronfman, Xindi Tang, Archana Soam, Tapas Baug, Yichen Zhang, Swagat Ranjan Das, L. K. Dewangan, L. Viktor Toth