High Energy Astrophysical Phenomena
Reconstruction of the dark matter density profile from cosmic positron anomaly data
K. M. Belotsky, F. V. Kostromin and M. L. Solovyov
In this work we continue our investigations of the possibility of explanation of the positron anomaly (PA) in
cosmic rays with the help of annihilating or decaying dark matter (DM) component by varying its space distribution. In the contrast of our previous studies, where we first assumed some specific spatial distribution of DM component and looked at how it agrees with data, here we solve, in some sense, the inverse problem: we search for distribution, in a mathematical way, which satisfies observational data. A unique
algorithm has been implemented which, using linear
algebra and adaptive grid methods, adjusts distribution to the data. It allows telling in principle whether or not is possible to solve PA problem by variation of spatial distribution of DM sources. A positive result has been formally obtained. A class of solutions can be identified. Though the distributions obtained at the chosen injection spectra may seem slightly realistic, nonetheless it demonstrates a quite powerful possibility in explaining PA that could be realized in more realistic models.
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Astrophysics of Galaxies
The MAGPI Survey: forward modelled gas-phase metallicity gradients in galaxies at $z\sim 0.3$
Yifan Mai, Scott M. Croom, Emily Wisnioski et al. (+19 more)
We measure the seeing-deconvolved gas-phase
metallicity gradients of 70
star-forming
galaxies at $z\sim 0.3$ from the MAGPI survey and investigate their relationship with
galaxy properties to understand the mechanisms that influence the distribution of metals and shape the
evolution of the
galaxies. We use a
Bayesian modelling technique, Blobby3D, which accounts for seeing effects (beam smearing) and can model the substructures of the flux distribution. The median
metallicity gradient of our sample is $\nabla \mathrm{[O/H]}=-0.013^{+0.059}_{-0.033}$ dex/kpc. Among the
galaxies in our sample, 32.9% have negative
metallicity gradients (2$\sigma$ significance), 10.0% have positive gradients and 57.1% have flat gradients. The $\nabla \mathrm{[O/H]}$-$M_*$ relation of the MAGPI
galaxies generally agrees with theoretical predictions, where a combination of
stellar feedback, gas transport, and
accretion shapes the
metallicity profile, with the dominant processes varying with
galaxy mass. We find a positive correlation between $\nabla \mathrm{[O/H]}$ and gas velocity dispersion ($r=0.36$), indicating that stronger gas
turbulence is associated with flatter or inverted
metallicity gradients, likely due to enhanced gas mixing. Additionally, smaller
galaxies tend to have flatter or positive gradients, suggesting that metal dilution by gas
accretion or removal via feedback-driven winds may outweigh metal enrichment in small
galaxies.
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All authors Yifan Mai, Scott M. Croom, Emily Wisnioski, Andrew J. Battisti, J. Trevor Mendel, Marcie Mun, Caroline Foster, Katherine E. Harborne, Claudia D. P. Lagos, Iris Breda, Tianmu Gao, Kathryn Grasha, Tamal Mukherjee, Adriano Poci, Rhea-Silvia Remus, Piyush Sharda, Sarah M. Sweet, Sabine Thater, Lucas M. Valenzuela, Glenn van de Ven, Tayyaba Zafar, Bodo Ziegler
Solar and Stellar Astrophysics
The SOFIA Massive (SOMA) Radio Survey. III. Radio Emission from Intermediate-Mass Protostars
Francisco Sequeira-Murillo, Viviana Rosero, Joshua Marvil et al. (+6 more)
We present results from Very Large Array (VLA)
radio continuum observations of twelve intermediate-mass (IM) protostars, as part of the SOFIA Massive
Star Formation Survey. Using these observations, we studied their morphology, multiplicity and
radio spectral energy distributions (SEDs). Across our target regions, we resolve multiple compact sources and report eight new detections, four of which are entirely new and four that have counterparts at other wavelengths, but are detected here for the first time at
radio frequencies. Based on
radio morphologies and spectral indices, we assess the nature of the detected sources, highlighting seven that display jet-like structures and spectral indices consistent with ionized jets. Combining our results with the SOMA
Radio I and II results, we expand the overall sample to 29 protostars, covering a bolometric luminosity range from $L_{\rm bol}\sim 10^2$ to $10^6\:L_\odot$. These sources help define a potential evolutionary sequence in the
radio versus bolometric luminosity diagram. IM protostars have
radio luminosities that are lower than expected from a simple power law extrapolation from low-mass protostars. However, this result is consistent with theoretical expectations from protostellar
evolution models, which show low levels of photoionization and reduced shock ionization emission due to expanded
stellar radii during this phase. Overall our expanded SOMA
Radio sample provides new constraints on theoretical models of massive protostellar
evolution, especially the connection to ionized gas structures.
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All authors Francisco Sequeira-Murillo, Viviana Rosero, Joshua Marvil, Jonathan C. Tan, Ruben Fedriani, Yichen Zhang, Prasanta Gorai, James M. De Buizer, Maria T. Beltrán
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
High-overtone ringdown fits: start time, no-hair tests, and correlations
Erin Coleman and Eliot Finch
Overtones are known to improve the performance of fits to the ringdown, both in numerical-relativity simulations and gravitational-wave observations. Although the overtone frequencies are a concrete prediction of general relativity, it remains an open question whether they are excited to the extent that fits would suggest. In this work, we take a pragmatic approach and investigate the practical utility of each additional overtone in extracting information from the ringdown. We look at the dependence of the ringdown start time on the number of overtones, and the feasibility of detecting deviations from general relativity in the ringdown frequencies. We suggest that there is no clear "maximum" overtone, but rather the utility of each additional overtone decreases compared to the one before. Finally, we perform
Bayesian parameter estimation (as opposed to least-squares fits) to obtain posterior distributions on the overtone amplitudes and phases, allowing us to investigate their correlation structure. Due to strong correlations it becomes increasingly hard to measure individual amplitudes and phases for the highest overtones. However, we find that the joint measurement of overtone amplitudes (i.e., the correlation structure itself) is sensitive to the frequencies and decay times of even the highest overtones, possibly offering an avenue to perform consistency tests with general relativity.
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Astrophysics of Galaxies · Cross-listed from gr-qc
Noble gravitational atoms: Self-gravitating black hole scalar wigs with angular momentum number
Miguel Alcubierre, Juan Barranco, Argelia Bernal et al. (+5 more)
We present new spherically symmetric solutions of the Einstein-Klein-Gordon equations in a quasi-stationary approximation that describe self-gravitating scalar field configurations around a black hole, including angular momentum number $\ell$. An approach analogous to the one which gives rise to $\ell$-
boson stars is used here to construct self-gravitating “gravitational atoms" with $\ell\ge0$. We refer to these new solutions as noble gravitational atoms, by analogy with noble atoms, which are characterized by closed electron shells. We show that, in the proper limit, noble gravitational atoms approach $\ell$-
boson stars globally, displaying noticeable differences only in a region very close to the event horizon. Noble gravitational atoms with $\ell>0$ sometimes present density maxima located at relatively large radii, with small density close to the horizon for $\ell>1$. Furthermore, they do not always present the typical density spike at the event horizon if $\ell > 0$; on the contrary, they sometimes exhibit a small dip there. When $\ell=0$, a spike can appear, but its contribution to the total mass density is always negligible. The size, density, and lifetime of these objects vary significantly depending on the parameters, being in some cases as large as
galaxies, as dilute as dark matter, and as long-lived as the Universe itself.
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All authors Miguel Alcubierre, Juan Barranco, Argelia Bernal, Juan Carlos Degollado, Alberto Diez-Tejedor, Miguel Megevand, Dario Nunez, Olivier Sarbach
Astrophysics of Galaxies
The Two-infall Model Revisited: Constraints on Milky Way Bulge Assembly from >30,000 Galactic Chemical Evolution Models and Machine Learning
Niall Miller, Meridith Joyce, Christian I. Johnson et al. (+3 more)
We constrain the formation history of the Milky Way bulge using a two-infall
galactic chemical
evolution (GCE)
algorithm implemented in the N'OMEGA+ code. We recover a best-fit scenario in which the bulge forms through an early, rapid starburst ($t_1 \sim 0.1$ Gyr, $\tau_1 \sim 0.09$ Gyr, and
star formation efficiency (SFE) $\sim 3~\mathrm{Gyr}^{-1}$), followed by a delayed, lower-mass second infall ($t_2 \sim 5.1$ Gyr, $\tau_2 \sim 1.7$ Gyr, and $\sigma_2 \sim 0.69$). Our model adopts mass- and
metallicity-dependent nucleosynthetic yields from modern
stellar grids and explores a wide GCE parameter space in infall timing, SFE, mass partitioning, initial mass function upper mass, and type Ia
supernova normalization, optimized via a hybrid genetic
algorithm with Markov Chain Monte Carlo refinement. The later infall features a reduced SFE ($\Delta\mathrm{SFE} \sim 0.72$), reproducing the metal-rich peak of the bulge
metallicity distribution function (MDF) and the decline in [$\alpha$/Fe] at high [Fe/H]. Our model naturally favors the M. Joyce et al. age–
metallicity relation over the ages in T. Bensby et al. Degeneracy and principal component analyses show that the infall history, SFE, and mass partitioning are strongly covariant—the bulge's observed MDF, abundance trends, and age distribution constrain only their combinations, not each parameter independently. The results support a composite bulge origin—an early, rapid collapse builds the majority of the mass, while a younger component is required to match the late-stage enrichment.
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All authors Niall Miller, Meridith Joyce, Christian I. Johnson, Jamie Tayar, Thomas Trueman, R. Michael Rich
Astrophysics of Galaxies
Spatially Resolved Physical Properties of Young Star Clusters and Star-forming Clumps in the Brightest z>6 Galaxy, the Strongly Lensed Cosmic Spear at z=6.2
Abdurro'uf, Dan Coe, Tom Resseguier et al. (+49 more)
We present spatially resolved analysis of
stellar populations in the brightest $z>6$
galaxy known to date (AB mag 23), the strongly lensed MACS0308$-$zD1 (dubbed the “
Cosmic Spear”) at $z_{\rm spec}=6.2$. New JWST NIRCam imaging and high-resolution NIRSpec IFU spectroscopy span the rest-frame ultraviolet to optical. The NIRCam imaging reveals bright
star-forming clumps and a tail consisting of three distinct, extremely compact
star clusters that are multiply-imaged by gravitational
lensing. The
star clusters have delensed effective radii of $R_{\rm{eff}} \lesssim 8$ pc,
stellar masses of $M_{*} \sim 10^{6}-10^{7}\,M_{\odot}$, and high
stellar mass surface densities of $\Sigma_{*} \gtrsim 2\times 10^{4}\,M_{\odot}~\rm{pc}^{-2}$. While their
stellar populations are very young ($\sim 6-11$ Myr), their dynamical ages exceed unity, consistent with the clusters being gravitationally bound systems. Placing the
star clusters in the size vs.~
stellar mass density plane, we find they occupy a region similar to other high-
redshift star clusters within
galaxies observed recently with JWST, being significantly more massive and denser than local
star clusters. Spatially resolved analysis of the brightest clump reveals a compact, intensely
star-forming core. The ionizing
photon production efficiency ($\xi_{\rm{ion}}$) is slightly suppressed in this central region, potentially indicating a locally elevated Lyman continuum escape fraction facilitated by feedback-driven channels.
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All authors Abdurro'uf, Dan Coe, Tom Resseguier, Calla Murphy, Xinfeng Xu, Angela Adamo, Namrata Roy, Alaina Henry, Vasily Kokorev, Gabriel Brammer, Seiji Fujimoto, Henry C. Ferguson, Amanda Pagul, Rogier A. Windhorst, Timothy Heckman, Jose M. Diego, Hollis B. Akins, Joseph Allingham, Ricardo O. Amorín, Danielle A. Berg, Maruša Bradač, Larry D. Bradley, Wenlei Chen, John Chisholm, Christopher J. Conselice, Pratika Dayal, Miroslava Dessauges-Zavadsky, Andreas L. Faisst, Steven L. Finkelstein, Yoshinobu Fudamoto, Lukas J. Furtak, Yuichi Harikane, Tiger Yu-Yang Hsiao, Yolanda Jimenez-Teja, Anton M. Koekemoer, Rebecca L. Larson, Ray A. Lucas, Matteo Messa, Lamiya Mowla, Minami Nakane, Gaël Noirot, Richard Pan, Massimo Pascale, Johan Richard, Massimo Ricotti, Luke Robbins, Daniel Schaerer, Fengwu Sun, Eros Vanzella, Brian Welch, Chris Willott, Adi Zitrin
High Energy Astrophysical Phenomena
UVOIR spectrum, X-ray emission, and proper motion of the isolated neutron star RX J2143.0+0654
George G. Pavlov, Vadim Abramkin and B. Posselt
We observed the isolated
neutron star RX J2143.0+0654 with the Hubble Space
Telescope (HST) in the UVOIR wavelength range (0.14-1.7 $\mu$m). The UV part is consistent with a Rayleigh-Jeans tail of a thermal spectrum, $f_\nu\propto \nu^2$, while a power-law spectrum, $f_\nu \propto \nu^\alpha$ with $\alpha \sim -0.8$, dominates in the NIR-optical. A joint fit of the UVOIR and contemporaneous X-ray spectra with a two-component blackbody with possible absorption features + power-law optical spectrum yields the following temperature and apparent radius of the colder component (which gives the main contribution in the UV): $kT_{\rm cold}\approx 45$ eV, $R_{\rm cold}\approx 6 d_{260}$ km, where $d_{260}$ is the distance in units of 260 pc. The temperature and radius of the hotter component, $kT_{\rm hot}\approx 106$ eV and $R_{\rm hot} \approx 1.5d_{260}$ km, the parameters of an absorption feature at 0.74 keV, and the properties of X-ray pulsations, are the same as found in previous X-ray observations. In the NIR images the
neutron star is possibly surrounded by extended emission with a characteristic size of $\sim 2''$ and flux densities of about 1.7 and 0.9 $\mu$Jy at 1.54 and 1.15 $\mu$m, respectively. Comparison with a previous HST observation in the optical 14 years ago shows a proper motion $\mu\approx 6$ mas yr$^{-1}$, which corresponds to a small transverse velocity of $7d_{260}$ km s$^{-1}$. It is consistent with the hypothesis that the
neutron star was born in the vicinity of the
solar system about 0.5 Myr ago.
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Astrophysics of Galaxies
The GLEAM 4-Jy (G4Jy) Sample: IV. Multiwavelength data and analysis
Sarah V. White, Precious K. Sejake, Kshitij Thorat et al. (+17 more)
We provide an updated 'multiwavelength' version of the G4Jy catalogue (available at https://github.com/svw26/G4Jy, https://zenodo.org/communities/g4jy/records, and through VizieR), which has 127 new host-
galaxy identifications, as described in Paper III of this paper series. We also supplement the
redshift information (0.0 < z < 3.6), gathered in Paper III, with $griz$ photometry available through DR10 of the DESI Legacy Surveys. Together, this legacy
dataset allows us to investigate the multiwavelength properties of these southern
radio-bright
galaxies, which includes an initial analysis of
radio spectral-
curvature for this complete sample (S_151MHz > 4 Jy). For example, we present (for the first time in the literature) the
radio-power–size diagram as a function of
radio spectral-
curvature, [P–D](SCI), noting that the spectral-
curvature index (SCI) can act as a proxy for the spectral age of the
radio source. This
radio-power–size–age diagram shows a predominance of
radio galaxies with SCI > 0.15 and D < 200 kpc, which are candidates for both remnant
radio-
galaxies and young
radio sources, and a vast range of linear sizes for candidate restarted
radio-
galaxies (having SCI < -0.15). We also show that (i) G4Jy sources populate the entirety of WISE colour-colour space, (ii) optically point-like sources (i.e. candidate
quasars) are brighter than the well-studied K–z relation (as expected), and (iii) there is no relation between the SCI of the
radio source and its host-
galaxy properties.
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All authors Sarah V. White, Precious K. Sejake, Kshitij Thorat, Heinz Andernach, Thomas M.O. Franzen, O. Ivy Wong, Anna D. Kapinska, Joseph R. Callingham, Christopher J. Riseley, Nick Seymour, Randall Wayth, Lister Staveley-Smith, Rajan Chhetri, Natasha Hurley-Walker, John Morgan, Paul Hancock, Francesco Massaro, Abigail Garcia-Perez, Ana Jimenez-Gallardo, Harold A. Pena-Herazo
Astrophysics of Galaxies
The Drivers of the Decline in Supermassive Black Hole Growth at $z<2$
Zhibo Yu, W. N. Brandt, Fan Zou et al. (+4 more)
It is well established that
cosmic supermassive black hole (SMBH) growth peaks at $z\approx1.5-2$, followed by a strong decline of $\approx1-1.5\,\rm dex$ toward the present day, with the comoving number density of higher-luminosity active
galactic nuclei (AGNs) peaking at higher
redshift (referred to as "AGN downsizing"). We leverage the best current measurements of the SMBH
accretion distribution, based upon data from nine well-characterized extragalactic fields with a "wedding-cake" design, to investigate and quantify the drivers of the drastic decline in
cosmic SMBH growth. The decline in the typical Eddington ratio ($\lambda_\mathrm{Edd}$) of AGNs (decreasing by $\approx1.35\,\rm dex$ from $z\approx1.5-2$ to $z\approx0.2$) is the dominant driver for the broad decline in SMBH growth, rather than a shift of
accretion activity to less-massive SMBHs. As $\lambda_\mathrm{Edd}$ decreases toward lower
redshift, the primary contributor to the
cosmic SMBH
accretion density ($\rho_\mathrm{BHAR}$) has shifted from high-$\lambda_\mathrm{Edd}$ AGNs to low-$\lambda_\mathrm{Edd}$ AGNs, even though the latter always dominate the comoving AGN number density at $z<4$. We also find that the decline in SMBH growth toward lower SMBH mass in less-massive
galaxies is primarily due to the decreasing outburst luminosity rather than the duty cycle.
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All authors Zhibo Yu, W. N. Brandt, Fan Zou, Bin Luo, Qingling Ni, D. P. Schneider, Fabio Vito
Solar and Stellar Astrophysics
Can meridional flow variations explain the observed rising/declining phase asymmetry in the solar cycle?
Soumitra Hazra, Allan Sacha Brun and Laurene Jouve
Accurate prediction of the 11-year
solar cycle remains a major challenge in
solar physics and is important for space weather
forecasting. A persistent property of the cycle is its asymmetry: the rise phase is usually much shorter than the decay phase. This asymmetry is often linked to variations in the Sun's meridional circulation, but it is unclear whether these variations are mainly deterministic, produced by Lorentz-force feedback, or
stochastic in nature. We investigate this question using kinematic flux-transport dynamo simulations that include three types of time-dependent meridional flow: deterministic variations,
stochastic fluctuations, and hybrid combinations of both. We evaluate cycle asymmetry using the ratio of rise to decay times and correlations of cycle amplitude with rise time, rise rate, and decay rate. Our results show that the temporal
evolution of the meridional flow strongly controls cycle asymmetry. When both the meridional circulation and the Babcock-Leighton mechanism vary stochastically, the model does not produce cycles in which the decay phase is consistently longer than the rise phase. In contrast, deterministic variations motivated by Lorentz-force feedback and linked to the latitude of maximum toroidal field reproduce the observed asymmetry. In these cases, the meridional flow weakens near cycle maximum, stays reduced for some time, and then recovers, producing a longer decay phase. Hybrid models that mix deterministic and
stochastic variability also match the observed rise-decay asymmetry. Across all simulations, cycle amplitude correlates strongly with rise rate, while correlations with rise time and decay rate are weaker but remain significant. These results highlight the key role of meridional flow variability in shaping
solar cycle asymmetry and show that incorporating such variability can improve
forecasting tools such as
Solar Predict.
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Solar and Stellar Astrophysics
Analytical Solutions for the Dynamics of Planetary Nebulae with and without Common Envelope Evolution
G. Garcia-Segura
We present new analytical solutions for the dynamics of planetary nebulae. These equations consider the temporal variation of the mechanical luminosity as well as the common envelope
evolution scenario. By comparing a database of nebulae with these solutions, a large portion of planetary nebulae can be better explained by the common envelope
evolution scenario, especially the fast and slow ones. Single AGB
stellar models can only reproduce nebulae with expansion velocities between 20 and 30 km/s.
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Astrophysics of Galaxies
SAGAN-VI: When Jets Meet Filaments – Environmental Imprints on the Growth of Giant Radio Galaxies
Mousumi Mahato, Elmo Tempel, Shishir Sankhyayan et al. (+2 more)
Giant radio galaxies (GRGs) represent the largest individual astrophysical structures, rivalling
galaxy clusters in physical extent. Understanding how they attain such scales demands examining their large scale
cosmic surroundings, particularly the under explored filament environment. We quantify the three dimensional (3D) distance of GRGs from the nearest filament spine; test how this distance correlates with their growth and formation of different morphological classes; assess whether their
radio jets exhibit preferred orientations relative to filament axes; and examine how filament anisotropy from spine to periphery modulates
radio morphology. We employed a filament catalogue from the SDSS together with the largest GRG catalogue currently available. For each source, we measured the comoving distance to the nearest filament spine, the projected jet spine orientation angle, and quantified lobe asymmetry via the arm length ratio (ALR). These metrics trace proximity, directionality, and the impact of filamentary environment on morphology. We then compared GRGs with a control sample of small
radio galaxies (SRGs) to constrain the environmental factors that regulate the attainment of
giant sizes. We validated the robustness of our results via bootstrap resampling and non parametric statistical tests. Our results show that GRGs and SRGs have similar filament occupancy. By contrast, GRGs preferentially display larger
alignment angles relative to filament spines, while SRG orientations are consistent with a random distribution. GRGs further show enhanced morphological asymmetry, reflected in lower ALR values than SRGs. Attainment of
giant sizes is not governed by proximity to filaments; rather, it correlates with jet filament
alignment. Abridged.
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All authors Mousumi Mahato, Elmo Tempel, Shishir Sankhyayan, Pratik Dabhade, Kshitij Chavan
Earth and Planetary Astrophysics
Was the Solar System's dynamical instability triggered by a (sub)stellar flyby?
Sean N. Raymond and Nathan A. Kaib
An instability among the
giant planets' orbits can match many aspects of the
Solar System's current orbital architecture. We explore the possibility that this dynamical instability was triggered by the close passage of a
star or substellar object during the Sun's embedded cluster phase. We run N-body simulations starting with the
giant planets in a resonant chain and an outer planetesimal disk, with a wide-enough
planet-disk separation to preserve the
planets' orbital stability for $>$100 Myr. We subject the system to a single flyby, testing a wide range in flyby mass, velocity and closest approach distance. We find a variety of outcomes, from flybys that over-excite the system (or strip the
planets entirely) to flybys too weak to perturb the
planets at all. An intermediate range of flybys triggers a dynamical instability that matches the present-day
Solar System. Successful simulations – that match the
giant planets' orbits without over-exciting the cold classical Kuiper belt – are characterized by the flyby of a substellar object ($3-30 M_{Jup}$) passing within 20 au of the Sun. We performed Monte Carlo simulations of the Sun's birth cluster phase, parameterized by the product of the
stellar density $\eta$ and the cluster lifetime $T$. The balance between under- and over-excitation of the young
Solar System is at $\eta T \approx 5 \times 10^4$~Myr pc$^{-3}$, in a range consistent with previous work. We find a probability of $\sim$1% that the
Solar System's dynamical instability was triggered by a substellar flyby. The probability increases to $\sim$5% if the occurrence rate of free-floating
planets and low-mass brown
dwarfs is modestly higher than predicted by standard
stellar initial mass functions.
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Earth and Planetary Astrophysics
Growth and thermal evolution of icy planetesimals
Jun Kimura, Ryusei Satoh, Kentaro Terada et al. (+1 more)
Icy planetesimals are likely to supply volatiles to terrestrial
planets and serve as building blocks of icy bodies in the outer
Solar System. Samples from the C-type asteroid Ryugu, collected by the Hayabusa-2 spacecraft, indicate a low-temperature history with aqueous alteration and organic materials. In contrast, iron meteorites with isotopic ratios similar to carbonaceous chondrites suggest exposure to higher temperatures. These findings imply that the thermal
evolution of icy planetesimals is highly diverse. Since direct exploration provides only localized data, understanding this diversity requires comparing observational results with model calculations incorporating key evolutionary processes. We develop a model including radial growth, impact heating, water phase changes, aqueous alteration, and structural differentiation, to re-evaluate the thermal
evolution of icy planetesimals during the first 100 Myr after CAI formation. The model considers final radius (10-1000 km), growth onset (1.0 or 2.0 Myr after CAI), growth duration (0.4 or 4.0 Myr), and growth mode (linear or runaway). Our results show that larger planetesimals generally reach higher temperatures, but growth timing and mode significantly affect thermal
evolution. Early
accretion leads to higher temperatures, with some bodies reaching the Fe-FeS eutectic (1250 K), while delayed or prolonged growth reduces heating. Our results show that the constituent materials of Ryugu, which kept below 40 degC, likely formed near the surface of a hydrated mineral layer. This is possible even in planetesimals several hundred kilometers in size due to efficient heat transport via convection. If
accretion begins 2.0 Myr after CAI and completes in 0.4 Myr, a wide region in such a body could yield Ryugu's material.
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All authors Jun Kimura, Ryusei Satoh, Kentaro Terada, Sho Sasaki
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Rapidly Spinning Massive Pulsars as an Indicator of Quark Deconfinement
Christoph Gärtlein, Violetta Sagun, Oleksii Ivanytskyi et al. (+2 more)
We study rotating hybrid
stars, with particular emphasis on the effect of
spin on the deconfinement phase transition and
star properties. Our analysis is based on a hybrid equation of state with a phase transition from hadronic matter containing hyperons to color-superconducting
quark matter, where the
quark phase is modeled within a relativistic density functional approach. By varying the strength of the vector repulsion and diquark pairing couplings in the microscopic
quark Lagrangian, we construct a set of hybrid
star sequences with different
quark-matter onset densities. This framework ensures consistency with astrophysical and gravitational wave constraints on mass, radius, and
tidal deformability.
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All authors Christoph Gärtlein, Violetta Sagun, Oleksii Ivanytskyi, David Blaschke, Ilídio Lopes
Astrophysics of Galaxies
Danger Zone: Establishing Buffers for Enhanced Classification in BPT Diagrams
Changhyun Cho, Ahmad Nemer, Ivan Yu. Katkov et al. (+1 more)
This study utilizes unsupervised machine learning, specifically the uniform
manifold approximation and projection (UMAP)
algorithm, to classify optical spectra originating from
star-forming regions, Seyferts, and low-ionization (
nuclear) emission-line regions (LI(N)ERs) based on their line ratios. Typically, the ionization source of a region is determined from intensity ratio of different combinations of pairs of spectral lines. However, using current boundary definitions, $\sim10$% of spectra change classes between diagnostic diagrams. We apply the machine learning technique to $\sim$1.3 million optical spectra from 6,439
galaxies observed in the MaNGA survey. By training UMAP on consistently classified data, we can classify these “ambiguous” spectra, and delineate boundary zones where such ambiguities arise. Furthermore, we identify physically interesting subsets within the ambiguous spectra. Future work will incorporate additional parameters, such as alternative emission line ratios and velocity dispersions, to enhance classification accuracy.
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All authors Changhyun Cho, Ahmad Nemer, Ivan Yu. Katkov, Joseph D. Gelfand
Solar and Stellar Astrophysics
Chemical Signatures of AGB Mass Transfer in Gaia White Dwarf Companions
Natsuko Yamaguchi, Kareem El-Badry, Henrique Reggiani et al. (+2 more)
We present a homogeneous abundance analysis of 160 main-sequence
stars in astrometric white-
dwarf + main-sequence (WD+MS) binaries with orbits from
Gaia DR3. These systems have AU-scale separations and are thought to have undergone mass transfer (MT) when the WD progenitor was an asymptotic
giant branch (AGB)
star. Using high-resolution spectroscopy, we measure chemical abundances of the MS
stars, focusing on s-process elements. Since s-process nucleosynthesis occurs mainly in AGB
stars, s-process enhancement in the MS
star is a key signature of
accretion from an AGB companion. We identify 43 barium
dwarfs – 39 of them newly discovered – roughly doubling the known population in astrometric WD+MS binaries and extending it to lower
metallicities than previously studied. The s-process abundances show large
star-to-
star variations that correlate with component masses and with
metallicity but not with orbital separation. At the lowest
metallicities, three barium
dwarfs display strong CH and $\rm C_2$ absorption bands, confirming a link between barium
stars and CEMP-s
stars and implying that AGB mass transfer usually leads to strong carbon enhancement at low
metallicity. By comparing the observed abundance patterns to AGB nucleosynthesis models, we show that the diversity of s-process enhancements can be explained by variations in donor mass,
metallicity, and most importantly, the number of thermal pulses the AGB
star experienced before the onset of MT. Variation in the depth of the accretors' convective envelopes, with which accreted material is diluted, strengthens correlations with MS
star mass and
metallicity. Our results establish
Gaia WD+MS binaries – which are homogeneously selected and probe shorter orbital periods than previous barium-
star samples – as a powerful laboratory for constraining mass transfer physics and the origin of chemically peculiar
stars.
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All authors Natsuko Yamaguchi, Kareem El-Badry, Henrique Reggiani, René Andrae, Sahar Shahaf
Instrumentation and Methods for Astrophysics
Stellar Multiplicity via Speckle Interferometry with the 3.6 m Devasthal Optical Telescope
Km Nitu Rai, Neelam Panwar, Jeewan C Pandey et al. (+3 more)
Conventional ground-based optical
telescopes, even those with large apertures, primarily observe
stars, close binaries, and multiple systems as unresolved point sources through photometric measurements. Spectroscopy can identify multiple
stellar components within a system, but both techniques are fundamentally limited in resolving
stellar surfaces and providing direct angular separations. Although photometric and spectroscopic observations yield critical information on magnitudes/flux,
metallicities, and orbital properties, complementary high-angular-resolution methods are required to constrain additional system characteristics, including angular orbital parameters, model-independent distances, radii, and
stellar masses. The limitations of these two methods arise due to the Diffraction Limit of the
telescopes and atmospheric
turbulence. Speckle Interferometry (SI) is a clever and affordable method for ground-based
telescopes to work around atmospheric
turbulence. In this work, we utilize the speckle images obtained by the 3.6 m DOT and demonstrate the capability of SI to resolve binary systems, measure their orbital separations, and determine their position angles. For systems with faint companions where conventional analysis fails, we employ
Bayesian inference to model speckle patterns and estimate orbital parameters with high precision. These results establish the effective methodology for using a medium-sized, 4-m class
telescope like the DOT as a high-resolution
stellar interferometer and demonstrate the potential of speckle interferometry as a powerful technique to advance optical interferometric studies within Indian astronomy.
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All authors Km Nitu Rai, Neelam Panwar, Jeewan C Pandey, T S Kumar, Subrata Sarangi, Prasenjit Saha
Solar and Stellar Astrophysics
von Zeipel-Kozai-Lidov oscillations in nearby bright stars. I. Lambda Ophiuchi
Idel Waisberg, Ygal Klein and Boaz Katz
The challenge of constraining both the inner and the outer orbits in multiple
stars has resulted in a growing abyss between the rich theoretical and the sparse observational studies of von Zeipel-Kozai-Lidov (ZKL) oscillations in
stellar systems. Here we solve for the full orbital architecture of the bright intermediate-mass nearby system Lambda Ophiuchi based on astrometric measurements of the outer orbit (period of 129 years) compiled in the Sixth Catalog of Orbits of Visual Binary
Stars and new VLTI/
GRAVITY interferometric measurements that are used to determine the inner orbit (period of 42 days). The orbits are retrograde and misaligned by either $88.5\pm1.9^o$ or $113.5\pm1.9^o$, which in either case results in the inner binary currently undergoing ZKL oscillations. While pure Newtonian point source
evolution would have predicted the
stars in the inner binary to have merged long ago, in reality the eccentricity oscillations are significantly modulated by general relativistic,
tidal and rotational bulge precession. We show that due to the effect of “slaved” precession the dynamics can still be solved semi-analytically. We find that the (currently unknown) inclination angles between the
stellar spins axes and the inner orbital axis play a very important role in the amplitude of the ZKL oscillations, which is at a minimum $\Delta e = e_{\mathrm{max}} - e_{\mathrm{min}} \simeq 0.15$ and could be as high as $\Delta e \simeq 0.70$. We argue that currently feasible spectroscopic and interferometric observations could allow for a complete and unique dynamical solution for this system.
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Astrophysics of Galaxies
Probing Infrared eXcess to Investigate Early-Universe Dust (PIXIEDust)
Tom J. L. C. Bakx, Hiddo S. B. Algera, Jean-Baptiste Jolly et al. (+25 more)
Despite the implied presence of
dust through reddened UV emission in high-
redshift galaxies, no
dust emission has been detected in the (sub)millimetre regime beyond $z > 8.3$. This study combines around two hundred hours of Atacama Large Millimeter/submillimeter Array (ALMA) and Northern Extended Millimeter Array (NOEMA) observations on ten $z > 8$
galaxies, revealing no significant
dust emission down to a $1 \sigma$ depth of $2.0$, $2.0$, and $1.5 \,\mu$Jy at rest-frame 158, 88 $\mu$m, and across all the data, respectively. This constrains average
dust masses to be below $< 10^{5}$ M$_{\odot}$ at $3 \sigma$ and
dust-to-
stellar mass ratios to be below $3.7 \times{} 10^{-4}$ (assuming $T_{\rm dust} = 50$ K and $\beta_{\rm dust} = 2.0$). Binning by
redshift ($8 < z < 9.5$ and $9.5 < z < 15$), UV-continuum slope ($\beta_{\rm UV} \lessgtr -2$) and
stellar mass ($\log_{10} M_{\ast}/{\rm M_{\odot}} \lessgtr 9$) yields similarly stringent constraints. Combined with other studies, these results are consistent with inefficient
dust build-up in the $z > 8$ Universe, likely due to inefficient
supernova production, limited interstellar grain growth and/or ejection by
outflows. We provide data and tools online to facilitate community-wide high-
redshift dust searches.
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All authors Tom J. L. C. Bakx, Hiddo S. B. Algera, Jean-Baptiste Jolly, Clarke Esmerian, Kirsten Knudsen, Laura Sommovigo, Joris Witstok, Stefano Carniani, Jianhang Chen, Stephen Eales, Andrea Ferrara, Yoshinobu Fudamoto, Masato Hagimoto, Takuya Hashimoto, Hanae Inami, Akio K. Inoue, Theo Khouri, Ikki Mitsuhashi, Gunnar Nyman, Gustav Olander, Stephen Serjeant, Renske Smit, Ilsang Yoon, Jorge Zavala, Susanne Aalto, Caitlin M. Casey, Yoichi Tamura, Wouter Vlemmings
Astrophysics of Galaxies
Forecasting Dark Matter Subhalo Constraints from Stellar Streams using Implicit Likelihood Inference
Tri Nguyen, Rutong Pei, Zhuofu Li et al. (+9 more)
The evidence for dark matter (DM) remains compelling, although attempts to understand its particle nature remain inconclusive. One promising method to study DM is detecting DM subhalos through their gravitational interactions with
stellar streams. In this study, we apply Neural Posterior Estimation (NPE) to constrain subhalo interaction parameters, including mass, scale radius, velocity, and encounter geometry, from
stellar stream kinematics. We generate particle spray simulations based on the Lagrange Cloud stripping technique, focusing on the ATLAS-Aliqa Uma stream as a test case. We train multiple NPE models across multiple observational scenarios, quantifying how kinematic completeness affects inference and
forecasting constraints from upcoming surveys including LSST, 4MOST, and 10-year
Gaia data. Our results demonstrate that NPE can produce accurate and well-calibrated posteriors. In the idealized case with full 6D coordinates, we achieve subhalo mass uncertainties of 15-20% for a $10^7 \, \mathrm{M_\odot}$ subhalo, with 5D coordinates (excluding radial velocities) achieving similar performance. Under realistic observational conditions, mass uncertainties range from 50% (present-day) to 20-40% (future scenarios), with comparable performance between the photometric-only LSST sample and a smaller sample that includes
Gaia proper motions and 4MOST radial velocities. Most notably, we find that velocity bimodality emerges when phase space is poorly sampled, whether due to missing kinematic information or limited
stellar tracers. Combining large photometric samples with targeted spectroscopic follow-up can effectively resolves this degeneracy. These results demonstrate the power of implicit likelihood inference for optimizing
stellar stream observational strategies and
forecasting DM subhalo constraints from upcoming surveys.
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All authors Tri Nguyen, Rutong Pei, Zhuofu Li, Nora Shipp, Scott Dodelson, Denis Erkal, Peter S. Ferguson, Tjitske K. Starkenburg, Markus M. Rau, Alexander H. Riley, Alan Junzhe Zhou, the LSST Dark Energy Science Collaboration
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quasinormal ringing of Kerr black holes. III. Excitation coefficients for equatorial inspirals from the innermost stable circular orbit
Matteo Della Rocca, Laura Pezzella, Emanuele Berti et al. (+2 more)
The remnant of a black hole binary merger settles into a stationary configuration by "ringing down" through the emission of gravitational waves that consist of a superposition of damped exponentials with discrete complex frequencies - the remnant black hole's quasinormal modes. While the frequencies themselves depend solely on the mass and
spin of the remnant, the mode amplitudes depend on the merger dynamics. We investigate quasinormal mode excitation by a point particle plunging from the innermost stable circular orbit of a Kerr black hole. Our formalism is general, but we focus on computing the quasinormal mode excitation coefficients in the frequency domain for equatorial orbits, and we analyze their dependence on the remnant black hole
spin. We find that higher overtones and subdominant multipoles of the radiation become increasingly significant for rapidly rotating black holes. This suggests that the prospects for detecting overtones and higher-order modes are considerably enhanced for highly spinning merger remnants.
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All authors Matteo Della Rocca, Laura Pezzella, Emanuele Berti, Leonardo Gualtieri, Andrea Maselli
Astrophysics of Galaxies
Tracing nitrogen enrichment across cosmic time with JWST
E. Cataldi, F. Belfiore, M. Curti et al. (+22 more)
We present a comprehensive analysis of the nitrogen-to-oxygen (N/O) abundance ratio in a sample of ~ 660
star-forming
galaxies at
redshift z ~ 1-6, with a median
redshift of z = 3.0, using deep JWST/NIRSpec spectroscopy. Leveraging detections of faint auroral emission lines in 92
galaxies at z>1 from both the MARTA survey and a large compilation of high-
redshift literature objects, we derive direct electron temperature-based abundances for nitrogen and oxygen using rest-frame optical lines. We establish the first high-
redshift calibrations of strong-line N/O diagnostics based on 'direct' abundance measurements, finding a mild
evolution for the N2O2 = log([NII]6585/[OII]3727,3729) diagnostic and no clear
evolution for the N2S2 = log([NII]6585/[SII]6717,6731) diagnostic compared to local realisations. We then investigate the N/O-O/H relation across
cosmic time using both 'direct' abundances and strong-lines based measurements (additional 535
galaxies). We find evidence for mild but systematic nitrogen enhancement at high
redshift:
galaxies at z>1 exhibit N/O ratios elevated by ~0.18 dex (median offset) at fixed O/H compared to local trends, with a more pronounced enhancement at low
metallicity (i.e. 12 + log(O/H) < 8.1), where the offset reaches up to ~0.4-0.5 dex. We consider several scenarios to explain the observed trends, including bursty
star formation, differential metal loading, and inflows of pristine gas. Our results provide the most extensive confirmation of elevated N/O ratios at high-
redshift to date based on rest-optical diagnostics and within a self-consistent frame.
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All authors E. Cataldi, F. Belfiore, M. Curti, B. Moreschini, A. Marconi, R. Maiolino, A. Feltre, M. Ginolfi, F. Mannucci, G. Cresci, X. Ji, A. Amiri, M. Arnaboldi, E. Bertola, C. Bracci, M. Ceci, A. Chakraborty, F. Cullen, Q. D'Amato, C. Kobayashi, I. Lamperti, C. Marconcini, M. Scialpi, L. Ulivi, M. V. Zanchettin
Astrophysics of Galaxies
LEGA-C stellar populations scaling relations. I: Chemo-archaeological downsizing trends at z~0.7
Anna R. Gallazzi, Stefano Zibetti, Arjen van der Wel et al. (+11 more)
We analyze
stellar population properties of 552
galaxies at
redshift 0.6<z<0.77 from the LEGA-C spectroscopic survey. This first paper in a series presents the catalog of revised absorption indices for LEGA-C DR3 and inferred physical parameters, and derives
benchmark scaling relations for the general massive
galaxy population at intermediate
redshift. We estimate light-weighted mean ages and
stellar metallicities by interpreting key
stellar absorption features and rizYJ photometry in a
Bayesian framework with a comprehensive library of model spectra based on
stochastic star formation and
metallicity histories and
dust attenuations. We discuss systematic uncertainties within our method and compared to other spectral fitting approaches. We derive volume-weighted scaling relations of light-weighted mean ages and
stellar metallicities with
stellar mass for the general
galaxy population at <z>=0.7 and masses >10^10Msun. The downsizing trends observed locally were already in place 6 Gyr ago. We observe bimodal age distribution as a function of mass, transitioning around 10^11Msun. No bimodality appears in the
stellar metallicity-mass relation, which changes from steep to flat across 10^10.8Msun. Similar trends emerge for age and
metallicity with velocity dispersion, but with sharper transition from young to old around log(sigma)=2.3. Differences with respect to trens with
stellar mass suggest that age primarily depends on velocity dispersion below and above the transition regime, while both
stellar mass and velocity dispersion contribute to
stellar metallicity. The catalogs of revised absorption index measurements for LEGA-C DR3 and inferred
stellar population physical parameters will be released to public repositories. (Abridged)
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All authors Anna R. Gallazzi, Stefano Zibetti, Arjen van der Wel, Angelos Nersesian, Yasha Kaushal, Rachel Bezanson, Francesco D'Eugenio, Eric F. Bell, Joel Leja, Laura Scholz-Diaz, Po-Feng Wu, Camilla Pacifici, Michael Maseda, Daniele Mattolini
Astrophysics of Galaxies
The dynamic central environment of NGC 3516 revealed by XRISM
Anna Juráňová, Erin Kara, Ehud Behar et al. (+15 more)
We present a detailed, time-resolved analysis of the Fe K band of the Seyfert 1.5
galaxy NGC 3516 observed with XRISM. The 249 ks observation spanning $\sim$310 ks in elapsed time reveals an exceptionally rich and time-variable absorption spectrum. Six distinct absorption components are detected across multiple ionization states, spanning more than an order of magnitude in ionization parameter and a wide range of systemic velocities, from a potential inflow ($+4300~\rm km~s^{-1}$) to a mildly relativistic ultra-fast
outflow ($-9800~\rm km~s^{-1}$). Despite their diversity, the components exhibit relatively small broadening ($\lesssim$$400~\rm km~s^{-1}$), implying comparable internal dynamics within a medium of a complex structure. Time-resolved spectroscopy reveals pronounced variability in three highly ionized absorbers, with Fe XXV$-$Fe XXVI features that appear and disappear on timescales of tens of kiloseconds. This behavior likely reflects a combination of geometrical transits of clumpy gas and ionization-state changes driven by continuum variability. An additional temporary absorption feature in the red wing of the Fe K$\alpha$ line, consistent with Fe XXV absorption, indicates a possible transient ultra-fast inflow at $\sim$$15\,000~\rm km~s^{-1}$ ($\sim$5% $c$). Finally, the continuum light curve exhibits a tentative $\sim$40 ks oscillatory pattern, accompanied by correlated shifts of a weak, narrow Fe K$\alpha$ emission feature, suggesting dynamic coupling between the continuum and the line-emitting region. Together, these results reveal that the
nuclear environment of NGC 3516 is dominated by rapidly evolving, multi-phase gas flows, where
accretion, ejection, and ionization processes are tightly coupled on sub-parsec scales.
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All authors Anna Juráňová, Erin Kara, Ehud Behar, Elisa Costantini, Jon M. Miller, Daniele Rogantini, James N. Reeves, Valentina Braito, Jacobo Ebrero, Luigi Gallo, Noa Keshet, Gerard A. Kriss, Missagh Mehdipour, Hirofumi Noda, Atsushi Tanimoto, Francesco Tombesi, Tracey J. Turner, Satoshi Yamada