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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 12 January

High Energy Astrophysical Phenomena

Uniform models of neutron and quark (strange) stars in General Relativity

G. S. Bisnovatyi-Kogan and E. A.Patraman

Models of neutron and strange stars are considered in the approximation of a uniform density distribution. A universal algebraic equation, valid for any equation of state, is used to find the approximate mass of a star of a given density without resorting to the integration of differential equations. Equations of state for neutron stars had been taken for degenerate neutron gas and for more realistic ones, used by Bethe, Malone, Johnson (1975). Models of homogeneous strange stars for the equation of state in the "quark bag model" have a simple analytical solution. The solutions presented in the paper for various equations of state differ from the exact solutions obtained by the numerical integration of differential equations by at most $ \sim 20 \%$. The formation of strange stars is examined as a function of the deconfinement boundary (DB), at which quarks become deconfined. Existing experimental data indicate that matter reaches very high densities in the vicinity of the DB. This imposes strong constraints on the maximum mass of strange stars and prohibits their formation at the final stages of stellar evolution, because the limiting mass of neutron stars is substantially higher and corresponds to considerably lower matter densities.
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Astrophysics of Galaxies

Isochrone Fitting of Galactic Globular Clusters – VII. NGC1904 (M79), NGC4372, and revision of NGC288, NGC362, NGC5904 (M5), NGC6205 (M13), and NGC6218 (M12)

George A. Gontcharov, Sergey S. Savchenko, Olga S. Ryutina et al. (+8 more)

We estimate key parameters for the Galactic globular clusters NGC1904 and NGC4372 and update the parameters for NGC288, NGC362, NGC5904, NGC6205, and NGC6218, which were analysed in our previous papers. We fit various colour-magnitude diagrams (CMDs) of the clusters using isochrones from the DSED and BaSTI. The CMDs are constructed from data sets provided by the HST, Gaia, SMSS, a large compilation of Stetson, and other sources, using multiple filters for each cluster. Our cross-identification of almost all the data sets with those from Gaia or HST allows us to use their astrometry to precisely select cluster members in all the data sets. We obtain the following estimates for NGC288, NGC362, NGC1904, NGC4372, NGC5904, NGC6205 and NGC6218, respectively: metallicities [Fe/H]$=-1.28$, $-1.26$, $-1.64$, $-2.28$, $-1.33$, $-1.56$, and $-1.27$ dex; ages $12.94$, $10.33$, $13.16$, $12.81$, $11.53$, $12.75$, and $13.03$ Gyr; distances $8.83$, $9.00$, $12.66$, $5.17$, $7.24$, $7.39$, and $4.92$ kpc; reddenings $E(B-V)=0.022$, $0.029$, $0.031$, $0.545$, $0.045$, $0.024$, and $0.210$ mag; extinctions $Av=0.09$, $0.09$, $0.11$, $1.58$, $0.13$, $0.09$, and $0.67$ mag; and extinction-to-reddening ratio $Rv=3.9$, $3.0$, $3.8$, $2.9$, $2.9$, $3.6$, and $3.2$. We confirm that the differences in horizontal branch morphology among the 16 Galactic globular clusters analysed in our studies can be explained by variations in their metallicity, age, mass-loss efficiency, and the loss of low-mass members during cluster evolution. Accordingly, most clusters indicate a relatively high mass-loss efficiency, consistent with the Reimers mass-loss law with $\eta>0.3$.
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All authors George A. Gontcharov, Sergey S. Savchenko, Olga S. Ryutina, Charles J. Bonatto, Jae-Woo Lee, Vladimir B. Il'in, Maxim Yu. Khovritchev, Alexander A. Marchuk, Aleksandr V. Mosenkov, Denis M. Poliakov, Anton A. Smirnov

Astrophysics of Galaxies

CASCO: Cosmological and AStrophysical parameters from Cosmological simulations and Observations IV. Testing warm dark matter cosmologies with galaxy scaling relations: A joint simulation-observation study using DREAMS simulations

M. Silvestrini, C. Tortora, V. Busillo et al. (+9 more)

Small-scale discrepancies in the standard Lambda cold dark matter paradigm have motivated the exploration of alternative dark matter (DM) models, such as warm dark matter (WDM). We investigate the constraining power of galaxy scaling relations on cosmological, astrophysical, and WDM parameters through a joint analysis of hydrodynamic simulations and observational data. Our study is based on the DREAMS project and combines large-volume uniform-box simulations with high-resolution Milky Way zoom-in runs in a $\Lambda$WDM cosmology. To ensure consistency between the different simulation sets, we apply calibrations to account for resolution effects, allowing us to exploit the complementary strengths of the two suites. We compare simulated relations, including stellar size, DM mass and fraction within the stellar half-mass radius, and the total-to-stellar mass ratio, with two complementary galaxy samples: the SPARC catalog of nearby spirals and the LVDB catalog of dwarf galaxies in the Local Volume. Using a bootstrap-based fitting procedure, we show that key cosmological parameters ($\Omega_m$, $\sigma_8$) and supernova feedback strength can be recovered with good accuracy, particularly from the uniform-box simulations. While the WDM particle mass remains unconstrained, the zoom-in simulations reveal subtle WDM-induced trends at low stellar masses in both the DM mass and total-to-stellar mass ratio. We also find that the galaxy stellar mass function exhibits a measurable dependence on the WDM particle mass below log10(M_*/Msun) <~ 8, which appears separable from the impact of feedback, suggesting it as a promising complementary probe. Our results highlight the importance of combining multi-resolution simulations with diverse observational datasets to jointly constrain baryonic processes and DM properties.
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All authors M. Silvestrini, C. Tortora, V. Busillo, Alyson M. Brooks, A. Farahi, A. M. Garcia, N. Kallivayalil, N. R. Napolitano, J. C. Rose, P. Torrey, F. Villaescusa-Navarro, M. Vogelsberger

High Energy Astrophysical Phenomena

Revealing the diversity of Type IIn supernova progenitors through their environments

Zexi Niu, Ning-Chen Sun, Emmanouil Zapartas et al. (+4 more)

Type IIn supernovae (SNe IIn) are hydrogen-rich explosions embedded in dense circumstellar medium (CSM), which gives rise to their characteristic narrow hydrogen emission lines. The nature of their progenitors and pre-explosion mass loss remains, however, poorly understood. Using high-resolution Hubble Space Telescope (HST) imaging, we analyze the local stellar environments of a volume-limited sample (z < 0.02) of 31 SNe IIn. The environments of SNe IIn are found to be very diverse; the SN could reside within a star-forming region (Class 1), outside a star-forming region (Class 2), or in much older environments without any obvious signs of star formation (Class 3). The bright SNe IIn (Mpeak < -19.5 mag) predominantly occur in Class 1 environments, indicative of very massive progenitors, while the faint SNe IIn (Mpeak < -15.5 mag) are associated with Classes 2 and 3 environments, suggesting the least massive progenitors. Meanwhile, normal SNe IIn with -19.5 < Mpeak < -15.5 mag occur in all three types of environments, suggesting a diversity in their progenitor mass, lifetime, and evolutionary pathways. Moreover, the directly detected SN IIn progenitors are systematically brighter and/or bluer than the youngest stellar populations in their environments, suggesting that they were either in a non-quiescent state when observed or had experienced binary interactions. These results point to a significantly diverse origin for progenitors of SNe IIn, spanning a wide range of masses, evolutionary stages, and potential binary interaction histories.
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All authors Zexi Niu, Ning-Chen Sun, Emmanouil Zapartas, Conor L. Ransome, Justyn R. Maund, Cesar Rojas-Bravo, Jifeng Liu

High Energy Astrophysical Phenomena

High-resolution simulations of non-thermal emission from LS 5039

Ralf Kissmann, David Huber and Philipp Gschwandtner

In a previous study, we investigated the relativistic wind dynamics in the LS 5039 system. In this work, we analyse energetic-particle transport within this modelling context, where we simulate the high-energy particle distribution and ensuing emission of non-thermal radiation. From these high-resolution simulations, we compute the non-thermal emission from this system and compare it to corresponding observations. We modelled the LS 5039 system assuming a wind-driven scenario. Our numerical model uses a joint simulation of the dynamical wind interaction together with the transport of energetic leptons from the shocked pulsar wind. We computed the non-thermal emission from this system in a post-processing step from the resulting distribution of energetic leptons. In this computation, we took into account the synchrotron and inverse Compton emission, relativistic beaming, and {\gamma}{\gamma}-absorption in the stellar radiation field. We investigated the dynamical variation of the energetic particle spectra on both orbital and on short timescales. Our model successfully reproduces many of the spectral features of LS 5039. We also find a better correspondence between our predicted orbital light curves and the corresponding observations in soft x-rays, low-energy, and high-energy gamma rays than in our previous modelling efforts. We find that our high-resolution and large-scale simulations can successfully capture the relevant parts of the wind-collision region that are related to particle acceleration and emission of non-thermal radiation. The quality of the fit strengthens the wind-driven assumption underlying our model. Desirable extensions for the future include a dynamical magnetic-field model for the synchrotron regime, a revision of our injection parameters, and a consideration of an additional hadronic component that could explain recent observations in the 100~TeV regime.
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High Energy Astrophysical Phenomena

The combined X-ray and $\gamma$-ray modeling of millisecond pulsars PSR J0030+0451 in the dissipative magnetospheres

Gang Cao and Xiongbang Yang

Modeling of the NICER X-ray light curves of millisecond pulsars PSR J0030+0451 provides a strong evidence for the existence of non-dipole magnetic fields. We study the X-ray and $\gamma$-ray emission of PSR J0030+0451 in the dissipative dipole plus off-centred quadrupole magnetospheres. The dissipative FF+AE dipole magnetospheres by combining force-free (FF) and Aristotelian electrodynamics (AE) are solved by a 3D pseudo-spectral method in the rotating coordinate system. We use the FF+AE dipole plus off-centred quadrupole fields with minimum free parameters to reproduce two hotspot configurations found by the NICER observations. The X-ray and $\gamma$-ray emission from PSR J0030+0451 are simultaneously computed by using a ray-tracing method and a particle trajectory method. The modelled X-ray and $\gamma$-ray emission is then directly compared with those of PSR J0030+0451 from the NICER and Fermi observations. Our results can well reproduce the observed trends of the NICER X-ray and Fermi $\gamma$-ray emission for PSR J0030+0451.
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Cosmology and Nongalactic Astrophysics

Modified Gravity and the Origin of the Excess Radio Galaxy Number-Count Dipole

John. W. Moffat

Recent analyses of wide-area radio-galaxy surveys have reported a statistically significant excess in the cosmic number-count dipole, with an amplitude exceeding the purely kinematic expectation of the standard $\Lambda$CDM model by a factor of $\sim 3$–$4$, quoted at a significance level of up to $5.4\sigma$. While residual observational systematics and local-structure effects cannot be definitively excluded, this result motivates the exploration of alternative physical interpretations beyond the minimal $\Lambda$CDM framework. We investigate whether Scalar–Tensor–Vector Gravity (STVG-MOG) can provide a consistent explanation for an enhanced large-scale anisotropic dipole without violating existing constraints from early-universe cosmology, the cosmic microwave background (CMB) dipole, galaxy dynamics, weak lensing, or the observed late-time matter power spectrum. The radio number-count dipole probes ultra-large-scale, anisotropic structure and coherent gravitational response, rather than virialized dynamics or linear growth alone. In STVG-MOG, a scale- and time-dependent effective gravitational coupling preserves standard cosmological evolution at early times and on small to intermediate scales, while amplifying gravitational response on gigaparsec scales. This scale-selective enhancement can increase the large-scale structure contribution to the radio dipole without overproducing power on smaller scales. If the observed dipole excess reflects a physical cosmological signal rather than residual systematics, STVG-MOG offers a viable and testable alternative interpretation. It is demonstrated that the radio dipole anomaly provides a novel probe of gravitational physics on the largest observable scales.
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Astrophysics of Galaxies

A Guided Unconditional Diffusion Model to Synthesize and Inpaint Radio Galaxies from FIRST, MGCLS and Radio Zoo

Rémi Poitevineau, Emma Tolley and Verlon Etsebeth

We present a masked-guided approach for a denoising diffusion probabilistic model (DDPM) trained to generate and inpaint realistic radio galaxy images. The inpainting capability is particularly relevant for reconstructing incomplete observations, improving downstream tasks such as source characterization and morphological classification. We train the model on a combination of the FIRST survey, Radio Galaxy Zoo, and cutouts from the MGCLS survey, enabling it to capture a broad range of radio galaxy morphologies across different observational regimes. We evaluate the realism of the generated samples through statistical comparisons with real data, ensuring consistency in key morphological and intensity distributions. Our unconditional model produces morphologically plausible galaxies while maintaining diversity, highlighting the suitability of diffusion models for this task. This approach provides a scalable alternative to computationally expensive simulations and enables effective data augmentation for machine learning applications in radio astronomy, including source detection, classification, and image reconstruction.
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Earth and Planetary Astrophysics

Instantaneous thermally-driven erosion can explain dearth of dark near-Sun asteroids

Georgios Tsirvoulis, Mikael Granvik, Leonard Schirner et al. (+3 more)

Recent models of the near-Earth asteroid population show that asteroids must be super-catastrophically destroyed when they evolve to orbits with perihelion passages well inside of Mercury's orbit. The heliocentric distances at which the disruptions typically occur are tens of solar radii, which is too far from the Sun for asteroids to be destroyed by sublimation and tidal disruption. The typical disruption distance also appears to be larger for darker asteroids. Here, by carrying out irradiance experiments in vacuum that replicate the conditions in the near-Sun environment, we show that CI meteorite simulants are destroyed within minutes when exposed to the level of solar irradiance encountered at heliocentric distances of up to about 0.2 au. Our results provide an explanation for the scarcity of dark, carbonaceous asteroids with perihelion distances less than 0.2 au, and for the observed mass-loss rate of the asteroid-like object 322P/SOHO~1 assuming its composition is similar to CI carbonaceous chondrites.
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All authors Georgios Tsirvoulis, Mikael Granvik, Leonard Schirner, Athanasia Toliou, Jooyeon Geem, Axel Hagermann

Earth and Planetary Astrophysics

Exoplanet transit search at the detection limit: detection and false alarm vetting pipeline

Jakob Robnik, Uroš Seljak, Jon M. Jenkins et al. (+1 more)

One of the primary mission goals of the Kepler space telescope was to detect Earth-like terrestrial planets in the habitable zone around Sun-like stars. These planets are at the detection limit, where the Kepler detection and vetting pipeline produced unreliable planet candidates. We present a novel pipeline that improves the removal of localized defects prior to the planet search, improves vetting at the level of individual transits and introduces a Bayes factor test statistic and an algorithm for extracting multiple candidates from a single detection run. We show with injections in the Kepler data that the introduced novelties improve pipeline's completeness at a fixed false alarm rate. We apply the pipeline to the stars with previously identified planet candidates and show that our pipeline successfully recovers the previously confirmed candidates, but flags a considerable portion of unconfirmed candidates as likely false alarms, especially in the long period, low signal-to-noise ratio regime. In particular, several known Earth-like candidates in the habitable zone, such as KOI 8063.01, 8107.01 and 8242.01, are identified as false alarms, which could have a significant impact on the estimates of $\eta_{\oplus}$, i.e., the occurrence of Earth-like planets in the habitable zone.
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All authors Jakob Robnik, Uroš Seljak, Jon M. Jenkins, Steve Bryson

Earth and Planetary Astrophysics

Functionalization of Benzene Ices by Atomic Oxygen

Elettra L. Piacentino, Alexandra McKinnon, Nora Hänni et al. (+6 more)

Small aromatic molecules, including functionalized derivatives of benzene, are known to be present throughout the different stages of star and planet formation. In particular, oxygen-bearing monosubstituted aromatics, likely including phenol, have been identified in the coma of comet 67P. This suggests that, earlier in the star and planet formation evolution, icy grains may act as both reservoirs and sites of functionalization for these small aromatics. We investigate the ice-phase reactivity of singlet oxygen atoms (O($^1$D)) with benzene, using ozone as a precursor that is readily photodissociated by relatively low-energy. Our experiments show that O($^1$D) efficiently reacts with benzene, forming phenol, benzene oxide, and oxepine as the main products. Phenol formation is temperature-independent, consistent with a barrierless insertion mechanism. In contrast, the formation of benzene oxide/oxepine shows a slight temperature dependence, suggesting that additional reaction pathways involving either ground-state or excited-state oxygen atoms may contribute. In H$_2$O and \COO ice matrices we find that dilution does not suppress formation of phenol. We extrapolate an experimental upper limit for the benzene-to-phenol conversion fraction of 27-44$\%$ during the lifetime of an interstellar cloud, assuming O($^1$D) production rates based on CO$_2$ ice abundances and a cosmic-ray induced UV field. We compare these estimates with a new analysis of data from the comet 67P, where the C$_6$H$_6$O/C$_6$H$_6$ ratio is 20$\pm$6$\%$. This value lies within our estimated range, suggesting that O($^1$D)-mediated chemistry is a viable pathway for producing oxygenated aromatics in cold astrophysical ices, potentially enriching icy planetesimals with phenol and other biorelevant compounds.
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All authors Elettra L. Piacentino, Alexandra McKinnon, Nora Hänni, Amit Daniely, Estefania Rossich Molina, Tamar Stein, Jennifer Bergner, Mahesh Rajappan, Karin I. Öberg

High Energy Astrophysical Phenomena

A Study of Two Type IIb Supernovae: SNe 2008aq and 2019gaf

Mridweeka Singh, Devendra K. Sahu, Raya Dastidar et al. (+12 more)

We present photometric and spectroscopic studies of two core-collapse supernovae (SNe) 2008aq and 2019gaf in the optical wavelengths. Light curve and spectral sequence of both the SNe are similar to those of other Type IIb SNe. The pre-maximum spectrum of SN~2008aq showed prominent H $\alpha$ lines, the He lines started appearing in the near maximum spectrum. The near maximum spectrum of SN~2019gaf shows shallow H$\alpha$ absorption and He lines with almost similar strength. Both the SNe show transition from hydrogen-dominated spectra to helium-dominated spectra within a month after maximum brightness. The velocity evolution of SN~2008aq matches well with those of other well-studied Type IIb SNe, while SN~2019gaf shows higher velocities. Close to maximum light, the H $\alpha$ and He I line velocities of SN~2019gaf are $\sim$ 2000 km sec$^{-1}$ and $\sim$ 4000 km sec$^{-1}$ higher than other well-studied Type IIb SNe. Semi-analytical modeling indicates SN~2019gaf to be a more energetic explosion with a smaller ejecta mass than SN~2008aq. The zero-age main-sequence (ZAMS) mass of the progenitor estimated using the nebular spectra of SN~2008aq ranges between 13 to 20 M$_\odot$, while for SN~2019gaf, the inferred ZAMS mass is between 13 to 25 M$_\odot$. The [O I] to [Ca II] lines flux ratio favors a less massive progenitor star in a binary system for both the SNe.
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All authors Mridweeka Singh, Devendra K. Sahu, Raya Dastidar, Rishabh Singh Teja, Anjasha Gangopadhyay, G. C. Anupama, D. Andrew Howell, K. Azalee Bostroem, Curtis McCully, Jamison Burke, Arti Joshi, Daichi Hiramatsu, Hyobin Im, Shubham Srivastav, Kuntal Misra

Instrumentation and Methods for Astrophysics

Advanced computing for reproducibility of astronomy Big Data Science, with a showcase of AMIGA and the SKA Science prototype

Julián Garrido, Susana Sánchez, Edgar Ribeiro João et al. (+3 more)

The Square Kilometre Array Observatory (SKAO) faces unprecedented technological challenges due to the vast scale and complexity of its data. This paper provides an overview of research by the AMIGA group to address these computing and reproducibility challenges. We present advancements in semantic data models, analysis services integrated into federated infrastructures, and the application to astronomy studies of techniques that enhance research transparency. By showcasing these astronomy work, we demonstrate that achieving reproducible science in the Big Data era is feasible. However, we conclude that for the SKAO to succeed, the development of the SKA Regional Centre Network (SRCNet) must explicitly incorporate these reproducibility requirements into its fundamental architectural design. Embedding these standards is crucial to enable the global community to conduct verifiable and sustainable research within a federated environment.
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All authors Julián Garrido, Susana Sánchez, Edgar Ribeiro João, Roger Ianjamasimanana, Manuel Parra, Lourdes Verdes-Montenegro

Instrumentation and Methods for Astrophysics

A free-fall-based switching criterion for P^3 T N-body methods in collisional stellar systems

Long Wang, David M. Hernandez, Zepeng Zheng et al. (+1 more)

The P$^3$T scheme is a hybrid method for simulating gravitational $N$-body systems. It combines a fast particle-tree (PT) algorithm for long-range forces with a high-accuracy particle-particle (PP, direct $N$-body) solver for short-range interactions. Preserving both PT efficiency and PP accuracy requires a robust PT-PP switching criterion. We introduce a simple free-fall-based switching criterion for general stellar systems, alongside the commonly used velocity-dispersion-based ($\sigma$-based) criterion. Using the petar code with the P$^3$T scheme and slow-down algorithmic regularization for binaries and higher-order multiples, we perform extensive simulations of star clusters to evaluate how each criterion affects energy conservation and binary evolution. For systems in virial equilibrium, we find that the free-fall-based criterion is generally more accurate for low-$\sigma$ or loose clusters containing binaries, whereas the $\sigma$-based criterion is better suited for high-$\sigma$ systems. Under subvirial or fractal initial conditions, both criteria struggle to maintain high energy conservation; however, the free-fall-based criterion improves as the tree timestep is reduced, whereas the $\sigma$-based degrades due to its low-accuracy treatment of two-body encounters.
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All authors Long Wang, David M. Hernandez, Zepeng Zheng, Wanhao Huang

Earth and Planetary Astrophysics

Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts

E. Poultourtzidis, G. Lacedelli, E. Pallé et al. (+49 more)

We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM~J0902+7138), TOI-4529 (G~2–21), and TOI-5388 (Wolf~346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of $4.65$, $5.88$, and $2.59$ days, and they orbit early-M dwarfs (M2.0V, M1.5V, and M3.0V, respectively). We were able to precisely determine the radius of all three planets with a precision of $< 7\, \%$, the mass of TOI-1243 b with a precision of $19\, \%$, and upper mass limits for TOI-4529 b and TOI-5388 b. The radius of TOI-1243 b is $2.33\pm0.12\, {R_{\oplus}}$, its mass is $7.7 \pm 1.5\,{M_{\oplus}}$, and the mean density is $0.61 \pm 0.15 \, {\rho_\oplus}$. The radius of TOI-4529 b is $1.77 ^{+0.09}_{-0.08} \, {R_{\oplus}}$, the $3 {\sigma}$ upper mass limit is $4.9 \, {M_{\oplus}}$, and the $3 {\sigma}$ upper density limit is $0.88\, {\rho_\oplus}$. The third planet, TOI-5388 b, is Earth-sized with a radius of $0.99 ^{+0.07}_{-0.06} \, {R_{\oplus}}$, a $3 {\sigma}$ upper mass limit of $2.2 \, {M_{\oplus}}$, and a $3 {\sigma}$ upper density limit of $2.2\, {\rho_\oplus}$. While TOI-5388 b is most probably rocky, given its Earth-like radius, TOI-1243 b and TOI-4529 b are located in a highly degenerate region in the mass-radius space. TOI-4529 b appears to lean toward a water-world composition. TOI-1243 b has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample.
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All authors E. Poultourtzidis, G. Lacedelli, E. Pallé, I. Carleo, C. Magliano, S. Geraldía-González, J. A. Caballero, G. Morello, J. Orell-Miquel, H. M. Tabernero, F. Murgas, G. Covone, F. J. Pozuelos, P. J. Amado, V. J. S. Béjar, S. Chairetas, C. Cifuentes, D. R. Ciardi, K. A. Collins, I. J. M. Crossfield, E. Esparza-Borges, G. Fernández-Rodríguez, A. Fukui, Y. Hayashi, A. P. Hatzes, Th. Henning, E. Herrero, K. Horne, S. B. Howell, K. Isogai, J. M. Jenkins, Y. Kawai, F. Libotte, E. Matthews, P. Meni-Gallardo, I. Mireles, J. C. Morales, N. Narita, B. B. Ogunwale, H. Parviainen, A. Quirrenbach, A. Reiners, I. Ribas, R. Sefako, A. Shporer, R. P. Schwarz, G. Srdoc, L. Tal-Or, S. Vanaverbeke, N. Watanabe, C. N. Watkins, F. Zong Lang

Astrophysics of Galaxies

The converging gas flow around the infrared dark cloud G28.3

H. Beuther, C. Gieser, H. Linz et al. (+7 more)

Aims: The G28.37+0.07 star-forming region is a prototypical infrared dark cloud (IRDC) located at the interface of a converging gas flow. This study characterizes the properties of this dynamic gas flow. Methods: Combining data from the Northern Extended Millimeter Array (NOEMA) with single-dish data from the IRAM30m observatory, we mapped large spatial scales (~81pc^2) at high angular resolution (7.0”x2.6” corresponding ~2.3x10^4au or ~0.1pc) down to core scales. The spectral setup in the 3mm band covers many spectral lines as well as the continuum emission. Results: The data reveal the proposed west-east converging gas flow in all observed dense gas tracers. We estimate a mass-flow rate along that flow around 10^-3M_sun/yr. Comparing these west-east flow rates to infall rates toward sources along the line of sight, the gas flow rates are roughly a factor of 25 greater than than those along the line of sight. This confirms the dominance of longitudinal motions along the converging gas flow in G28.37. For comparison, in the main north-south IRDC formed by the west-east converging gas flow, infall rates along the line of sight are about an order of magnitude greater than those along the west-east flow. In addition to the kinematic analysis, a comparison of CH_3CN-derived gas temperatures with Herschel-derived dust temperatures typically show higher gas temperatures toward high-density sources. We discuss whether mechanical heating from the conversion of the flow's kinetic energy into thermal energy may explain some of the observed temperature differences. Conclusions: The differences between flow rates along the converging flow, perpendicular to it, and toward the sources at the IRDC center indicate that at the interfaces of converging gas flows - where most of the active star formation takes place - originally more directed gas flows can convert into multidirectional infall motions.
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All authors H. Beuther, C. Gieser, H. Linz, Q. Zhang, S. Feng, A. Ahmadi, J.D. Soler, D. Semenov, M.R.A. Wells, S. Reyes-Reyes

High Energy Astrophysical Phenomena

Asymmetric distribution of Fe-peak elements in Cassiopeia A revealed by XRISM

Toshiki Sato, Shin-ichiro Fujimoto, Koji Mori et al. (+20 more)

The elemental abundances of the Fe-peak elements (such as Cr, Mn, Fe and Ni) and Ti are important for understanding the environment of explosive nuclear burning for the core-collapse supernovae (CC SNe). In particular, the supernova remnant Cassiopeia A, which is well known for its asymmetric structure, contains three “Fe-rich blobs,” and the composition of the Fe-peak elements within these structures could be related to the asymmetry of the supernova explosion. We report a highly asymmetric distribution of the Fe-peak elements in Cassiopeia A as revealed by XRISM observations. We found that the southeastern Fe-rich region has a significant Mn emission above the 4$\sigma$ confidence level, while the northwestern Fe-rich region has no clear signature. In addition to the significant difference in Mn abundance across these regions, our observations show that the Ti/Fe, Mn/Cr, and Ni/Fe ratios vary from region to region. The observed asymmetric distribution of Fe-peak elements could be produced by (1) the mixing of materials from different burning layers of the supernova, (2) the asymmetric distribution of the electron fraction in the progenitor star and/or (3) the local dependence of the neutrino irradiation in the supernova innermost region. Future spatially resolved spectroscopy of Cassiopeia A using X-ray microcalorimeters will enable more detailed measurements of the distribution and composition of these elements, providing a unique tool for testing asymmetric supernova physics.
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All authors Toshiki Sato, Shin-ichiro Fujimoto, Koji Mori, Jun Kurashima, Hiroshi Nakajima, Paul P. Plucinsky, Manan Agarwal, Liyi Gu, Adam Foster, Kai Matsunaga, Hiroyuki Uchida, Aya Bamba, Jacco Vink, Yukikatsu Terada, Hironori Matsumoto, Lia Corrales, Hiroshi Murakami, Satoru Katsuda, Makoto Sawada, Haruto Sonoda, Ehud Behar, Masahiro Ichihashi, Hiroya Yamaguchi

High Energy Astrophysical Phenomena

Temporal variability of polarization in blazars

Filippo Bolis, Emanuele Sobacchi and Fabrizio Tavecchio

We investigate the temporal variability of polarization of synchrotron radiation from blazar jets. Multiwavelength observations revealed high-amplitude rotations of the electric vector position angle (EVPA), both in the optical and in the X-rays. More often, the polarization degree and the EVPA show a seemingly erratic variability. To interpret these observations, we present a geometric and deterministic model in which off-axis, compact emitting features (i.e.,~blobs) propagate along the jet with the local velocity of the flow. The dynamics of the blobs is determined by the jet electromagnetic fields, which are calculated self-consistently using an analytical model of magnetically dominated outflows. The jet is axisymmetric, and its electromagnetic fields do not have a turbulent component. We show that the observed polarization is sensitive to the initial spatial configurations of the blobs. For the same jet structure, we observe several remarkably complex polarization patterns, including large EVPA rotations of $180^{\circ}$ or more in both directions and more erratic fluctuations. Simultaneous high-amplitude variations of the polarization degree and the EVPA can coincide with peaks of the observed luminosity. However, seemingly uncorrelated variations are also possible. We discuss the feasibility of constraining the particle acceleration mechanism from multifrequency polarimetric observations.
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Astrophysics of Galaxies

Possible evidence for a pair-instability supernova nature of ultra-early JWST sources

Andrea Ferrara, Stefano Carniani, Takahiro Morishita et al. (+1 more)

Recent JWST observations have revealed a population of unexpectedly bright sources at ultra-high redshift ($z > 15$), challenging current models of early galaxy formation. One extreme example is 'Capotauro', an F356W-dropout identified in the CEERS survey and initially interpreted as a luminous galaxy at $z\sim30$, but subsequently found to be variable over an $\sim 800$ day baseline. Motivated by this variability, we explore the alternative hypothesis that Capotauro is a pair-instability supernova (PISN) originating from a massive ($250-260\,M_\odot$), metal-free star. Using state-of-the-art PISN light curves, spectral energy distributions, and synthetic spectra, we show that a PISN at $z\simeq 15$ can plausibly reproduce the observed brightness, temporal evolution, photometry, and NIRSpec spectrum. We compare this scenario with alternative interpretations, including a local Y0 brown dwarf, and discuss observational tests to discriminate among them. If confirmed, this event would provide a rare window onto Population III stars, and highlights the importance of transient contamination in ultra-high redshift galaxy samples.
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All authors Andrea Ferrara, Stefano Carniani, Takahiro Morishita, Massimo Stiavelli

Astrophysics of Galaxies

Expanding the C$_3$H$_6$O$_2$ Isomeric Interstellar Inventory: Discovery of Lactaldehyde and Methoxyacetaldehyde in G+0.693-0.027

M. Sanz-Novo, V. M. Rivilla, I. Jiménez-Serra et al. (+17 more)

The tentative detection of 3-hydroxypropanal (HO(CH$_2$)$_2$C(O)H) toward the Galactic center molecular cloud G+0.693-0.027 prompts a systematic survey in this source aimed at detecting all C$_3$H$_6$O$_2$ isomers with available spectroscopy. We use an ultra-deep broadband spectral survey of G+0.693-0.027, carried out with the Yebes 40 m and IRAM 30 m telescopes, to conduct the astronomical search. We report the first interstellar detection of lactaldehyde (CH$_3$CH(OH)C(O)H) and methoxyacetaldehyde (CH$_3$OCH$_2$C(O)H), together with the second detections (i.e., confirmation) of methyl acetate (CH$_3$C(O)OCH$_3$) and hydroxyacetone (CH$_3$C(O)CH$_2$OH), and new detections in this source of both $anti$- and $gauche$- conformers of ethyl formate (CH$_3$CH$_2$OC(O)H), the latter tentatively. In contrast, neither propionic acid, CH$_3$CH$_2$C(O)OH, nor glycidol, c-CH$_2$OCHCH$_2$OH (i.e., the most and the least stable species within the C$_3$H$_6$O$_2$ family, respectively) were detected, and we provide upper limits on their fractional abundances of $\leq$1.5 $\times$ 10$^{-10}$ and $\leq$3.7 $\times$ 10$^{-11}$. Interestingly, all C$_3$H$_6$O$_2$ isomers can be synthesized through radical-radical reactions on the surface of dust grains, ultimately tracing back to CO as the parent molecule. We suggest that formation of the detected isomers is mainly driven by successive hydrogenation of CO, producing CH$_3$OH and CH$_3$CH$_2$OH as the primary parent species. Conversely, propionic acid is thought to originate from the oxygenation of CO via the HOCO intermediate, which help us rationalize its non-detection. Overall, our findings notably expand the known chemical inventory of the interstellar medium and provide direct observational evidence that increasingly complex chemistry involving O-bearing species occurs in space.
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All authors M. Sanz-Novo, V. M. Rivilla, I. Jiménez-Serra, L. Colzi, S. Zeng, A. Megías, D. San Andrés, Á. López-Gallifa, A. Martínez-Henares, Z. T. P. Fried, B. A. McGuire, S. Martín, M. A. Requena-Torres, B. Tercero, P. de Vicente, L. Kolesniková, E. R. Alonso, E. J. Cocinero, J. C. Guillemin, I. Kleiner

Cosmology and Nongalactic Astrophysics

Robust Preference for Dark Sector Interactions

Tian-Nuo Li, William Giarè, Guo-Hong Du et al. (+4 more)

Recent DESI baryon acoustic oscillation data reveal deviations from $\Lambda$CDM cosmology, conventionally attributed to dynamical dark energy (DE). We demonstrate that these deviations are equally, if not better, explained by interactions between dark matter and dark energy (IDE), without requiring a time-varying DE equation of state. Using a unified framework, we analyze two IDE models - coupled quintessence and coupled fluid - against the latest CMB (Planck, ACT, SPT), DESI BAO, and SN (including DES-Dovekie recalibrated) data. Both IDE scenarios show robust evidence for non-vanishing interactions at the 3-5$\sigma$ level, with marginalized constraints significantly deviating from the $\Lambda$CDM limit. This preference persists even under DES-Dovekie SN recalibration, which weakens dynamical DE evidence. Crucially, for the same number of free parameters, IDE models provide fits to low- and high-redshift data that match or exceed the performance of the CPL dynamical DE parametrization. Our results establish IDE as a physically motivated alternative to dynamical DE, highlighting the necessity of future cosmological perturbation measurements (e.g., weak lensing, galaxy clustering) to distinguish between these paradigms.
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All authors Tian-Nuo Li, William Giarè, Guo-Hong Du, Yun-He Li, Eleonora Di Valentino, Jing-Fei Zhang, Xin Zhang

High Energy Astrophysical Phenomena

Direct detection of the non-thermal X-ray emission from the Arches star cluster

Roman Krivonos, Alexey Vikhlinin, Andrei Bykov et al. (+2 more)

The compact stellar clusters have emerged as particularly promising candidates for cosmic rays (CR) accelerators. The star clusters, recently observed in gamma-rays, are also known sources of non-thermal X-ray emission, which is due to synchrotron or inverse-Compton scattering of relativistic electrons. Thus, the search for the non-thermal X-ray emission from stellar clusters is of particular interest. Until recent time the X-ray emission of the Arches star cluster in the Galactic Center was mixed with non-thermal emission of the surrounding molecular cloud, associated with reflection of hard X-ray irradiation. This reflected emission has been observed to fade, giving us a chance to characterize intrinsic non-thermal emission of the Arches cluster. In this work we demonstrate that Fe K_alpha line emission at 6.4 keV, attributed to the reflected non-thermal emission of the molecular cloud in 2000-2010, is not detected in deep observations with XMM-Newton in 2020 and Chandra in 2022, leaving stellar cluster well isolated. We showed that the Arches non-thermal emission is localized in the cluster's core and characterized by a relatively weak, hard (Gamma~1.5) power-law spectral continuum with 2-10 keV flux of ~10E-13 ergs/s/cm^2.
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All authors Roman Krivonos, Alexey Vikhlinin, Andrei Bykov, Sergey Sazonov, Maïca Clavel

Cosmology and Nongalactic Astrophysics

New $H(z)$ measurement at Redshift = 0.12 with DESI Data Release 1

Ze-fan Wang, Lei Lei and Yi-zhong Fan

The Hubble parameter ($H(z)$) is a function of the redshift and a reliable measurement is very important to understand the expansion history of the Universe. In this work, we perform full-spectrum fitting using BAGPIPES on more than four thousand massive, passively evolving galaxies released by the DESI collaboration to estimate their cosmological-independent stellar ages and star-formation histories, and derive a new measurement of $H(z=0.12)=71.33 \pm 4.20~{\rm km~s^{-1}~Mpc^{-1}}$, which is well consistent with those derived in other ways.
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High Energy Astrophysical Phenomena

Multi-wavelength properties of changing-state active galactic nuclei: I. the evolution of soft excess and X-ray continuum

Arghajit Jana, Claudio Ricci, Alessia Tortosa et al. (+11 more)

Changing-state active galactic nuclei (CSAGNs) exhibit rapid variability, with mass accretion rates that can change by several orders of magnitude in a few years. This provides us with a unique opportunity to study the evolution of the inner accretion flow almost in real time. Here, we used over 1000 observations to study the broadband X-ray spectra of a sample of five CSAGNs, spanning three orders of magnitude in Eddington ratio ($\lambda_{\rm Edd}$), using phenomenological models to trace the evolution of key spectral components. We derive several fundamental parameters, such as the photon index, soft excess strength, reflection strength, and luminosities of the soft excess and primary continuum. We find that the soft excess and primary continuum emissions show a very strong positive correlation ($p \ll 10^{-10}$), suggesting a common physical origin. The soft excess strength does not show any dependency on the reflection parameter, suggesting that in these objects the soft excess is not dominated by a blurred ionized reflection process. On the other hand, the strength of the soft excess is found to be strongly positively correlated with the Eddington ratio ($p \ll 10^{-10}$), and we find that the soft excess vanishes below $\log \lambda_{\rm Edd} \sim -2.5$. Moreover, we find a clear `V'-shaped relation for $\Gamma-\lambda_{\rm Edd}$, with a break at $\log \lambda_{\rm Edd} = -2.47 \pm 0.09$. Our findings indicate a change in the geometry of the inner accretion flow at low Eddington ratios, and that the soft excess is primarily produced via warm Comptonization.
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All authors Arghajit Jana, Claudio Ricci, Alessia Tortosa, George Dimopoulos, Benny Trakhtenbrot, Franz E. Bauer, Matthew J. Temple, Michael Koss, Kriti Kamal Gupta, Hsian-Kuang Chang, Yaherlyn Diaz, Dragana Illic, Kristína Kallová, Elena Shablovinskaya

Instrumentation and Methods for Astrophysics · Cross-listed from cs.DC

Bringing Computation to the data: Interoperable serverless function execution for astrophysical data analysis in the SRCNet

Manuel Parra-Royón, Julián Garrido-Sánchez, Susana Sánchez-Expósito et al. (+10 more)

Serverless computing is a paradigm in which the underlying infrastructure is fully managed by the provider, enabling applications and services to be executed with elastic resource provisioning and minimal operational overhead. A core model within this paradigm is Function-as-a-Service (FaaS), where lightweight functions are deployed and triggered on demand, scaling seamlessly with workload. FaaS offers flexibility, cost-effectiveness, and fine-grained scalability, qualities particularly relevant for large-scale scientific infrastructures where data volumes are too large to centralise and computation must increasingly occur close to the data. The Square Kilometre Array Observatory (SKAO) exemplifies this challenge. Once operational, it will generate about 700~PB of data products annually, distributed across the SKA Regional Centre Network (SRCNet), a federation of international centres providing storage, computing, and analysis services. In such a context, FaaS offers a mechanism to bring computation to the data. We studied the principles of serverless and FaaS computing and explored their application to radio astronomy workflows. Representative functions for astrophysical data analysis were developed and deployed, including micro-functions derived from existing libraries and wrappers around domain-specific applications. In particular, a Gaussian convolution function was implemented and integrated within the SRCNet ecosystem. The use case demonstrates that FaaS can be embedded into the existing SRCNet ecosystem of services, allowing functions to run directly at sites where data replicas are stored. This reduces latency, minimises transfers, and improves efficiency, aligning with federated, data-proximate computation. The results show that serverless models provide a scalable and efficient pathway to address the data volumes of the SKA era.
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All authors Manuel Parra-Royón, Julián Garrido-Sánchez, Susana Sánchez-Expósito, María Ángeles Mendoza, Rob Barnsley, Anthony Moraghan, Jesús Sánchez, Laura Darriba, Carlos Ruíz-Monje, Edgar Joao, Javier Moldón, Jesús Salgado, Lourdes Verdes-Montenegro

Astrophysics of Galaxies

Emulator-Based Inference of Cosmological Subgrid Models

Nesar Ramachandra, Nicholas Frontiere, Michael Buehlmann et al. (+4 more)

The formation of structure in the Universe at large scales is dominated by gravity, with baryonic physics becoming significant at $\sim{\rm Mpc}$ scales. To capture the impact of baryonic physics, cosmological simulations must model gas dynamics and a host of relevant astrophysical processes. A recent extension of the Hardware/Hybrid Accelerated Cosmology Code (HACC) couples its gravity solver with a modern smoothed particle hydrodynamics method. This extension incorporates sub-resolution models for chemical enrichment, black hole and star formation, AGN kinetic and thermal feedback, supernova-driven feedback, galactic winds, and metal-line cooling. We present an inference framework based on high-fidelity emulators to aid in model calibration against observational targets, e.g., the galaxy stellar mass function, radial gas density profiles, and the cluster gas fraction. The emulators are trained on simulation suites comprising 64 boxes with side-length $128\,h^{-1}$Mpc and 16 boxes with side-length $256\,h^{-1}$Mpc with $2\times 512^3$ and $2\times 1024^3$ particles, respectively. Our analysis reveals two distinct AGN kinetic feedback modes – a low-feedback mode yielding strong agreement with the observed radial gas density profiles of massive X-ray clusters, and a high-feedback mode providing a better fit to cluster gas fraction data, but systematically underestimating gas densities in inner regions.
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All authors Nesar Ramachandra, Nicholas Frontiere, Michael Buehlmann, Kelly R. Moran, J.D. Emberson, Katrin Heitmann, Salman Habib

Astrophysics of Galaxies

WISE/CatWISE Constraints on Dysonian Waste-Heat Technosignatures in Nearby Galaxies

Bo-Lun Huang, Zhen-Zhao Tao and Tong-Jie Zhang

We search for galaxy-scale (Dysonian) waste heat in the mid-infrared using WISE. Starting from the 2MASS Redshift Survey (2MRS), we cross-match to CatWISE2020 and AllWISE, apply standard MIR AGN/starburst vetoes (Stern, Assef R90, Jarrett), and treat W1 and W2 as stellar baselines and W3 and W4 as constraining bands. For each galaxy and for blackbody waste heat temperatures T=150-600 K, we convert W3/W4 photometry into conservative 3-sigma per-galaxy upper limits on the bolometric waste heat luminosity using the WISE bandpass (RSR) color correction. The resulting distributions have median caps of ~(5-9) x 10^8 L_sun across T=150-600 K. Aggregated at the population level, the one-sided 95% upper bound on the fraction of nearby galaxies that could host waste heat above a given threshold monotonically decreases with threshold and asymptotes to ~1/6500 at high thresholds (set by the sample size). Sensitivity transitions from W4 at T <= 200K to W3 at T >= 300K. Interpreted with the AGENT formalism, a fiducial Milky Way like stellar luminosity L_=3 x 10^10 L_sun implies typical per galaxy caps of alpha = L_wh/L_ <= 1.7-2.9% over T=150-600 K (e.g., alpha <= 1.8% at T=300 K). At T ~= 300K, no more than f_95 ~= 1.61 x 10^-4 (~= 0.0161%) of nearby galaxies can host KIII-scale systems reprocessing >= 21% of a Milky Way-like stellar luminosity into ~ 300K waste heat.
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Astrophysics of Galaxies

Photometric Redshift Estimation Using Scaled Ensemble Learning

Swagata Biswas, Shubhrangshu Ghosh, Avyarthana Ghosh et al. (+5 more)

The development of the state-of-the-art telescopic systems capable of performing expansive sky surveys such as the Sloan Digital Sky Survey, Euclid, and the Rubin Observatory's Legacy Survey of Space and Time (LSST) has significantly advanced efforts to refine cosmological models. These advances offer deeper insight into persistent challenges in astrophysics and our understanding of the Universe's evolution. A critical component of this progress is the reliable estimation of photometric redshifts (Pz). To improve the precision and efficiency of such estimations, the application of machine learning (ML) techniques to large-scale astronomical datasets has become essential. This study presents a new ensemble-based ML framework aimed at predicting Pz for faint galaxies and higher redshift ranges, relying solely on optical (grizy) photometric data. The proposed architecture integrates several learning algorithms, including gradient boosting machine, extreme gradient boosting, k-nearest neighbors, and artificial neural networks, within a scaled ensemble structure. By using bagged input data, the ensemble approach delivers improved predictive performance compared to stand-alone models. The framework demonstrates consistent accuracy in estimating redshifts, maintaining strong performance up to z ~ 4. The model is validated using publicly available data from the Hyper Suprime-Cam Strategic Survey Program by the Subaru Telescope. Our results show marked improvements in the precision and reliability of Pz estimation. Furthermore, this approach closely adheres to-and in certain instances exceeds-the benchmarks specified in the LSST Science Requirements Document. Evaluation metrics include catastrophic outlier, bias, and rms.
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All authors Swagata Biswas, Shubhrangshu Ghosh, Avyarthana Ghosh, Yogesh Wadadekar, Abhishek Roy Choudhury, Arijit Mukherjee, Shailesh Deshpande, Arpan Pal

High Energy Astrophysical Phenomena

What can be learnt from UHECR anisotropies observations Paper III: Update with new data and Galactic magnetic fields models

D. Allard, J. Aublin, B. Baret et al. (+1 more)

Context. At large angular scales, the Pierre Auger Observatory has reported a significant dipole modulation in right ascension, while at intermediate angular scales, localized flux excesses have been identified by both the Auger and Telescope Array collaborations. These observations were investigated in the first two papers of this series. Aims. We examine the implications of these anisotropy measurements and assess to what extent they can be used to constrain the origin of UHECRs and the astrophysical or physical parameters of viable source scenarios. Methods. As in the first two papers of this series, we generate realistic UHECR sky maps for a wide range of astrophysical models consistent with current spectral and composition constraints, assuming that UHECR sources trace the distribution of galaxies in the Universe. We update our previous studies by incorporating the most recent models of the Galactic magnetic field and apply the same large- and intermediate-scale anisotropy analyses as those used by the Auger Collaboration to simulated datasets with current experimental exposure. Results. The main novelty of this third paper is the improved compatibility between simulations and data, in particular regarding the reconstructed dipole direction, when using several of the recently proposed Galactic magnetic field models. Despite this progress, our main conclusions remain unchanged: although the observed anisotropies are compatible with an extragalactic origin of UHECRs, present data and magnetic-field uncertainties do not allow strong constraints to be placed on the nature, spatial distribution, or density of UHECR sources. Conclusions. Further progress in the interpretation of UHECR anisotropies will require improved constraints on cosmic magnetic fields, advances in source modeling, and significantly larger experimental exposures
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All authors D. Allard, J. Aublin, B. Baret, E. Parizot

Solar and Stellar Astrophysics

The magnetic helicity driven solar-type dynamo

V.V. Pipin

(1)The previous theoretical studies showed that in the presence of the small-scale dynamo the large-scale vorticity can produce the the divergent-type helicity flux breaking the equatorial reflection symmetry of the magnetic fluctuations in the stellar convection zone. This effect was called the new Visniac flux (hereafter the NV flux). Similarly to the $\alpha$ effect, the NV flux is able to maintain the large-scale turbulent dynamo. 2) Methods:Using the mean-field dynamo model we study the effect of the NV flux on the solar type dynamos. We found that the NV flux results to a increase of the dynamo efficiency for the turbulent generation of the large-scale poloidal magnetic field of the Sun. The dynamic effect of the NV flux on the magnetic field evolution results into concentrating the dynamo waves toward the equator. Using the numerical simulations of the mean-field dynamo model we compare the helicity production rates by the turbulent dynamo effects, like the $\alpha$ effect and the NV flux. We found that the new dynamo source can produce the large-scale dynamo even if the kinetic $\alpha$ effect is zero.3) Conclusions:The new findings suggest the crucial role of the large-scale vorticity and fluctuating magnetic field in the large-scale dynamo inside the stellar convection zones.
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