Earth and Planetary Astrophysics
Prebiotic Chemistry Insights for Dragonfly: Thermodynamics of Amino Acid Synthesis in Selk Crater on Titan
Ishaan Madan and Ben K.D. Pearce
Saturnian moon Titan presents a compelling testbed for probing prebiotic chemistry beyond early Earth. Impact-generated melt pools provide transient aqueous habitats in an otherwise cryogenic environment. We use Cantera
equilibrium models to assess whether mixtures of hydrogen cyanide (HCN), acetylene (C2H2), and ammonia (NH3) can drive amino acid synthesis in Selk-sized craters. Across twenty-one amino acids (twenty proteinogenic plus beta-alanine), NH3-free systems yield only proline, alanine, and beta-alanine, whereas adding as little as 1% NH3 (relative to H2O) renders almost the full suite accessible, with yields peaking at 2% and tapering thereafter. The NH3-free alanine result implies alternative pathways beyond classical Strecker or aminonitrile hydrolysis, suggesting acetylene, abundant on Titan but scarce on early Earth, as a plausible feedstock. We identify acrylonitrile (detected on Titan) as a thermodynamically favorable intermediate that can convert to alanine under aqueous conditions in an NH3-free pathway. For glycine and alanine production from nitrile hydrolysis, comparison with laboratory kinetics shows that our
equilibrium models predict near-complete conversion, while observed rates yield only partial products over weeks. Yet estimated chemical equilibration times (years-centuries) are far shorter than melt lifetimes, supporting plausibility of
equilibrium in situ. These predictions are directly testable with Dragonfly mass spectrometer (DraMS), for which we recommend pre-flight standards to test proline, alanine, beta-alanine, cysteine, and methionine. The first three offer the best chances for amino acid detection regardless of ammonia availability; the latter two offer diagnostic tools for determining the presence of reactive sulfur in post-impact Titan ponds.
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Astrophysics of Galaxies · Cross-listed from gr-qc
$Q$-balls, neural networks and galaxy rotation curves
Alexandre M. Pombo, Lorenzo Pizzuti and Alessandra di Giacomo
Can a dynamically robust (aka stable) $Q$-ball reproduce the rotation curve of a disk
galaxy? In an astrophysical environment, $Q$-balls are non-topological
solitons that are transparent and only perceived by their gravitational effects. Traditionally, scalar $Q$-balls are modelled with a
polynomial potential, but
axion-like periodic potentials are also expected to support such solitonic configurations. In the presence of angular momentum, $Q$-balls acquire a toroidal structure with a central density void, qualitatively resembling the axially-symmetric structure of disk
galaxies. Motivated by this similarity, we investigate whether rotating scalar $Q$-balls can reproduce the observed rotation curves of disk
galaxies. In this work, we use a recently developed hybrid numerical framework that combines a high-accuracy pseudo-spectral method with a physics-informed neural network approach to construct both static and rotating $Q$-ball solutions. We assess their ability to act as the dark matter
halos in
galaxies by fitting the observed rotation curves of a sample of disk
galaxies from the SPARC catalogue. Our simplified model provides an overall good agreement with observational data, and a reasonable fit when compared to standard dark matter profiles such as the Navarro-Frenk-White; we have further found an average constraint on the scalar field particle's mass $m\sim 10^{-27}$ eV, in agreement with similar
galactic-scale
soliton solutions.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Freezing-in the Axiverse
Christopher Dessert, Soubhik Kumar and Joshua T. Ruderman
The presence of multiple light
axions in the infrared is a generic feature of many ultraviolet (UV) scenarios. In many cases the number of
axions ${\cal N}$ is ${\cal O}(10-100)$ or more. Even in the scenario where these
axions interact very weakly with the Standard Model (SM), the presence of ${\cal N}$ light
axions poses a challenge to the stringent constraint on the number of relativistic degrees of freedom $N_{\rm eff}$. In order to remain agnostic about the UV, we adopt an effective field theory (EFT) approach, and parametrize the interactions of ${\cal N}$
axions with the SM to quantify the contribution to $N_{\rm eff}$. We consider operators up to dimension six, uncovering one previously-unconsidered charge radius operator, and pay particular
attention to the
flavor structure of the
axion-SM
fermion couplings and consider EFTs based on anarchy, textures, and minimal
flavor violation. For various choices of such EFTs, we identify the discovery space for current and future
cosmic microwave background surveys, including the Simons Observatory and CMB-HD. We show this discovery space depends sensitively on the
flavor structure and exhibits a rich interplay with terrestrial and astrophysical probes.
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Cosmology and Nongalactic Astrophysics
Dark Photons in the Radio Sky: I. Resonant Conversions in Halos
Ethan Baker and Hongwan Liu
Mixing between dark
photons and visible
photons leads to substantial anisotropies in the
cosmic microwave background due to resonant conversions of visible
photons into dark
photons in baryonic matter found in dark matter
halos. In this work, we forecast the sensitivity of the Square Kilometre Array (SKA) to this signal. We find that SKA could be the first experiment to discover dark
photons with a mass between $10^{-13}$ and $5\times 10^{-12}$ eV and kinetic mixing parameter $\epsilon$ as small as $\sim 10^{-8}$ by cross-correlating their data with a low-
redshift galaxy survey, potentially improving on the sensitivity from a similar analysis using Planck data by a factor of 4 in $\epsilon$. This improvement is largely due to an enhancement of the signal at low frequencies and the unique experimental advantages of
radio telescopes such as small beam sizes.
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Earth and Planetary Astrophysics
A Submillimeter Survey of CS Excitation in Protoplanetary Disks: Evidence of X-ray-Driven Sulfur Chemistry
Charles J. Law, Romane Le Gal, Karin I. Öberg et al. (+12 more)
The sulfur chemistry in protoplanetary disks influences the properties of nascent
planets, including potential habitability. Although the inventory of sulfur molecules in disks has gradually increased over the last decade, CS is still the most commonly-observed sulfur-bearing species and it is expected to be the dominant gas-phase sulfur carrier beyond the water snowline. Despite this, few dedicated multi-line observations exist, and thus the typical disk CS chemistry is not well constrained. Moreover, it is unclear how that chemistry - and in turn, the bulk volatile sulfur reservoir - varies with
stellar and disk properties. Here, we present the largest survey of CS to date, combining both new and archival observations from ALMA, SMA, and NOEMA of 12
planet-forming disks, covering a range of
stellar spectral types and
dust morphologies. Using these data, we derived disk-integrated CS gas excitation conditions in each source. Overall, CS chemistry appears similar across our sample with rotational temperatures of ${\approx}$10-40 K and column densities between 10$^{12}$-10$^{13}$ cm$^{-2}$. CS column densities do not show strong trends with most source properties, which broadly suggests that CS chemistry is not highly sensitive to disk structure or
stellar characteristics. We do, however, identify a positive correlation between
stellar X-ray luminosity and CS column density, which indicates that the dominant CS formation pathway is likely via ion-neutral reactions in the upper disk layers, where X-ray-enhanced S$^+$ and C$^+$ drive abundant CS production. Thus, using CS as a tracer of gas-phase sulfur abundance requires a nuanced approach that accounts for its emitting region and dependence on X-ray luminosity.
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All authors Charles J. Law, Romane Le Gal, Karin I. Öberg, Ke Zhang, Yuri Aikawa, Sean M. Andrews, Jaehan Bae, Alice S. Booth, Gianni Cataldi, L. Ilsedore Cleeves, Feng Long, François Ménard, Chunhua Qi, Richard Teague, David J. Wilner
High Energy Astrophysical Phenomena
Changing-Look AGN Powered By Disk Tearing
Nicholas Kaaz, Matthew Liska, Charlotte Ward et al. (+1 more)
Changing-look active
galactic nuclei (CLAGN) feature order-of-magnitude variability in both the continuum and broad line luminosities on months-to-years long timescales, and are currently unexplained. Simulations have demonstrated that rotating black holes sometimes tear apart tilted
accretion disks. These tearing events violently restructure the disk on timescales much shorter than a viscous timescale, hinting at a connection to CLAGN. Here, we show that disk tearing can power changing-look events. We report synthetic observations of an extremely high resolution three-dimensional general-relativistic magnetohydrodynamic simulation of a geometrically thin, tilted
accretion disk around a rapidly rotating, $10^8\,M_\odot$ black hole. We perform ray-tracing calculations that follow the disk light to both a line of sight camera and to a distribution of cameras in a prescribed
torus-like broad line region. The continuum photoionizes the broad line region and we calculate the resulting spectrum. Both the continuum and line luminosities undergo order of magnitude swings on months-to-years long timescales. We find shorter, weeks long variability driven by the
geometric precession of the inner disk and an intraday quasi-periodic oscillation driven by radial breathing of the inner disk. When the torn disk precesses, it causes asymmetric illumination of the broad line region, driving time-evolving red-to-blue asymmetries of the broad emission lines that may be a smoking gun for disk tearing. We also make predictions for future photometric observations from ULTRASAT and Vera Rubin Observatory, both of which may play an important role in detecting future changing-look events.
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All authors Nicholas Kaaz, Matthew Liska, Charlotte Ward, Jordy Davelaar
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Ultralight Dark Matter from the Edge of Field Space
Mathias Becker, Francesco D'Eramo and Ville Vaskonen
We introduce a novel class of bosonic dark matter candidates that we dub wallions, featuring boundaries in field space. The wallion mass is exponentially suppressed when the separation between boundaries far exceeds their intrinsic width and remains radiatively stable under self-interactions. We study the early-universe
evolution of wallions and the associated cosmological signatures. Finally, we show that instanton effects can dynamically generate field-space boundaries and discuss possible experimental probes once the wallion couples to Standard Model fields.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
$L_\mu-L_\tau$ gauge bosons in beam dumps and supernovae
Nikita Blinov, Patrick J. Fox, Kevin J. Kelly et al. (+2 more)
We study the phenomenology of a sub-GeV $L_\mu-L_\tau$ gauge
boson. We find discrepancies with existing literature in sensitivity projections for the upcoming SHiP experiment and in the treatment of
supernovae cooling constraints. We present a quantitative analysis of different production modes in beam dumps and compare our results to previous work. In the context of
supernovae, we re-evaluate the standard
supernova cooling bounds from SN1987A and analyze additional
supernova-based probes: diffusive cooling, constraints from the existence of low-energy
supernovae, and the absence of a high-energy
neutrino signal from SN1987A.
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All authors Nikita Blinov, Patrick J. Fox, Kevin J. Kelly, Ryan Plestid, Tao Zhou
Astrophysics of Galaxies
Think inside the box: cosmic variance and large-scale conformity of high-redshift massive galaxies in the FLAMINGO simulations
Seunghwan Lim, Sandro Tacchella, Roberto Maiolino et al. (+2 more)
We use the highest-resolution FLAMINGO hydrodynamical simulation to quantify
cosmic variance and large-scale coherence in the
evolution of massive
galaxies at high
redshift. FLAMINGO combines a $(1\,\mathrm{cGpc})^3$ volume with baryonic resolution sufficient to identify ${\gtrsim}\,10^3$ independent JWST-like survey volumes of $(100\,\mathrm{cMpc})^3$, providing unprecedented statistics to characterize the extremes of
cosmic variance. At $z\,{\simeq}\,6$, the total variance in the number of
haloes with $M_{200}\,{\simeq}\,10^{11.5}\,\mathrm{M_\odot}$ (or $M_\ast\,{\simeq}\,10^{10}\,\mathrm{M_\odot}$) is 2–3 times the Poisson expectation, while this ratio decreases with
redshift. Similarly, at $z\,{\gtrsim}\,4$, the variance in the most massive
halo per JWST-like field is twice the Poisson prediction. We find a pronounced large-scale conformity: in volumes ranked by the
stellar mass of their most massive
galaxy ($M_{\ast,\mathrm{max}}$), the
stellar-to-
halo mass relation and
star-formation efficiency are coherently elevated or suppressed throughout the full $(100\,\mathrm{cMpc})^3$ volume. When accounting for
galaxies outside the volume, this signal persists only to radii $\lesssim 50\,\mathrm{cMpc}$, demonstrating that the detectable conformity is enhanced by the survey footprint. Moreover, $M_{\ast,\mathrm{max}}$ is a better predictor of the volume-wide efficiency of massive
galaxies than the total number counts, which mainly trace clustering. Finally, the
stellar fraction of the most massive
galaxies peaks at $f_\ast\,{=}\,M_\ast\,/\,(M_{200}f_{\rm b,cosmic})\,{\simeq}\,0.2$ at $z\,{\simeq}\,5$, with a narrower dispersion in $f_\ast$ at fixed
redshift and stronger
redshift evolution than commonly assumed. These results show that both
cosmic variance and footprint-confined conformity must be modelled when interpreting early massive
galaxy populations in JWST fields.
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All authors Seunghwan Lim, Sandro Tacchella, Roberto Maiolino, Christopher C. Lovell, Joop Schaye
Solar and Stellar Astrophysics
Is a 1D perturbative method sufficient for asteroseismic modelling of $\beta$ Cephei pulsators? Implications for measurements of rotation and internal magnetic fields
J.S.G. Mombarg, V. Vanlaer, S.B. Das et al. (+6 more)
Asymmetries in the observed rotational splittings of a multiplet contain information about the
star's rotation profile and internal
magnetic field. However, to exploit this information, highly accurate theoretical predictions are needed. We aim to quantify the difference in the predicted mode asymmetries between a 1D perturbative method, and a 2D method that includes a 2D
stellar structure model, which takes rotation into account. We then put these differences in the context of asteroseismic measurements of internal
magnetic fields. We couple the 1D pulsation codes GYRE and StORM to the 2D
stellar structure code ESTER and compare the oscillation predictions with the results from the 2D TOP pulsation code. We focus on ZAMS models representative of rotating $\beta$~Cephei pulsators, going up to 20% of the critical rotation rate. We find a generally good agreement between the oscillation frequencies resulting from the 1D and 2D pulsation codes. Since the
magnetic asymmetries are small compared to the differences in the rotational asymmetries resulting from the 1D and 2D predictions, accurate measurements of the
magnetic field are in most cases challenging. Differences in the predicted mode asymmetries between 1D perturbative methods and 2D non-perturbative methods can greatly hinder accurate measurements of internal
magnetic fields in main-sequence pulsators with low-order modes. Nevertheless, reasonably accurate measurements could be possible with $n_{pg} \ge 2$ modes if the internal rotation is roughly below 10% of the critical rotation frequency for (aligned)
magnetic fields on the order of a few hundred kG. While the differences between the 1D and 2D predictions are mostly too large for internal
magnetic field detections, the rotational asymmetries predicted by StORM are in general accurate enough for asteroseismic modelling of the
stellar rotation in main-sequence
stars.
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All authors J.S.G. Mombarg, V. Vanlaer, S.B. Das, M. Rieutord, C. Aerts, L. Bugnet, S. Mathis, D.R. Reese, J. Ballot
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Cosmological Limits on Strong Dark Forces
Peter W. Graham, Harikrishnan Ramani, Olivier Simon et al. (+1 more)
We showcase cosmology's ability to constrain long-range forces between dark matter particles. Specifically, we consider a fermionic dark matter interacting via a Yukawa-coupled light scalar, focusing on regimes where the dark forces are stronger than gravitational and yet unconstrained. We show that the dark sector dynamics, both at the background and perturbation levels, is far richer than what can be captured with just the static interparticle Yukawa potential. The background dynamics includes an attractor that funnels a wide range of initial conditions onto an
evolution unique to each parameter space. In a large swath of parameter space beyond existing limits, the dark sector deviates drastically from cold dark matter in observable epochs. We rule out this parameter space using existing constraints on dark-sector equation of state and small-scale
cosmic perturbations, thus setting the strongest constraints yet on dark matter self-interactions at length scales shorter than 100 kpc. In addition, we briefly discuss repulsive dark forces and place cosmological limits that are stricter than in the attractive case.
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All authors Peter W. Graham, Harikrishnan Ramani, Olivier Simon, Erwin H. Tanin
Cosmology and Nongalactic Astrophysics
Mitigating Nonlinear Systematics in Weak Lensing Surveys II: Stability and Diagnostics with Intrinsic Alignment
Shiming Gu, Ludovic van Waerbeke, Francis Bernardeau et al. (+1 more)
The Bernardeau-Nishimichi-Taruya (BNT) transform provides a powerful framework for analysing tomographic
cosmic shear data by improving the localization of shear correlations in physical scale. It operates by performing a linear combination of the shear data vector in $\ell$-space, yielding a transformed vector that is better localized in both
redshift and $k$-space. BNT is particularly useful for estimating cosmological parameters while minimizing the impact of poorly understood nonlinear physics, without discarding large amounts of information as is typically done with simple scale cuts. In our previous work, we showed that BNT outperforms traditional weak-
lensing analyses; however, that study did not include intrinsic
alignments (IA). In the present work, we assess the robustness of our BNT-based $k$-cut framework in the presence of realistic IA models. We consider two cases: (i) when the assumed IA model used in sampling is close to, but not identical to, the true one, and (ii) when the assumed IA model is significantly biased compared to the true one. In the first case, the $k$-cut framework yields precise and unbiased $S_8$ constraints even with limited knowledge of large-scale modes. Using Euclid-like mock data and a stringent $k$-cut of $k \le 0.1\;{\rm Mpc^{-1}}$ for all tomographic bins, we found that BNT can constrain $S_8$ with a precision better than 2% while non-BNT has lost all constraining power. In the second case, the BNT transform serves as a powerful diagnostic tool, revealing internal inconsistencies in $k$-space and
redshift-space both exceeding 5$\sigma$ when the functional form of the sampling and fiducial IA models differ fundamentally.
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All authors Shiming Gu, Ludovic van Waerbeke, Francis Bernardeau, Sébastien Fabbro
Cosmology and Nongalactic Astrophysics · Cross-listed from physics.flu-dyn
Conservation of magnetic-helicity fluctuations due to spatial decorrelation of fluxes in decaying MHD turbulence
Justin Kin Jun Hew, David N. Hosking, Christoph Federrath et al. (+2 more)
Hosking & Schekochihin (2021, Phys. Rev. X 11, 041005) have proposed that statistically isotropic decaying MHD
turbulence without net
magnetic helicity conserves the mean square fluctuation level of
magnetic helicity in large volumes – or, equivalently, the integral over space of the two-point correlation function of the
magnetic-helicity density, denoted $I_H$. Formally, the conservation and gauge invariance of $I_H$ require the vanishing of certain boundary terms related to the strength of long-range spatial correlations. These boundary terms represent the ability (or otherwise) of the
turbulence to organise fluxes over arbitrarily large distances to deplete or enhance fluctuations of
magnetic helicity. In this work, we present a theory of these boundary terms, employing a methodology analogous to that of Batchelor & Proudman (1956, Philos. Trans. R. Soc. A 248, 369) to determine the relevant asymptotic forms of correlation functions. We find that long-range correlations of sufficient strength to violate the conservation of $I_H$ cannot develop dynamically if the
evolution equation for the
magnetic vector potential is chosen to be local in space. Likewise, we find that such correlations cannot develop for a wide class of gauge choices that make this equation non-local (including the Coulomb gauge). Nonetheless, we also identify a class of non-local gauge choices for which correlations that are sufficiently strong to violate the conservation of $I_H$ do appear possible. We verify our theoretical predictions for the case of the Coulomb gauge with measurements of correlation functions in a high-resolution numerical simulation.
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All authors Justin Kin Jun Hew, David N. Hosking, Christoph Federrath, James R. Beattie, Neco Kriel
Astrophysics of Galaxies
Warped Disk Galaxies: Statistical Properties from DESI Legacy Imaging Surveys DR8
Yiheng Wang, Han Qu, Jiafeng Lu et al. (+3 more)
Warped structures are often observed in disk
galaxies, yet their physical origin is still under investigation. We present a systematic study of warped edge-on disk
galaxies based on imaging data from the DESI Legacy Imaging Surveys DR8, with the expectation that this large sample size, enabled by wide-area surveys, will offer new perspectives on the formation of disk warps. Using a deep learning approach, we trained an EfficientNet-B3 convolutional neural network to classify the morphology of edge-on-disk
galaxies into warped and non-warped categories. Our model was trained on a curated and visually verified set of labeled
galaxy images and applied to a large
dataset of over 595,651 edge-on disk
galaxies selected from the
Galaxy Zoo DESI catalog. Our results provide the largest warp catalog to date, consisting of 23996 warped edge-on disk
galaxies, and reveal statistical trends between warp occurrence and
galaxy properties. Compared to their non-warped counterparts, these warped disk
galaxies tend to have bluer colors, lower
stellar masses, higher gas fractions and
star-formation rates, smaller Sérsic indices and larger disk sizes. In addition, warped disk
galaxies show higher projected number densities of neighboring
galaxies than their non-warped counterparts, particularly within \( R_{\mathrm{proj}} \lesssim 50~\mathrm{kpc} \), where the local number density is roughly twice as high.
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All authors Yiheng Wang, Han Qu, Jiafeng Lu, Huiyuan Wang, Enci Wang, Xi Kang
Cosmology and Nongalactic Astrophysics
Probing Time-Dependent Physics with Phase-Folding CMB Maps
Yilun Guan
Time-resolved observations of the
Cosmic Microwave Background (CMB) offer a powerful probe of time-dependent cosmological signals, such as a
stochastic gravitational wave background passing through Earth, which imprints a time-varying deflection on the CMB, and time-dependent
cosmic birefringence, which induces an oscillating polarization rotation. However, analyses based on time-division CMB maps are fundamentally limited by the mapmaking cadence, restricting sensitivity to frequencies below $\sim 10^{-5}$ Hz. In this paper we develop a phase-folding mapmaking framework to enable targeted searches of such periodic cosmological signals with frequencies up to the detector sampling rate of $O(100)$ Hz. We demonstrate the power of this framework with two cosmological applications: (1) constraining a
stochastic gravitational wave background via its time-dependent
lensing signature, and (2) the search for an oscillating polarization rotation from
axion-like particles. We show that this technique transforms CMB experiments into broadband probes of the oscillating sky, extending their constraining power from the microhertz regime up to $O(100)$ Hz-an expansion of over seven orders of magnitude in frequency. This provides a new observational window, complementary to other approaches by probing under-explored frequency ranges for gravitational waves and
axion-like particles.
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Astrophysics of Galaxies
A ring-shaped starburst as a galactic wind-generating mechanism: Morphology, emission, and mass ejection
J. A. Osorio-Caballero, A. Rodríguez-González and Z. Meliani
Star formation bursts promote the ejection of material from the hosting
galaxies due to the momentum and energy injected by winds from massive
stars and
supernova explosions. Numerical or analytical models generally consider that the mass, momentum, and energy injections result from bursts in a
nuclear star formation region. However,
star formation bursts have recently been observed in ring-like regions in the
nuclear part of the
galaxies. One example is NGC 253, which has shown a central toroidal burst and an asymmetric
galactic wind observed in thermal X-ray emission. The general aim of this work is to study the effect of mechanical energy injection from
stellar winds and
supernova explosions in
star-forming bursts distributed in rings around the
nucleus of the
galaxy NGC 253. Additionally, these partial objectives allow us to analyze the asymmetry of the
outflows due to the bursts position as well as to study the formation of filaments with optical emission and make comparisons with recent observations of
galaxies with these types of
star-forming bursts. We used the hydrodynamic code AMRVAC to simulate
galactic wind ejection coming from a central ring-like starburst located at different vertical positions. We showed that including a ring-shaped starburst (RSS) generates a more complex structured wind than what would be expected for a spherical starburst injection. Besides the interaction between the wind generated by the RSS and the host
galaxy, it can generate dense filamentary structures with H alpha emission. The mass flux analysis of our models shows that the variation in the vertical position of the starburst can generate a variation in the mass flux of each lobe of the wind up to an order of magnitude. However, this difference is sustained only for a short period, with the flux tending to be symmetrical once it enters into a free-wind solution.
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Solar and Stellar Astrophysics
Collisions in a system of conical jet/counterjet outflows
A. C. Raga, Z. Meliani, A. Rodríguez-González et al. (+4 more)
Stars predominantly form in compact, non-hierarchical clusters. The gas
outflows ejected by protostars can intersect and interact with each other, resulting in complex interactions that affect the dynamics, morphology, and
evolution of these
outflows. Determining the probability of an encounter between them requires a
Bayesian approach that considers the collimation, length (or age), and separation between young
stellar objects in the clusters. In this study, we employ a Monte Carlo approach to estimate this probability as a function of the jet opening angle and the ratio between the jet length and the separation between
stars. We propose a function that predicts the number of interactions within a cluster based on the opening angle of the gas
outflows ejected by protostars.
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All authors A. C. Raga, Z. Meliani, A. Rodríguez-González, S. Cabrit, G. Pineau des Forêts, J.I. Castorena, A. Esquivel
Earth and Planetary Astrophysics
Global Distribution of the Key Species on the Surface of Europa
Jiazheng Li, Yinsi Shou, Cheng Li et al. (+1 more)
The icy surface of Europa is continuously bombarded by ions and electrons from Jupiter's magnetosphere. The bombardment of the particles dissociates water molecules on the surface of Europa and introduces
impurities to the icy surface. Such processes lead to the generation of the nonwater species on the surface of Europa. These chemical species are closely related to the chemistry of the icy crust and the subsurface ocean, as well as Europa's habitability. However, our knowledge of the global distribution of these species is limited due to the sparse satellite and
telescope observations on Europa. In this study, we combine a Europa
plasma model and a chemical-transport model to simulate the global distribution of the key nonwater species on the surface of Europa. The initial results from our model agree well with the existing observations on the distributions of H2SO4 and SO2 but they show a significant discrepancy with the observed distribution of H2O2. Sensitivity tests on the reaction rate coefficients indicate that the simulated global distribution of all three species fit the observations well if the reaction rate coefficients in the ice are reduced by one order of magnitude. This finding provides a useful constraint on the rate coefficient of the chemical reactions in the ice. Furthermore, our model predicts that the O2 on the surface ice of Europa is concentrated on the leading hemisphere. The simulated global distribution of the key species on Europa may provide useful guidance for future missions to Europa, such as Europa Clipper and JUICE.
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All authors Jiazheng Li, Yinsi Shou, Cheng Li, Xianzhe Jia
Cosmology and Nongalactic Astrophysics
From M100 to NGC 7331: A Multiband Study and Physical Parameters in Nearby Galaxies
Julio C. Bertua Marasca, Homer Dávila Gutiérrez, Víctor Huamán Ticona et al. (+2 more)
We study five nearby
galaxies (M100/NGC 4321, NGC 1300, M 74, M 60, and NGC 7331) by combining multiband imaging (optical, UV, NIR, and X-rays) with simple photometric measurements to show how each spectral window traces different physical components: UV/blue emphasizes recent
star formation, NIR outlines the old
stellar mass and internal structure, and X-rays reveal compact sources and hot gas. For M100 we present a multiband mosaic with X-ray contours including the SN 1979C region. We compare isophotal morphology in NGC 1300 (barred) and M 74 (unbarred), quantify ellipticity and equivalent radius in M 60, and illustrate a Tully-Fisher distance estimate for NGC 7331, discussing assumptions (inclination, internal corrections) and consistency with classical scales. Our results underscore that a layered view reduces interpretative biases and that straightforward integrations of public data with open-source software yield robust introductory-level physical diagnostics.
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All authors Julio C. Bertua Marasca, Homer Dávila Gutiérrez, Víctor Huamán Ticona, Josué I. Mosquera Hadatty, Alejandro A. Ramírez Valadez
Earth and Planetary Astrophysics
Adsorption of volatiles on dust grains in protoplanetary disks
Lile Wang, Feng Long, Haifeng Yang et al. (+2 more)
The adsorption of volatile molecules onto
dust grain surfaces fundamentally influences
dust-related processes, including condensation of gas-phase molecules,
dust coagulation, and
planet formation in protoplanetary disks. Using advanced ab-initio density functional theory with r$^2$SCAN+rVV10 van der Waals functionals, we calculate adsorption energies of H$_2$, H$_2$O, and CO on carbonaceous (
graphene, amorphous carbon) and silicate (MgSiO$_3$) surfaces. Results reveal fundamentally different adsorption mechanisms: weak physisorption on carbonaceous surfaces ($|\Delta\epsilon_{\rm ad}|\sim 0.1-0.2~{\rm eV}$) versus strong chemisorption on silicates ($|\Delta\epsilon_{\rm ad}|\sim 0.5-1.5~{\rm eV}$) via coordination bonds. Kinetic Monte Carlo simulations incorporating these energies demonstrate divergent surface
evolution: carbonaceous grains exhibit distinct condensation radius compared to silicates, while the cocrystal of H$_2$O and CO significantly increases the desorption temperature of CO. The actual radii of gas-phase molecule depletion could thus be a comprehensive result of temperatures, chemical compositions, and even
evolution tracks. Meanwhile, silicates maintain chemisorbed molecular coatings throughout most disk regions. Such dichotomy in surface coverage could also provide a natural mechanism for carbon depletion in inner planetary systems.
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All authors Lile Wang, Feng Long, Haifeng Yang, Ruobing Dong, Shenzhen Xu
Instrumentation and Methods for Astrophysics
TIME Commissioning Observations: I. Mapping Dust and Molecular Gas in the Sgr A Molecular Cloud Complex at the Galactic Center
Selina F. Yang, Sophie M. McAtee, Benjamin J. Vaughan et al. (+24 more)
We present the processing of an observation of Sagittarius A (Sgr A) with the Tomographic Ionized-carbon Mapping Experiment (TIME), part of the 2021-2022 commissioning run to verify TIME's hyperspectral imaging capabilities for future line-intensity mapping. Using an observation of Jupiter to calibrate detector gains and pointing offsets, we process the Sgr A observation in a purpose-built pipeline that removes correlated noise through common-mode subtraction with correlation-weighted scaling, and uses map-domain principal component analysis to identify further systematic errors. The resulting frequency-resolved maps recover strong 12CO(2-1) and 13CO(2-1) emission, and a continuum component whose spectral index discriminates free-free emission in the circumnuclear disk (CND) versus thermal
dust emission in the 20 km s$^{-1}$ and 50 km s$^{-1}$ molecular clouds. Broadband continuum flux comparisons with the Bolocam
Galactic Plane Survey (BGPS) show agreement to within $\sim$5% in high-SNR molecular clouds in the Sgr A region. From the CO line detections, we estimate a molecular hydrogen mass of between $5.4 \times 10^5 M_\odot$ and $5.7 \times 10^5 M_\odot$, consistent with prior studies. These results demonstrate TIME's ability to recover both continuum and spectral-line signals in complex
Galactic fields, validating its readiness for upcoming extragalactic CO and [C II] surveys.
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All authors Selina F. Yang, Sophie M. McAtee, Benjamin J. Vaughan, Abigail T. Crites, Victoria L. Butler, Dongwoo T. Chung, Ryan P. Keenan, Dang Pham, Shwetha Prakash, James J. Bock, Charles M. Bradford, Tzu-Ching Chang, Yun-Ting Cheng, Audrey Dunn, Nicholas Emerson, Clifford Frez, Jonathon Hunacek, Chao-Te Li, Ian N. Lowe, King Lau, Daniel P. Marrone, Evan C. Mayer, Guochao Sun, Isaac Trumper, Anthony D. Turner, Ta-Shun Wei, Michael Zemcov
Cosmology and Nongalactic Astrophysics
Revisiting the Hubble tension problem in the framework of holographic dark energy
Jun-Xian Li and Shuang Wang
The Hubble tension problem is one of the most significant challenges in modern cosmology. In this paper, we study the Hubble tension problem in the framework of
holographic dark energy (HDE). To perform a systematic and comprehensive analysis, we select six representative theoretical models from all four categories of HDE. For the observational data, we adopt the
Baryon Acoustic Oscillation (BAO) data from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) along with a collection of alternative BAO measurements,
Cosmic Microwave Background (CMB) distance priors from $Planck$ 2018, and type Ia
supernovae (SN) data from the PantheonPlus, Union3, and DESY5 compilations. We find that HDE models that employ the Hubble scale or its combinations as the infrared (IR) cutoff cannot alleviate the Hubble tension problem. In contrast, HDE models that employ the future event horizon as the IR cutoff can partially mitigate the Hubble tension problem. It must be stressed that these two key conclusions hold true for cases of adopting different theoretical HDE models and different observational data. Our findings advocate for further exploration of HDE models using other types of cosmological observations.
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Cosmology and Nongalactic Astrophysics
Unbiased analysis of primordial non-Gaussianity: the multipoles of the full relativistic power spectrum
Chris Addis, Sêcloka L. Guedezounme, Jessie Hammond et al. (+5 more)
A major goal of ongoing and future cosmological surveys of the large-scale structure is to measure local type
primordial non-Gaussianity in the
galaxy power spectrum through the scale-dependent bias. General relativistic effects have been shown to be degenerate with this measurement, therefore requiring a non-Newtonian approach. In this work, we develop a consistent framework to compute integrated effects, including
lensing convergence, time delay, and integrated Sachs–Wolfe, along with the local relativistic projection and wide-separation corrections in the multipoles of the power spectrum. We show that, for a Euclid-like H$\alpha$-line
galaxy survey and a MegaMapper-like Lyman-break
galaxy survey, ignoring these effects leads to a bias on the best fit measurement of the amplitude of
primordial non-Gaussianity, $f_{\rm NL}$, of around $ 3\,\sigma$ and $ 20 \, \sigma$ respectively. When we include these corrections, the uncertainty in our knowledge of the luminosity function leads to further uncertainty in our measurement of $f_{\rm NL}$. In this work, we show that this degeneracy can be partly mitigated by using a bright-faint multi-tracer analysis, where the observed
galaxy sample is subdivided into two separate populations based on luminosity, which provides a $15$–$20\%$ improvement on the forecasted constraints of local type $f_{\rm NL}$. In addition, we present a novel calculation of the full multi-tracer covariance with the inclusion of wide-separation corrections~– all of these results are implemented in the Python code CosmoWAP.
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All authors Chris Addis, Sêcloka L. Guedezounme, Jessie Hammond, Chris Clarkson, Federico Montano, Stefano Camera, Sheean Jolicoeur, Roy Maartens
Instrumentation and Methods for Astrophysics
Development of a planar cable-driven parallel robot for submillimeter and terahertz beam mapping measurements
Evan C. Mayer, Ian N. Lowe, Daniel P. Marrone et al. (+20 more)
The spatial sensitivity pattern of millimeter-wavelength receivers is an important diagnostic of performance and is affected by the
alignment of coupling optics. Characterization can be challenging in the field, particularly in the decentered and tightly packed optical configurations that are employed for many astronomical millimeter-wave cameras. In this paper, we present the design and performance of a lightweight and reconfigurable beam mapper, consisting of a bank of thermal sources positioned by a planar cable-driven
robot. We describe how the measurement requirements and mechanical constraints of the Tomographic Ionized-carbon Mapping Experiment (TIME) optical relay drive the design of the mapper. To quantify the positioning performance, we predict the beam patterns at each surface to derive requirements and use a non-contact computer-
vision based method built on OpenCV to track the payload position with an accuracy better than 1.0 mm. We achieve an in-plane absolute payload position error of 2.7 mm (RMSE) over a $\sim$400 mm $\times$ 400 mm workspace and an in-plane repeatability of 0.81 mm, offering substantial improvements in accuracy and speed over traditional handheld techniques.
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All authors Evan C. Mayer, Ian N. Lowe, Daniel P. Marrone, James J. Bock, Charles M. Bradford, Victoria L. Butler, Tzu-Ching Chang, Yun-Ting Cheng, Dongwoo T. Chung, Abigail T. Crites, Audrey Dunn, Nicholas Emerson, Clifford Frez, Jonathon Hunacek, Ryan P. Keenan, Chao-Te Li, King Lau, Guochao Sun, Isaac Trumper, Anthony D. Turner, Benjamin Vaughan, Ta-Shun Wei, Michael Zemcov
Instrumentation and Methods for Astrophysics
Comprehensive Study of the Lunar Energetic Particle Environment with LunPAN
Johannes Hulsman, Elisa Alessi, Leonardo Andreasi et al. (+14 more)
LunPAN (Lunar Particle Analyzer Network) is a three-year mission proposal designed to comprehensively map the particle spectra in the lunar radiation field. It aims to provide precise measurements of
Galactic Cosmic Rays (GCR),
Solar Energetic Particles (SEP), and albedo particles, including charged particles,
neutrons, and gamma-rays, originating from the Moon's surface. Therefore it will contribute to fundamental space physics, lunar geology sciences, space weather prediction, and radiation risk assessment for future lunar explorations. This is achieved through two state-of-the-art instruments; Pix.PAN and NeuPix. Pix.PAN is a compact
magnetic spectrometer designed for precise measurements of penetrating charged particles, ranging from 100 MeV to 10 GeV. Based on the Mini.PAN project, Pix.PAN employs thin silicon pixel sensors optimized for energy resolution and particle identification. NeuPix is a hybrid active pixel sensor system capable of detecting
neutrons, gamma-rays, and lower-energy charged particles between 10MeV and 100 MeV. Utilizing innovative sensor-converter combinations, NeuPix will provide spectral measurements of lunar albedo
neutrons and gamma-ray fluxes. Currently, the LunPAN mission is accepted by ESA's "Small Missions for Exploration - Destination the Moon" call for a pre-A phase study. We will discuss mission outline and expected scientific performance of the PixPAN and NeuPix.
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All authors Johannes Hulsman, Elisa Alessi, Leonardo Andreasi, Philipp Azzarello, Benedikt Bergmann, Mathilda Bolis, Petr Burian, Franck Cadoux, Michael Campbell, Camilla Colombo, Hugo Cintas, Antoine Delille, Jindra Jelinek, Xavi LLorpart, Hugo Santos, Mikko Viitala, Xin Wu
High Energy Astrophysical Phenomena
Ultra-extreme high-frequency-peaked BL Lacs: A potential population of MeV synchrotron blazars
A. Sciaccaluga, F. Tavecchio, T. Sbarrato et al. (+1 more)
We investigate the potential existence of a new population of BL Lacs, called ultra-extreme high-energy-peaked BL Lacs (UEHBLs), whose synchrotron emission component peaks in the MeV band, extending the blazar sequence beyond its current limit. To model the spectral energy distribution of these new sources, we applied the hybrid shock-
turbulence acceleration framework previously developed for extreme high-frequency-peaked BL Lacs. We present three representative realizations that produce synchrotron peaks between $0.2$ and $2$ MeV and evaluate their multiwavelength signatures. Our results show that UEHBLs would be undetectable with current GeV (
Fermi) and future TeV (CTA) facilities due to severe Klein-Nishina suppression of inverse-Compton scattering, but are ideal targets for proposed MeV missions such as COSI, AMEGO-X, and e-ASTROGAM. We further identified a sample of hard X-ray sources from the Swift-BAT catalogs that exhibit the spectral properties expected of UEHBLs, representing promising follow-up targets of this population. If confirmed, UEHBLs would provide unique insight into particle acceleration in relativistic jets, imposing strong constraints on the maximum achievable electron energies. We also discuss the expected polarization and variability signatures, including the possibility of synchrotron-driven thermal instabilities leading to MeV
flares. These findings underscore the critical importance of the MeV band for discovering and characterizing the most extreme accelerators among blazars.
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All authors A. Sciaccaluga, F. Tavecchio, T. Sbarrato, G. Bonnoli
Instrumentation and Methods for Astrophysics
POLAR-2 – Latest Developments of the Next Generation GRB Polarimeter
Johannes Hulsman, Philipp Azzarello, Joerg Bayer et al. (+20 more)
Gamma-Ray Bursts (GRBs) are among the most energetic events in the Universe. Despite over 50 years of research and measurements their
prompt emission remains poorly understood, with key questions surrounding the structure of relativistic jets,
magnetic field configurations, and dominant radiation mechanisms. Polarization measurements are critical in resolving these uncertainties. The POLAR mission, operational in 2016-2017 on Tiangong-2, provided the most statistically significant GRB polarization data. Its results indicated low time-averaged polarization with hints of temporal
evolution. However, POLAR's limited sensitivity, small effective area, and restricted energy range prevented more detailed time- and energy-resolved analyses in addition to a larger sample of GRB polarization measurements. POLAR-2 is designed to address these limitations by offering a fourfold increase in effective area (at least) and an extended energy range of 30-800 keV by utilizing Silicon Photomultipliers (SiPMs) and an updated module design, enabling the differentiation of competing GRB emission models. The instrument comprises of 100 polarimeter modules (each with 64 plastic scintillator bars), wherein the polarization angle is extracted through Compton Scattering of the gammas. The polarimeter module design was validated during an ESRF beam test campaign in 2023. The instrument was developed by a joint effort of Switzerland, China, Poland and Germany and is planned for launch in 2027. Currently, POLAR-2 is in its production phase with the first module targets being produced. We will provide an overview of the current status of the development.
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All authors Johannes Hulsman, Philipp Azzarello, Joerg Bayer, Franck Cadoux, Mariachiara Celato, Nicolas De Angelis, Yannick Favre, Aaron Feder, Jochen Greiner, Alejandro Guzman, Coralie Husi, Vishal Kumar, Hancheng Li, Mobin Mobaseri, Gabriel Pelleriti, Agnieszka Pollo, Nicolas Produit, Dominik Rybka, Andrea Santangelo, Jianchao Sun, Chris Tenzer, Xin Wu, Shuang-Nan Zhang
High Energy Astrophysical Phenomena
Compelling Evidence for a Harmonic in the Light Curve of the Supermassive Black Hole Binary Candidate PKS J1309+1154
A. C. S. Readhead, M. F. Aller, A. G. Sullivan et al. (+23 more)
We recently discovered a supermassive black hole binary (SMBHB) candidate, PKS J1309+1154, in the combined 46-yr University of Michigan
Radio Astronomy Observatory (UMRAO) plus Owens Valley
Radio Observatory (OVRO) blazar monitoring programs at 14.5/15 GHz. The light curve of PKS 1309+1154 exhibits a 17.9 year periodicity. We also reported a hint of a first harmonic with a 9 year periodicity in this object. Further analysis of the PKS J1309+1154 light curve provides compelling evidence that both the fundamental and the harmonic are real, confirming the existence of real periodicities in blazar light curves. This is the first case, to our knowledge, of watertight evidence for a fundamental and a harmonic periodicity in a blazar light curve. It makes PKS J1309+1154 a strong\/ supermassive black hole binary (SMBHB) candidate, and thus the third such candidate to be revealed through long-term
radio monitoring, the other two being PKS J0805–0111 and PKS 2131–021, both discovered through the OVRO 40 m
Telescope monitoring program. It is argued that hundreds of SMBHB candidates will be discovered by the Vera Rubin and Simons Observatories. Coherent searches for gravitational waves from a network of SMBHB candidates, starting immediately, are strongly motivated.
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All authors A. C. S. Readhead, M. F. Aller, A. G. Sullivan, R. D. Blandford, P. Mróz, P. V. De la Parra, B. Molina, E.R. Most, M. L. Lister, A. Synani, H. Aller, M. C. Begelman, Y. Ding, M. J. Graham, F. Harrison, T. Hovatta, I. Liodakis, W. Max-Moerbeck, V. Pavlidou, T. J. Pearson, V. Ravi, R. A. Reeves, T. Surti, K. Tassis, S. E. Tremblay, J. A. Zensus
High Energy Astrophysical Phenomena
Bright Cosmic-Ray Source as a Solution to Auger-TA Tensions
Alexander Korochkin, Dmitri Semikoz and Peter Tinyakov
The ultra-high-energy
cosmic ray (UHECR) spectra measured by the Pierre Auger Observatory (Auger) and the
Telescope Array (TA) agree very well below $10^{19.5}$ eV but differ significantly at higher energies. We show that these differences can be explained by a single nearby source superimposed on a nearly isotropic background. Taking into account deflections in
Galactic and extragalactic
magnetic fields, such a source can account for the excess in the TA spectrum without producing excessive anisotropy. The required hard spectrum of the source and intermediate-mass composition are consistent with previous fits of the Auger-only spectrum and composition. This scenario offers several additional advantages: (i) the source produces a broad excess partially overlapping the TA hotspots, suggesting their possible explanation; (ii) without additional tuning, it reproduces the $\sim90^\circ$ shift in dipole direction observed between the Auger-only and combined Auger-TA analyses; and (iii) the best-fit position of the source lies near M82, the brightest nearby starburst
galaxy, making it a plausible source of the UHECR.
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Earth and Planetary Astrophysics
Rapid-response characterization of near-Earth asteroid 2024 YR4 during a Torino Scale 3 alert
Maxime Devogèle, Olivier R. Hainaut, Marco Micheli et al. (+32 more)
On 27 December 2024, near-Earth object (NEO) 2024 YR$_4$ was discovered by the ATLAS survey and identified as a virtual impactor. A few weeks later, it eventually reached level 3 on the Torino Scale and was the first and only asteroid to be ever classified at that level. Here we report an intensive observational campaign combining time-series photometry in the visible, broadband visible and near-infrared colors, and low-resolution visible reflectance spectroscopy to assess its physical properties.
Fourier analysis of the lightcurves yields a synodic rotation period of $P = 19.46341 \pm 0.00008$ min, placing 2024 YR$_4$ among the fast rotators, even if such rotation is common for objects of similar $H$ magnitude. Its visible and near-infrared colors and spectra are most consistent with an Sq or K taxonomic classification, though some ambiguity remains. Finally, its phase curve exhibits a notably shallow slope ($G = 0.51 \pm 0.11$), from which we derive an absolute magnitude of $H_\mathrm{R} = 23.82\pm0.09$ mag. After color correction and taking into account other models for the phase function, we report an absolute magnitude of $H_\mathrm{V} = 24.14\pm0.25$ mag. These characterizations, rotation period, taxonomy, and surface properties, would have been crucial for risk assessment and mitigation planning had the initially high impact probability scenario been confirmed, underscoring the importance for planetary defense of a rapid, coordinated international response.
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All authors Maxime Devogèle, Olivier R. Hainaut, Marco Micheli, Petr Pravec, Juan Luis Cano, Francisco Ocaña, Luca Conversi, Nicholas Moskovitz, Julia de León, Zuri Gray, Mikael Granvik, Grigori Fedorets, Jules Bourdelle de Micas, Simone Ieva, Elisabetta Dotto, Tracie Beuden, Carson Fuls, Teddy Kareta, Stefano Bagnulo, Maria Antonella Barucci, Mirel Birlan, Andrea Farina, Kamil Hornoch, Petr Fatka, Peter Kušnirák, Francesca Ferri, Marcello Fulchignoni, Monica Lazzarin, Fiorangela La Forgia, Elena Mazzotta Epifani, Alessandra Mura, Davide Perna, Philippe Bendjoya, Jean-Pierre Rivet, Alberto Cellino