Abstract In the solution of the Jeans equations for axisymmetric galaxy models the “b-ansatz” is often adopted to prescribe the relation between the vertical and radial components of the velocity dispersion tensor, and close the equations. However, b affects the resulting azimuthal velocity fields quite indirectly, so that the analysis of the model kinematics is usually performed after numerically solving the Jeans equations, a time consuming approach. In a previous work we presented a general method to determine the main properties of the kinematical fields resulting in the b-ansatz framework before solving the Jeans equations; results were illustrated by means of disk galaxy models. In this paper we focus more specifically on realistic ellipsoidal galaxy models. It is found that how and where b affects the galaxy kinematical fields is mainly dependent on the flattening of the stellar density distribution, moderately on the presence of a Dark Matter halo, and much less on the specific galaxy density profile. The main trends revealed by the numerical exploration, in particular the fact that more flattened systems can support larger b-anisotropy, are explained with the aid of simple ellipsoidal galaxy models, for which most of the analysis can be conducted analytically. The obtained results can be adopted as guidelines for model building and in the interpretation of observational data.

Abstract Optical and infrared surveys have detected increasing numbers of disc accretion outbursts in young stars. Some models of these FU Ori-type events predict that the outburst should start at near- to mid-infrared wavelengths before an optical rise is detected, and this lag between infrared and optical bursts has been observed in at least two systems. Detecting and characterizing infrared precursors can constrain the outburst trigger region, and thus help identify the mechanism producing the outburst. However, because FU Ori objects are generally young and usually embedded in dusty protostellar envelopes, it is not clear whether or how well such infrared precursors can be detected in the presence of strong envelope extinction. To explore this question, we combine time-dependent outburst models of the inner disc with an outer dusty disc and protostellar envelope, and calculate the resulting spectral energy distributions (SEDs) using the radiative transfer code RADMC3D. We find that, for envelope mass infall rates ≳ 10−5M⊙ yr−1 (rc/30 au)−1/2, where rc is a characteristic inner radius for the infalling envelope, the infrared precursor is only apparent in the SED when viewed along an outflow cavity. At other inclinations, the precursor is most easily distinguished with limited envelope extinction at infall rates ≲ 10−6M⊙ yr−1 (rc/30 au)−1/2. We also show that far-infrared and submm/mm monitoring can enable the indirect detection of precursor evolution long before the optical outburst, emphasizing the potential of long-wavelength monitoring for studying the earliest stages of protostar formation.

Abstract Active galactic nuclei (AGN) are important drivers of galactic evolution; however, the underlying physical processes governing their properties remain uncertain. In particular, the specific cause for the generation of the broad-line region is unclear. There is a region where the underlying accretion disc atmosphere becomes cool enough for dust condensation. Using models of the disc’s vertical structure, accounting for dust condensation and irradiation from the central source, we show that their upper atmospheres become extended, dusty, and radiation-pressure-supported. Due to the density–temperature dependence of dust condensation, this extended atmosphere forms as the dust abundance slowly increases with height, resulting in density and temperature scale heights considerably larger than the gas pressure scale height. We show that such an atmospheric structure is linearly unstable. An increase in the gas density raises the dust sublimation temperature, leading to an increased dust abundance, a higher opacity, and hence a net vertical acceleration. Using localised 2D hydrodynamic simulations, we demonstrate the existence of our linear instability. In the non-linear state, the disc atmosphere evolves into “fountains” of dusty material that are vertically launched by radiation pressure before being exposed to radiation from the central source, which sublimates the dust and shuts off the radiative acceleration. These dust-free clumps then evolve ballistically, continuing upward before falling back towards the disc under gravity. This clumpy ionized region has velocity dispersions ≳ 1000 km s−1. This instability and our simulations are representative of the Failed Radiatively Accelerated Dusty Outflow (FRADO) model proposed for the AGN broad-line region.

Abstract Shock fronts driven by active galactic nuclei in galaxy cluster cores represent a promising mechanism for heating the intracluster medium and offsetting radiative cooling. Despite their potential importance, they are challenging to detect and have been identified in only about ten massive clusters. We present the first systematic detection and characterization of AGN-driven shocks in simulated clusters from the TNG-Cluster magnetohydrodynamic cosmological zoom-in simulations of galaxies. TNG-Cluster exhibits a rich variety of spatially-resolved X-ray structures, including realistic populations of X-ray cavities, as well as shocks, produced by its AGN feedback model, without collimated, relativistic jets, nor cosmic rays. We produce mock Chandra observations with 600 ks exposures for 100 clusters, mass-matched (M500c = 1.2-8.5 × 1014 M⊙) to the ten observed clusters exhibiting shocks. Using observational techniques, we detect 50 shocks in 30 of the 100 clusters, with ∼35 per cent hosting multiple shocks. These shocks typically lie within a hundred kiloparsec of the central SMBH, are weak (Mach < 2, median ∼ 1.1), and are associated with X-ray cavities in about half of the cases. Both in observations and in TNG-Cluster, shocks tend to be located at larger radii than cavities, with median offsets of 46 and 27 kpc, respectively. The observationally inferred shock powers are comparable to the cluster cooling luminosities (1044 − 46 erg s−1), suggesting that shocks in the simulation are a crucial heating mechanism. Our results indicate that shocks play a role as important as cavities in balancing cooling in cluster cores, acting isotropically and up to larger distances.

Abstract We used CO (2-1) and CO (1-0) data cubes to identify molecular clouds and study their kinematics and dynamics in three nearby galaxies and the inner Milky Way. When observed at similar spatial and velocity resolutions, molecular clouds in the same mass range across these galaxies show broadly comparable physical properties and similar star formation rates (SFRs). However, this comparability depends on smoothing Milky Way clouds to match the resolution of the extragalactic observations. The beam effect can artificially inflate cloud sizes, leading to inaccurate estimates of radius, density, and virial parameters. By comparing high-resolution and smoothed Milky Way data, we established criteria to exclude beam-affected clouds in the extragalactic sample. After applying this filter, cloud properties remain consistent across galaxies, though some clouds in NGC 5236 show elevated velocity dispersions, likely due to environmental effects. In the inner Milky Way, molecular clouds fall into two groups: those with clumps and those without. Clump-associated clouds are more massive, denser, have higher velocity dispersions, lower virial parameters, and stronger 8μm emission, suggesting more intense feedback. Strong correlations are found between cloud mass and total clump mass, clump number, and the mass of the most massive clump. These results suggest that a cloud’s physical conditions regulate its internal clump properties and, in turn, its star-forming potential.

Abstract Within the standard six-parameter Lambda cold dark matter (ΛCDM) model, a 2-3σ tension persists between baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) and observations of the cosmic microwave background (CMB). Although this tension has often been interpreted as evidence for dynamical dark energy or a sum of neutrino masses below the established minimum, recent studies suggest it may instead originate from an underestimation of the reionization optical depth, particularly when inferred from large-scale CMB polarization. Jhaveri et al. propose that a suppression of large-scale primordial curvature power could partially cancel the contribution of τ to the CMB low-ℓ polarization power spectrum, leading to a biased low τ measurement in standard analyses. In this work, we investigate whether punctuated inflation - which generates a suppression of primordial power on large scales through a transient fast-roll phase - can raise the inferred τ value and thereby reconcile the consistency between CMB and BAO. For simple models with step-like features in the inflaton potential, we find that the constraint on τ and the CMB-BAO tension remain nearly identical to those in the standard six-parameter ΛCDM model. We provide a physical explanation for this negative result.

Abstract Taking advantage of the near-infrared calcium triplet lines, we determine metallicities for a sample of more than 3,500 red giant stars in the field of the Small Magellanic Cloud (SMC). We find a median metallicity of [Fe/H]=-1.05±0.01 dex with a negative metallicity gradient of -0.064±0.007 dex deg−1 between 1.○2 to 6.○0 consistent with an outside-in evolution scenario. For the first time, we detect hints of a positive metallicity gradient within 1.○2, likely reflecting radial migration or centralised chemical enrichment. Azimuthal metallicity asymmetries are detected, with flatter gradients in the eastern and southern quadrants and steeper ones in the north and west. They are consistent with tidal interaction effects from the Large Magellanic Cloud (LMC). Finally, in spite of a clear distance and velocity bifurcations in the east, they seem to share a common chemical origin, in agreement with other studies.

Abstract Recent cosmological parameter analyses combining DESI DR2 Baryon Acoustic Oscillation (BAO) data with external probes, such as Pantheon+ Supernovae (SNe) observations, have reported deviations of the dark energy equation-of-state parameters (ω0, ωa) from the standard ΛCDM model predictions (ω0 = −1, ωa = 0). A notable aspect of these results is the role of Ωm0 prior information from SNe, which is known to exhibit tension with BAO-only constraints. In this study, we rigorously investigate this effect through a statistical analysis using 1000 mock DESI DR2 BAO data realizations. We demonstrate that the strong degeneracy between ω0, ωa, and Ωm0 causes significant biases in the estimated dark energy parameters when the Ωm0 prior mean deviates from its true underlying value. Specifically, applying an Ωm0 prior mean of 0.33 (consistent with some SNe-only constraints) to mock data, assuming a true ΛCDM universe (Ωm0 = 0.30, ω0 = −1, ωa = 0), yields biased estimates such as ω0 ≈ −0.82 ± 0.06 and ωa ≈ −0.82 ± 0.4. This systematic shift, driven by the Ωm0 prior, moves the estimated parameters towards the non-ΛCDM region, offering a qualitative resemblance to outcomes reported in current combined DESI DR2 BAO + Pantheon+ SNe analyses (e.g., $\omega _0 = -0.888^{+0.055}_{-0.064}$, ωa = −0.17 ± 0.46). Our findings suggest that these observed non-ΛCDM parameters may largely arise from statistical biases due to Ωm0 prior tensions between datasets. This study proposes a potential resolution to current cosmological tensions without necessarily invoking new physics.

Abstract The pattern of individual mode frequencies in solar-like oscillators provides valuable insight into their properties and interior structures. The identification and characterisation of these modes requires high signal-to-noise and frequency resolution. The KEYSTONE project unlocks the asteroseismic potential of the K2mission by providing individually reduced, high-quality time series data, global asteroseismic parameters, and spectroscopic analysis for 173 solar-like oscillators. In this work, we build on the KEYSTONE project and present the first analysis of the pattern of individual modes in the oscillation spectra for the K2KEYSTONE stars. We perform a robust identification and characterisation of the modes through peakbagging methods in the open-source analysis tool PBjam. We present over 6000 mode frequencies, widths, and heights for 168 stars in the sample, covering the HR diagram from FGK dwarfs to sub-giants and the lower red giant branch, providing a significant increase in the number of individual mode frequency detections for main sequence and sub-giant oscillators. This study also presents sample-wide trends of oscillation patterns as a function of the fundamental stellar properties, and improves the precision of the global asteroseismic parameters. These measurements are part of the legacy of the K2mission, and can be used to perform detailed modelling to improve the precision of fundamental properties of these stars. The results of this analysis provides evidence for the validity of using PBjamto identify and characterise the modes resulting from the observations of the future PLATOmission.

Abstract Using very long baseline interferometry, the Event Horizon Telescope (EHT) collaboration has resolved the shadows of two supermassive black holes. Model comparison is traditionally performed in image space, where imaging algorithms introduce uncertainties in the recovered structure. Here, we develop a deep learning framework to infer the physical parameters of General Relativistic Magnetohydrodynamic (GRMHD) simulations directly from visibility space data. By working in the native domain of the interferometer, our method avoids introducing potential errors and biases from image reconstruction. First, we train and validate our framework on synthetic data derived from GRMHD simulations that vary in magnetic field state, spin, and Rhigh. Applying these models to the real data obtained during the 2017 EHT campaign, and only considering total intensity, we do not derive meaningful constraints on either spin or Rhigh. At present, our method is limited both by theoretical uncertainties in the GRMHD simulations and variations between snapshots of the same underlying physical model. However, we demonstrate that spin and Rhigh could be recovered using this framework through continuous monitoring of our sources, which mitigates variations due to turbulence. In future work, we anticipate that including spectral or polarimetric information will greatly improve the performance of this framework.