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TDCOSMO
No full textTime-delay cosmography leverages strongly lensed quasars to measure the Universe’s current expansion rate, H0, independently from other methods. The latest TDCOSMO milestone measurement primarily used quadruply lensed quasars for their mass profile constraints. However, doubly lensed quasars, being more abundant and offering precise time delays, could expand the sample by a factor of 5, significantly advancing towards a 1% precision measurement of H0. We present the first TDCOSMO analysis of a doubly imaged source, HE 1104−1805, including the measurement of the four necessary ingredients. First, by combining 17 years of data from the SMARTS, Euler, and WFI telescopes, we measured a time delay of 176.3 days. Second, using MUSE data, we extracted stellar velocity dispersion measurements in three radial bins with 5% to 13% precision. Third, employing F160W HST imaging for lens modelling and marginalising over various modelling choices, we measured the Fermat potential difference between the images. Fourth, using wide-field imaging, we measured the convergence added by objects not included in the lens modelling. By combining these four ingredients, we measured the time delay distance and the angular diameter distance to the deflector, favouring a power-law mass model over a baryonic and dark matter composite model. The measurement was performed blindly to prevent experimenter bias and resulted in a Hubble constant of × λint km s−1Mpc−1, where λint is the internal mass sheet degeneracy parameter. This is in agreement with the TDCOSMO-2025 milestone and its precision for λint = 1 is comparable to that obtained with the best-observed quadruply lensed quasars (4–6%). This work is a stepping stone towards a precise measurement of H0 using a large sample of doubly lensed quasars, supplementing the current sample. The next TDCOSMO milestone paper will include this system in its hierarchical analysis, constraining λint and H0 jointly with multiple lenses
Moonlit sky polarization patterns from Cerro Paranal
No full textWe investigated the polarization patterns from the moonlit sky as observed from the European Southern Observatory at Cerro Paranal. The moonlit sky background can be significant in astronomical observations and thus be a source of contamination in polarimetric studies. Based on sky observations during full Moon with FORS2 in imaging polarimetric mode, we measured the polarization degree and intensity at different wavelengths and scattering angles from the Moon, and we compared them to theoretical and phenomenological single- and multiple-scattering models. Single-scattering Rayleigh models are able to reproduce the wavelength dependence of the polarization as long as strong depolarization factors that increase with wavelength are introduced. Intensity data, however, require the inclusion of single Mie scattering from larger aerosol particles. The best models that simultaneously fit polarization and intensity data are a combination of the two single-scattering processes, Rayleigh and Mie, plus an unpolarized multiple-scattering component. Both Mie and multiple scattering become more dominant at longer wavelengths. Other factors such as cloud depolarization and the sunlight contribution at twilight were also investigated. The present study underscores the importance of accounting for moonlight scattering to enhance the accuracy of polarimetric observations of astronomical targets
Observations of counter-streaming ions in and around the diamagnetic cavity of comet 67P
No full textContext. Ion speeds at comet 67P/Churyumov-Gerasimenko significantly exceed local neutral gas speeds, a discrepancy that challenges current ion-neutral coupling models. The presence of counter-streaming ion populations is a proposed solution, as it can reconcile high individual velocities with a low bulk flow speed and potentially drive wave activity through ion-ion instabilities.
Aims. We aim to identify and statistically characterize counter-streaming ion populations to provide the first quantitative constraints on this phenomenon.
Methods. We analyzed high- and standard-resolution data from the Ion Composition Analyser (ICA), part of the Rosetta Plasma Consortium (RPC) on board the Rosetta spacecraft. The events were selected from periods when Rosetta was inside or near the diamagnetic cavity, a key region for cometary plasma dynamics.
Results. A total of 112 events are identified in the high-resolution data and 338 in the standard-resolution data, both inside and outside the diamagnetic cavity. In general, the anticometward ion population exhibits higher energy and particle counts compared to the cometward ion population. The angular separation between the two flows is peaked in the range of 150°–180°. The superposition of these high-speed flows produce net bulk velocities of a few km/s.
Conclusions. Our findings provide statistical evidence of counter-streaming ions at a comet and demonstrate that they can lead to a low net bulk speed. Return flows can be explained by gyration of the ions in the magnetic field just outside the diamagnetic cavity
Large-scale radio bubbles around the black hole transient V4641 Sgr
No full textContext. Black holes (BHs) in microquasars can launch powerful relativistic jets that have the capacity to travel up to several parsecs from the compact object and interact with the interstellar medium. Recently, the detection of large-scale very-high-energy (VHE) gamma-ray emission around the black hole transient V4641 Sgr and other BH-jet systems suggested that jets from microquasars may play an important role in the production of galactic cosmic rays.
Aims. V4641 Sgr is known for its superluminal radio jet discovered in 1999, but no radio counterpart of a large-scale jet has been observed. The goal of this work is to search for a radio counterpart of the extended VHE source.
Methods. We observed V4641 Sgr with the MeerKAT radio telescope at the L and UHF bands and produced deep maps of the field using high dynamic range techniques.
Results. We report the discovery of a large-scale (∼35 pc), bow-tie-shaped, diffuse, radio structure around V4641 Sgr, with similar angular size to the extended X-ray emission discovered by XRISM. However, it is not spatially coincident with the extended VHE emission. After discussing the association of the structure with V4641 Sgr, we investigate the nature of the emission mechanism. We suggest that the bow-tie structure arose from the long-term action of large-scale jets or disk winds from V4641 Sgr. If the emission mechanism is of synchrotron origin, the radio/X-ray extended structure implies acceleration of electrons up to more than 100 TeV as far as tens of parsecs from the black hole
Spatially resolved PAH
No full textRam pressure stripping (RPS) plays a crucial role in shaping galaxy evolution in dense environments, yet its impact on the molecular and dusty phases of the interstellar medium remains poorly understood. We present JWST/NIRCam 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission maps for the nine most striking RPS galaxies in the Abell 2744 cluster at redshift zcl = 0.306, tracing the effects of environmental processes on small dust grains. Exploiting multi-band JWST/NIRCam and HST photometry, we performed a spatially resolved ultraviolet (UV) to mid-infrared (MIR) spectral energy distribution (SED) fitting to characterise stellar populations in both galactic disks and clumps detected in the stripped tails. We detected PAH3.3 emission in eight of the nine galaxies at 5σ, with morphologies revealing disk truncation and elongation along the RPS direction. In three galaxies, PAH3.3 emission is also found in star-forming clumps embedded in the stripped tails up to a distance of 40 kpc. Star formation rates inferred from PAH3.3 emission are in agreement with those derived from SED fitting averaged over the past 100 Myr within an intrinsic scatter of 0.4 dex, but the relation appears to be age-dependent. The spatial correlation between the PAH strength, stellar age, and star formation rate (SFR) is consistent across disks and tails and demonstrates that PAH-carrying molecules can survive and become stripped by ram pressure. Finally, age gradients revealed by the SED fitting provide observational evidence of the fireball model in star-forming, stripped clumps of galaxies at z ∼ 0.3. This work represents the first detailed study of PAH emission in cluster galaxies, offering new insights into the fate of dust and star formation in extreme environments
CLASH-VLT: The variance in the velocity anisotropy profiles of galaxy clusters
No full textThe velocity anisotropy profiles, br, of galaxy clusters are directly related to the shape of the orbits of their member galaxies. Knowledge of br is important in order to understand the assembly process of clusters and the evolutionary processes of their galaxies, and to improve the determination of cluster masses based on cluster kinematics.
We determined the br of nine massive clusters at redshift 0.19 łeq z łeq 0.45 from the CLASH-VLT dataset, with ≃ 150 to 950 spectroscopic members each, to understand how much cluster-to-cluster variance exists in the br of different clusters and what the main driver of this variance is.
We selected spectroscopic cluster members with the ļumps algorithm calibrated on cosmological simulations. We applied the code to the distribution of cluster members in projected phase-space to constrain the cluster mass profile, M(r), using priors derived from a previous gravitational lensing analysis. Given the best-fit solution for M(r), we then solved the inversion of the Jeans equation to determine br without assumptions of its functional form. We also ran the code to identify subclusters and characterize the dynamical status of our clusters.
The average łangle ̊angle is slightly radial; the anisotropy increases from β ≃ 0.2 at the cluster center to β ≃ 0.5 at the virial radius. There is substantial variance in the br of the individual clusters that cannot be entirely accounted for by the observational uncertainties. Clusters of lower mass and with a low concentration per given mass have more tangential br profiles. A comparison with previous works in the literature suggests that orbits are more radial in clusters at higher z. A comparison with cluster-sized halos in cosmological hydrodynamical simulations indicates a very good agreement for the average łangle ̊angle, but a smaller variance in the profiles than observed.
Massive clusters cannot be characterized by a unique universal br. The orbital distribution of cluster galaxies carries information on the merging history of the cluster
Hole expansion behavior of hot-rolled steel related to punching morphology considering banded microstructure
No full textThe hole expansion behavior serves as a key metric for assessing the formability of automotive structural components containing holes. With the growing emphasis on decarbonization in automotive manufacturing, hot-rolled steels have gained attention as promising substitutes for cold-rolled counterparts. Owing to their thermomechanical processing characteristics, hot-rolled steels frequently exhibit banded microstructures oriented along the rolling direction; however, the effect of these banded structures on hole expansion behavior remains insufficiently understood. In the present work, two hot-rolled steels with distinct banded morphologies were investigated under punching conditions in accordance with ISO 16630. The study focused on the evolution of microstructural features within the shear-affected zone (SAZ) and at the hole-edge surface before and after hole expansion. The findings indicate that the banded arrangement facilitates circumferential crack propagation along the hole edge, thereby improving hole expansion performance. This advantageous effect is particularly evident when the fracture zone constitutes a large fraction of the hole-edge surface, promoting stress relief through the generation of cross cracks. In contrast, when the fracture zone is limited, fracture initiation in the burr zone at the hole periphery leads to visible hole expansion cracks, contributing to the safe identification of failure during service. Additionally, the matrix hardness and strength were found to play a decisive role in governing hole expansion behavior, with a positive correlation established between edge hardening induced by punching and the hole expansion ratio
Design of Si3N4-TFLN Heterogeneous Integrated Device with Phase Modulation and Frequency Doubling: Performance Optimization and Application Prospects
No full textElectro-optic phase modulation is a core technology for signal processing in optical communication and microwave photonics, yet the current multifunctional integrated devices for high-bandwidth phase modulation and efficient frequency doubling suffer from critical bottlenecks including large crosstalk, excessive chip area, bandwidth-voltage trade-off and single material performance limitations. To address these issues, this study proposes a Si₃N₄-TFLN heterogeneous integrated design scheme by synergizing the low-loss property of silicon nitride and the strong electro-optic effect of thin-film lithium niobate. A dual-drive Mach-Zehnder modulator (DD-MZM) and a racetrack micro-ring resonator (MRR) with high quality-factor and large free spectral range are cascaded to realize the monolithic integration of high-precision phase modulation and microwave signal frequency doubling. Co-simulation results show that the designed device achieves an electro-optic modulation bandwidth of 72 GHz and a half-wave voltage-length product of 2.8 V·cm, which well reconciles the bandwidth-voltage trade-off. The device exhibits a frequency doubling efficiency of 15%, 30.4% higher than that of the single TFLN-based MRR. The cascaded coupling structure suppresses the functional crosstalk to -38 dB, and the total chip layout area is only 3.648 mm², over 60% smaller than that of the existing similar devices. This work provides a high-performance on-chip solution for high-density integrated systems in optical communication, microwave photonics and quantum information processing
Proton acceleration during the interaction of a coronal-mass-ejection-driven shock and a current sheet
No full textConext. Shock geometry plays a critical role in the acceleration of energetic particles. To isolate its effect, it is essential to study particle behavior under different shock geometries while maintaining comparable shock properties such as strength, speed, and turbulence conditions within a continuous period of time.
Aims. We aim to study the physical process of the interaction between an interplanetary shock and a current sheet, and compare the dynamic behavior of energetic protons under different shock geometries separated by the current sheet using the Electron-Proton Telescope on board the Solar Orbiter (SolO) on 14 March 2023.
Methods. We applied a partial-variance-increment (PVI) method to detect the magnetic structure in the upstream region of the shock. We reconstructed the proton pitch-angle distribution (PAD) in the solar wind frame to analyze the particle dynamics. We calculated the first-order flux anisotropy in the solar-wind frame of reference.
Results. We find that the differential flux of 60 keV–2 MeV protons is enhanced by 2.5 times from the current sheet to the shock. During the quasi-parallel shock interval, the first-order flux anisotropy in the solar-wind frame is consistent with diffusive shock acceleration. Nevertheless, the flux anisotropy exhibits a bipolar shape during the quasi-perpendicular shock interval. The coexistence of positive and negative flux anisotropy suggests that the magnetic field is wandering around the shock and connected to the shock surface with different acceleration efficiencies. That the flux anisotropy peaks at a transition energy may indicate that it is influenced by the current sheet. The transition energy is greater during the quasi-perpendicular interval, implying more efficient proton acceleration.
Conclusions. We suggest that the current sheet is an important ingredient that affects the local shock geometry and, thus, the particle acceleration efficiency and flux anisotropy. This effect can accumulate as the shock propagates outward from the Sun and should be taken into account when interpreting particle spectral profiles at greater distances
G183: An outer galaxy filament feeding a massive protostar
No full textWe present the first detailed multi-tracer observation of a 5-pc long outer Galaxy filament, G183, and the massive young stellar object (YSO) IRAS 05480+2545 associated with it. Using the IRAM 30-m telescope at λ = 1.4 and 3 mm, we probed the molecular gas distribution at angular resolutions of ~12″–28″ (0.1–0.3 pc at d = 2.1 kpc). The velocity-resolved C18O(1–0) observations conclusively show a main filament with a skeleton of ridges. The main filament is a 5 pc long velocity-coherent structure with a continuous and quiescent velocity field along its length up to the star-forming hub that accretes mass from the filament. The internal gas kinematics of most of the G183 filament is dominated by thermal motions (σNT/cs ~ 1) and large-scale velocity gradients arising due to outflows and accretion of matter in the massive YSO. The dispersion-size relation almost up to 1 pc is consistent with Larson’s law, suggesting that the origin of the filament is a turbulence cascade. The massive YSO, S1, with no corresponding radio continuum detection is characterized as a high-mass protostellar object with a mass of 156 M⊙ and an M/L ratio of 0.04. We identify a kinematic signature of the accretion of material from the filament onto the YSO, S1. The rates of molecular gas accretion and entrainment in S1 are estimated to be 8.6 and 2.6 (in units of 10−4 M⊙ yr−1), respectively. In comparison to the inner Galaxy high-mass star-forming filaments forming massive stars, G183 has a lower column density; however, the accretion and outflow rates in S1 are similar. The detection of hydrocarbons such as CH3CN and HC3N indicates the presence of hot-core chemistry in S1. These results highlight the universality of physical processes involved in massive star formation across a range of Galactic environments