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Hierarchical summaries for primordial non-Gaussianities
No full textInternational audienceThe advent of Stage IV galaxy redshift surveys such as DESI and Euclid marks the beginning of an era of precision cosmology, with one key objective being the detection of primordial non-Gaussianities (PNG), potential signatures of inflationary physics. In particular, constraining the amplitude of local-type PNG, parameterised by , with , would provide a critical test of single versus multi-field inflation scenarios. While current large-scale structure and cosmic microwave background analyses have achieved -, further improvements demand novel data compression strategies. We propose a hybrid estimator that hierarchically combines standard -point and -point statistics with a field-level neural summary, motivated by recent theoretical work that shows that such a combination is nearly optimal, disentangling primordial from late-time non-Gaussianity. We employ PatchNet, a convolutional neural network that extracts small-scale information from sub-volumes (patches) of the halo number density field while large-scale information is retained via the power spectrum and bispectrum. Using Quijote-PNG simulations, we evaluate the Fisher information of this combined estimator across various redshifts, halo mass cuts, and scale cuts. Our results demonstrate that the inclusion of patch-based field-level compression always enhances constraints on , reaching gains of - at low (), and capturing information beyond the bispectrum. This approach offers a computationally efficient and scalable pathway to tighten the PNG constraints from forthcoming survey data
Locating Centers of Clusters of Galaxies with Quadruple Images: Witt's Hyperbola and a New Figure of Merit
No full textInternational audienceFor any elliptical potential with an external parallel shear, Witt has proven that the gravitational center lies on a rectangular hyperbola derived from the image positions of a single quadruply lensed object. Moreover, it is predicted that for an isothermal elliptical potential the source position both lies on Witt's Hyperbola and coincides with the center of Wynne's Ellipse (fitted through the four images). Thus, by fitting Witt's Hyperbolae to several quartets of images - ten are known in Abell 1689 - the points of intersection provide an estimate for the center for the assumed isothermal elliptical potential. We introduce a new figure of merit defined by the offset of the center of Wynne's Ellipse from Witt's Hyperbola. This offset quantifies deviations from an ideal elliptical isothermal potential and serves as a discriminant to exclude poorly fitted quadruples and assign greater weight to intersections of hyperbolae of better fitting systems. Applying the method to 10 quads (after excluding 7 poorly fitted quads) in Abell 1689, we find the potential is centered within 11" of the BCG, X-ray center, flexion-based center and the center found from a total strong lensing analysis. The Wynne-Witt framework thus delivers a fast, analytic, and self-consistency-checked estimator for centers in clusters with multiple quads
Mid- and Far-Infrared Spectral Signatures of Mineral Dust from Low- to High-Latitude Regions: significance and implications
No full textInternational audienceMineral dust absorbs and scatters solar and infrared radiation, thereby affecting the radiance spectrum at the surface and top-of-atmosphere and the atmospheric heating rate. While half of the outgoing thermal radiation is emitted in the far infrared (FIR, 15–100 μm), knowledge of the optical properties and thermal radiative effects of dust is currently limited to the mid-infrared region (MIR, 3–15 μm). In this study we performed pellet spectroscopy measurements to evaluate the MIR and FIR contribution to dust absorbance and explore the variability and spectral diversity of the dust signature within the 2.5–25 μm range. Thirteen dust samples re-suspended from parent soils with contrasting mineralogy were investigated, including low and mid latitude dust (LMLD) sources in Africa, America, Asia, and Middle East, and high latitude dust (HLD) from Iceland. Results show that the absorbance of dust in the FIR up to 25 μm is comparable in intensity to that in the MIR. Also, spectrally different absorption (position and shape of the peaks) is observed for HLD compared to LMLD, due to differences in mineralogical composition. Corroborated with the few available literature data on absorption properties of natural dust and single minerals up to 100 μm wavelength, these data suggest the relevance of MIR and FIR interactions to the dust radiative effect for low to high latitude sources. Furthermore, the dust spectral signatures in the MIR and FIR could potentially be used to characterise the mineralogy and differentiate the origin of airborne particles based on infrared remote sensing observations
Identity and the Self. How Archaeology Creates Protohistoric Identities
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Combining LIDAR, all-sky camera, and ECMWF-ERA5 reanalysis to investigate contrail formation and evolution over Clermont-Ferrand, France on June 2, 2023
No full textInternational audienceContrails formed by aircraft in the upper troposphere contribute to anthropogenic climate forcing. However, the conditions driving their formation and persistence remain incompletely understood. This study combines a ACTRIS/EARLINET ground-based LIDAR, all-sky camera imagery, ADS-B aircraft tracking, and ECMWF-ERA5 reanalysis to analyse contrails formation and evolution over Clermont-Ferrand, France, on June 2, 2023. Twelve contrails are documented throughout the day, including five persistent and seven non-persistent contrails. Persistent contrails formed at 10.36 km altitude or lower are observed under ice-supersaturated conditions (relative humidity with respect to ice, RHi > 105 %) and at temperatures between 217 and 223 K. Non-persistent contrails produced by higher altitudes aircrafts, are associated with lower RHi mostly below 100 % and colder temperatures (214-217 K). The horizontal persistent contrail widths range from 0.53 ± 0.10 to 1.60 ± 0.44 km (all-sky camera estimation) and 0.35 ± 0.14 to 1.90 ± 0.32 km (LIDAR estimation), and vertical extents varied from 340 ± 10 to 440 ± 20 m. The optical properties of these contrails have also been estimated by LIDAR. Aerosol backscatter coefficient vary from 0.02 to 0.05 km-1 sr-1, scattering ratios from 8 to 20, volume linear depolarization from 0.13 to 0.24 and particle linear depolarization from 0.17 to 0.45. The maximum contrail observation duration by camera is 180 min. The study highlights the potential of ground-based remote sensing for contrail monitoring
Enhanced long-duration gravitational-wave transient sources search pipeline with denoising and tree clustering algorithms
No full textInternational audienceWe present a two-stage upgrade to the PySTAMPAS pipeline that boosts the search for long-duration (10 to 10^3 s) transients in gravitational-wave detector data. First, a denoising scheme combines complex 2D wavelet shrinkage with an adaptive pixel threshold to suppress noise while retaining signal power. Second, a KDTree nearest-neighbour algorithm clusters surviving pixels in O(log n) time, replacing the standard clustering approach. Tests with one week of LIGO O3b data show a large reduction in false-alarm rate and up to a factor-of-two improvement in search sensitivity. The computational time is also significantly reduced. These gains extend the sensitivity of all-sky, all-time searches to weaker and shorter transients, enabling rapid and deeper analyses in forthcoming LIGO-Virgo-KAGRA observation campaigns
Spin-filament alignments to unravel galaxy evolution and model intrinsic alignments
No full textInternational audienceBy the 2040s, several all-sky surveys will have transformed our view of the large-scale structure. However, one of the major outstanding questions in astrophysics will remain: understanding how galaxies acquire and evolve their angular momentum and how this connects to the cosmic web. Measuring the alignments between galaxy spins and cosmic filaments across cosmic time, and understanding what this reveals about galaxy evolution, requires surveys that also characterise intrinsic alignments, i.e. correlations in galaxy shapes produced by the cosmic web itself rather than by lensing. Intrinsic alignments are a major source of systematic error in weak-lensing measurements of the fundamental parameters of the Universe. Addressing both questions together will necessitate new types of MOS surveys that combine kinematic information with high-completeness redshifts down to at least 24-25mag. To achieve our science goals, we require a new generation of wide-field spectroscopic facilities that can obtain spin-filament alignment measurements for millions of galaxies while simultaneously delivering sub-Mpc resolution of the cosmic web and spatially-resolved kinematics required to map the spin-filament connection at the level of individual galaxies within their local cosmic environment. Such a program would provide a unique legacy survey of galaxies and cosmic structures from kiloparsec to megaparsec scales, establishing ESO's leadership in bridging the physics of galaxy evolution with the systematic-control requirements for Stage-IV cosmological surveys
Strong and weak wave turbulence regimes in Bose-Einstein condensates
No full textWhen a turbulent Bose-Einstein condensate is driven out-of-equilibrium at a scale much smaller than the system size, nonlinear wave interactions transfer particles towards large scales in an inverse cascade process. In this work, we study numerically wave turbulence in a three-dimensional Bose-Einstein condensate in forced and dissipated inverse cascade settings. We observe that when the forcing rate increases, thereby increasing the particle flux, the turbulence spectrum gradually transitions from the weak-wave Kolmogorov-Zakharov cascade to a critical balance state characterized by a range of scales with balanced linear and nonlinear dynamic timescales. Further forcing increases lead to a coherent condensate component superimposed with Bogoliubov-type acoustic turbulence. The role of vortices in such a strongly forced state is marginal, which makes this new state very different from the strongly turbulent state composed of a tangle of quantized vortex lines. We then use our predictions and numerical data to formulate a new out-of-equilibrium equation of state for the 3D inverse cascade
La ZA PYGAR : des Pyrénées aux plaines agricoles, un territoire drainé par la Garonne
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Reconstructing Sewer Network Topology Using Graph Theory
No full textInternational audienceTo manage sewer networks, reliable data is needed, which is often challenging. This study proposes a novel methodology to reconstruct the sewer network topology using graph theory. Two core procedures—flow adjustment and edge addition—re-establish hydraulically consistent flow paths and restore connectivity in disconnected portions of the network by reversing and adding links. The proposed approach operates at the pipe level, repairing directional reachability. It leverages only the existing network topology to reconstruct connectivity, guided by the principle that every node must have a downstream path to an outlet. The methodology is first applied to reconstruct the sewer network of Montpellier Metropolis in the South of France. Then it is validated by deliberately removing and reversing edges and applying the algorithms to test the methodology’s capability in recovering the correct topology. Both methods performed well individually, especially at lower percentages of reversal (1%) and removal (1%), with a correctness of 0.99 for flow adjustment and 0.8 for edge addition. Although the results were poorer when combining the methods and increasing data degradation—particularly at 10% reversal and 10% removal (correctness of 0.64)—the methodology continued to produce a functionally consistent and logically coherent network, highlighting its robustness given the absence of supporting attribute data