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French HEP community input to the European Strategy for Particle Physics
No full textInternational audienceIn view of the European Strategy for Particle Physics process, the French HEP community has organized a national process of collecting written contributions and has pursued a series of workshops culminating with a national symposium held in Paris on January 20-21, 2025 that involved over 280 scientists https://indico.in2p3.fr/event/34662/. The present document summarises the main conclusions of this bottom-up approach centred on the physics and technology motivations
Positive and negative DC glow discharges: A comparative study to characterize self-organized patterns on water surface
No full textInternational audienceSelf-organized patterns (SOPs) in plasma discharges arise from the complex interplay of electric field, reactive species, and charged particles, driven by non-linear plasma dynamics. While studies have explored SOP formation in various configurations, no systematic comparison of positive and negative DC glow discharges (NGD) has been conducted to explain why SOPs form exclusively when polarization is negative. This study aims to analyze SOP formation mechanisms by comparing the electrical, optical, and spectral properties of positive and negative DC glow discharges interacting with a grounded water surface. Key differences in gas temperature, electric field, and reactive species distribution are hence identified. For positive DC glow discharges, the gas temperature remains in the 350–370 K range, while the reduced electric field remains below 100 Td across the gap. The plasma is dominated by OH• and N2* species, whose excitation results from direct electron impact and energy transfer in a low-field environment. The absence of strong ionization and electric field gradients leads to a spatially homogeneous emission layer on the liquid surface, resulting in a circular uniform plasma pattern without self-organization. In contrast, SOP emerges exclusively under NGD at currents above 15 mA. These discharges are characterized by a non-linear reduced electric field, peaking at 485 Td at 1 mm from the cathode pin, dropping below 100 Td in the central gap and rising to 460 Td near the water surface. There, the plasma layer still contains not only OH• and N2* species but also N2+ ions, the latter being critical for SOP formation. SOP morphology evolves with gap size: at 7 mm, patterns transition from specks to filaments, with pattern diameters and thickness as high as 5.5 mm and 210 μm, respectively. Lowering water surface tension with surfactants reduces SOP size and modifies pattern morphology. Our results deepen understanding of plasma self-organization mechanisms, particularly the role of polarity and liquid surface dynamics
Euclid Quick Data Release (Q1). Photometric redshifts and physical properties of galaxies through the PHZ processing function
No full textInternational audienceThe ESA Euclid mission will measure the photometric redshifts of billions of galaxies in order to provide an accurate 3D view of the Universe at optical and near-infrared wavelengths. Photometric redshifts are determined by the PHZ processing function on the basis of the multi-wavelength photometry of Euclid and ground-based observations. In this paper, we describe the PHZ processing used for the Euclid Quick Data Release, the output products, and their validation. The PHZ pipeline is responsible for the following main tasks: source classification into star, galaxy, and QSO classes based on photometric colours; determination of photometric redshifts and of physical properties of galaxies. The classification is able to provide a star sample with a high level of purity, a highly complete galaxy sample, and reliable probabilities of belonging to those classes. The identification of QSOs is more problematic: photometric information seems to be insufficient to accurately separate QSOs from galaxies. The performance of the pipeline in the determination of photometric redshifts has been tested using the COSMOS2020 catalogue and a large sample of spectroscopic redshifts. The results are in line with expectations: the precision of the estimates are compatible with Euclid requirements, while, as expected, a bias correction is needed to achieve the accuracy level required for the cosmological probes. Finally, the pipeline provides reliable estimates of the physical properties of galaxies, in good agreement with findings from the COSMOS2020 catalogue, except for an unrealistically large fraction of very young galaxies with very high specific star-formation rates. The application of appropriate priors is, however, sufficient to obtain reliable physical properties for those problematic objects. We present several areas for improvement for future Euclid data releases
Uncovering extraplanar gas in UGCA 250 with the Ultra-deep MHONGOOSE Survey
No full textInternational audienceWe use the neutral atomic hydrogen (H I ) observations of the edge-on galaxy UGCA 250, taken as part of the MeerKAT H I Observations of Nearby Galactic Objects-Observing Southern Emitters (MHONGOOSE) surv e y to inv estigate the amount, morphology, and kinematics of extraplanar gas. The combination of high column density sensitivity and high spatial resolution of the surv e y o v er a large field of view is ideal for studying the underlying physics go v erning the e xtraplanar gas. These data reveal nine additional detections within the field of view along with UGCA 250, with eight of them being within ∼200 km s -1 of the galaxy's systemic velocity. The galaxy seems to have a tail-like feature e xtending a way from it in the southern direction up to ∼41 kpc (in projection). We also detect a cloud at anomalous velocities, but we did not find any optical counterpart. We construct a detailed tilted ring model for this edge-on galaxy to gain a deeper understanding of the vertical structure of its neutral hydrogen. The model that best matches the data features a thick disc with a scale height of ∼3 ±1 kpc and an H I mass of about 15 per cent of the total H I mass. This extraplanar gas is detected for the first time in UGCA 250. Our analysis fa v ours a mixed origin for the extraplanar gas in UGCA 250, likely arising from a combination of internal stellar feedback and external tidal interactions.</div
VLTI/GRAVITY upper limit on near-infrared emission from the nearby 33 M⊙ black hole Gaia BH3
No full textInternational audienceContext. The recent astrometric discovery of the nearby (590 pc) massive (33 M⊙) dormant black hole candidate Gaia BH3 offers the possibility to angularly resolve the black hole from its companion star by using optical interferometry.Aims. Our aim is to detect emission in the near-infrared K band from the close-in environment of Gaia BH3 caused by accretion.Methods. Gaia BH3 was observed with the GRAVITY instrument using the four 8-meter Unit Telescopes of the VLT Interferometer. We searched for the signature of emission from the black hole in the interferometric data using the CANDID, PMOIRED, and exoGravity tools.Results. With a present separation of 18 mas, the Gaia BH3 system can be well resolved angularly by GRAVITY. We did not detect emission from the black hole at a contrast level of Δm = 6.8 mag with respect to the companion star, that is, fBH/f⋆ < 0.2%. This corresponds to an upper limit on the continuum flux density of fBH < 1.9 × 10−16 W m−2 μm−1 in the K band. In addition, we did not detect emission from the black hole in the hydrogen Brγ line.Conclusions. The non-detection of near-infrared emission from the black hole in Gaia BH3 indicates that its accretion of the giant star wind is presently occurring at most at a very low rate. This is consistent with the limit of fEdd < 4.9 × 10−7 derived previously on the Eddington ratio for an advection-dominated accretion flow. Deeper observations with GRAVITY may be able to detect the black hole as the companion star approaches periastron around 2030
Unveiling blazar synchrotron emission: a multiwavelength polarimetric study of HSP and LSP populations
No full textInternational audiencePolarimetric properties of blazars allow us to put constraints on the acceleration mechanisms that fuel their powerful jets. By studying the multiwavelength polarimetric behaviour of high synchrotron peaked (HSP) and low synchrotron peaked (LSP) blazars, we aim to explore differences in their emission mechanisms and magnetic field structure in the acceleration region. In this study, we take advantage of several X-ray polarisation observations of HSP by the IXPE, including four new observations of Mrk 501, and optical polarisation observations of LSP from RoboPol and many others. We find that the polarisation degree (PD) distribution of HSP in X-rays is systematically higher than in optical and mm-radio wavelengths, as reported in previous IXPE publications. The distribution of the X-ray electric vector position angles (PA) is centered around the jet axis with most of the observations consistent with zero difference within uncertainties. In fact, the distribution of the offset of the PA from the jet axis is consistent between the LSP and HSP populations (with PA measured in optical for the first, X-ray for the latter), suggesting a common magnetic field structure close to the acceleration region, in strong support of the emerging energy stratified picture of particle acceleration followed by energy loss in blazar jets
OntoPortal-Astro, a semantic artefact catalogue for astronomy
No full textInternational audienceThe astronomy communities are widely recognised as mature communities for their open science practices. However, while their data ecosystems are rather advanced and permit efficient data interoperability, there are still gaps between these ecosystems. Semantic artefacts (SAs) – e.g., ontologies, thesauri, vocabularies or metadata schemas – are a means to bridge that gap as they allow to semantically described the data and map the underlying concepts. The increasing use of SAs in astronomy presents challenges in description, selection, evaluation, trust, and mappings. The landscape remains fragmented, with SAs scattered across various registries in diverse formats and structures – not yet fully developed or encoded with rich semantic web standards like OWL or SKOS – and often with overlapping scopes. Enhancing data semantic interoperability requires common platforms to catalogue, align, and facilitate the sharing of FAIR (Findable, Accessible, Interoperable and Reusable) SAs. In the frame of the FAIR-IMPACT project, we prototyped a SA catalogue for astronomy, heliophysics and planetary sciences. This exercise resulted in improved vocabulary and ontology management in the communities, and is now paving the way for better interdisciplinary data discovery and reuse. This article presents current practices in our discipline, reviews candidate SAs for such a catalogue, presents driving use cases and the perspective of a real production service for the astronomy community based on the OntoPortal technology, that will be called OntoPortal-Astro
Discriminating scalar ultralight dark matter from quasi-monochromatic gravitational waves in LISA
No full textInternational audienceA scalar ultralight dark matter (ULDM) candidate would induce oscillatory motion of freely falling test masses via its coupling to Standard Model fields. Such oscillations would create an observable Doppler shift of light exchanged between the test masses, and in particular would be visible in space-based gravitational waves (GW) detectors, such as LISA. While this kind of detection has been proposed multiple times in the recent years, we numerically investigate if it is possible to extract a scalar ULDM signal in a space-based GW detector, and in particular how to differentiate such a signal from a GW signal. Using one year of realistic orbits for the LISA spacecrafts and Bayesian methods, we find that LISA will indeed be able to discriminate between the two signals
The Contribution of Turbulent Active Galactic Nucleus Coronae to the Diffuse Neutrino Flux
No full textInternational audienceActive galactic nuclei (AGN) can accelerate protons to energies of ∼10–100 TeV, with secondary production of high-energy neutrinos. If the acceleration is driven by magnetized turbulence, the main properties of the resulting proton and neutrino spectra can be deduced based on insights from particle-in-cell simulations of magnetized turbulence. We have previously shown that these properties are consistent with the TeV neutrino signal observed from the nearby active galaxy NGC 1068. In this work, we extend this result to a population study. We show that the produced neutrino flux depends mainly on the energetics of the corona—the relative fractions of X-ray, magnetic, and nonthermal proton energy—and on the spectral energy distribution of the AGN. We find that coronae with similar properties can explain neutrinos from the candidate AGN for which IceCube has reported an excess, albeit less significant than NGC 1068. Building on this framework, we show how the neutrino signal evolves with AGN luminosity, and use this AGN sequence to predict the diffuse neutrino flux from the extragalactic population, showing that it can account for the diffuse neutrino signal observed by IceCube in the ∼1–100 TeV energy range
Generation of zonal flows and impact on transport in competing drift waves and interchange turbulence
No full textInternational audienceThe generation and radial structure of zonal flows are studied in competing collisional drift waves and interchange turbulence using the reduced flux-driven nonlinear model Tokam1D. Zonal flows are generated in both the interchange dominated and adiabatic regimes with the former favoring radially structured flows and avalanche transport. The distance to the instability threshold proves to be key, with a more stable radial flow structure emerging near the threshold and increased energy stored in the flows for interchange turbulence. The avalanches are shown to perturb zonal flow structures in drift-wave turbulence and to reactivate them in the interchange regime. Finally, the ExB staircases with radially structured, stable in time zonal flows are proved beneficial for the overall confinement