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Integrated Study of Martian Dust: Detection of Local Dust Storms, Estimation of Vertical Distribution, and Surface Pressure Analysis Using OMEGA Observations
No full textInternational audienceUnderstanding the Martian dust cycle is essential for clarifying the atmospheric circulation and meteorological phenomena. Unlike Earth, Mars has a thin atmosphere primarily composed of CO2, where atmospheric dust plays a dominant role in regulating the energy balance and driving atmospheric motion. Among various dust-related phenomena, Local Dust Storms (LDS), defined as storms that span less than 1.6 × 106 km2 or last fewer than three Martian days (Cantor et al., 2001), are particularly important for studying localized dust lifting and its potential connection to regional or global dust events (Martin and Zurek, 1993; Cantor et al., 2001; Hinson and Wang, 2010; Wang and Richardson, 2015). However, due to their limited spatial extent and short lifetimes, LDS have remained challenging to detect and characterize comprehensively.In this study, we developed a method for identifying LDS using data from the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) imaging spectrometer onboard Mars Express (Bibring et al., 2004). Specifically, we used the strong CO₂ absorption band at 2.77 µm to retrieve dust optical depth. This band is sensitive to altitudes around 20–30 km and offers the critical advantage of being largely insensitive to surface reflectance properties. Applying this retrieval method to data from Martian Years (MY) 27 through 29, we detected 146 LDS events. Our statistical analysis revealed clear seasonal and diurnal patterns. LDS occurrences were most frequent during southern summer (Ls = 270°–360°), consistent with past findings that identify this season as conducive to dust activity (e.g., Smith, 2004; Montabone et al., 2015). However, we also observed an anomalously high frequency of LDS during northern summer in MY27 (Ls = 130°–150°), a period not typically associated with elevated dust activity. Furthermore, a noticeable increase in LDS activity was detected just before the onset of the Global Dust Storm (GDS) in MY28. Diurnally, LDS were most often observed near noon, implying that storm initiation may begin in the morning hours. Their spatial distribution varied significantly with season. During Ls = 0°–180°, LDS tended to be confined to specific regions such as Chryse Planitia and southern Acidalia. In contrast, during Ls = 180°–360°, LDS appeared more widely across mid-latitudes, with a notable absence in the northern high-latitude region (above 40°N). These results offer new insight into the role of LDS in the broader Martian dust cycle, particularly their potential influence on triggering regional or global events
Éditorial du dossier "Le handicap, une priorité pour toutes et tous"
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Modeling Light Signals Using Data from the First Pulsed Neutron Source Program at the DUNE Vertical Drift ColdBox Test Facility at CERN Neutrino Platform
No full textInternational audienceIn this paper, we present a first quantitative test of detected light signals produced in a pulsed neutron source run in a small vertical drift LArTPC at the CERN neutrino platform ColdBox test facility. The ColdBox cryostat, detectors, neutron sources, and particle interactions are modeled and simulated using Fluka. A good agreement is found in the detected number of photoelectrons, with values below 650 photoelectrons in both data and simulation, for all four X-ARAPUCA photodetectors on the cathode in the LArTPC. A time constant is also fitted from the neutron-beam-off light signal spectrum and found consistent between data and MC. Several important systematic effects are discussed and serve as guides for future runs at larger LArTPCs
Algorithmes quantiques pour les équations aux dérivées partielles : circuits quantiques et applications physiques
No full textCurrent classical simulations of physical phenomena face many limitations, particularly when dealing with complex systems such as turbulent fluids, plasmas or strongly correlated quantum materials. These simulations often struggle with high computational costs, limited scalability across multiple dimensions and time scales, and difficulties in capturing inherently non-linear or chaotic behaviors. Even with access to powerful high performance computing (HPC) resources, accurately resolving fine-scale dynamics or long time evolutions remains a significant challenge. The development of novel numerical methods is therefore essential for both academic research and industrial applications. Quantum computers emerge as novel numerical tools for studying such systems and solving the partial differential equations that model them. Thanks to the superposition and entanglement properties of qubits, digital computations can be performed in novel ways, offering promising theoretical speedups for certain problems. In this context, this thesis contributes to the development and understanding of quantum algorithms, ranging from the design of quantum circuits to the numerical solutions of partial and ordinary differential equations. First, efficient quantum circuits are presented for the implementation of crucial routines that are prevalent in quantum algorithms (multi-controlled operations, quantum state preparation, diagonal operations), and for a novel routine: the quantum Laplace transform. These routines limited the efficiency of quantum algorithms due to generic implementations that required complexities scaling exponentially with the number of qubits. Now, these tasks can be performed with tailored quantum circuits that leverage the structure of the physical problems. In the second part, quantum numerical schemes are introduced to address anisotropic transport equations and non-linear Hamiltonian ODEs. These schemes are composed of three steps (initialization, evolution, and measurement) and are based on high-ordered finite-difference and product formula approximations, also known as Trotterization. Efficient protocols to measure quantities of interest are presented, and a novel numerical analysis based on the vector norm instead of the generic operator norm is introduced, proving that the number of time-steps can be reduced by a factor that scales exponentially with the number of qubits while reaching similar accuracy. Additionally, non-linear Madelung transforms are studied to solve fluid equations on quantum computers. The various results of this thesis are illustrated with classical simulations of the quantum algorithms and simulations on real quantum hardware. This work lays the foundations for the practical simulations of classical physical systems on both current noisy-intermediate-scale quantum devices and future fault-tolerant quantum computers.Les simulations classiques actuelles des phénomènes physiques présentent de nombreuses limitations, en particulier lorsqu'il s'agit de systèmes complexes tels que les fluides turbulents, les plasmas ou les matériaux quantiques fortement corrélés. Ces simulations rencontrent souvent des difficultés liées à des coûts de calculs élevés, une mise à l'échelle limitée à travers plusieurs dimensions ou échelles temporelles, ainsi qu'à la complexité de capturer des dynamiques intrinsèquement non-linéaires ou chaotiques. Même avec l'accès à des ressources de calcul haute performance (HPC), la résolution précise des dynamiques à fine échelle ou des évolutions sur de longues périodes reste un défi majeur. Le développement de nouvelles méthodes numériques est donc essentiel, tant pour la recherche académique que pour les applications industrielles. Les ordinateurs quantiques émergent comme de nouveaux outils numériques pour l'étude de tels systèmes et la résolution des équations aux dérivées partielles qui les modélisent. Grâce aux propriétés de superposition et d'intrication des qubits, les calculs numériques peuvent être réalisés de manière inédite, offrant des avantages théoriques prometteurs pour certains problèmes. Dans ce contexte, cette thèse contribue au développement et à la compréhension des algorithmes quantiques, allant de la conception de circuits quantiques à la résolution numérique d'équations différentielles partielles et ordinaires. Dans une première partie, des circuits quantiques efficaces sont présentés pour l'implémentation de routines couramment utilisées dans les algorithmes quantiques (opérations multi-contrôlées, préparation d'états quantiques, opérations diagonales), ainsi que pour une nouvelle routine : la transformée de Laplace quantique. Ces routines limitaient l'efficacité des algorithmes quantiques en raison d'implémentations génériques dont la complexité croissait de manière exponentielle avec le nombre de qubits. Désormais, ces tâches peuvent être réalisées à l'aide de circuits quantiques adaptés qui exploitent la structure des problèmes physiques. Dans une seconde partie, des schémas numériques quantiques sont introduits pour résoudre des équations de transport anisotropes et des équations différentielles ordinaires hamiltoniennes non linéaires. Ces schémas se composent de trois étapes (initialisation, évolution et mesure) et reposent sur des approximations en différences finies d'ordre élevé et des formules de Trotterisation. Des protocoles efficaces pour mesurer des grandeurs d'intérêt sont présentés, et une nouvelle analyse numérique, basée sur la norme vectorielle plutôt que sur la norme d'opérateur générique, est introduite. Cette approche permet d'atteindre une précision donnée tout en réduisant le nombre de pas de temps par un facteur qui croît de manière exponentielle avec le nombre de qubits. De plus, une étude de différentes transformations de Madelung non linéaires est présentée afin de résoudre certaines équations fluides sur ordinateur quantique. Les différents résultats de cette thèse sont illustrés par des simulations classiques des algorithmes quantiques ainsi que par des simulations sur des processeurs quantiques actuels. Ce travail pose les bases de la simulation pratique de systèmes physiques classiques, aussi bien sur les dispositifs quantiques actuels de type NISQ (noisy intermediate-scale quantum) que sur les futurs ordinateurs quantiques tolérants aux erreurs
Conception d’une horloge optique à réseau transportable à base d’ytterbium pour application à la géodésie chronométrique
No full textThis thesis presents the design of an optical lattice clock at LTE, based on a new species for the lab: neutral 171Yb atoms. The clock is developed with a focus on transportability. The work includes the development of a vacuum system, laser cooling stages, and frequency stabilization techniques suitable for field deployment and compatible with remote frequency dissemination systems.Cette thèse présente la conception d'une horloge à réseau optique réalisée au sein du laboratoire LTE, basée sur une nouvelle espèce atomique pour l'équipe : l'atome neutre de 171Yb. Le développement de cette horloge a été mené avec une attention particulière portée à sa transportabilité. Les travaux incluent la mise en place d'un système à vide, des étapes de refroidissement laser, ainsi que des techniques de stabilisation en fréquence, le tout pensé pour une utilisation sur le terrain et compatible avec les systèmes de dissémination de fréquence à distance
The Galaxy Activity, Torus, and Outflow Survey (GATOS). VII. The 20–214 μm Imaging Atlas of Active Galactic Nuclei Using SOFIA
No full textInternational audienceWe present a 19.7–214 μ m imaging atlas of local (4–181 Mpc; median 43 Mpc) active galactic nuclei (AGN) observed with FORCAST and HAWC+ on board the SOFIA telescope with angular resolutions ~3 ″ –20 ″ . This atlas comprises 22 Seyferts (17 Type 2 and five Type 1) with a total of 69 images, 41 of which have not been previously published. The AGN span a range of luminosities of log 10 ( L bol [ erg s - 1 ] ) = [ 42 , 46 ] with a median of log 10 ( L bol [ erg s − 1 ] ) = 44.1 ± 1.0 . We provide the total fluxes of our sample using aperture photometry for point-source objects and a 2D Gaussian fitting for objects with extended host galaxy emission, which was used to estimate the unresolved nuclear component. Most galaxies in our sample are pointlike sources; however, four sources (Centaurus A, Circinus, NGC 1068, and NGC 4388) show extended emission in all wavelengths. The 30–40 μ m extended emission in NGC 4388 is coincident with the narrow-line region at PA ~ 50°, while the dusty extension at longer wavelengths arises from the host galaxy at PA ~ 90°. Our new observations allow us to construct the best-sampled parsec-scales (spectral energy distributions, SEDs) available between 30 and 500 μ m for a sample of nearby AGN. We estimate that the average peak wavelength of the nuclear SEDs is ~40 μ m in νF ν , which we associate with an unresolved extended dusty region heated by the AGN
Searching for HI around MHONGOOSE galaxies via spectral stacking
No full textInternational audienceThe observed star formation rates of galaxies in the Local Universe suggests that they are replenishing their gas reservoir across cosmic time. Cosmological simulations predict that this accretion of fresh gas can occur in a hot or a cold mode, yet the existence of low column density (∼10 17 cm −2 ) neutral atomic hydrogen (H I ) tracing the cold mode has not been unambiguously confirmed by observations. We present the application of unconstrained spectral stacking to attempt to detect the emission from this H I in the circumgalactic medium (CGM) and intergalactic medium (IGM) of six nearby star-forming galaxies from the MHONGOOSE sample for which full-depth observations are available. Our stacking procedure consists of a standard spectral stacking algorithm coupled with a one-dimensional spectral line finder designed to extract a reliable signal close to the noise level. In agreement with previous studies, we find that the amount of signal detected outside the H I disk is much smaller than implied by simulations. Furthermore, the column density limit that we achieve via stacking (∼10 17 cm −2 ) suggests that direct detection of the neutral CGM and IGM component might be challenging in the future, even with the next generation of radio telescopes
A new classification of ex situ and in situ Galactic globular clusters based on a method trained on Milky Way analogues in the TNG50 cosmological simulations
No full textInternational audienceWe present a novel method combining existing cosmological simulations and orbital integration to study the hierarchical assembly of globular cluster (GC) populations in the Milky Way (MW). Our method models the growth and evolution of GC populations across various galactic environments as well as the dynamical friction and mass loss experienced by these objects. This allowed us to follow the trajectory of ∼18 000 GCs over cosmic time in 198 MW-like galaxies from TNG50. This cosmological-scale tracking of the dynamics of in situ and ex situ GC populations with such a large statistical sample allowed us to confirm the presence of an overlap between the two populations in MW-like galaxies, occurring below an energy threshold of E < -0.7|E circ (r * hm )|, where E circ (r * hm ) is the energy of a circular orbit at the galaxy's stellar half-mass radius r * hm . Our results challenge the validity of current classification schemes commonly adopted in the literature, which ultimately fail to provide a clear separation between the two populations. Instead, they tend to isolate only a subset of the ex situ GCs. More precisely, we argue that it is highly unlikely to find in situ clusters at E > -0.7|E circ (r * hm )|, and that the real challenge lies in distinguishing the two populations below this energy threshold. In this context, we provide new predictions regarding the origins of the MW's GCs observed with Gaia, as well as a comparison with existing literature. Additionally, we highlight that even if ex situ clusters share a common origin, they inevitably lose their dynamical coherence in the E-L z space within MW-like galaxies. We observe a dispersion of GC groups as a function of E and L z , primarily driven by the evolution of the galactic potential over time and by dynamical friction, respectively.</div
The GECKOS survey : Identifying kinematic sub-structures in edge-on galaxies
No full textInternational audienceThe vertical evolution of galactic discs is governed by the sub-structures within them. Several of these features, including bulges and kinematically distinct discs, are best studied in edge-on galaxies, as the viewing angle allows the easier separation of component light. For this work, we examined the diversity of kinematic sub-structure present in the first 12 galaxies observed from the GECKOS survey, a VLT/MUSE large programme providing a systematic study of 36 edge-on Milky Way-mass disc galaxies. Employing the N GIST analysis pipeline, we derived the mean luminosity-weighted line-of-sight stellar velocity ( V ⋆ ), velocity dispersion ( σ ⋆ ), skew ( h 3 ), and kurtosis ( h 4 ) for the sample, and examined 2D maps and 1D line profiles. Common clear kinematic signatures were observed: all galaxies display h 3 – V ⋆ sign mismatches in the outer disc regions consistent with a (quasi-)axisymmetric, rotating disc of stars. After scrutinising visual morphologies, we found that the majority of this sample (8/12) possess boxy-peanut bulges and host the corresponding kinematic structure predicted for stellar bars viewed in projection. Inferences were made on the bar viewing angle with respect to the line of sight from the strength of these kinematic indicators; we found one galaxy whose bar is close to side-on with respect to the observer, and two that are close to end-on. Four galaxies exhibit strong evidence for the presence of nuclear discs, including central h 3 – V ⋆ profile anti-correlations, croissant-shaped central depressions in σ ⋆ maps, strong gradients in h 3 , and positive h 4 plateaus over the expected nuclear disc extent. The strength of the h 3 feature corresponds to the size of the nuclear disc, measured from the h 3 turnover radius, taking into account geometric effects. We can explain the features within the kinematic maps of the four unbarred galaxies via disc structure(s) alone. We do not find any need to invoke the existence of dispersion-dominated bulges in any of the sample galaxies. Obtaining the specialised data products for this paper and the broader GECKOS survey required significant development of existing integral field spectroscopic (IFS) analysis tools. Therefore, we also present the N GIST pipeline: a modern, sophisticated, and easy-to-use pipeline for the analysis of galaxy IFS data, and the key tool employed by the GECKOS survey for producing value-added data products. We conclude that the variety of kinematic sub-structures seen in GECKOS galaxies requires a contemporary view of galaxy morphology, expanding on the traditional view of galaxy structure, and uniting the kinematic complexity observed in the Milky Way with the extragalactic
Euclid preparation: LXXXI. The impact of nonparametric star formation histories on spatially resolved galaxy property estimation using synthetic Euclid images
No full textInternational audienceWe analyzed the spatially resolved and global star formation histories (SFHs) for a sample of 25 TNG50-SKIRT Atlas galaxies to assess the feasibility of reconstructing accurate SFHs from Euclid-like data. This study provides a proof of concept for extracting the spatially resolved SFHs of local galaxies with Euclid, highlighting the strengths and limitations of SFH modeling in the context of next-generation galaxy surveys. We used the spectral energy distribution (SED) fitting code Prospector to model both spatially resolved and global SFHs using parametric and nonparametric configurations. The input consisted of mock ultraviolet--near-infrared photometry derived from the TNG50 cosmological simulation and processed with the radiative transfer code SKIRT. We show that nonparametric SFHs provide a more effective approach to mitigating the outshining effect by recent star formation, offering improved accuracy in the determination of galaxy stellar properties. Also, we find that the nonparametric SFH model at resolved scales closely recovers the stellar mass formation times (within 0.1~dex) and the ground truth values from TNG50, with an absolute average bias of ~dex in stellar mass and ~dex in both specific star formation rate and mass-weighted age. In contrast, larger offsets are estimated for all stellar properties and formation times when using a simple -model SFH, at both resolved and global scales, highlighting its limitations. These results emphasize the critical role of nonparametric SFHs in both global and spatially resolved analyses, as they better capture the complex evolutionary pathways of galaxies and avoid the biases inherent in simple parametric models