Stellar feedback redistributes gas in galaxies, shaping their star formation histories and the structure of the interstellar medium (ISM). Most previous studies of feedback-driven gas flows have focused on edge-on galaxies or examined only some of the wavelengths in the electromagnetic spectrum, limiting the ability to trace the full star formation cycle. Here, we present a multi-wavelength...
We explore the internal dynamics and formation scenarii of the central regions of galaxies, by ways of Milky Way-like galaxy simulations. Using the SWIFT hydro+N-Body simulation code, we model the growth and evolution of Nuclear Stellar Discs (NSDs)/Nuclear Stellar Clusters (NSCs) under different physical recipes: with and without an initial gaseous disk & with and without stellar feedback...
Carbonaceous asteroids are considered to best preserve the early Solar System's mineralogical and molecular phases, but they have undergone transformation through space weathering and aqueous alteration. Sample-return missions like NASA’s OSIRIS-REx and JAXA’s Hayabusa2 have provided uncontaminated materials from asteroids Bennu and Ryugu, respectively, allowing for direct analysis. My study...
Gaia is a space mission from the European Space Agency (ESA) that was launched in 2013. Apart from the survey of stars, it is also highly valuable to study solar system objects (SSO) with high precision. Its latest data release in October 2023 includes 66 months of data on about 160,000 SSOs. Gaia’s precise measurements can reveal astrometric signals of binary asteroids, for example the...
A comprehensive analysis of Mercury's Low-Latitude Boundary Layer (LLBL) has been studied using MESSENGER observations from 11 March 2011 to 30 April 2015. LLBL events were classified into three distinct categories based on energy dispersion trends: increasing, decreasing, and unclear cases. The results indicate significant differences in plasma transport mechanisms, energy evolution, and...
Methane is the second most abundant component of Titan's atmosphere (~5% at the surface). The temperature and pressure enables liquid methane at the surface, forming lakes. In the atmosphere, methane can condense and form clouds, and rain. Titan clouds are monitored from Earth telescopes, but detailed images are scarce and come from the Cassini-Huygens mission that took place between 2004 and...
The next generation of galaxy surveys has the potential to significantly deepen our understanding of the Universe, though this potential hinges on our ability to rigorously address systematic uncertainties. This was previously beyond reach in field-based implicit likelihood cosmological inference frameworks. We aim at inferring the initial matter power spectrum after recombination to diagnose...
Cosmic voids are the largest objects emerging in the cosmic web, covering the majority of the volume of the Universe. They are a well-established probe to gather cosmological information from the large-scale structure, as well as interesting regions to study how an underdense environment affects the behaviour of astrophysical objects. Unfortunately, identifying voids from galaxy surveys is a...
Since 1995, more than 5,000 exoplanets have been discovered, largely thanks to the transit detection method. However, most exoplanetary systems do not exhibit transits, limiting this method to detecting only about 10% of existing exoplanets. To gain a more comprehensive understanding of exoplanet populations, alternative detection approaches are needed.
One particularly intriguing trend in...
In the Solar system, planetary radio emission is strongly correlated to incident magnetic power (similar to the Poytning flux). To test this observational law in other stellar systems, and use it to determine interesting observation targets, we need to get an estimation of the stellar magnetic field of the host stars.
Here, we work on the compilation of measures of stellar magnetic fields...
Galaxy clusters are the most massive gravitationally bound structures in the universe. They are mostly made of dark matter, inducing a deep gravitational potential well, in which baryons are accreted from the cosmic web and heated up to millions of Kelvins, we call it the Intra-Cluster Medium (ICM). Lots of complex and linked physics processes happen in the ICM, one of them is turbulence. In...
The timing argument (TA) associates the motion of the Milky Way (MW) and Andromeda Galaxy (M31) to their internal gravity, and aims to find the total mass of the Local Group (LG). However, the classical TA always overestimates the LG mass, presumably because it ignores the hierarchical scenario and other interactions such as that with the Large Magellanic Cloud (LMC). This work focuses on the...
Primordial black holes could constitute part or all of dark matter but they require large inhomogeneities to form in the early universe. These inhomogeneities can strongly backreact on the large scale dynamics of the universe. Stochastic inflation provides a way of studying this backreaction and getting an estimation of the abundance of primordial black holes. Because stochastic inflation...
Star formation plays a crucial role in shaping its environment and is central to the evolution of planets, the interstellar medium, galaxies, and the universe as a whole. To bridge the gap between galactic-scale processes—where the initial conditions for star formation are set—and the formation of individual stars, we conducted state-of-the-art numerical simulations of a portion of a galaxy....
The study of X-ray and extreme ultraviolet (together, XUV) emission from stars has experienced a renewed interest in recent years. The focus has shifted from the study of stellar physics towards the effects of these emissions on exoplanet atmospheres, and is now part of a bigger field concerned with star-planet interactions. Particular attention is given to M dwarfs, low-mass, cool stars that...
Oceanic tides play a fundamental role in the evolutionary dynamics of some orbital systems, influencing energy dissipation significantly. Their detailed understanding and precise quantification provide answers ranging from the fate of an orbit to the history of a planet. Achieving this understanding entails a stepwise incorporation of physical parameters, while accurate quantification demands...
The Weak Lensing Shear is a powerful probe of cosmology. Along with Galaxy Clustering and the cross-correlation of those two probes, it gives the most effective set of Data, used by cosmological observations, to constrain cosmological parameters and study the large-scale structure of the universe. Yet, the nature of the Dark Energy, representing around 68% of the energy content of our current...
Next-generation large galaxy surveys, such as Euclid and DESI, will provide unprecedented datasets to tackle fundamental cosmological questions: What is the nature of dark matter? What drives the accelerated expansion of the universe? Exploring these mysteries requires the analysis of the three-dimensional distribution of large-scale structures, collectively known as the cosmic web, which form...
Solar flares are fast increases in the X-ray flux. When they reach Earth, these energetic radiations ionize the atmosphere, increasing thus the electron density down to the lowest D-region of the ionosphere (60km). This, in turn, causes a greater absorption of the HF waves, which are frequency bands used by several actors like civil aviation and emergency services. Real-time detection of solar...
The Sun is a fascinating physics laboratory where periodically phases of strong activity and of quietness alternate during a eleven years cycle. The phase of strong activity is linked to the appearance of sunspots. These sunspots are cooled down regions of the sun and are the place of energetic events called solar eruptions.
Solar eruptions are major events corresponding either to solar...
La physique solaire a encore beaucoup de défis à relever, tels que l'origine de son cycle solaire de 11 ans, la formation de taches solaires et leur rôle sur l'établissement du cycle magnétique, ou le déclenchement des éruptions solaires et le chauffage de son atmosphère étendue. Pour étudier ces questions difficiles il est nécessaire de développer de nouveaux outils afin de les traiter comme...
The largest structures in the Universe to fully overcome cosmic expansion by their gravitational attraction are galaxy clusters. When they are still in their formation phase, they are called galaxy protoclusters and are expected to play an important role in star formation, giving rise to an epoch called the Cosmic Noon (cosmological redshift $z \sim 2-3$). My goal is to find precise...
The James Webb Space Telescope (JWST) has discovered a very surprising type of galaxy, a large population of compact red objects known as Little Red Dots (LRDs). To this day, this population remains misunderstood because of two opposing explanations: either they can be compact dusty star forming galaxies or Active Galactic Nucleus (AGNs). In both cases, the physics involved is very extreme,...
MOONS/ Multi Object Optical and Near-infrared Spectrograph is a new fibre fed spectrograph that will be installed at the ESO’s/ European Southern Observatory’s VLT/Very Large Telescope at La Paranal, Chile. MOONS which will operate from 6000A to 18000A wavelength range will have very high multiplex of 1000 fibres and will use the full 25 arcminutes field of view of 8m mirror VLT and will make...
The solar convective envelope generates, by dynamo effect, a surface magnetic field whose strength evolves on an 11-year cycle, with a change in polarity at the end of each cycle. A similar magnetic variability exists in other solar-type stars, influencing their dynamics. Furthermore, solar-like oscillators experience acoustic modes whose properties, such as their frequency, amplitude and...
Résumé:
Du fait de sa masse et de son abondance, l’hélium joue un rôle fondamental dans de nombreux processus astrophysiques. La compréhension des phénomènes physiques qui lui sont associés ainsi que la détermination de son abondance ont des répercussions dans des domaines aussi variés que la cosmologie, la modélisation stellaire ou l'étude du vent solaire. Si des caractérisations des...
Space weathering is the physical and chemical alteration of planetary surfaces caused by exposure to the space environment and specifically to the solar wind and to micrometeoroid impacts. It is currently the main process affecting the surface of Mercury.
Whereas on most of the surface space weathering appears to have reached saturation, the process is still ongoing in the youngest...
M-type stars, the most common in the universe, are a major focus for surveys because they are well-suited for detecting low-mass planets in the habitable zone. Despite their importance in the formation and evolution of low-mass planets, little is known about giant planets (GPs) in M star systems. Detecting long period GPs is difficult with transit methods and challenging with radial velocities...
We compute by means of post-Newtonian (PN) methods the innermost stable circular orbit of comparable-mass compact binaries. Two methods are used with equivalent results: equations of motion in harmonic coordinates and Hamiltonian formalism in ADM coordinates.
The suprathermal electrons in the solar wind are categorized in two different
populations. The halo is nearly isotropic while the strahl is highly anisotropic.
Following previous studies, we characterize the strahl by its pitch angle width.
We aim at finding correlations between this quantity and local plasma or mag-
netic field parameters, and to compare these correlations with prediction...
The Quasi-Thermal Noise (QTN) spectroscopy is an efficient tool to study, in the frequency domain, the fluctuations due to the thermal motion of the charged particles in a plasma that surrounds a passive antenna. This noise is ubiquitous, and most of the time, is dominant around the electronic plasma frequency. The voltage power spectrum of the electrostatic fluctuations depends on the...
The study of Martian ices provides key information into the formation mechanisms of gullies on Mars. Using infrared spectroscopy data from CRISM (Mars Reconnaissance Orbiter, NASA), this work focuses on seasonal CO2 ice deposits near Mars' poles, with particular attention to Sisyphi Cavi, where active gullies are observed. The properties of CO2 ice are characterized by evaluating its...
Mars’ surface is currently one of the environments in the solar system, where the research about prebiotic chemistry is the more active, because of the possibility of a past biologic activity considering Mars gathered the conditions required for the emergence of life at the time it arose on Earth [1].
In this context, a gas chromatograph mass spectrometers (GCMS) instrument was sent to Mars...
Cold dark matter is typically modelled as a collisionless and self-gravitating fluid with negligible velocity dispersion and can be thought of as a 2D (3D) sheet of particles in 4D (6D) phase-space whose topology evolves as per the Lagrangian equations of motion of particles. The collapse of dark matter particles in the neighborhood of an initial overdensity into points of singularity, i.e....
The last and unique measurement of the CMB blackbody spectrum was made by COBE-FIRAS in 1991. However, deviations from the perfect blackbody spectrum serve as a probe of the thermal history of the universe. To test the technology and feasibility of a space mission aimed at measuring these so-called spectral distortions, the balloon-borne mission BISOU (Balloon Interferometer for Spectral...
A presentation on adaptive optics, how it can be used in microscopy, the main differences and difficulties when compared to astronomical applications. I will then give some details on my use case of clarified rat’s brain imagery.
Optical interferometry enables levels of resolution beyond the capabilities of current direct imaging telescopes by coherently combining light from multiple apertures. When applied to a single telescope, it enhances resolution up to the diffraction limit of the telescope, helps to mitigate the effects of atmospheric turbulence and enables spectro-imaging.
Considering these advantages, my talk...
The search for alternative theories of gravity is motivated by several considerations, such as Dark Energy, or the existence of singularities in General Relativity. A general subclass of modified gravity theories are scalar-tensor theories, which have been developed in the last decades. It is rather interesting to search for observables that could constrain those theories. Black Holes are...
The Epoch of Reionisation marks the transition between the end of the cosmic dark ages and the beginning of the universe as we know it today. During this time the radiation from the first stars and galaxies ionised the neutral hydrogen around them, fundamentally transforming the universe. The EoR is one of the last major phases of cosmic evolution that remains mostly unexplored as no direct...
In the three-body problem with two equal small masses, the Lagrange equilibrium is well-known. But what if we start inclining the small masses' orbits? We find numerical evidence of a family of quasi-periodic orbits emerging from the Lagrange equilibrium. We then draw links to the restricted problem, as well as the P12 family in the case of equal masses.
CN-bearing constituents in refractory organic residues have been reported across various regions of the Solar System, from the moons of the giant planets to the dark refractory material observed on some comets and in rare ultracarbonaceous micrometeorites recovered on Earth. These compounds form and evolve through thermal, photochemical, and irradiation-driven chemical pathways. Consequently,...
Context : Stars are formed in the neutral regions of a Galaxy. However, in the Milky Way, the neutral and ionised regions represent almost the same volume. To have a better understanding of the star formation, we then need to understand which phenomena are responsible of the ionisation in the Milky Way. The common view is that the star radiation is the phenomenon which creates ionized regions....
Despite the tremendous number of exoplanets detected, planet-forming scenarios are not yet able to fully explain the large diversity of planets. They form in protoplanetary disks, by accreting gas and dust in their surroundings. It is thus necessary to study the composition of disks, especially the Carbon-to-Oxygen ratio (C/O), to better constrain planet formation. In this context, the James...
