Radio interferometry is a great tool to study Jupiter’s magnetic field, and NenuFAR provides quality low-frequencies observation of it from 10 to 85 MHz. As we expect star-planet interactions from gas giants near to their star to be visible in this range of frequencies, we try to detect them using radio imaging. This should provide useful information and constraints on these planets’ magnetic...
In a famous anagram, Newton wrote that the laws of nature are described by differential equations. However, these equations are not solvable in the general case, in the sense that their solutions cannot be expressed through elementary functions. Stemming from this observation, the theory of dynamical systems aims to determine not the exact state of a system over time, but rather the...
We present methodological advances to perform implicit likelihood inference of cosmology from arbitrarily complex models of cosmological surveys, while efficiently and extensively checking for systematics. This novel approach makes it possible to fully utilise our prior theoretical understanding of the initial matter power spectrum after inflation, in order to investigate the effects of known...
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...
During the last 15 years, our knowledge about the atmosphere of Venus has
expanded greatly, mainly due to the contribution of two dedicated
orbiters: Venus Express from ESA (2006-2014) and Akatsuki from JAXA
(2015-present). Both missions included a comprehensive payload which
enabled them to measure key parameters about the atmosphere from the
surface to the topmost layers. Among their...
The Event Horizon Telescope (EHT) collaboration released in 2019 the first horizon-scale images of the supermassive black hole M87*, dominated by a bright, unresolved ring. General relativity (GR) predicts that embedded whitin this images lie observable, thin, ring-shaped features produced by photons on extremely bent orbits: the "photon rings".
In a parametric framework of GR, the idea of...
The study of supernovae is an area of great interest in astrophysics. After their explosion, the supernova remnant (SNR) goes through different phases, dispersing its energy into the interstellar medium (Truelove & McKee 1999). At the end of its evolution, the shock behaves like a Taylor-Sedov blast wave. It is during this phase that the SNR may collide with other objects, such as molecular...
NOIRE (Nanosatellite pour un Observatoire Interferometrique Radio dans l’Espace) is an instrumental concept study. NOIRE aims to ba a very low frequency observatory. It will be an interferometer composed of a swarm of about 50 satellites. This instrument will enable to observe various objects and phenomena mostly unknown. Many scientific topics can be covered by NOIRE. This new type of...
SPHERE has been a high-contrast instrument on sky at the Very Large Telescope since 2014. It makes infrared images of young giant planets, circumstellar disks, and characterizes them by spectroscopy and polarimetry. The next upgrade of SPHERE aims at improving the exoplanet detection capabilities, in particular closer to the star. To achieve this goal, the adaptive optics system will be...
The projection factor, or p-factor, is a way to link the observed radial velocity of the atmosphere of the star to the velocity of the photosphere. It was introduced in the context of the Baade-Wesslink technique, to determine distances of pulsating stars. However, after almost a century of using the method and of efforts put in the calibration of this factor, results still seem to be...
Stellar magnetism still remains poorly understood : there is a huge variety of topology and magnetic phenomena which need to be characterized regarding the different stellar physical parameters such as the Rossby number.
The resulting magnetic activity is here use as a observable to improve our understanding of spot characteristics (area, lifetime...) and link these properties to the dynamo...
Understanding the presence, characteristics, and origin of water within the inner solar system can be enhanced by analyzing the properties (composition, dynamics) of ices present on terrestrial planets such as Mars and Mercury. This analysis, conducted through infrared spectroscopy, relies on data collected by instruments such as CRISM (Compact Reconnaissance Imaging Spectrometer for Mars)...
The emergence of constellations of CubeSats provides a new paradigm in the observation of planetary bodies such as the Earth, Moon or Mars. The desire to observe planetary atmospheres in near-real time highlights the need for new miniaturized instruments with sufficient spectral resolution to meet scientific requirements. The main goal of this presentation is to describe the design of a...
Studying Jovian low-frequency magnetospheric radio-emissions (≤40 MHz) allows to remotely probe their generation mechanism (especially the electron Cyclotron Maser – ECM) and the acceleration processes of electrons that power it. Those emissions have different time scales : from milliseconds (fast drifting radio bursts) to hours, and are mainly polarized elliptically (both circular and linear...
Since the commissioning of the NeoNarval instrument at TBL in 2019, concerns have been raised regarding the quality of results in polarimetry and precision in velocimetry. Data from NeoNarval fails to reproduce the 10% magnetic population in OB stars as obtained by its predecessor Narval among other instruments, and under-reports the field strength of well-studied magnetic stars....
Titan, the largest moon on Saturn, is the only moon in the Solar System to have a substantial atmosphere. It is also the only body besides Earth to have a liquid stable at its surface. For Titan, this liquid is composed of hydrocarbons, mainly methane, forming lakes and seas at the surface. The knowledge we have on Titan is based on observations from Earth, and from space missions, especially...
In the coming years, space probes will be sent to the surface of ocean worlds of the solar system such as Titan, Europa and Enceladus to characterize their habitability and search for traces of life. In particular, the Dragonfly mission which was confirmed in June 2019 is expected to launch in 2028 and to land on Titan in 2034.
My thesis is intended to contribute to three main objectives in...
The QUIJOTE MFI instrument (2012-2018) observed the sky at four frequency bands, namely 11, 13, 17 and 19Ghz, at 1 degree angular resolution. We can use the full database of MFI observations to characterize the correlation properties of the atmospheric signal in those frequency bands. This information will be useful to improve the current sky models at these frequencies, and could be used in...
Since their discovery about 30 years ago, observations of Trans-Neptunian Objects (TNOs) have been limited. These small icy bodies orbiting beyond Neptune were observed in the 0.5 to 2.5 µm range, where only bands of water and methanol ice could be detected and identified on non-dwarf planets (diameter < 800 km). In autumn 2022, a large JWST program began observing 54 TNOs, in the 0.7 to 5.1...
Since gas has recently been discovered in debris disks, the current model of planetary accretion and
evolution doesn't take this gas into account.
However, planets have already been discovered in debris disks with significant amounts of gas (e.g.
Beta pic), and models predict that this gas can be regenerated by collisions for 100 Myr, 10 times
more than in protoplanetary disks.
Because of...
The study focuses on electromagnetic waves radiated by the Langmuir wave turbulence generated by electron beams in the solar wind and corona during type III solar radio bursts. The waveforms used for analysis are provided by 2D/3V large-scale and long-term Particle-In-Cell simulations. They allow us to highlight different nonlinear interaction processes between waves, such as the...
The D-layer is the lowest layer of the Earth’s ionosphere, situated between 60 and 90 km. It is also the least known, as it is both too high for balloons and too low for satellites. However, it is a highly variable layer, which is perturbed by a variety of external sources: the Sun, electron precipitations from the radiation belts, gamma rays from supernovae, lightning strokes…. In the context...
The endless quest for dark matter could end with the discovery of primoridal black holes, object which form from the collapse of large inhomogeneities in the very early universe. Stochastic inflation provides a way of studying the backreaction of these large inhomogeneities and estimating the number of primordial black holes. Because stochastic inflation focuses on large scales, a separate...
The distribution of matter in the Universe is a powerful probe of cosmology. Measuring the efficiency with which gravity produces clusters against expanding Universe is the key to understanding, e.g. the equation of state of dark energy. Numerous projects aim at measuring the matter distribution across time in the Universe but no observable gives the perfect figure of this distribution...
Interstellar dust is about one percent of the mass of the interstellar medium. However, its presence significantly impacts stellar formation scenarios and observations in the visible, the infrared and the sub-mm, e.g. via the dust grains opacity, the surface chemistry, the coupling with the gas and the magnetic field, and the formation of planetary cores.
We are currently working on...
We report detection of the low frequency carbon radio recombination lines (RRLs) towards several galactic radio sources using the NenuFAR array. Based at Nançay Radio astronomy station, NenuFAR (New Extension in Nançay Upgrading LOFAR) is a LOFAR extension and SKA precursor that can detect Carbon atoms at quantum numbers between n = 400 and n = 850, thanks to its frequency range spanning from...
On Titan, methane is at the origin of all characteristics of the climate and the prebiotic chemistry that take place there. Methane and minor gases from photochemistry, produce clouds and precipitation that sculpt the satellite's landscape. Despite the many observations made by Cassini and Huygens, we still have a limited understanding of the couplings between the different cycles taking place...
In Titan, the two major gases nitrogen (N2) and methane (CH4) are ionized and/or photolyzed at high altitudes by the sunlight and the energetic particles from Saturn's magnetosphere, resulting in rich atmospheric chemistry and a wide variety of carbon and nitrogen-bearing atmospheric compounds. In the present work, we focus on studying the vertical profiles of trace species in the lower...
In order to reach a greater sensitivity, future CMB missions will need to have their focal plane to be cooled down to 100 mK typically. This will require a 2 µW cooling power delivered in a continuous and stable way. The current cooling technologies do not meet these requirements anymore. To achieve those goals, a Closed-Cycle Dilution Refrigerator is in development, using a mixture of 3He and...
In the case of an optical link with a LEO satellite, it is crucial to maximize the duration of the downlink,
even at low elevations, in order to transfer the largest amount of data possible at each pass. However, in
this context, amplitude fluctuations (or scintillation) are challenging the operation of Adaptive Optics
(AO) systems, starting with their wavefront sensing subsystems.
Indeed,...
Galaxy clusters are a powerful cosmological probe: they track the most recent evolution of large scale structure and therefore are fundamental for testing the cosmological model in the recent Universe. To compare the observations of galaxy clusters with theoretical predictions and thus constrain the cosmological parameters of the underlying model, precise knowledge of cluster masses and...
Galaxy clusters are the most massive gravitationally bound structures in the Universe. They lie at the nodes of the cosmic web and are connected to each others by cosmic filaments. These objects are mostly made of dark matter which generates a gravitational potential well in which cosmic gas is trapped and heated, we call it the Intra-Cluster Medium (ICM). Assuming hydrostatic equilibrium,...
The gravitational wave (GW) spectrum is a vast frontier, teeming with diverse sources and spanning a wide range of frequencies. The groundbreaking work of LIGO/Virgo in the kHz regime has unveiled approximately 100 compact binary mergers, with ongoing observations in its O4 run promising new and intriguing detections. In the nHz band, pulsar timing arrays (PTAs) are diligently exploring the...
Gamma-Ray Bursts (GRB) are the most luminous explosions in the Universe. These intense flashes of gamma rays are either created by the collapse of very massive stars, or the merging of two compact objects - namely two neutron stars. The event of the 17th August 2017, as the first joint observation of a gamma-ray burst electromagnetic signal along with its gravitational wave counterpart, opened...
Primitive asteroids are remnants of the early stage of the Solar System evolution and may have preserved the mineralogical and molecular phases formed during this period.
In 2020, the Hayabusa2 mission of JAXA brought back to Earth, samples from the C-type asteroid Ryugu, a primitive near-Earth object, collected at two different locations and depths. The samples are now preserved and...
Extrasolar comets – or exocomets – are icy bodies placed on elliptical orbits which sublimate when they reach their periastron, producing extensive clouds of dust and gas – the so-called ‘cometary tails’. The most famous star known to harbor such objects is Beta Pictoris, a young (20 Myr) A-type star, for which transiting comets are detected daily using absorption spectroscopy.
However,...
Ultra high energy (UHE) cosmic rays, with energies above $10^{17}$ eV, can provide us key information on the most extreme processes in the Universe. When reaching the Earth, UHE cosmic rays penetrate the atmosphere and interact with air molecules, inducing a cascade of secondary particles, a so-called extensive air shower (EAS). The electromagnetic part of this cascade is mainly responsible...
It is well established that the paradigm of cosmological inflation is the correct framework for understanding the physics of the very first moments of our universe. It states that the universe went through a short phase of accelerated expansion in which the microscopic quantum fluctuations of its matter content were stretched to macroscopic scales, becoming the seed for all the observed...
My PhD project aims at improving the modelling of the Cosmic Dawn (z~25 to 10) and the Epoch of Reionization (z~10 to 6), periods in the history of the Universe that corresponds to the birth of the very first galaxies, and at developing novel methods for extracting model parameters from current and future 21cm observations by e.g. NenuFAR/LOFAR/HERA/SKA. To do so, I present LoReLi, a public...
Examining the rotational dynamics of an object can offer clues about the nature and properties of its interior. Our knowledge of Venus' internal structure is currently limited, in particular for its core whose size still lacks meaningful constraints, and whose state (liquid or solid) is unknown.
The variations of orientation of a planet are usually modeled as a rotation about a spin axis,...
High-resolution spectroscopy (HRS) enables the unprecedented atmospheric characterization of transiting exoplanets. However, conducting these ground-based observations requires careful data processing and analysis to eliminate the Earth's atmospheric contribution and the signature from the background host star.
In this presentation, I will introduce the techniques currently employed by the...
Observations made in recent years by the Kepler, Hubble, Spitzer and James Webb space telescopes have revealed the presence of an atmosphere around the temperate exoplanet K2-18b. According to the latest JWST observations, this H2-rich atmosphere contains significant proportions of carbon-bearing molecules such as CO2 and CH4. The detection of such molecules is extremely interesting in the...
Over the past few years, the JWST has made some remarkable discoveries. The JWST UNCOVER program, which made observations through the lensing cluster A2744, has led to the discovery of 16 galaxy candidates at redshifts between 9 and 11, and three candidates in the range 11 < z < 13. Detailed studies of these candidates show a rapid evolution of the mass-luminosity relation and the UV continuum...
Due to their sizes and postions, at the nodes of the cosmic web, galaxy clusters are particularly suited to study the mechanisms of baryon accretion throughout the large scale structures of the Universe. Filaments connected to clusters are crucial environments in this process, where baryons heat and interact, while being funnelled towards the clusters’ deep gravitational potentials. Galaxy...
Direct imaging of exoplanets will facilitate the search for habitable worlds by enabling the generalized characterization of their atmospheres. High-contrast imaging instruments equipped with coronagraphs suppress starlight, allowing the detection of faint exoplanetary companions. However, optical aberrations introduce starlight residuals (speckles) that hinder the detection performance in the...
It is yet to be understood what controls the star formation activity in high-redshift galaxy clusters. One recently proposed mechanism is that galaxy clusters can remain star-forming when fed by infalling groups and star-forming galaxies from large-scale structures surrounding them. Using the COSMOS2020 catalog that has half a million galaxies with high accuracy ($\sigma_{\Delta z /1+z} \sim...
Advancing cosmological parameter inference with reduced uncertainties is a vibrant area of research, especially with the wealth of data from next-generation surveys like Euclid, DESI, and the Vera Rubin Observatory. This talk focuses on Simulation-Based Inference (SBI), utilizing summary statistics such as the Power Spectrum P(k) and Bispectrum B(k). However, these summaries fail to fully...
This conference presentation delves into recent advancements in understanding the formation and evolution of Mars' moons, Phobos and Deimos. Building upon Bagheri et al.'s 2021 hypothesis suggesting the dislocation of a larger progenitor as the origin of these moons, the study by Hyodo et al. in 2022 challenges this idea. Hyodo et al. argue that under reasonable assumptions about the...
The Mars Express mission has been orbiting Mars since 2004, and it has acquired several observations of Phobos which were never published in the literature. We have analyzed resolved images of Phobos, available at the ESA Planetary Science archive, acquired between 2004 and 2022 by the High Resolution Stereo Camera (HRSC) on board the Mars Express spacecraft. We used both data acquired with...
Le climat et la météorologie de la planète Mars que nous connaissons aujourd'hui sont contrôlés par la présence d'aérosols minéraux soulevés par les vents qui créent de véritables tempêtes de poussières. Ces tempêtes peuvent être locales, régionales, et même certaines années globales. Dans ce dernier cas la quasi-totalité de la planète est alors cachée sous une épaisse couche de poussière....
During this talk, I will be discussing our findings on the mass-metallicity relation (MZ) in low-mass galaxies. Our sample consists of eight galaxies at a redshift of 7, which we identified in the JWST/NIRSpec data of the lensing cluster Abell 2744 as part of the JWST Cycle 1 program, UNCOVER. By combining ultra-deep NIRSpec observations with the strong gravitational lensing boost of Abell...
