The TRAPPIST-1 (T-1) planets are among the most promising candidates for the first detailed study of temperate terrestrial exoplanets with the James Webb Space Telescope (JWST). CEA is leading a guaranteed-time observation (GTO) program that is dedicated to the observation of 5 occultations of T-1b with the Mid-Infrared Instrument (MIRI) at 12.8 μm (ID: 1279), paired with a similar program at...
The development of satellite swarm technology offers new possibilities for space studies and comes with new challenges. Among them is the need of knowledge on the swarm topology and attitude, especially in the context of space based radio interferometry. This paper presents an algorithm that recovers the absolute swarm attitude without the help of external systems such as GNSS (Global...
Super-Eddington accretion is one scenario that may explain the rapid assembly of ∼ $10^9\,\rm M_\odot$ supermassive black holes (BHs) within the first billion year of the Universe. This critical regime is associated with radiatively inefficient accretion and accompanied by powerful outflows in the form of winds and jets. By means of hydrodynamical simulations of BH evolution in an isolated...
Adaptive optics (AO) corrected image restoration is particularly difficult, suffering from the lack of knowledge on the point spread function (PSF) in addition to usual difficulties. An efficient approach is to marginalize the object out of the problem and to estimate the PSF and (object and noise) hyperparameters only, before deconvolving the object using these estimations. Recent works have...
The study of CM chondrites allows to obtain information from the first steps of the Solar System history and so better understand the origin of the organic matter. The aim of this study is to determine how the organic compounds structure varies and how they are related to the mineral phases depending on the hydrothermal alteration of the chondrites.
I will present Time Of Flight Secondary Ion...
Understanding where the magnetic reconnection occurs at the Earth’s magnetopause is one of the important remaining questions about this phenomena. Since the last decades various models predicting the position of the X-line have been made. These models largely depend on the orientation of the magnetic field in the magnetosheath close to the magnetopause, such as the Maximum Magnetic Shear model...
In recent years, the interest in high-resolution UV spectropolarimetry in space has greatly increased. Space mission projects such as Arago (ESA) and Pollux on LUVOIR (NASA) are planned to launch in the 2030-2040 decades. UV spectropolarimetric observations in space will allow the study of stars, exoplanets, and their environments, especially stellar magnetic fields. Existing ground-based high...
Understanding the atmospheric circulation, radiative transfer, and atmospheric chemistry of exoplanets is crucial to more accurately characterize these objects. In particular, Hot Jupiters are the most observed type of exoplanets. In the last decade, observing efforts have been made to begin the atmospheric characterization of these objects, in parallel to modeling efforts to understand these...
Galaxy clusters are the most massive gravitationally bound objects in the Universe, and therefore contain an extraordinary amount of information for both cosmology and astrophysics. These are formed by gravitational collapse of dark matter and baryons from primordial density fluctuations. They then continue to accrete matter throughout their history, preferentially through cosmic filaments...
With the new generations of surveys, in astrophysics and cosmology, datasets available to the community become more complex. It is often stated that surveys such as Euclid or LSST will generate a volume of data which needs new methods of analysis. The increase in data volume generally implies more complexity which is translated into an increase of the dimensionality of the parameter space to...
Long gamma-ray bursts (LGRBs) are unique tools to probe first galaxies. They are associated with massive stars and their bright afterglows can be used as powerful background sources capable of unveiling the gas along their line of sight. Afterglow spectroscopy allows detailed studies of the properties of the interstellar medium (ISM) of star-forming galaxies up to the highest redshift....
This subject is about the astrophysics of the interstellar medium. In this presentation I will outline the Euclid mission and the relevance of the study of the Diffuse Galactic Light (DGL) in its context.
The following questions will be answered :
What is Euclic ? How does an interstellar medium study could have an impact on cosmological studies ? What is the Diffuse Galactic Light and its...
The generation of the slow solar wind is still an open problem of heliophysics. One of the existing theories to explain the observed properties of the slow wind is based on the "interchange reconnection": plasma elements, confined low in the solar atmosphere in closed magnetic field (both fieldline footpoints rooted on the photosphere), are dynamically released into open field (one fieldline...
Methanol was detected on Centaur Pholus and on Trans-Neptunian Objects (TNOs) 2002 VE95 and Arrokoth through direct observations of its NIR bands [1,2]. Methanol is commonly found alongside water ice, which is the most abundant species detected on the surface of TNOs [3]. TNOs are believed to have preserved the physico-chemical properties of the first stages of formation of the outer Solar...
Since the first detection of extrasolar planet around Main Sequence star in 1995, about 1000 exoplanets have been detected thanks to the radial velocity (RV) method. Thanks to the increasing monitoring time up to 30 years long-period giant planet with orbital properties close to the giant planets of the solar system can now be, in principle, detected, and recent studies have determined the...
Our Galaxy, the Milky Way, is a collection of hundreds of billions stars, gas and dust bound together by gravity. Reconstructing how all the stellar components of the Galaxy formed and assembled over time, by studying the properties of the stars which make it, is the aim of Galactic archeology. In these last years, thanks to the launch of the ESA Gaia astrometric mission, in 2013, and the...
In some high latitude craters, intriguing moraines are interpreted to have been deposited by CO2 ice glaciers, essentially frozen from when the local climate was colder (i.e., when Mars obliquity was low) [1]. This scenario has been little studied, but it suggests that the atmosphere could totally collapse into CO2 glaciers, leaving behind a residual atmosphere of only Argon and N2, but 20...
The final step of the life of a massive star is its collapse and explosion creating a supernova. During the collapse phase, several phenomena happen in the core of the star before the observed explosion. One of these phenomena is the development of instabilities. The collapse creates a shock wave that becomes stationary ∼150 km away from the surface of the proto-neutron star (PNS). All the...
The magnetopause boundary seems to escape the general classification of discontinuities since it mixes characteristics of shocks (magnetic field magnitude increase) and those typical for the rotational discontinuities (magnetic rotation), whereas it is very often described as a tangential discontinuity. As, the main issue is the amount of matter/momentum/energy from the solar wind and entering...
Primitive asteroids within the solar system are of scientific interest because they recorded the chemical and physical processes that occurred during the planetary formation in the protoplanetary disk.
The Hayabusa2 space mission (JAXA), launched in 2014, studied the asteroid Ryugu and collected samples from its surface. This is the first mission to collect samples of a C-type asteroid,...
Magnetic reconnection is a fundamental process that is ubiquitous in the universe and allows the conversion of the magnetic field energy into heating and acceleration of plasma. It’s also very important as it is responsible for the dominant transport of plasma, momentum, and energy across the magnetopause from the solar wind into the Earth magnetosphere. Coronal Mass Ejections (CMEs) and...
Galaxy clusters have proven themselves to be valuable probes of cosmology and astrophysics. However observing galaxy cluster merger events can give us additional insight on the properties of gas inside the intra-cluster medium, dark matter physics or the theory of gravitation, it is therefore of prime interest to devise a fast and reliable way of detecting which clusters have undergone recent...
The James Webb Space Telescope is poised to revolutionize many fields of astrophysics. One such field is planetary science in our own Solar System.
JWST will be able to study planetary atmospheres and small bodies in the infrared spectrum (from 1 to 27 microns). In the case of Solar System planets, this presents an amount of added difficulties, such as the brightness or extent of the planet...
In today's Universe, a star is more likely to be found in a galaxy of the mass of the Milky Way than in any other type of galaxy. Understanding how these galaxies formed and evolved is therefore a major challenge in astronomy and the Milky Way gives us the opportunity to study one of these galaxies from the inside with unique details. The history of stellar formation is one of the fundamental...
Direct observations are required to constrain the physical properties of exoplanet atmospheres. Direct imaging is still challenging as it requires to achieve very high contrasts at small separations. The current generation of instruments are reaching contrast performance that allows us to observe young and warm giant planets that are separated by a few AU from their host star, a favorable...
A novel method of dynamical identification of asteroids families allowed the identification of almost all of them in the inner part of the Main Belt. It also allowed the identification of some asteroids not belonging to any of these families. Thus, we assumed that these objects are remnant of primordial planetesimals and their composition should remain more or less intact since their...
Meteor showers are born when a single parent body (comet or asteroid) ejects several meteoroids, forming a stream which then meets the Earth.
A large number of meteor showers are recorded today, which would mean a similar large number of parent bodies existed in the near-Earth region in a recent past. This casts a doubt on methods used to find meteor showers. These methods rely on D-criteria,...
We report on six dipolarization fronts (DF) embedded in fast earthward flows detected by the Magnetospheric Multi-scale (MMS) mission during a substorm event on 23rd of July 2017. We analyzed the Ohm’s law for each event and found that ions are mostly decoupled from the magnetic field by the Hall fields. However, the electron pressure gradient term is also contributing to the ion decoupling...
While the Universe is expanding with increasing velocity, the question of what causes this cosmic acceleration remains unsolved. Acceleration seems to act against gravitational attraction, as if a new source of energy, dubbed dark energy, were responsible for it.
In this presentation I give an introduction to my PhD project, where I will attempt to tackle the question of the nature of dark...
The energy balance of the earth is an essential climate variable. At the top of the atmosphere, this variable may be measured by calculating the difference between incoming solar flux and outgoing reflected and infrared flux. This is the goal of the UVSQ-SAT mission, which validates miniaturized technology onboard a CubeSat with 1U specifications (11.10 cm × 11.10 cm × 11.35 cm). This...
Dust is everywhere on Mars: deposited on the surface and suspended into the atmosphere. It’s a key parameter that affects climate and controls some current surface properties. Dust movements extend over very different spatial scales (few meters to planet scale). To find a link between them, we studied the atmospheric dust by using the near-infrared imaging spectrometer OMEGA onboard Mars...
The Galactic centre is a prime observation target for Very High Energy gamma-rays. A point-like source (possibly linked to the Supermassive Black Hole SgrA*) as well as a diffuse emission covering the central 200 pc have been discovered. With now 16 years of survey by HESS and the latest data analysis tools of gammapy, we performed a spectral and morphological study of the GC, and we monitored...
Weak gravitational lensing is one of the most promising tools of cosmology to constrain models and probe the evolution of dark-matter structures. Yet, the current analysis techniques are only able to exploit the 2-pt statistics of the lensing signal, ignoring a large fraction of the cosmological information contained in the non-Gaussian part of the signal. Exactly how much information is...
Molecular clouds are surrounded by an atomic layer where hydrogen is in atomic form (H) instead of molecular form (H2). As one looks deeper into the cloud, the position where H2 becomes more abundant than HI is called the H/H2 transition. This transition controls the fraction of molecular gas, which constitutes the mass reservoir for star formation, as evidenced by the Schmidt-Kennicutt law....
By 2023, the Vera C. Rubin observatory will leap forward by generating the largest optical sky survey ever made called the Legacy Survey of Space and Time (LSST). Each night, the LSST will produce a stream of over 10 million alerts that will need to be classified in real-time.
The LSST will rely on alert brokers to process and redistribute this massive alert flow to the scientific...
To understand the physical processes behind the most violent events in our Universe, a new generation of space telescopes evolving in the hard X-ray domain is required with enhanced performances in detection sensitivity and angular resolution. Emerging super mirror techniques allow the development of improved resolution and high-energy efficiency spectro-imagers, leading to large focal plane...
Mercury is the innermost and smallest terrestrial planets. Improving knowledge of the planet is crucial to our understanding of the formation and evolution of terrestrial planets. Moreover, understanding the global geological history of Mercury will help to explain the role of planet size and solar distance concerning the magmatic and tectonic history of terrestrial planets. Between 2008 and...
Modelling the emission of Galactic dust is a main challenge for CMB polarization experiments. Current models make use of Planck total intensity data plagued by the difficulty of separating dust emission from the Cosmic Infrared Background (CIB). We address this outstanding difficulty from a new perspective compared to previous attempts. We will show that dust and CIB may be statistically...
The gas mass fraction in galaxy clusters is a convenient tool to use in the context of cosmological studies.
Indeed this quantity allows to constrain the universal baryon fraction $\Omega_b/\Omega_m$, as well as other parameters like the matter density $\Omega_m$, the Hubble parameter $h$ or the Equation of State of Dark Energy $w$.
This gas mass fraction is also sensitive to baryonic...
For the past two decades, outbursts have been observed from the centre of the Milky Way where a supermassive black hole called Sgr A* is believed to reside. Recent observations have shown that the source of these outbursts is close to the event horizon and have an orbital motion around the black hole. Many scenarios are envisaged to explain this phenomenon without really reaching a consensus....
ComPol is a proposed CubeSat mission developed in the context of the ORIGINS excellence cluster with contributions from the Laboratory for Rapid Space Missions, Technische Universität München, Max Planck Institut für Physik, Politecnico di Milano and CEA Departement d'Astrophysique. The main goal of the mission is long-term observation of Hard X-ray/soft gamma ray polarisation of Cygnus X-1...
Recent studies have shown that star formation rate is 10 to 100 times lower to precedent models. Different processes can contribute to gas heating and angular momentum addition into the cloud which disperse it and limits star formation. Radiative feedback from massive stars is one of the major mechanism and has a huge impact on their molecular cloud parent and interstellar matter. Stellar...
Gamma-ray-emitting narrow-line Seyfert 1 galaxies (NLS1) constitute an intriguing small population of Active Galactic Nuclei (AGN) with debated fundamental properties, unexpected gamma-ray emission and anomalous variability features, possessing properties similar to low power flat-spectrum radio quasars (FSRQ). They are jetted, gamma/radio-loud Seyfert galaxies, with relatively low BH masses,...
Titan is the second-largest moon in our solar system and has a thick atmosphere. It has nitrogen (94.2%) and methane (5.65%) as it’s major constituents, with a lot of trace gases. Methane and nitrogen split due to the sun’s ultraviolet rays and high energetic particles (from Saturn’s magnetic field), and this results in a variety of organic compounds in the atmosphere. In this research, I am...
Gravitational wave (GW) standard sirens are well-established probes with which one can measure cosmological parameters, and are complementary to other probes like the cosmic microwave background or supernovae standard candles. We focus on dark GW sirens, specifically binary black holes (BBHs) for which there is only GW data. Our approach relies on the assumption of a source-frame mass model...
The Alpha Centauri system comprises the two solar-like stars A and B and the red dwarf Proxima. Together they are our closest cosmic neighbours, making them a particularly interesting target for exoplanet searches. We are analysing 3 years worth of astrometric data on Alpha Cen A/B with the hope of recovering an exoplanetary signal. This presents a unique set of challenges due to the proximity...
Over the last decade, the field of exoplanet research and study has entered a new era of atmospheric characterisation, made possible by the development of detection methods based on high-resolution spectroscopy. The instrumental capabilities of SPIRou, the infrared spectropolarimeter installed at CFHT, allow us to provide new constraints on the composition and atmospheric dynamics of hot...
Part of the ionizing continuum (Lyman continuum, LyC) produced by young stars can leak out of the host galaxy and ionize its surroundings. At high redshift, such LyC-leaking galaxies are among the best candidates to fully account for reionization (Robertson et al. 2013). However, direct measurements are extremely difficult as the LyC photons are easily absorbed by neutral gas on the observed...
