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...
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...
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...
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 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...
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,...
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...
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....
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...
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,...
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...
