Pre- and protostellar cores represent the earliest stage of the formation of a star. This phases are crucial for the future evolution of the star, as its final mass and the initial composition of the proto-planetary disk that may eventually form planet will be determined during these phases. In the past years, much progress has been done in our understanding of the chemical structure of these objects, thanks to the dramatic increase of the sensitivity of millimiter and sub-millimeter ground based telescopes. In fact, it is now possible to use chemistry as a tool to constrain both physical and chemical characteristics of these objects. However, most studies so far have used single dish observations with typical resolutions of a few tens of arc seconds, and the physical and chemical structures if cores on smaller scales remains poorly know. Here we propose to carry-out a study the physical and chemical properties of a large sample of Class 0 protostars, using both an observational and theorical/modelling approach. Our observations are part of an extensive survey of the line and continuum emission from young protostars with the Plateau de Bure interferometer at sub-arcsecond resolution. Follow-up observations with ALMA and NOEMA will be carried-out. We propose to develop a new chemo-dynamical model combining the results of state-of-the art MHD simulations of core collapse with a complete chemistry network and a radiative transfer model. The direct comparison between sub-arcsecond resolution observations and the predictions our chemo-dynamical model is expected to bring important constraints on the formation and evolution of pre- and protostellar cores, and in turn on star formation theories.

Circumstellar discs are the birthplaces of planets. They form around young protostars and dissipate in a few million years. Modern submillimeter and optical telescopes such as ALMA and VLT/SPHERE are now able to resolve thin structures in the bulk of these objects, such as rings, crescents or spirals, probing the very origin of planetary systems similar to our own. Our current understanding of these discs relies on a very crude modelling of a hypothetic magneto-hydrodynamic (MHD) turbulence thought to play an essential role in the evolution and structure of these systems. However, there is now compelling theoretical evidence that these discs are weakly turbulent, if not laminar, because of their low ionisation fraction and thus poor coupling to the magnetic field. This suggests that subtle MHD processes are driving the dynamics of these objects. Moreover, my recent theoretical breakthroughs demonstrate that these gaseous discs can self-organise, spontaneously creating thin structures surprisingly similar to the ones we observe. I propose that computing global non-ideal MHD models from massively parallel numerical simulations will shed a new light on these observations, connecting the long-term evolution of these objects to the formation of large-scale structures seen by ALMA and SPHERE. We expect MHDiscs to provide reliable global evolution models by coupling gas dynamics to dust and irradiation, which will be used to produce accurate synthetic observations. We will test our models by comparing our predictions to observational constraints (spectral energy distribution, dust spatial distribution, emissivity contrast), setting the stage for a deeper understanding of the formation of planetary systems.

High contrast imaging techniques are just starting to provide the first images of forming planets nested within the circumstellar disks surrounding young stars. These discoveries offer to dramatically refine our knowledge of the formation and phases of early dynamical evolution of planetary systems. The characterization of the gas accretion processes onto these planets can also remove critical uncertainties of planet evolution and planet migration models. We proposes a full incursion in the nascent field of protoplanet detection and characterization. FRAME will determine the physics involve during the planet accretion phase inspiring from the characterization strategies used on protostars. We will also develop specific data processing techniques to boost the detection of forming planets at shorter angular separations (10-100 au) in datacubes produced by medium and high-resolution spectrographs.

ABSTRACT. In regions of active star formation, the protoplanetary discs around young stars act as planetary factories. Recent observing campaigns have shown that the majority of protostars belong to multiple stellar systems: the younger the stars, the higher the degree of multiplicity. Young discs are then strongly affected by stellar multiplicity, unavoidably modifying the way in which planets form. The detailed evolution of multiple systems with discs and planets however remains to be explored. Since most current models have been designed for single stars, there is an urgent need to extend these models to multiple stars. This will pave the way for a better understanding of the process of planet formation within our galaxy. The Stellar-MADE project aims to provide a comprehensive view of disc dynamics and planet formation within multiple stellar systems. My team and I will thoroughly study multiples to: (1) Establish the formation channels of protoplanetary discs around young stellar objects; (2) Follow disc dynamics and grain growth in order to identify the regions of planetesimal formation; (3) Characterise planetary architectures and the resulting exoplanet population. To achieve our goals we will perform hydrodynamical and N-body simulations, developing and adapting state-of-the-art codes (Phantom, mcfost, Rebound). Our calculations will include a broad range of physical processes: disc thermodynamics, radiative transfer, gravitational perturbations, aerodynamic friction, dust growth, and Mean-Motion Resonances. This will allow us to identify and quantify stellar multiplicity effects across evolution. My previous work on binary stars constitutes proof-of-concept that it is possible to coherently connect protoplanetary disc evolution to planetary architectures. Unveiling the effects of stellar multiplicity on planet formation will be a major breakthrough. PROJECT OBJECTIVES. The aim of this project is to study the impact of stellar multiplicity on planet formation: from the onset of disc formation in gaseous clouds to the final stage where stars host stable planetary systems. Three scientific questions will drive the proposed investigation: i) What are the initial protoplanetary disc conditions around young stellar multiple objects? ii) Where do solid bodies and planetesimals grow within discs in multiple stellar systems? iii) What are the most stable planetary architectures in multiple stellar systems? SCIENTIFIC IMPACT. This project will unveil the effects of stellar multiplicity on planet formation, which will allow us to interpret the whole exoplanetary population under a new prism. Our expected results will become the stepping stone for future research on multiple stellar systems. As a matter of fact, stellar multiplicity is the norm – rather than the exception – in active star-forming regions. It is therefore key to understand the impact of stellar multiplicity on planet formation. The ground- breaking nature of this proposal will guarantee a high impact at the international level, placing the Stellar- MADE team at the forefront of the emerging field of research on disc and planet dynamics in multiples. Our results are expected to open new avenues for studying the disc chemical reservoir across stellar evolution, planetesimal formation, and its impact on exoplanet composition.

The discovery of extrasolar planets is a revolution in modern astrophysics which impacts not only our knowledge of planet formation and evolution, but also our understanding of the place of the Earth in the Universe. In this domain major advances have been made by using spectroscopic observations of transiting planets. Using this technique, we discovered an unexpected phenomenon : the evaporation of hot-Jupiters, and we made a detailed study of the atmosphere of the exoplanets HD209458b and HD189733b. Observations of transiting planets are now widely recognized as a powerful method to scrutinize the atmosphere of these exoplanets. The present “Exo-Atmos” programme is aimed at constraining both the extended upper atmosphere of evaporating planets, and the deeper atmosphere of a large variety of exoplanets, using transit spectroscopy observations. These objectives will be reached by two means: 1) We will observe with the best telescopes presently available: Very Large Telescope (VLT) and the Hubble Space Telescope (HST). 2) We will also enlarge the sample of planets for which atmosphere are detected and analysed. Indeed, we have obtained a large amount of time on the HST and the VLT telescopes to observe the atmospheres and evaporation of extrasolar planets. For instance, with 3 HST programs in 2012 we will observe a total of 10 planets (9 exoplanets + Venus as a benchmark). This will allow us to scrutinize the atmosphere of an unprecedented large sample of exoplanets, and will open the field of comparative exoplanetology. However, to obtain the best scientific return of these programs, a substantial financial support is required. Here we propose an ANR program to support this work. In addition to financial support for missions and equipment, we ask for 2 post-doctoral fellowships of 2 years, one for each of the two partners of the project. Finally, we ask for financial support for the acquisition of a powerful computer that will be dedicated to numerical simulations for the analysis and interpretation of HST spectroscopic observations, and modeling of the gas escape. These simulations will be designed to better constrain the structure, dynamics and composition of the atmospheres of planets observed by transit spectroscopy. In particular, a significant part of the CPU time will be dedicated to issues related to the evaporation of planets orbiting close to their star, an area in which our team has played a major role. Combined with the results of these simulations, the HST observations will allow to better constrain the escape rate and the evaporation mechanisms. At the end of this 3 year program "Exo-Atmos," we aim to better understand the atmosphere and evaporation of exoplanets.