Chemical Diversity in Protoplanetary Disks and Its Impact on the Formation History of Giant Planets

Giant planets can interact with multiple and chemically diverse environments in protoplanetary discs while they form and migrate to their final orbits. The way this interaction affects the accretion of gas and solids shapes the chemical composition of the planets and of their atmospheres. Here we investigate the effects of different chemical structures of the host protoplanetary disc on the planetary composition. We consider both scenarios of molecular (inheritance from the pre-stellar cloud) and atomic (complete chemical reset) initial abundances in the disc. We focus on four elemental tracers of different volatility: C, O, N, and S. We explore the entire extension of possible formation regions suggested by observations by coupling the disc chemical scenarios with N-body simulations of forming and migrating giant planets. The planet formation process produces giant planets with chemical compositions significantly deviating from that of the host disc. We find that the C/N, N/O, and S/N ratios follow monotonic trends with the extent of migration. The C/O ratio shows a more complex behaviour, dependent on the planet accretion history and on the chemical structure of the formation environment. The comparison between S/N* and C/N* (where * indicates normalisation to the stellar value), constrains the relative contribution of gas and solids to the total metallicity. Giant planets whose metallicity is dominated by the contribution of the gas are characterised by N/O* > C/O* > C/N* and allow for constraining the disc chemical scenario. When the planetary metallicity is instead dominated by the contribution of the solids we find that C/N* > C/O* > N/O*.Comment: 27 pages, 10 figures, 1 table. Published in The Astrophysical Journa

Formation d'étoiles : étude dynamique de la poussière interstellaire

The interstellar medium is composed by approximately 1% of dust in terms of mass. Surprisingly, this tiny amount of dust already plays a very important role in stellar formation. The dynamics of dust grains may differ from that of the gas particles, leading to local variations in concentration. However, very few studies have focused on the gas and dust differential dynamics during star formation. My thesis aims to fill this gap and is divided into four parts. In the first part, I develop a module dealing efficiently with dust dynamics that can simultaneously include multiple grain species intended to the multidimensional adaptive grid code RAMSES (Teyssier 2002). I then carefully test my module by comparing my results with known analytical solutions. I also show that my implementation is robust, fast and accurate. Then I perform star formation simulations that consider multiple dust species. This study establishes that a decoupling between the dust and the gas appears for grains of sizes larger or equivalent to a hundred micrometers. I also find that this decoupling depends strongly on the initial properties of the prestellar core. Then, I develop an analytical formalism, similar to the non-ideal magnetohydrodynamics but that includes the dynamics of charged grains. This formalism allows to highlight seven different coupling regimes between the grains, the magnetic field and the gas as a function of the grain size, its charge and its environment. In parallel, I investigate the dynamics of dust in the weakly ionized zones of protoplanetary disks in order to study the formation of chondrules. Chondrules are dust grains found in most meteorites and are key to understand the formation of disks and planets.Le milieu interstellaire se compose, en masse, d'environ 1% de poussière. Paradoxalement,malgré sa faible concentration, celle-ci un rôle très important dans la formation stellaire. La dynamique des grains de poussière peut différer de celle du gaz, entrainant des variations locales de concentration. Peu de travaux ont pourtant été consacrés à l'étude de cette dynamique différentielle lors de la formation stellaire. Ma thèse s'inscrit dans l'objectif de pallier ce manque et se décompose en quatre parties.Dans la première partie, je développe un module traitant efficacement la dynamique des poussières et pouvant simultanément inclure plusieurs espèces de grains pour le code multidimensionnel sur grille adaptative RAMSES (Teyssier 2002). Je teste ensuite mon module avec soin en comparant mes résultats à des solutions analytiques. Je montre par ailleurs que mon implémentation est robuste, précise et rapide.Par la suite j'effectue des simulations de formation d'étoiles incluant plusieurs espèces de poussières. Grâce à cette étude, j'établis qu'un découplage entre les grains et le gaz apparaît pour les grains d'une taille supérieure ou équivalente à la centaine de micromètres. Je trouve également que ce découplage dépend fortement des propriétés initiales du coeur préstellaire.Ensuite, je développe un formalisme analytique, similaire à la magnétohydrodynamique non idéale, mais incluant en plus la dynamique des grains chargés. Ce formalisme me permet de mettre en évidence sept différents régimes de couplage entre les grains, le champ magnétique et le gaz, selon la taille des grains, leur charge et leur environnement.En parallèle, j'étudie la dynamique des poussières dans les zones faiblement ionisées des disques protoplanétaires afin d'étudier la formation des chondrules. Ce sont des grains de poussière retrouvés dans la majorité des météorites et qui sont des éléments clés pour la compréhension de la formation des disques et des planètes

Star formation : Dynamical study of interstellar dust

Le milieu interstellaire se compose, en masse, d'environ 1% de poussière. Paradoxalement,malgré sa faible concentration, celle-ci un rôle très important dans la formation stellaire. La dynamique des grains de poussière peut différer de celle du gaz, entrainant des variations locales de concentration. Peu de travaux ont pourtant été consacrés à l'étude de cette dynamique différentielle lors de la formation stellaire. Ma thèse s'inscrit dans l'objectif de pallier ce manque et se décompose en quatre parties.Dans la première partie, je développe un module traitant efficacement la dynamique des poussières et pouvant simultanément inclure plusieurs espèces de grains pour le code multidimensionnel sur grille adaptative RAMSES (Teyssier 2002). Je teste ensuite mon module avec soin en comparant mes résultats à des solutions analytiques. Je montre par ailleurs que mon implémentation est robuste, précise et rapide.Par la suite j'effectue des simulations de formation d'étoiles incluant plusieurs espèces de poussières. Grâce à cette étude, j'établis qu'un découplage entre les grains et le gaz apparaît pour les grains d'une taille supérieure ou équivalente à la centaine de micromètres. Je trouve également que ce découplage dépend fortement des propriétés initiales du coeur préstellaire.Ensuite, je développe un formalisme analytique, similaire à la magnétohydrodynamique non idéale, mais incluant en plus la dynamique des grains chargés. Ce formalisme me permet de mettre en évidence sept différents régimes de couplage entre les grains, le champ magnétique et le gaz, selon la taille des grains, leur charge et leur environnement.En parallèle, j'étudie la dynamique des poussières dans les zones faiblement ionisées des disques protoplanétaires afin d'étudier la formation des chondrules. Ce sont des grains de poussière retrouvés dans la majorité des météorites et qui sont des éléments clés pour la compréhension de la formation des disques et des planètes.The interstellar medium is composed by approximately 1% of dust in terms of mass. Surprisingly, this tiny amount of dust already plays a very important role in stellar formation. The dynamics of dust grains may differ from that of the gas particles, leading to local variations in concentration. However, very few studies have focused on the gas and dust differential dynamics during star formation. My thesis aims to fill this gap and is divided into four parts. In the first part, I develop a module dealing efficiently with dust dynamics that can simultaneously include multiple grain species intended to the multidimensional adaptive grid code RAMSES (Teyssier 2002). I then carefully test my module by comparing my results with known analytical solutions. I also show that my implementation is robust, fast and accurate. Then I perform star formation simulations that consider multiple dust species. This study establishes that a decoupling between the dust and the gas appears for grains of sizes larger or equivalent to a hundred micrometers. I also find that this decoupling depends strongly on the initial properties of the prestellar core. Then, I develop an analytical formalism, similar to the non-ideal magnetohydrodynamics but that includes the dynamics of charged grains. This formalism allows to highlight seven different coupling regimes between the grains, the magnetic field and the gas as a function of the grain size, its charge and its environment. In parallel, I investigate the dynamics of dust in the weakly ionized zones of protoplanetary disks in order to study the formation of chondrules. Chondrules are dust grains found in most meteorites and are key to understand the formation of disks and planets

The binary channels to electron capture supernovae

Due to the second dredge-up and expected strong mass loss during the thermally pulsing super-AGB phase, the mass range for single stars to evolve as electron capture supernova (ECSN) is very narrow. In this short contribution, we briefly review alternative binary channels and present recent case A & B mass transfer simulations. In these models, the envelope is removed during Roche lobe overflow (RLOF), preventing the occurrence of the second dredge-up and the reduction of the H-free core below the Chandrasekhar mass. The newly formed helium star can then ignite carbon and may end its life as ECSN.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Propagation of Alfvén waves in the dusty interstellar medium

Context. Alfvén waves are fundamental magnetized modes that play an important role in the dynamics of magnetized flows such as the interstellar medium (ISM). Aims. In a weakly ionized medium, their propagation critically depends on the ionization rate as well as on the charge carriers. Depending on the gas density, these may be ions, electrons, or dust grains. The latter are particularly well known to have a drastic influence on the magnetic resistivities in the dense ISM, such as collapsing dense cores. Yet, in most calculations, for numerical reasons, the grain inertia is usually neglected. Methods. We carried out an analytical investigation of the propagation of Alfvén waves both in a single-size and multi-size grain medium such as the ISM and we obtained exact expressions giving wavenumbers as a function of wave frequencies. These expressions were then solved analytically or numerically by taking into account or neglecting grain inertia. Results. At long wavelengths, neglecting grain inertia is a very good approximation, however, the situation is rather different for wavelengths shorter than a critical value, which broadly scaled as 1/n, with n being the gas density. More precisely, when inertia is neglected, the waves do not propagate at short wavelengths or, due to the Hall effect, they develop for one circular polarization only, namely, a whistler mode such that ℛe(ω) ∝ k2. The other polarization presents a zero group velocity, namely, ℛe(ω) ∝ k0. When grain inertia is accounted for, the propagation of the two polarizations tend to be more symmetrical and the whistler mode is only present at density higher than ≃108 cm−3. At a lower density, it is replaced by a mode having ℛe(ω) ∝ k≃1.2. Interestingly, one of the polarization presents a distribution, instead of a single ω value. Importantly, for short wavelengths, wave damping is considerably reduced when inertia is properly accounted for. Conclusions. To properly handle the propagation of Alfvén waves at short wavelengths, it is necessary to self-consistently treat grain inertia. We discuss the possible consequences this may have in the context of diffuse and dense molecular gas regarding turbulence, magnetic braking, and protoplanetary disk formation as well as cosmic ray propagation in the dense ISM

Fast methods to track grain coagulation and ionization. III. Protostellar collapse with non-ideal MHD

Dust grains influence many aspects of star formation, including planet formation, opacities for radiative transfer, chemistry, and the magnetic field via Ohmic, Hall, and ambipolar diffusion. The size distribution of the dust grains is the primary characteristic influencing all these aspects. Grain size increases by coagulation throughout the star formation process. We describe here numerical simulations of protostellar collapse using methods described in earlier papers of this series. We compute the evolution of the grain size distribution from coagulation and the non-ideal magnetohydrodynamics effects self-consistently and at low numerical cost. We find that the coagulation efficiency is mostly affected by the time spent in high-density regions. Starting from sub-micron radii, grain sizes reach more than 100 μm in an inner protoplanetary disk that is only 1000 years old. We also show that the growth of grains significantly affects the resistivities, and indirectly the dynamics and angular momentum of the disk

Fast methods to track grain coagulation and ionization. II. Extension to thermal ionization

Thermal ionization is a critical process at temperatures T > 10 3 K, particularly during star formation. An increase in ionization leads to a decrease in nonideal magnetohydrodynamics (MHD) resistivities, which has a significant impact on protoplanetary disks and protostar formation. We developed an extension of the fast computational ionization method presented in our recent paper to include thermal ionization. The model can be used to inexpensively calculate the density of ions and electrons and the electric charge of each size of grains for an arbitrary size distribution. This tool should be particularly useful for the self-consistent calculation of nonideal MHD resistivities in multidimensional simulations, especially of protostellar collapse and protoplanetary disks

Fast methods to track grain coagulation and ionization. III. Protostellar collapse with non-ideal MHD

Dust grains influence many aspects of star formation, including planet formation, opacities for radiative transfer, chemistry, and the magnetic field via Ohmic, Hall, and ambipolar diffusion. The size distribution of the dust grains is the primary characteristic influencing all these aspects. Grain size increases by coagulation throughout the star formation process. We describe here numerical simulations of protostellar collapse using methods described in earlier papers of this series. We compute the evolution of the grain size distribution from coagulation and the non-ideal magnetohydrodynamics effects self-consistently and at low numerical cost. We find that the coagulation efficiency is mostly affected by the time spent in high-density regions. Starting from sub-micron radii, grain sizes reach more than 100 μm in an inner protoplanetary disk that is only 1000 years old. We also show that the growth of grains significantly affects the resistivities, and indirectly the dynamics and angular momentum of the disk

Fast methods to track grain coagulation and ionization. II. Extension to thermal ionization

Thermal ionization is a critical process at temperatures T > 10 3 K, particularly during star formation. An increase in ionization leads to a decrease in nonideal magnetohydrodynamics (MHD) resistivities, which has a significant impact on protoplanetary disks and protostar formation. We developed an extension of the fast computational ionization method presented in our recent paper to include thermal ionization. The model can be used to inexpensively calculate the density of ions and electrons and the electric charge of each size of grains for an arbitrary size distribution. This tool should be particularly useful for the self-consistent calculation of nonideal MHD resistivities in multidimensional simulations, especially of protostellar collapse and protoplanetary disks

Fast methods to track grain coagulation and ionization. II. Extension to thermal ionization

International audienceThermal ionization is a critical process at temperatures T > 10 3 K, particularly during star formation. An increase in ionization leads to a decrease in nonideal magnetohydrodynamics (MHD) resistivities, which has a significant impact on protoplanetary disks and protostar formation. We developed an extension of the fast computational ionization method presented in our recent paper to include thermal ionization. The model can be used to inexpensively calculate the density of ions and electrons and the electric charge of each size of grains for an arbitrary size distribution. This tool should be particularly useful for the self-consistent calculation of nonideal MHD resistivities in multidimensional simulations, especially of protostellar collapse and protoplanetary disks