Planet Population, Formation, and Habitability

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This project encompasses the theoretical interpretation and analysis of the observational results of the CARMENES survey through comparisons with theoretical predictions. In this way it derives key observational constraints for planet formation and evolution theory. This is necessary because the planet formation process is so complex that models cannot rely on first (physical) principles alone, but need observational guidance. In particular observational constraints from a well-defined, large observational sample with a known detection bias (as CARMENES) are of paramount importance since they make quantitative comparisons possible.A method that makes it possible to better understand the planetary formation and evolution process is planetary population synthesis. Using global planet formation and evolution models that combine the essence of many specialized models, synthetic populations of planets are generated and then compared statistically with observations. For this, we have created in the last years a framework for planet population synthesis. The most important element of our population synthesis framework is the global planet formation model, which directly predicts CARMENES' observable quantities (period and minimum mass). It is based on the core accretion paradigm, which states that giant planets form in a two-step process. First a critical core is built, which then triggers the accretion of the gaseous envelope. This happens in an evolving disk of gas and solids in which also other protoplanets grow, leading to dynamical interactions. The disk and the protoplanet exchange angular moment, meaning that orbital migration occurs.The statistical results of the CARMENES sample are central for the progress in the theoretical understanding how planets form around M-dwarfs. The comparison of the observational results with the population synthesis data will help to understand questions like: what are the architectures of planetary systems around low-mass stars? How do they differ from their counterparts around solar-like stars? Is it possible to derive from the planetary mass function how the disk masses change with stellar mass, and therefore the material available for planet formation? Is it possible to derive from the distribution of semimajor axes where the iceline - the preferred location of giant planet formation - is found in these disks, and how efficient orbital migration is? What does this mean for the availability of water on low-mass planets? Do the compact systems of several low-mass planets found in very high numbers by the Kepler satellite around solar-like stars also exist around M-dwarfs, potentially in a scaled-down version?