Demographics of Giant Planets: Constraints on Formation Theory and System Architectures - Professor Michael Meyer (University of Michigan)

The formation of giant planets dictates planetary system architectures and may have a vital impact on the habitability of terrestrial planets in the liquid water zone.  Determining their frequency versus their mass and orbital separation, as a function of host mass, provides a powerful test of theory.  Yet accurately assessing the giant planet population requires that very low mass brown dwarf companions are considered as a separate population, also providing constraints on their formation and evolution.    We have developed a parametric model that accurately predicts the occurrence rates of both giant planets and brown dwarf companions over a wide range of orbital separation and companion mass.  We find: a) planet and brown dwarf companion distributions are best constructed using the mass ratio and fixed normalizations  for host stars from < 0.3 to > 2.0 times the mass of the Sun; b) a natural explanation of the brown dwarf desert as local minima in companion mass ratio distributions (independent of the deuterium burning limit); c) a peak in the orbital distribution of giant planets near the predicted icelines; and d) no obvious dependence of the giant planet mass function on orbital separation from < 0.3 to > 300 AU.  We compare our results to predictions of planet formation theory and discuss ways to test our model.  These include obtaining characterization spectra, as well as new surveys of the very highest, and lowest, mass primaries that can be studied with the NASA/ESA/CSA James Webb Space Telescope, and ground-based high contrast imaging (including with the next generation of extremely large telescopes).