Long period exoplanets from dynamical relaxation

Recent imaging campaigns indicate the likely existence of massive planets (∼ 1− 10 MJ ) on ∼> 1000 year orbits about a few percent of stars. Such objects are not easily explained in most current planet formation models. In this Letter we use ensembles of 100 N-body simulations to evaluate the potential for planet scattering during relaxation of dynamically active systems to explain the population of giant planets with projected separations up to a few 100 AU. We find that such a mechanism could indeed be at play, and that statistical samples of long period planets could place interesting constraints on early stage planet formation scenarios. Results from direct imaging and microlensing surveys are complementary probes of this dynamical relaxation process. Subject headings: planets and satellites: formation — methods: N-body simulations