Abstract
It has been an interesting question as to why one-third of Kuiper Belt objects (KBOs) are trapped into the 3: 2 resonance but, in contrast, only a few KBOs are claimed to be associated with the 2 : 1 resonance. In a model proposed by Zhou et al., the stochastic outward migration of the Neptune could reduce the number of particles in the 2 : 1 resonance, and thus the objects in the 3 : 2 resonance become more distinct. As a complementary study, we investigate the effect of protostellar discs on the resonance capture. Our results show that the gaseous drag of a protostellar disc can trap KBOs into the 3 : 2 resonance rather easily. In addition, no objects are captured into the 2 : 1 resonance in our simulation.