Gravitationally Induced Explosive Outflows

Abstract

Over the past decade, there has been a significant increase in the reporting of extensive and luminous star-forming regions associated with explosive outflows. Nevertheless, there is still a lack of understanding of the possible physical mechanisms that produce such energetic and isotropic events. We propose a gravitational interaction as a likely mechanism that could trigger explosive outflows in dense star-forming regions. This could constrain the physical conditions that generate an explosive outflow produced by the close dynamical encounter of a runaway star with a clump cluster in dynamical equilibrium. We have produced a set of N-body simulations that account for the collision of a 10 M⊙ stellar object with a cluster of particles with a mass that ranges from 0 to 50 M⊙. We propose a parameter to describe the interaction, the evaporation parameter, which describes the fraction of stars that become unbound. The main result is that, when the cluster mass is less than or up to a few times the stellar mass, the collision will produce an explosive outflow, ejecting a significant fraction of the cluster members with velocities larger than the impact velocity. All of our models produce an explosive outflow, with different characteristics, which increases the probability that a close encounter could be responsible for producing the observed flows.