Orphaned Protostars
  We explore the origin of a population of distant companions (~1000 - 5000 AU)
to Class I protostellar sources recently found by Connelley and co-workers, who
noted that the companion fraction diminished as the sources evolved. Here we
present N-body simulations of unstable triple systems embedded in dense cloud
cores. Many companions are ejected into unbound orbits and quickly escape, but
others are ejected with insufficient momentum to climb out of the potential
well of the cloud core and associated binary. These loosely bound companions
reach distances of many thousands of AU before falling back and eventually
being ejected into escapes as the cloud cores gradually disappear. We use the
term orphans to denote protostellar objects that are dynamically ejected from
their placental cloud cores, either escaping or for a time being tenuously
bound at large separations. Half of all triple systems are found to
disintegrate during the protostellar stage, so if multiple systems are a
frequent outcome of the collapse of a cloud core, then orphans should be
common. Bound orphans are associated with embedded close protostellar binaries,
but escaping orphans can travel as far as ~0.2 pc during the protostellar
phase. The steep climb out of a potential well ensures that orphans are not
kinematically distinct from young stars born with a less violent pre-history.
The identification of orphans outside their heavily extincted cloud cores will
allow the detailed study of protostars high up on their Hayashi tracks at
near-infrared and in some cases even at optical wavelengths.
