Kavli Affiliate: Luis C. Ho
| First 5 Authors: Muxin Liu, Lile Wang, Xiaoting Fu, Luis C. Ho,
| Summary:
Outflowing stars impinging upon ambient gas experience accelerations due to
the gravitational feedback from the morphology of the interaction betweem the
outflow and the ambient gas. Such "negative dynamical friction" (NDF), in
contrast to the conventional "dynamical friction" (DF), is studied for its
impact on the dynamics of open clusters immersed in a uniform ambient gas. We
modify the $N$-body integration code REBOUND with both NDF and DF implemented
according to the outflow conditions of each star in a consistently constructed
model open cluster. The evolution of stars is also involved in determining the
gas-star interactions throughout their stellar lives. Compared to DF-only and
gas-free models with identical initial conditions, the NDF-affected cluster is
puffier and evaporates faster, as indicated by various diagnostics, including
lower velocity dispersions and larger half-mass and half-light radii. Neutron
stars with fast winds are expelled from the cluster due to their intensive NDF
effect, even without the "kicks" by asymmetric supernovae. Exploration of
parameter space confirms that the NDF effect is generally enhanced with higher
ambient gas densities, in qualitatively agreement with the expression of
acceleration. Outflow-ambient interactions should be considered for the proper
interpretation of the evolution of stellar dynamics in clusters.
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