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 interaction morphology between 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 (OCs) immersed in a uniform ambient gas. We modify
the $N$-body integration code texttt{REBOUND} with both NDF and DF implemented
according to the outflow conditions of each star in a consistently constructed
OC. 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 qualitative agreement with the expression of
acceleration. Outflow-ambient interactions should be considered for the proper
interpretation of the stellar dynamics evolution in clusters.
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