M. Steinhausen, C. Olczak, S. Pfalzner
Investigations of stellar encounters in cluster environments have
demonstrated their potential influence on the mass and angular momentum of
protoplanetary discs around young stars. In this study it is investigated in
how far the initial surface density in the disc surrounding a young star
influences the outcome of an encounter. Based on a power-law ansatz for the
surface density, $\Sigma(r) \propto r^{-p}$, a parameter study of star-disc
encounters with different initial disc-mass distributions has been performed
using N-body simulations. It is demonstrated that the shape of the disc-mass
distribution has a significant impact on the quantity of the disc-mass and
angular momentum losses in star-disc encounters. Most sensitive are the results
where the outer parts of the disc are perturbed by high-mass stars. By
contrast, disc-penetrating encounters lead more or less independently of the
disc-mass distribution always to large losses. However, maximum losses are
generally obtained for initially flat distributed disc material. Based on the
parameter study a fit formula is derived, describing the relative mass and
angular momentum loss dependent on the initial disc-mass distribution index p.
Generally encounters lead to a steepening of the density profile of the disc.
The resulting profiles can have a r^{-2}-dependence or even steeper independent
of the initial distribution of the disc material. From observations the initial
density distribution in discs remains unconstrained, so the here demonstrated
strong dependence on the initial density distribution might require a revision
of the effect of encounters in young stellar clusters. The steep surface
density distributions induced by some encounters might be the prerequisite to
form planetary systems similar to our own solar system.
View original:
http://arxiv.org/abs/1111.2466
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