Protostars and Planets VI, Heidelberg, July 15-20, 2013
ENVIRONMENTAL EFFECTS ON PLANET FORMATION IN THE CLUSTER GAS EXPULSION PHASE (< 20 MYR)
Steinhausen, Manuel (Max-Plank-Institut für Radioastronomie, Bonn)
Pfalzner, Susanne (Max-Plank-Institut für Radioastronomie, Bonn)
Most stars do not form in isolation but as part of a group of stars. Investigations of the effect of stellar encounters on protoplanetary discs have demonstrated its importance in dense environments during the early embedded cluster evolution. However, star cluster infant mortality suggests that a large fraction of the massive clusters dissolves within a few Myr, while only a small fraction survives the expulsion of the residual gas. In this study N-body simulations have been performed to investigate various expulsion scenarios. Hereby, the focus is on the significance of stellar encounters (i) before the remnant gas is expelled, (ii) during the expansion phase, and (iii) after the re-virialisation. It is shown that during the embedded phase multiple eccentric encounter events are dominating, preferentially in the dense inner cluster regions. The gas expulsion at the end of the star formation process leads to a rapid expansion of the cluster and a significant reduction of the fraction of bound stars. It is shown that in general unperturbed stars, located in the outer cluster regions, are expelled from the cluster, while a large fraction of highly disturbed stars in the central cluster parts remain bound. Consequently, encounters during the crucial first Myr of cluster development significantly shape the disc properties of the remnant cluster. Moreover, stars that are dispersed in the field are more suitable for planet formation, since they maintain their discs for a substantially prolonged timespan.
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