Pavel Kroupa: N-body movie

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Precautions:

You need at least 128MB RAM, and some patience. The art of animation is still being learned...

Code:

Aarseth's Nbody6 with modifications (Kroupa, Aarseth & Hurley 2000).

Assumptions:

Standard local Galactic tidal field; Plummer density profile, Rhalf=0.2pc, virial equilibrium; Stellar masses: 0.01-50Msol from KTG93 IMF; 40 binaries: Companion masses paired randomly; Taurus-Auriga-like period distribution (Kroupa'95); Latest stellar evolution (Hurley et al. 2000).

Short description:

The movie exemplifies dynamical processes that are important for young clusters. Stellar masses: Magenta: BDs (0.01-0.08Msol); Red: M dwarfs (0.08-0.5Msol); Green: "K" dwarfs (0.5-1Msol); Blue: massive stars (>1Msol).

Cluster evolution begins with the two most massive stars sinking to the cluster core within one crossing time, and forming a binary, after ejecting it's original companions as well as other low-mass members. It recoils after a very fast (barely visible) ejection of an original Mdwarf companion to the upper left. This hardens the massive binary. The cluster gains momentum and moves slowly towards the lower right. Further ejection events, mostly from the tight central binary, remove further stars from the cluster.

Observe the fast development of mass segregation, taking note of the distribution of BDs, and note how the dynamical evolution time-scale slows as the cluster expands and looses stars.