------------------------------------------------------------------------
 gctide-fin3.tex MNRAS, 2009, accepted
Date: Thu, 25 Jun 2009 16:13:03 +0200
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%astro-ph/0906.4459

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\title[On the dissolution of star clusters in the Galactic centre. I.  
Circular orbits.]{On the dissolution of star clusters in the Galactic  
centre. I. Circular orbits.}
\author[A. Ernst, A. Just, R. Spurzem]{A. Ernst$^{1,2}$\thanks{email:  
aernst@ari.uni-heidelberg.de}, A. Just$^{1}$\th
anks{email: just@ari.uni-heidelberg.de},
R. Spurzem$^{1}$\thanks{email: spurzem@ari.uni-heidelberg.de} \\
$^{1}$Astronomisches Rechen-Institut/Zentrum f\"ur Astronomie der  
Universit\"at Heidelberg,
M\"onchhofstrasse 12-14,
69120 Heidelberg, Germany\\
$^{2}$Max-Planck-Institut f\"ur Astronomie, K\"onigstuhl 17, 69117  
Heidelberg, Germany}

\begin{document}

\date{Accepted ... Received ...}

\pagerange{\pageref{firstpage}--\pageref{lastpage}} \pubyear{2002}

\maketitle

\label{firstpage}

\begin{abstract}
We present $N$-body simulations of dissolving star clusters close to  
galactic centres.
For this purpose, we developed a new $N$-body program called {\sc  
nbody6gc}
based on Aarseth's series of $N$-body codes. We describe the  
algorithm in detail.
We report about the density wave phenomenon in the tidal arms which  
has been recently
explained by K\"upper et al. (2008). Standing waves develop in the  
tidal arms.  The wave knots
or clumps develop at the position, where the emerging tidal arm hits  
the potential wall of the
effective potential and is reflected. The escaping stars move through
the wave knots further into the tidal arms. We show the consistency  
of the positions of the wave
knots with the theory in Just et al. (2009).
We also demonstrate a simple method to study the properties of tidal  
arms. By
solving many eigenvalue problems along the tidal arms, we construct  
numerically a 1D coordinate system whose directio
n is always along a principal axis of the local tensor of inertia.  
Along this coordinate system, physical quantities
can be evaluated. The half-mass or dissolution times of
our models are almost independent of the particle number which  
indicates that two-body
relaxation is not the dominant mechanism leading to the dissolution.  
This may be a typical
situation for many young star clusters. We propose a classification  
scheme which sheds
light on the dissolution mechanism.
\end{abstract}

\begin{keywords}
Star clusters -- Stellar dynamics
\end{keywords}