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 CNDdynamics A&A, 2002, in press
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%astro-ph/0203428

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%   \thesaurus{10  (09.03.1,  % ISM: clouds
%     09.11.1,  % ISM: kinematics and dynamics
%     10.03.1)  % Galaxy: Center
%              }
%
   \title{The Dynamics of the Circumnuclear Disk and its environment in
the Galactic Centre}

   \author{B.~Vollmer\inst{1} \and  W.J.~Duschl\inst{2,1}}

   \offprints{B.~Vollmer, e-mail: bvollmer@mpifr-bonn.mpg.de}

   \institute{Max-Planck-Institut f\"ur Radioastronomie, Auf dem H\"ugel
69,
          D-53121 Bonn, Germany. \and
       Institut f\"ur Theoretische
       Astrophysik der Universit\"at Heidelberg, Tiergartenstra{\ss}e
15,
              D-69121 Heidelberg, Germany.}


   \date{Received / Accepted}

   \titlerunning{Dynamics of the CND and its environment}

\abstract{
We address the question of the dynamics in the inner 50~pc of the
Galactic Centre. In a first step we investigate the cloud--cloud
collision
rate in the Circumnuclear Disk (CND) with the help of a three
dimensional N--body code using gas particles that can have inelastic
collisions. The CND might be a longer lived structure than previously
assumed.
The whole disk--like structure of the CND can thus survive for several
million years. A realistic simulation of the CND shows the observed disk

height structure. In a second step the environment of the CND
is taken into account.
Retrograde and prograde encounters of a cloud of several
10$^{4}$~M$_{\odot}$ falling onto an already existing nuclear disk
using different energy loss rates per collision are simulated.
The influence of the energy loss rate per collision on the evolution
of the mass accretion and cloud collision rates is strongest
for a prograde encounter.
A composite data cube of two different snapshots of a prograde encounter

together with the CND shows striking similarity with the observed Sgr~A
cloud
complex. The current appearance of the
Galactic Centre environment can thus be explained by at least two
dynamically
distinct features together with the CND.
The current mass accretion rate within the CND ranges between
10$^{-3}$ and 10$^{-4}$~M$_{\odot}$\,yr$^{-1}$.
It can rise up to several 10$^{-2}$~M$_{\odot}$\,yr$^{-1}$
during massive accretion events.
\keywords{
Galaxy: Center -- ISM: clouds -- ISM: kinematics and dynamics}
}

\maketitle

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