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From: Chang Won Lee  cwlee@protostar2.harvard.edu 
To: gcnews@aoc.nrao.edu
Subject: submit gdyn_abs.tex, accepted for publication in ApJ

%astro-ph/9810043
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\title{SPH Simulations of Galactic Gaseous Disk with Bar: Distribution and 
Kinematic
Structure of Molecular Clouds toward the Galactic Center}

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\author{C. W. Lee$^{1,2}$, H. M. Lee$^1$, H.B. Ann$^1,3$ \& K.H. Kwon$^1$
}
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\institute{
$^1$Department of  Earth  Science,  Pusan  National  University, Pusan
609-735, Korea

$^2$Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, MA 021
38, USA; cwlee@cfa.harvard.edu

$^3$Department of Astronomy, Seoul National  University, Seoul 151-742, Korea
}
E-mail: cwlee@cfa.harvard.edu, hmlee@astro.snu.ac.kr,
hbann@astrophys.es.pusan.ac.kr, khkowen@astrophys.es.pusan.ac.kr

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\begin{abstract}
We have performed Smoothed Particle Hydrodynamic (SPH)
simulations to study  the response of molecular clouds in the Galactic disk
to a rotating bar and their subsequent evolution in the Galactic Center (GC) 
region.
The Galactic potential in our models  is contributed by
three axisymmetric
components (massive halo, exponential disk, compact bulge) and
a non-axisymmetric bar. These components are assumed to be invariant
in time in the frame corotating with the bar.
Some noticeable features such as
an elliptical outer ring, spiral arms, a gas-depletion region,
and a central concentration have been developed due to the influence
of the bar.
The rotating bar induces non-circular motions
of the SPH particles, but hydrodynamic collisions tend to suppress the
random components of the velocity. The velocity field of the SPH particles
is consistent with the kinematics of molecular clouds observed
in HCN ($1-0$) transition; these clouds are
thought to be very dense clouds. However, the $l-v$ diagram of the clouds
traced by CO is quite different from that of our SPH simulation, being
more similar
to that obtained from simulations using collisionless particles.
The $l-v$ diagram of a mixture of collisional
and collisionless particles gives better
reproduction of the kinematic structures of the GC clouds observed in the CO
line.
The fact that the kinematics of HCN clouds can be reproduced by the SPH 
particles
suggests that the dense clouds in the GC are formed via cloud collisions induced
by rotating bar.
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