For the Summer of 2004, I worked with my Advisor
Dr Bob Benjamen on the Orbital decay of high velocity
clouds(HVC).The objective was to verify
the fate of high velociy gas clouds(HVC) as they orbit a galaxy.


What I did/am doing

I started off reading about the Ballistic model of Halo rotaion
of Diffused Ionized Gas(DIG).The Ballistic model
suggests that in spiral galaxies, clouds are
ejected from the disc and follow a ballistic
trajectories through the halo.It was mainly
to get insight on the behavior of gas clouds

I worked with models that were generated
using FORTRAN and visualized with IDL

Dr Benjamin had written a Fortran program which,
,randomly selects points
and gets them to go in an orbit aroung the galaxy.
I mainly worked with Dr Benjamin's program which I modified such
that it gets a "cloud" of points going
in an orbit .

Because I had to deal with equations of
motion ,I used a set of six
coupled differential eqautions
For accuracy I started off with eqautions with
known solutions.Using IDL I could verify whether the
mechanical energy and angular momentum of the
system is conserved.From the plots I got, the mechanical energy
and angular momentum are conserved(plot below)to a very
close percentage(about 0.01%).

(top;kinetic,bottom;potential;striaght line;total energy)

(top x and y,striaght line;z angular momentum)

Seeing that energy and angular momentum are conserved
I used another system in which a cloud of points in a galaxy are chosen and allowed
to orbit the galaxy(I got to write the fortran program for it)
Using the Runge-Kutta method of numerical recipes.

Using one of Dr Benjamin's IDL programs,the
motion of the cloud of points could be followed over time
The cloud of points follow and orbit around the galactic
center,spreading out in doing so.
I then ran several models to observe any
change in the breakup of the cloud as several
initial parameters are changed.
Sample runs

What Next?

I did my runs neglecting drag. It would be
nice to try runs with drag. It
will also be nice to study the
orbits of clouds further away from the galaxy
and the effect of posible outflows from the galactic center.
I still have to do runs which consider the effect of magnetic
force on the drag of the clouds or the self
gravity of the cloud
Last but not the least,we have to work on how
to convince people the models could be real.



My Final Presentation

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