1. The Fate of Intergalactic Gas Clouds
Jeremy Harrison
Chicago State University

2. Introduction to High Velocity Gas Clouds (HVC;s)
How does drag affect HVC’s?
How long will it take our galaxy to “eat” high velocity clouds?

3. AN ALL SKY MAP OF HIGH VELOCITY CLOUDS
(Wakker et al 2003)

4. A few values and formulas

6. Solve using Runge-Kutta Method.
Numerical Analysis,
Computer programs
Solve using Runge-Kutta Method.
• The gravitational field, g, comes from the mass model of the Galaxy.
• The drag coefficient,b, depends on cloud column density and the ambient density of the Galaxy.
• Runge-Kutta has various test steps along the way to get a feel of how the slope is going!

7. x Equatorial cloud 1 Equatorial cloud 2 Equatorial cloud 3 Complex H
No drag S.
drag C.
Drag 21
Density floor
Rot.
Scale 5
C. Drag 18
21 &
Rot. Scale
Equatorial cloud 1 x
Equatorial cloud 2
Equatorial cloud 3
Complex H
Magellanic stream
Polar Cloud

8. Equatorial Cloud 1 (No drag)

9. Equatorial Cloud 2 (N=1020 cm-2; Standard drag)

10. Equatorial Cloud 1 (N=1020 cm-2; Rotation drops as e-z/(5 kpc)

11. Polar Orbit Cloud 1 (N=1020 cm-2; Standard drag)

12. Complex H (N=1018 cm-2; Standard drag)

13. Dramatic (but Preliminary) Conclusions
In the presence of drag, gas clouds tend to quickly move to circular orbits.
For “standard” parameters, clouds moving in the equatorial plane reach a stable circular orbit in less than 750 Myrs. For clouds in polar orbits, it takes more than 2000 Myrs to circularize!
Clouds typically end up at R~10 to 20 kpc.
For clouds with column density > 1021 cm-2, the orbits are nearly ballistic. However, we do see some small decrease in velocity and a small change in z-component of angular momentum

14. Special Thanks To My advisor , Dr. Robert A. Benjamin and
NSF for funding the REU program.