Simulating Collisions of Galaxies

Research Team

Lucio Mayer
Rejean Dupuis
Vishal Goklani

Research Adviser: Neal Katz

Galactic Interactions

Encounters
Mergers

Groups --> Low velocity dispersion --> Mergers
Clusters --> High velocity dispersion --> High speed encounters
Harassment - repeated high speed encounters

Our Simulations

Single high speed encounter between small late type spiral and equal mass perturber
Perturber = external force added to particles' accelerations
Galaxy: M=2x10¹¹ M_O with halo plus disk
- halo: truncated isothermal sphere, 80% of total mass
- disk: stars + gas, exponential profile
N=50,000; softening < 1 kpc; time step = 0.001 Gyr; TREESPH with no star formation

Conclusions

MPEG Movies
- encounter velocity = 1000 km/s, impact parameter = 10 kpc (10.2 Mb)
- encounter velocity = 2000 km/s, impact parameter = 5 kpc (10.2 Mb)
Movies and rotation curves suggest the galaxy is undergoing a morphological transformation
Density plots clearly show the central gas density is increasing

Future Work

Extend to longer timescales to discover the nature of the remnants
Explore a wider parameter space of initial conditions
Include star formation
More analysis (velocity dispersion vs. time, evolution of shape, mass loss)

Hypothesis

Late type Sc-Sd, LSB --> dSph
HSB spirals (systems with bulge) --> S0