Tidal Tails of Interacting Galaxies

[Tidal tails sample image] Below are the static images used in my January 2008 Computational Physics exercise (part of Physics II), with some accompanying animations.

Warning! The animated gifs should be opened with care. Some are >1MB. On some systems programs seem to use a lot of memory (RAM) to open them.

Stage 1: A Single Model Galaxy

  1. After 0 iterations - initialisation
  2. Time step (h) = 0.01, after 1e6 iterations - still a stable circular orbit
  3. Time step (h) = 5.0, after 1e6 iterations - circular orbit just breaking down

Stage 2: Two Interacting Galactic Centres

Attraction of Static Masses

Time step (h) = 0.01

  1. After 0 iterations - initialisation
  2. Softening length = 0.5, after 2.6e4 iterations - Particles have passed each other at the origin, and stop at ~ same distance as at start
  3. (Animated) Softening length = 0.5 - See warning
  4. Softening length = 0, after 5.2e4 iterations - Particles reach middle and experience very large forces, and fly out at large speed (note distance)
  5. (Animated) Softening length = 0 - See warning

Parabolic orbits

Time step (h) = 0.01, softening length = 0.5
Starting coordinates: galaxy 1 (0,0), galaxy 2 (35,-50)
Starting velocities: galaxy 1 (0,0), galaxy 2 (0,0.181)

  1. One mass fixed, galaxy trails - 2e6 iterations
  2. One mass fixed, energy plot - 2e6 iterations
  3. Two masses, galaxy trails - 2e6 iterations
  4. Two masses, energy plot - 2e6 iterations
  5. Two masses, galaxy trails - 1e7 iterations
  6. Two masses, energy plot - 1e7 iterations

Stage 3: Two Interacting Galaxies with Test Masses

Softening length = 0.5
Starting coordinates: galaxy 1 (0,0), galaxy 2 (35,-50)
Starting velocities: galaxy 1 (0,0), galaxy 2 (0,0.181)

  1. (Animated) Tidal Tails at same scale as s2_10.gif above - See warning (1.0MB), time step (h) = 0.01
  2. Iteration 0 from above animation
  3. Iteration 23000 from above animation
  4. Iteration 26000 from above animation
  5. Iteration 31000 from above animation
  6. Iteration 38000 from above animation
  7. Iteration 56000 from above animation
  8. Iteration 75000 from above animation
  9. (Animated) Tidal Tails Close up - See warning (3.4MB), time step (h) = 0.001
  10. Iteration 230000 from above animation
  11. Iteration 260000 from above animation
  12. Iteration 310000 from above animation