Astr 5460     Mon., Oct. 4, 2004
   This week: Galaxy Interactions
Tides
Simulations
Warps
Dynamical Friction
Shells
(Ch. 7, Combes et al., parts)
  Unless noted, all figs and eqs from Combes et al or Longair.

Galactic Tides

Galactic Tides

Galactic Tides
Tidal forces experienced by an object of diameter d in gravitational interaction with galaxy mass M a distance D away:
Ftide ~ GMd/D3 (differentiating Newton)
(Why not exactly equal?)
Therefore tidal forces very sensitive to D

Galactic Tides
The text goes into some detail about an analytical approach under a number of simplifying assumptions (p. 183-186).
I’m not going to go through it in class, but do look at it.  It is similar to some items in Chapter 6 we skipped.
The real way to do this anyway is through numeric simulation.

Galactic Tides
M51 and simulation (Toomre & Toomre 1972)

Galactic Tides
Antennae Galaxies: http://www.cita.utoronto.ca/~dubinski/antennae/antennae.html

Galactic Tides
Gas and simulation in text (TT72).

Galactic Tides
Simulation of “The Mice” in text.
Redone more recently by Barnes.

Galactic Simulations
Joshua Barnes: http://www.ifa.hawaii.edu/faculty/barnes/transform.html
John Dubinksi:
http://www.cita.utoronto.ca/~dubinski/nbody/
Chris Mihos:
http://burro.astr.cwru.edu/models/models.html
Bob Berrington (yes, our Bob):
http://physics.uwyo.edu/~rberring/
There are others…

For Next Time
More on interactions, distortions, and dynamical friction.
Chapter 8 in Combes et al. on radio sources.
Continue on Data Reduction and Analysis
New problem set, old homework returned.