Dynamics of Interactions & Mergers

Astronomy 626: Spring 1995

Bridges & Tails

The narrow `taffy-like' filaments seen in many interacting galaxies led to speculations that magnetic or other non-gravitational forces are involved in their formation. These speculations were finally put to rest by Toomre & Toomre's (1972; hereafter TT72) study of tidal interactions between disk galaxies.

As TT72 showed, bridges and tails are naturally produced by gravitational interactions between disk galaxies.

Orbit Decay

Tidal interactions distort galaxies, imparting energy and momentum to their internal constituents at the expense of their relative orbit. The decay of the relative orbit is most easily understood in terms of the transfer of angular momentum from the motions of the galaxies to their internal degrees of freedom.

Transfer of angular momentum may be understood in several different ways:

Violent Relaxation

Fueling of Starbursts


Joshua E. Barnes (barnes@zeno.ifa.hawaii.edu)

Last modified: April 25, 1995