Cold minor-merger size growth
= Cold minor-merger size growth
{title2=$R_g\propto M^2$}
For repeated <minor galaxy mergers> with negligible internal satellite binding energy and zero orbital energy at infinity, <parabolic dry-merger energy accounting> leaves total energy nearly constant. The <virial theorem> then gives <gravitational radius> $R_g\propto M^2$ and mean-square speed proportional to $M^{-1}$. Small satellite mass does not by itself imply negligible internal binding energy.