I am aware of upper limits to the mass of burning stars and neutron stars, beyond which they degenerate into neutron stars and black holes respectively. And also, if I understand it right, there is a maximum event horizon radius for black holes, related to the CMB, beyond which the black hole will evaporate down to an equilibrium "temperature" / "volume".
But is there any theoretical upper limit to the "size" of a single galaxy in any meaningful sense? It appears that all of the largest galaxies are of the elliptical type.
And if there are upper limits, what brings about these limits, and what happens to galaxies that exceed them through collision/absorption, collapse into the central black hole, etc?
I guess I'm wondering if there is something exotic at play, like if gravity can't hold a galaxy together past a certain size due to relativistic effects, or something like that.