On the homepage of the galaxies research group at CfA SAO, it states, "Astronomers discovered that as many as 25% of galaxies are currently merging with others." They do not provide a reference for this statement. I'm wondering what scientific articles demonstrate this expectation?
More specifically, is this expectation purely based on theoretical calculations from e.g. cosmological simulations of the Universe, or is it motivated from observations of merging galaxies?