AN ARGUMENT AGAINST MERGERS OF THE FAINT BLUE GALAXIES

The population of ''excess'' faint blue galaxies with B < 24 cannot be removed through merging between z almost-equal-to 0.35 and the presen t. At z = 0.35, the B luminosity density of galaxies with L > 0.1L is 2-5 times greater than the local luminosity density. While merging ca n reduce the number density of galaxies, it cannot substantially chang e the luminosity density. I show that the luminosity density of the me rged galaxies would exceed the total luminosity in ellipticals (the li kely merger products), even when there has been substantial fading of the faint galaxies. Likewise, there is not enough mass in spiral galax ies to have accreted these galaxies without heating the disks beyond w hat is observed. Assuming that the faint blue galaxies fade by DELTAB = 2.2 and have mass-to-light ratios typical of irregular galaxies, onl y 5%-15% of the mass in galaxies at z = 0.35 can have merged into the local population of elliptical and spiral galaxies. These arguments ar e independent of the correlation function of the faint blue galaxies a nd the recent history of the merger rate, and they are valid for 0 < O MEGA less-than-or-equal-to 1.