Stellar kinematics of merging galaxies: Clues to the origins of elliptical galaxies

There is significant evidence suggesting that mergers of galaxies produce elliptical galaxies. To determine whether the known kinematic properties of elliptical galaxies are consistent with those of their suggested progenitors, we have examined the stellar velocity dispersion in 11 nuclear regions within starbursting infrared-luminous galaxies. All of these galaxies are in some stage of merging. The new data are presented and statistically analyzed in combination with data from the literature. We find that the kinematic and photometric properties of these galaxies suggest that they are the progenitors of low-luminosity (L < L*) elliptical galaxies. Dissipative collapse of gas followed by star formation is apparently not producing a core of high-density high-velocity dispersion stars like those found in very bright elliptical galaxies. We suggest that only the ultraluminous infrared galaxies can possibly produce L* ellipticals. We further present the results of population synthesis models that show that intermediate-age stellar populations should contribute significantly to the light of merger remnants even after the morphological signs of merging have vanished.