Program: GS-2007A-Q-17

Over the last three decades multi-wavelength observations and numerical simulations have shown that spiral-spiral mergers are capable of forming elliptical galaxies. A critical question which remains unanswered is whether these mergers are capable of forming giant elliptical galaxies (gEs). The answer will have an impact on recent results which show the red-sequence of (presumably) early-type galaxies in place as early as z $\sim$ 1. Recent results suggest that the high-mass end of the red-sequence can only be formed via dissipationless merging of early-type galaxies. However, some kinematic observations of mergers in the local universe appear to support this conclusion, while others show it possible to form massive ellipticals via dissipative spiral-spiral mergers. The controversy lies in observations of luminous and ultra-luminous infrared galaxies (LIRGs/ULIRGs). Using the infrared CO stellar absorption line (2.29$\micron$), estimates of the dynamical mass show merger remnants with m$_{dyn}$ $\leq$ m*. Measurements made with the optical Ca triplet line (8500 {\AA}) show mergers with m$_{dyn}$ $>$ m*. Thus, optically measured velocity dispersions ($\sigma$) are {\it larger} than those measured in the infrared. To date, observations of both the CO and Ca triplet absorption lines have been made almost solely for LIRGs/ULIRGs (with 1 exception). The goal of this project is to measure the infrared CO absorption line in a sample of non-LIRG/ULIRG mergers for which optical Ca triplet measurements have been published. The goal is to determine whether the mismatch between the Ca triplet and CO absorption is the result of stellar population effects or some other physical property.