The Fate of Ultra-luminous Mergers

Abstract

Essentially all Ultra-Luminous IR Galaxies (ULIRGs) are in disturbed, interacting or merging systems. It is known that interactions tend to induce galactic starbursts. Thus, elliptical galaxies which are formed in mergers will tend to have high metallicity, low dust and molecular gas content, and faint structural distortions, as observed for the bone fide elliptical galaxy population. The old stellar population in the merged galaxies will probe the new gravitational potential, relaxing rapidly to give a de Vaucouleurs surface-brightness profile if the remnant is elliptical-like. We examine the old stellar population in 10 nearby (z < 0.15) ULIRGs, using deep near-IR imaging photometry. These data reveal signs of elliptical-like structure in the near-IR one-dimensional surface brightness profiles, supporting the hypothesis that ultra-luminous mergers evolve into elliptical galaxies.