  For the past several years, our group has pursued a vigorous ground-based
program aimed at understanding the nature of ultraluminous infrared galaxies.
We recently published the results from a optical/near-infrared spectroscopic
survey of a large statistically complete sample of ultraluminous infrared
galaxies (the "IRAS 1-Jy sample"). We now present the results from our recently
completed optical/near-infrared imaging survey of the 1-Jy sample. These data
provide detailed morphological information on both large scale (e.g., intensity
and color profiles, intensity and size of tidal tails and bridges, etc) and
small scale (e.g., nuclear separation, presence of bars, etc) that helps us
constrain the initial conditions necessary to produce galaxies with such high
level of star formation and/or AGN activity. The nature of the interdependence
between some key spectroscopic and morphological parameters in our objects
(e.g., dominant energy source: super-starburst versus quasar, nuclear
separation, merger phase, star formation rate, and infrared luminosity and
color) is used to clarify the connection between starbursts, ultraluminous
infrared galaxies, and quasars.
