Inner structure and global kinematics: arp 220 revisited

With an infrared luminosity of 1012.2Lo-dot, Arp 220 is one of the prototypical Ultraluminous Infrared Galaxies. It's high IR luminosity, the presence of tidal tails detected in the optical, the double infrared and radio nuclei, and the perturbed optical ionized gas kinematics measured at large scales support the fact that Arp 220 is the late phase of an on-going merger. This, along with the most accepted evolutionary theories for ULIRGs, indicate that Arp 220 may evolve into an intermediate mass elliptical galaxy. Nonetheless, there are several questions that still remain open, such as the exact location and number of nuclei, their relation with the X-ray emission, and the kinematic behavior of the galaxy at different scales. Here we give an overview of what we know about Arp 220 up-to-date, regarding the NIR and radio regime, and report on new insights in kinematics and the structure on larger spatial scales of the merger making use of IRAM PdBI observations.