ELLIPTICAL-LIKE LIGHT PROFILES IN INFRARED IMAGES OF MERGING SPIRAL GALAXIES

Theoretical studies indicate that in collisions between disk galaxies, dynamical friction and subsequent relaxation will eventually produce a mass distribution indistinguishable from that of an elliptical galaxy. However, there are also theoretical and observational arguments against this process1,2. Schweizer's pion-eering paper3, which showed that the V-light profile of the merging galaxy NGC7252 is indeed well fitted by the r1/4 de Vaucouleurs law, remains the only observational evidence in support of this idea. In most candidate mergers the optical structure is complicated because of emission from star-forming regions and obscuration by dust lanes, and there is no overall resemblance to ellipticals. In the near-infrared, extinction and the effects of hot young stars are much reduced. Accordingly we have obtained ? images of six galaxies which are believed to be mergers of disk galaxies. Two of the six, NGC2623 and Arp220, appear to obey the r1/4 law to the limits of our images, offering new support for the idea that mergers of spirals can evolve into elliptical-like objects. © 1990 Nature Publishing Group.