Deep Fabry-Perot Imaging of NGC 6240: Kinematic Evidence for Merging Galaxies

Abstract We have observed the superluminous, infrared galaxy NGC 6240 (z = 0.025) at Ha with the Hawaii Imaging Fabry-Perot Interferometer (HIFI – Bland and Tully 1989). During the past decade, observational evidence from all wavebands indicates that the unusual appearance of NGC 6240 has resulted from a collision between two gas-rich systems, a view which is supported by our spectrophotometnc data. However, the origin of the enormous infrared luminosity (4 × 1011 L0) detected by IRAS remains highly controversial, where opinions differ on the relative roles of large-scale shocks, massive star formation or a buried “active” nucleus. These mechanisms are discussed in the light of our Fabry-Perot observations.