2007MNRAS.382..951R

We present the results of H- and K-band very large telescope/Spectrograph for INtegral Field Observations in the Near Infrared (VLT/SINFONI) integral field spectroscopy of the Ultraluminous Infrared Galaxy (ULIRG) IRAS 19254-7245 (the Super-antennae), an interacting double galaxy system containing an embedded active galactic nuclei. Deep K-band spectroscopy reveals Paα arising in a warped disc with position angle of 330° and an inclination i = 40°-55°. The kinemetric parameters derived for H₂ are similar to Paα. Two high-ionization emission lines, [Sivi] and [Alix], are detected and we identify as [NIII] the line observed at 1.94µm. Diluting non-stellar continuum, which was previously detected, has decayed, and the H-band continuum emission is consistent with pure stellar emission. Based on H₂emission-line ratios, it is likely that at the central 1-kpc region H₂ is excited by ultraviolet fluorescence in dense clouds while shock excitation is dominant further out. This scenario is supported by very low Paα to H₂line ratio detected outside the nuclear region and non-thermal ortho/para ratios (∼2.0-2.5) close to the nucleus.