VLT/SINFONI integral field spectroscopy of the Super-antennae

Abstract

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 19 254-7245 (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, [Si vi] and [Al ix], are detected and we identify as [Ni ii] the line observed at 1.94 μm. Diluting non-stellar continuum, which was previously detected, has decayed, and the H-band continuum emission is consistent with pure stellar emission. Based on H2 emission-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 H2 line ratio detected outside the nuclear region and non-thermal ortho/para ratios (∼2.0-2.5) close to the nucleus. © 2007 The Authors. Journal compilation © 2007 RAS.