2003ApJ...595L..17R

We present an L-band spectrum of the ultraluminous infrared galaxy IRAS 19254-7245 (the Superantennae), obtained with the Infrared Spectrometer and Array Camera on the Very Large Telescope. The high signal-to-noise ratio allows us to study the main spectral features with unprecedented detail for an extragalactic source. We argue that the main energy source in the IR is an obscured active galactic nucleus. This is indicated by the low equivalent width of the 3.3 µm polycyclic aromatic hydrocarbon feature, the broad absorption feature at 3.4 µm, and the steep continuum at λ>3.7 µm (f_λ∝λ^2.7). The substructure of the 3.4 µm absorption feature indicates that the absorption is due to hydrocarbon chains of six to seven carbon atoms.