Follow-up NIR spectroscopy of ULIRGs observed by ISO

We discuss low resolution near-infrared spectroscopy of an unbiased sample of 24 ultraluminous infrared galaxies (ULIRGs), selected from samples previously observed in the mid-infrared with ISO. Qualitatively, the NIR spectra of our 24 ULIRGs resemble those of starbursts. The spectroscopic classification in the NIR is in very good agreement with the MIR. For a subset of our sample for which extinction corrections can be derived from Pace and Br gamma, we find rather high Pa alpha luminosities, in accordance with the powering source of these galaxies being star formation. Furthermore, we identified two unusual objects, the first exhibiting extreme [FeII] emission and the second strong emission in H-2 rotation-vibration emission.