1996A&AS..115..253L

We present 1.428 to 2.5µm spectra of a sample of ten infrared luminous galaxies, obtained with the Fourier Transform Spectrograph at the CFH Telescope. This critical wavelength range lies on the boundary between spectral regions dominated by emission from stars or from dust and non-thermal sources. Because of the large spectral range covered, non-stellar contributions can be identified through their effect on the continuum. Stellar energy distributions are characterised by their continua as well as by molecular features, essentially due to CO and H₂O. Eight of the luminous IRAS galaxy spectra are consistent with essentially stellar but highly obscured emission, and two clearly show an additional non-stellar contribution. The preliminary analysis of the starburst spectra is based on evolutionary population synthesis and on a library of near-IR stellar spectra obtained with the same instrument. Limits on the burst durations and the relative contributions of emission components, and estimates of the extinction are derived. The discussion accounts for the area over which the spectra are integrated and to some extent for the inhomogeneous space distribution of the components. While strong CO absorption identifies powerful bursts aged ∼9Myr or more, a near-IR stellar energy distribution dominated by giant stars can hide the blue emission from a very young burst, revealed only by emission lines (NGC253). Model predictions and the detailed analysis of individual starburst spectra will be presented more extensively in a following paper.