A low-resolution near-infrared spectral library of M-, L-, and T-dwarfs

We present complete near-infrared (0.85-2.45 mu m), low-resolution (R similar to 100) spectra of a sample of 54 disk M-, L-, and T-dwarfs with reliable optical or near infrared spectral-type classification from the literature. The observations were obtained with a prism-based optical element, the Amici device, which provides a complete spectrum of the source on the detector. Our observations indicate that low-resolution near-infrared spectroscopy can be used to determine the spectral classification of late-type field dwarfs in a fast but accurate way. We derive a set of near-infrared spectral indices that are useful to the classification of field dwarfs not seriously affected by reddening. Finally, we show that the comparison of Amici spectra with model atmospheres allows us to obtain a reliable estimate of the dwarf effective temperatures.