2004AJ....127.1131W

We present the results of near-infrared imaging and low-resolution near-infrared spectroscopy of low-mass objects in the NGC 1333 molecular cloud. A JHK survey of an 11'.4x11'.7 area of the northern cluster was conducted to a sensitivity of K≤16 mag. Using near-infrared magnitudes and colors from this and previously published surveys, 25 brown dwarf candidates were selected toward the high-extinction cloud core. Spectra in the K band were obtained and comparisons of the depths of water vapor absorption bands in our candidate objects with a grid of dwarf, subgiant, and giant standards were made to derive spectral types. These data were then used to derive effective temperatures and stellar luminosities that, when combined with theoretical tracks and isochrones for pre-main-sequence objects, resulted in estimates for their masses and ages. The models suggest a median age for the sample of less than 1 Myr with substellar masses for at least nine of the candidates, including the X-ray flare source ASR 24. Surface gravities have been estimated for the brown dwarf candidates and, for a given spectral type, are found to more closely resemble dwarfs than giants. Using the near-infrared imaging data and age estimates from the spectroscopic sample, an extinction-limited sample in the northern cluster was defined. Consistent with recent studies of other young clusters, this sample exhibits an accretion disk frequency of 0.75±0.20 and a mass spectrum slope across the hydrogen-burning limit of α≤1.6, where dN/dM∝M^–α.