L dwarfs found in Sloan Digital Sky Survey commissioning imaging data

This paper describes the discovery of seven dwarf objects of spectral type L (objects cooler than the latest M dwarfs) in commissioning imaging data t aken by the Sloan Digital Sky Survey (SDSS). Low-resolution spectroscopy sh ows that they have spectral types from L0 to L8. Comparison of the SDSS and the Two Micron All Sky Survey (2MASS) photometry for several of these obje cts indicates the presence of significant opacity at optical wavelengths. T his comparison also demonstrates the high astrometric accuracy (better than 1 " for these faint sources) of both surveys. The L dwarfs are shown to oc cupy a distinctive region of color-color space as measured in the SDSS filt ers, which should enables their identification in a straightforward way. Th is should lead eventually to a complete sample of many hundreds of these lo w-mass objects, or about 1 per 15 deg(2) to i' approximate to 20, in the co mplete SDSS data set.