Characterization of M, L, and T Dwarfs in the Sloan Digital Sky Survey

Abstract

An extensive sample of M, L and T dwarfs identified in the Sloan Digital Sky\nSurvey (SDSS) has been compiled. The sample of 718 dwarfs includes 677 new\nobjects (629 M dwarfs, 48 L dwarfs) together with 41 that have been previously\npublished. All new objects and some of the previously published ones have new\noptical spectra obtained either with the SDSS spectrographs or with the Apache\nPoint Observatory 3.5m ARC telescope. Spectral types and SDSS colors are\navailable for all objects; approximately 35% also have near-infrared magnitudes\nmeasured by 2MASS or on the Mauna Kea system. We use this sample to\ncharacterize the color--spectral type and color--color relations of late type\ndwarfs in the SDSS filters, and to derive spectroscopic and photometric\nparallax relations for use in future studies of the luminosity and mass\nfunctions based on SDSS data. We find that the (i*-z*) and (i*-J) colors\nprovide good spectral type and absolute magnitude (M_i*) estimates for M and L\ndwarfs. Our distance estimates for the current sample indicate that SDSS is\nfinding early M dwarfs out to about 1.5 kpc, L dwarfs to approximately 100 pc\nand T dwarfs to near 20 pc. The T dwarf photometric data show large scatter and\nare therefore less reliable for spectral type and distance estimation.\n