COLORS AND KINEMATICS OF L DWARFS FROM THE SLOAN DIGITAL SKY SURVEY

摘要

We present a sample of 484 L dwarfs, 210 of which are newly discovered from the Sloan Digital Sky Survey (SDSS)Data Release 7 spectroscopic database. We combine this sample with known L dwarfs to investigate their izJHKScolors. Our spectroscopically selected sample has -0.1 mag bluer median J KS color at a given spectral type (forL0–L4) than previously known L dwarfs, which reflects a bias toward redder L dwarfs in past selection criteria.Wepresent photometric distance relations based on iz and iJ colors and derive distances to our L dwarf sample.We combine the distances with SDSS/2MASS proper motions in order to examine the tangential velocities. Forthe majority of our spectroscopic sample, we measured radial velocities and present three-dimensional kinematics.We also provide Hα detections for the fraction of our sample with sufficient quality spectra. Comparison of thevelocities of our L dwarf sample to a kinematic model shows evidence for both cold and hot dynamical populations,consistent with young and old disk components. The dispersions of these components are similar to those foundfor M dwarfs. We also show that J - KS color is correlated with velocity dispersion, confirming a relationshipbetween J - KS color and age.