Colors and Kinematics of L Dwarfs From the Sloan Digital Sky Survey
Abstract
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 izJHKS colors. Our spectroscopically selected sample has 0.1 magnitude bluer median J-KS colors at a given spectral type (for L0 to L4) than previously known L dwarfs, which reflects a bias towards redder L dwarfs in past selection criteria. We present photometric distance relations based on i-z and i-J 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. For the 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 the velocities 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 found for M dwarfs. We also show that J-KS color is correlated with velocity dispersion, confirming a relationship between J-KS color and age.