The Brown Dwarf Kinematics Project (BDKP). IV. Radial Velocities of 85 Late-M and L dwarfs with MagE

摘要: Radial velocity measurements are presented for 85 late M- and L-type very low mass stars brown dwarfs obtained with the Magellan Echellette (MagE) spectrograph. Targets primarily have distances within 20 pc of Sun, more distant sources selected their unusual spectral energy distributions. We achieved precisions 2--3 km/s, combined these astrometric spectrophotometric data to calculate $UVW$ velocities. Most members thin disk Galaxy, dispersions indicate a mean age 5.2$\pm$0.2 Gyr pc. find significantly different kinematic ages between late-M (4.0$\pm$0.2 Gyr) L (6.5$\pm$0.4 in our sample that contrary predictions from prior simulations. This difference appears be driven by dispersed population unusually blue which may prevalent local volume-limited than deeper magnitude-limited surveys. The exhibit an asymmetric $U$ distribution net inward flow, similar gradients recently detected stellar samples. Simulations incorporating dwarf evolution Galactic orbital dynamics unable reproduce asymmetry, suggesting non-axisymmetric perturbations or two distinct populations. also age-activity correlation massive stars. identify several surface gravities, new substellar candidate nearby young moving groups: binary DENIS J08230313$-$4912012AB, low-probability member $\beta$ Pictoris Moving Group; 2MASS J15104786-2818174, moderate-probability 30-50 Myr Argus Association.