BDKP. V. Radial & rot. velocities of M, L, T dwarfs

We find a kinematic age of 3.5+/-0.3Gyr for local T dwarfs, consistent with nearby late M dwarfs (4.1+/-0.3Gyr). Removal of thick-disk L dwarfs in the local ultracool dwarf sample gives a similar age for L dwarfs (4.2+/-0.3Gyr), largely resolving the local L dwarf age anomaly. The kinematic ages of local late M, L, and T dwarfs can be accurately reproduced with population simulations incorporating standard assumptions of the mass function, star formation rate, and brown dwarf evolutionary models.

A kinematic dispersion break is found at the L4-L6 subtypes, likely reflecting the terminus of the stellar main sequence. We provide a compilation of precise radial velocities for 172 late M, L, and T dwarfs within ~20pc of the Sun.