Program: GS-2006B-Q-59

Over the past several years, our team has spectroscopically classified hundreds of late-type dwarfs selected photometrically from 2MASS. Through this effort we have uncovered 35 low-gravity late-M and L dwarfs within the immediate Solar Vicinity ($<$60 pc). Low gravity indicates that these objects are very young, have lower mass, and have more extended atmospheres than typical field M and L dwarfs of the same temperature. Many of these objects are expected to be low-mass brown dwarf members of the nearby young groups TW Hya, $\beta$ Pic, AB Dor, and Tuc-Hor, which are confined largely to the southern sky. In addition, we are finding low-gravity brown dwarfs even at high northern declinations ($\sim$+40 deg). This proposal is part of a campaign to better characterize our entire sample, including this mysterious northern subset. Here we would like to 1) acquire optical spectra for those sources having only near-IR spectra or to improve the SNR for those with poor optical data, and 2) to characterize the strength of lithium, a standard indicator of substellarity but a potentially problematic one at low gravities. Studying the nature of these objects will help us better understand the low-mass end of star formation in sparse associations and more accurately measure the properties of low-temperature atmospheres at low gravities.