Program: GS-2004B-Q-30

Using 2MASS data, we have completed the first systematic, all-sky survey for ultracool dwarfs within 20 parsecs of the Sun. With follow-up observations of 95\% of our candidates, we have identified 100 new nearby late-M and L dwarfs, tripling the local census. In this proposal, we aim to complete observations of the final 100 candidates. Spectral types provide the most reliable distance estimates ($\sigma_d \sim \pm 15\%$) for L dwarfs, but it is crucial that those types are derived from {\sl optical} spectra. Experience has shown that near-infrared classifications often differ by 2-3 spectral classes from the optical benchmarks, corresponding to $\Delta M_J = 1$ to 1.5 magnitudes, or $\delta d \sim 60 - 100\%$. Systematic errors of this magnitude obviously results in substantial uncertainties in derived space densities. We therefore propose to finalise our luminosity function analysis by observing 47 moderately-bright southern sources with the CTIO 4-metre, while using GMOS on the Gemini telescopes to obtain red spectra of the remaining 53 fainter (J$>$15.2) candidates. The latter sample is likely to include the coolest, lowest-luminosity L dwarfs in the immediate Solar Neighbourhood.