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Low-Mass Stars in the Sloan Digital Sky Survey: Galactic Structure, Kinematics, and the Luminosity Function

Modern sky surveys, such as the Sloan Digital Sky Survey and the Two-Micron All Sky Survey, have revolutionized the study of low-mass stars. With millions of photometric and spectroscopic observations, intrinsic stellar properties can be studied with unprecedented statistical significance. Low-mass stars dominate the local Milky Way and are ideal tracers of the Galactic potential and the thin and thick disks. Recent efforts, driven by SDSS observations, have sought to place the local low-mass stellar population in a broader Galactic context. I highlight a recent measurement of the luminosity and mass functions of M dwarfs, using a new technique optimized for large surveys. Starting with SDSS photometry, the field luminosity function and local Galactic structure are measured simultaneously. The sample size used to estimate the LF is nearly three orders of magnitude larger than any previous study, offering a definitive measurement of this quantity. The observed LF is transformed into a mass function and compared to previous studies. Ongoing investigations employing M dwarfs as tracers of Galactic kinematics are also discussed. SDSS spectroscopy has produced databases containing tens of thousands of low-mass stars, forming a powerful probe of the kinematic structure of the Milky Way. SDSS spectroscopic studies are complemented by large proper motion surveys, which have uncovered thousands of common proper motion binaries containing low-mass stars. Additionally, the SDSS spectroscopic data explore the intrinsic properties of M dwarfs, including metallicity and magnetic activity. The highlighted projects demonstrate the advantages and problems with using large data sets and will pave the way for studies with next-generation surveys, such as PanSTARRS and LSST.