Exploring galactic structure with the Fan Observatory bench optical spectrograph

This dissertation describes a measurement of the vertical Galactic density law and metallicity distribution. In addition, the design, construction, and performance of the Fan Observatory Bench Optical Spectrograph are discussed.; The Galactic density law and metallicity distribution are explored using G and K giants selected from multiple catalogues. A photometric survey covering 185 square degrees at the North Galactic Pole has been conducted using a combined Washington and DDO filter system specially tuned for luminosity class discrimination in late type stars, and with which stellar metallicities can be estimated. The bright magnitude range is supplemented with giant stars selected from the Hipparcos and Tycho-2 catalogues based on reduced proper motion. Several hundred giant candidates have been observed spectroscopically to confirm their luminosity classifications and measure metal abundances. The density distribution is constructed and best fit by a three component exponential density law, with a thin disk scale height of 300 parsecs, a thick disk scale height of 1100--1200 parsecs, and a thick disk normalization of 2% relative to the thin disk in the Galactic midplane. The vertical metallicity distribution exhibits a -0.1 dex kpc-1 gradient to z = 3.5 kiloparsecs and an abrupt drop at ∼5 kiloparsecs. Evidence is presented that the thin disk, thick disk, and halo are chemically distinct entities, and that the thick disk was formed through a primordial minor merger.; The Fan Observatory Bench Optical Spectrograph (FOBOS) has recently seen first light through the 40 inch reflecting telescope at the University of Virginia's Fan Mountain Observatory. The instrument is intended for single-object optical spectroscopy with moderate resolution (R ∼ 1500--3000) capabilities using a fiber-fed bench spectrograph to maintain stability. The specifications of the instrument were motivated by several ongoing projects in Galactic astronomy that require consistently well-measured radial velocities for reasonably large numbers of broadly distributed and relatively bright stars. The spectrograph will be useful throughout the optical spectrum for observing stars brighter than V ∼ 14. Test data indicates that the instrument is stable and capable of accurately measuring radial velocities with precisions better than 3 km sec-1 at a resolution of R ∼ 1500 and with minimal calibration overhead.