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Stellar Tracers and Galactic Exploration
This dissertation discusses various techniques for studying the structure of the Milky Way via the use of stellar tracers. One of the most widely used stellar tracers is blue horizontal branch stars, which are prized for their predictable and substantial intrinsic brightnesses and their old ages. We begin by creating a z based photometric color cut for the selection of blue horizontal branch stars which may be used in data produced by the Panoramic Survey Telescope and Rapid Response System. Using this color cut, we select a sample of blue horizontal branch stars and pass them through a newly devised search algorithm which is capable of finding overdensities in incomplete and patchy data. From this, we rediscover a number of well known Milky Way features and discover a new constraining detection of the Sagittarius tidal streams. If we use spectroscopy in addition to photometry, we can isolate another stellar tracer, main sequence stars. A main sequence star's intrinsic magnitude is a function primarily of the mass and metallicity of the star; so with spectroscopy and photometry we can easily estimate the distance to these types of objects. We collect a sample of F-M type dwarf stars from the Sloan Digital Sky Survey spectroscopic data set. Having spectroscopy and astrometry, we may assign six-dimensional phase information to these objects and then use that information to study their bulk motions as a function of position. Here, instead of looking for large structure, we instead look to aberrations from large structure: using this relationship between motion and position as a probability density function, we select and characterize significant outliers. We also identify phenomenological objects such as hypervelocity and Hills stars. These types of stars are indirect probes of the Milky Way and are most useful for studying: the potential of the Milky Way, the locations of extreme overdensities such as spiral arms or black holes, and the structure of observationally obscure areas like the Galactic nucleus. During these studies of the motions and positions of stellar tracers in the Milky Way, accurate reports of the proper motions are of critical importance. To investigate this we closely examine proper motions in the Sloan Digital Sky Survey and the PPMXL proper motion catalogs and devise metrics for estimating the accuracy of these proper
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520 Astronomie
520 Astronomy and allied sciences
530 Physik
530 Physics