UC Santa Cruz

The availability of large sky surveys, including the SDSS and DESI, have revolutionized research across various fields from the large-scale structure of the universe to the evolutionary historiesof the Milky Way and its satellite galaxies. In my thesis, I utilize machine learning methods to analyze the large datasets from SDSS and DESI. I first show new measurements of the mean transmitted flux in the hydrogen \lya\ and a measurement of the relative transmitted flux in \lyb. This measurement uses 27,008 quasar spectra from the Fourteenth Data Release (DR14) of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). The \tlya\ values show a smooth increase by a factor of 5 over the redshift range $z=2.4-4.4$. I then investigate the spatial distribution, kinematics and metallicity of the Draco and Sextans dwarf spheroidal galaxies using DESI data. For Draco, I find minimal evidence for an extended distribution of stars and conclude it has not been significantly tidally disturbed or undergone extensive tidal stripping. For Sextans, through 6D orbit integration, I identify 16 candidate extra-tidal stars and argue that Sextans may have had significant dynamical interactions, possibly with other dwarf galaxies before accretion by the Milky Way.