| BL Lacertae objects compose an especially exotic subclass of Active Galactic Nuclei (AGN) characterized by strong multiwavelength emission, notable polarization, marked variability, and nearly featureless optical spectra. Their observed properties are explained in the standard paradigm as low-luminosity radio galaxies with a beamed radio jet pointed toward the observer. Their rarity and spectral properties require large areal multiwavelength surveys for efficient recovery. In this dissertation, I assemble large samples of many hundreds of BL Lac objects from a combination of SDSS optical spectroscopy, FIRST/NVSS radio imaging, and RASS X-ray imaging. I present 3 separate samples---an X-ray selected sample (266 objects), a radio selected sample (501 objects), and an optically selected sample (743 objects). These are among the largest samples ever derived from uniform selection approaches, and approximately 80% of the BL Lac objects presented here are SDSS discoveries. These large samples generally support the standard AGN unification model. However, we also discover a relatively large population of radio-quiet BL Lac candidates (∼102 objects) that are not predicted by the standard model. We present multiwavelength follow-up observations for a subset of these fascinating radio-quiet objects, and we discuss mechanisms that might explain their strange optical spectra. |
