Surveys of the Galactic Center and the Nature of the Galactic Center Lobe

Abstract

The Galactic center (GC) is a dense and chaotic region filled with unusual sources, such as intense star forming regions, dense star clusters, nonthermal radio filaments, and a massive black hole. The proximity of the GC region makes it an ideal place to study the unusual processes that tend to manifest themselves in Galactic nuclei. This thesis uses single-dish and interferometric radio continuum, radio recombination line, polarized radio continuum, and mid-IR observations to study the wide variety of physical processes seen in the GC region on physical scales from 0.1 to 100 parsecs. These observations provide one of the most sensitive studies of the radio continuum emission in the central 500 parsecs. I also study the properties of nonthermal radio filaments, which can constrain their origin and the structure of the magnetic field in the GC region. The presence of massive star clusters and a massive black hole suggest that starburst and AGN phenomena can manifest themselves in our Galaxy. This thesis explores this possibility by studying a 150-pc-tall, shell-like structure called the Galactic center lobe (GCL). Our observations examine the spectral index, dust emission, polarized continuum emission, and ionized gas throughout the GCL. I find strong evidence supporting the idea that the GCL is a true three-dimensional shell located in the GC region with nested layers of ionized, magnetized, and mid-IR--emitting components. I compare the physical conditions of the GCL to proposed models for its origin and find best agreement with starburst outflows seen in other galaxies, yet consistent with the currently observed pressure and star formation rate in the central tens of parsecs of our Galaxy. (abridged)