SOFIA and Herschel Observations of Far-Infrared Fine Structure Lines from Deep Within the Galactic Center

The Central Molecular Zone (CMZ) is the approximately 250 pc radius region at the center of our Galaxy. It contains a black hole, a large stellar bar, massive stellar clusters, and a number of the densest molecular clouds in the Galaxy (most forming stars but some not) on a variety of orbits. Our detailed understanding of structures within the CMZ is possible because of its proximity, and it is therefore a model for all normal galactic nuclei, near and far. Here we report observations of far-infrared fine structure lines with SOFIA/FIFI-LS, Herschel/PACS, and SOFIA-upGREAT that clarify the physical structure of the Galactic Center Arches and Sickle regions, which lie deep within the CMZ's most energetic zone, some 5 to 10 pc from the central black hole. This allows us to probe the roles that hot stellar clusters, distributed B-type stars, and interactions between magnetic fields and molecular clouds play in producing the radiation field across the inner 10 pc of the Galactic Center.