SOFIA-upGREAT Imaging Spectroscopy of the [C ii] 158 μm Fine-structure Line of the Sgr B Region in the Galactic Center

We report SOFIA-upGREAT spectroscopic imaging of the [C ii] 158 mu m spectral line, as well as a number of [O i] 63 mu m spectra, across a 67 x 45 pc field toward the Sgr B region in our Galactic center. The fully sampled and velocity-resolved [C ii] images have 0.55 pc spatial and 1 km s(-1) velocity resolutions. We find that Sgr B extends as a coherent structure spanning some 34 pc along the Galactic plane. Bright [C ii] emission encompasses Sgr B1 (G0.5-0.0) and the G 0.6-0.0 H ii region and passes behind and beyond the luminous star-forming cores toward Sgr B2 (G0.7-0.0). Sgr B is a major contributor to the entire Galactic center's [C ii] luminosity, with surface brightness comparable to [C ii] from the Arches region. [C ii], 70 mu m, and 20 cm emissions share nearly identical spatial distributions. Combined with the lack of [C ii] self-absorption, this indicates that these probes trace UV on the near surfaces of more extended clouds visible in CO isotopologues and 160 mu m continuum. Stars from regions of local star formation likely dominate the UV field. Photodissociation regions and H ii regions contribute similar amounts of [C ii] flux. The extreme star formation cores of Sgr B2 contribute negligible amounts to the total [C ii] intensity from the Sgr B region. Velocity fields and association with a narrow dust lane indicate that they may have been produced in a local cloud-cloud collision. The cores are likely local analogs of the intense star formation regions where ideas to explain the "C+ deficit" in ultraluminous galaxies can be tested.