High Resolution Radio Recombination Line Observations of Compact HII Regions: Kinematics of the Ionized Gas in the Core of Sgr B2
Session 13 -- HII Regions
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [13.02] High Resolution Radio Recombination Line Observations of Compact HII Regions: Kinematics of the Ionized Gas in the Core of Sgr B2

C. G. De Pree (UNC-CH), R. A. Gaume (NRL), M. J. Claussen (NRAO-VLA), W. M. Goss (NRAO-VLA)

The massive star-forming region Sgr B2 has been observed with the Very Large Array in all three hybrid configurations at 1.3 cm in the radio recombination lines (RRLs) H66$\alpha$ and He66$\alpha$. The observations are sensitive to structures ranging in angular scales from 0\farcs08 to 60\arcsec, which is essential in a region containing ultracompact HII regions and more diffuse cometary'' and shell'' emission. Line emission has been detected from five continuum sources (Sgr B2 C, E, F, G and K3) where previously only upper limits were known. We present integrated line parameters (velocity resolution $\sim$10 km s$^{-1}$) for each of the detected sources in Sgr B2. For several of the compact sources in the core of Sgr~B2, high spatial resolution images will be discussed. Many of the shell'' type HII regions have double-peaked emission-line profiles (split by up to 50 km s$^{-1}$) consistent with expanding shells, and one of the most compact HII regions (source F) has extremely broad lines ($\sim$100 km s$^{-1}$ FWHM). The compact HII regions in the core of Sgr B2 exhibit line widths and velocity structures expected for very young HII regions; there is evidence for rotation or outflow in the ionized gas. We present detailed images of the velocity structure in selected core sources and preliminary physical explanations for the observed velocity structures in the context of early star formation.