AAS 197, January 2001
Session 43. High Mass Star Formation
Display, Tuesday, January 9, 2001, 9:30am-7:00pm, Exhibit Hall

## [43.10] AST/RO Mapping Observations of HII Regions in CI

M. Huang, T.M. Bania, A. Bolatto, R.A. Chamberlin, J.G. Ingalls, J.M. Jackson (BU), G.W. Wright (Lucent), A.P. Lane, A.A. Stark, R.W. Wilson, X. Zhang (CfA)

We have mapped a sample of Southern Hemisphere HII regions in 492~GHz atomic carbon (CI) emission using the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO). Our sample consists of 12 HII regions from the Caswell and Haynes (1987) radio recombination line catalogue. These sources are chosen to be compact and isolated. All sources have known distances. The square maps are fully sampled and are 8\times8 arcmin in extent.

Ten of the HII regions have isolated CI emission peaks. Two dimensional Gaussian fits to the maps are used to derive the peak positions and sizes of the emission regions. On average the CI peaks have an offset (2.1±.1\prime) with respect to the 5~GHz radio continuum peaks, which is small compared with the size of the average size CI emission regions (10±\prime). The average size of the CI regions is 4.1±2.3 times of that of the radio continuum.

The mean CI column density averaged over the Gaussian is 3.7±.2\times1017~{\rm cm}-2, assuming an optically thin condition. Using the known distances to the sources, we estimate the linear sizes and CI masses of the CI regions. The average size of the CI regions is 10± parsecs. The CI masses range from 0.02 to 23 solar masses. Correlations between CI emission properties and the excitation parameters of the HII regions are also investigated.

This research was supported by the NSF under a cooperative agreement with the Center for Astrophysical Research in Antarctica (CARA), grant number NSF OPP 89-20223. CARA is a National Science Foundation Science and Technology Center.