Ionized Gas in Sagittarius B2 Main on Scales of 0.065 Arcsecond (600 AU)

This is the authors' abstract. We don't add key points for this paper.

The ionized gas in the Sagittarius B2 Main star-forming region has been imaged with ~65 mas (600 AU) resolution using the Very Large Array (VLA) at 7 mm in the A configuration. These observations have ~4-5 times the resolution of the previous highest resolution images of this source. These VLA observations show that the central four ultracompact H II (UC H II) regions in Sgr B2 Main (F1, F2, F3, and F4) break up into ~20 separate UC H II regions. The individual sources have small resolved sizes (~10 -3 pc), high derived emission measures (EM ~ 10 9 pc cm -6 ), and high rms electron densities ( n e ~ 10 6 cm -3 ). We compare the observed radius and derived emission measure of each of these regions with those expected for a UC H II region in pressure equilibrium with its environment, using previously published temperatures and densities for the Sgr B2 molecular core ( n H 2 =2 × 10 7 cm -3 ). We find that the observed emission measures are in fact higher than those predicted in a simple pressure-confinement model, suggesting that the molecular densities on scales that confine the UC H II regions may be higher than 2 × 10 7 cm -3 .