Peering into the heart of a high-mass star forming region: Bispectrum speckle interferometry of the ultracompact H II region K3-50 A

Abstract

We present K'-band bispectrum speckle interferometry of the ultracompact H II region K3-50A. Our image resolves the central 1″ × 1″ region into at least 7 point-like objects. We find K′-band counterparts for all but one of the N-band sources discovered by Okamoto et al. (2003), and there are additional K′-band sources which were unresolved in the N-band images. Our reconstructed image also reveals the fine-structure of the cone-shaped nebulosity extending to the south. The brightest K′-band source is located exactly at the tip of the cone-shaped nebulosity. The nebula shows several arcs and the orientation of its main axis agrees very well with the direction of the CO outflow from K3-50A. This nebulosity therefore very likely represents the clumpy inner surface of a partially evacuated cavity excavated by the strong outflows.