Kinematics of the ultracompact HII region W3(OH): constraints derived from high n radio recombination

We observed the ultracompact HII region W3(OH) with #approx# 6'' spatial resolution in the H66#alpha#, H76#alpha#, and H110#alpha# radio recombination lines with the goal of constraining its structure and kinematics via the lineshapes. We find that the H66#alpha# line has a LSR center velocity of -50.7#+-#0.3 km s"-"1 and FWHM of 36.0 #+-# 1.8 km s"-"1; the H76#alpha# line has a LSR center velocity of -50.3#+-#0.2 km s"-"1 and FWHM of 40.7#+-#2.1 km s"-"1; and the H110#alpha# line has a LSR center velocity of -63.1#+-#3.9 km s"-"1 and FWHM of 69.4#+-#16.2 km s"-"1. The H110#alpha# line profile is significantly impact broadened, and is the first detection of this phenomena in a compact or ultracompact HII region. The broadening is not as strong as simple modeling predicts, a discrepancy most likely due to clumpiness in the ionized gas. The linewidths and velocities best support and 'accelerated champagne flow' kinematic model. (orig.)Available from TIB Hannover: RN 9303(332) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman