Cometary compact H II regions are stellar-wind bow shocks

摘要: Comet-shaped H II regions, like G34.3 + 0.2, are easily explained as bow shocks created by wind-blowing massive stars moving supersonically through molecular clouds. The required velocities of the dense clumps less than about 10 km/s, comparable to velocity dispersion in OB associations. An analytic model matches gross characteristics seen radio continuum and structure inferred from hydrogen recombination line observations. champagne flow cannot account for these structures. VLBI observations masers associated with shells cometary compact regions should reveal tailward proper motions predominantly parallel shell, rather perpendicular. It is predicted that over a decade baseline, high signal-to-noise VLA this class objects will show headward pattern motion direction symmetry axis, but not expansion. Finally, shock-generated coronal infrared lines also predicted. 57 refs.