PHOTOEVAPORATED FLOWS FROM H-II REGIONS

We model the dynamics of a fast, isothermal ionized stellar wind loade d with mass injected from photoevaporated globules surrounding the mas sive star. The effect of the mass injection is to produce a density pr ofile such that the ionization front can be trapped for 10(5) yr, depe nding on the physical characteristics of the neutral globules inside t he H II region. We find that for neutral globules with sizes R(g) simi lar to 0.01 pc, masses of M(g) similar to 1 M., and number densities N -g similar to 2 x 10(4) pc(-3), thought to be representative of globul es in regions of massive star formation, the implied mean density and size of the mass-loaded regions of ionized gas are about 10(3)-10(4) c m(-3) and about 0.1 pc, respectively, similar to those of compact H II regions. Dust absorption of ionizing photons is important and decreas es the densities of the mass-loaded winds with respect to their dust-f ree counterparts. Also, mass-loaded winds with dust evolve more slowly , since the dusty globules survive for longer times than the dust-free ones. Our models predict ionized hows with mass flow rates of M simil ar to 10(-5) to 10(-4) M. yr(-1). These ionized flows could be studied in radio recombination lines. Assuming N-g does not decline sharply w ith distance to the central star, the ionized flow will recombine afte r the characteristic ''Stromgren'' radius r(S) at which the ionizing p hoton rate goes to zero. Therefore, after this radius a neutral flow w ill accelerate adiabatically to a terminal velocity of v(HI) similar t o 40 km s(-1). Neutral flows of this type could be searched for in the neutral hydrogen line at 21 cm in absorption against the continuum of the compact H II regions.