the accretion disc does extend down close to the star there is little doubt that the radiation pressure acting on the gas will drive such a wind and is likely to dominate the dynamics.

The Transition to UCHII Region
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It has long been a puzzle as to why the massive YSOs do not ionize their surrounding molecular gas as soon as they become luminous enough. All objects above about 10$^{4}$L should emit copious amounts of Lyman continuum radiation if they are fully on the zero age main sequence (ZAMS). It is commonly accepted that massive stars begin core hydrogen burning whilst still accreting and so the ZAMS assumption appears justified.

One possibility is that the infall of molecular material ’quenches’ the H II region (Walmsley 1995). The critical accretion rate for this to occur is obtained from inserting an infalling spherically symmetric density distribution into the Strömgren radius equation. The rates are high, but not as high as the $\sim$10$^{-3}$ needed to overcome radiation pressure on the dust in the same spherical treatment. In this scenario, the H II region is not absent, but just very dense ($\sim10^{12}$ cm$^{-3}$ with a Strömgren radius close to the star. One problem 