L and thus are about 12 M, just where accretion could easily result in a low surface gravity. The emission line spectrum with broad profiles of a few hundred  are reminiscent of B supergiants. The low surface gravity leads directly to low escape speeds and increased mass-loss.

Another feature of large central stars would be to help explain the near- IR line profiles in equatorial wind sources like S106IR. The current attempts to model the H I lines result in double-peaked rather than single-peaked lines (Sim et al. 2005). If the central star is larger than the ZAMS one assumed, then the rotation of the inner disc is much slower, reducing the rotational splitting of the disc wind. The slower, denser stellar wind from the poles may also help fill in the profile to improve agreement with observations. Such a wind could also help trap the Lyman continuum radiation before it can ionize the surroundings.

Whichever of the above mechanisms prevents the formation of an H II region during the massive YSO phase; quenching by infall, outflows or accretion swelling the star, all are associated with ongoing accretion. This would tend to indicate that the onset of the H II 