  Massive young stellar objects (YSOs) are powerful infrared H I line emitters.
It has been suggested that these lines form in a outflow from a disk
surrounding the YSO. Here, new two-dimensional Monte Carlo radiative transfer
calculations are described which test this hypothesis. Infrared spectra are
synthesised for a YSO disk wind model based on earlier hydrodynamical
calculations. The model spectra are in qualitative agreement with the observed
spectra from massive YSOs, and therefore provide support for a disk wind
explanation for the H I lines. However, there are some significant differences:
the models tend to overpredict the Br alpha/Br gamma ratio of equivalent-widths
and produce line profiles which are slightly too broad and, in contrast to
typical observations, are double-peaked. The interpretation of these
differences within the context of the disk wind picture and suggestions for
their resolution via modifications to the assumed disk and outflow structure
are discussed.
