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Keywords:

  • radiative transfer;
  • methods: numerical;
  • stars: early-type;
  • stars: winds, outflows

ABSTRACT

Massive young stellar objects (YSOs) are powerful infrared H i line emitters. It has been suggested that these lines form in an outflow from a disc surrounding the YSO. Here, new two-dimensional Monte Carlo radiative transfer calculations are described which test this hypothesis. Infrared spectra are synthesized for a YSO disc 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 disc wind explanation for the H i lines. However, there are some significant differences: the models tend to overpredict the Brα/Brγ 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 disc wind picture and suggestions for their resolution via modifications to the assumed disc and outflow structure are discussed.