Two-dimensional Monte Carlo simulations of H i line formation in massive young stellar object disc winds

• Published in: Monthly Notices of the Royal Astronomical Society Vol. 363; no. 2; pp. 615 - 627
• Main Authors: Sim, S. A., Drew, J. E., Long, K. S.
• Format: Journal Article Book Review
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 21.10.2005; Blackwell Science; Oxford University Press
• Subjects: Astronomy; Hydrogen; Infrared radiation; methods: numerical; Monte Carlo simulation; outflows; radiative transfer; Spectrum analysis; stars: early-type; stars: winds; stars: winds, outflows; Stellar winds; Young stellar object; Line formation; Line widths; Equivalent width; Numerical method; Infrared spectra; methods: numerical; stars: winds, outflows; Early type stars; Monte Carlo methods; stars: early-type; H lines; Models; Radiative transfer
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2005.09472.x

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.