A circumstellar disc in a high-mass star forming region

We present an edge-on Keplerian disc model to explain the main component of the 12.2 and 6.7GHz methanol maser emission detected toward NGC7538IRS1N . The brightness distribution and spectrum of the line of bright masers are successfully modeled with high amplification of background radio continuum emission along velocity coherent paths through a maser disc. The bend seen in the position-velocity diagram is a characteristic signature of differentially rotating discs. For a central mass of 30M⊙, suggested by other observations, our model fixes the masing disc to have inner and outer radii of ∼ 350AU and ∼ 1000AU. Subject headings: star formation – masers – Interstellar medium – discs