European Workshop on Astronomical Molecules, Zwolle 2004 NGC7538-IRS1 N: modelling a maser disc Michele Pestalozzi, M. Elitzur, J. Conway, R. Booth

European Workshop on Astronomical Molecules, Zwolle 2004 Discs in high-mass star-forming regions Zhang et al Cesaroni et al Shepherd et al Sandell et al. 2003

European Workshop on Astronomical Molecules, Zwolle 2004 NGC7538-IRS1N: “the” disc Pestalozzi et al GHz Gaume et al Minier et al. 1998

European Workshop on Astronomical Molecules, Zwolle 2004 The data R.A. / DEC disp. / LOS Vel. Pestalozzi et al Minier et al. 1998

European Workshop on Astronomical Molecules, Zwolle 2004 Comparison 6.7 / 12.2 GHz

European Workshop on Astronomical Molecules, Zwolle 2004 Assumptions: 1.Keplerian rotating disc seen edge-on 2.Gain per unit length between R 0 and R i : power-law (1 / r p ) 3.Amplification of a continuum background (T b ~ 10 4 K) 4. Maser is unsaturated Geometry

European Workshop on Astronomical Molecules, Zwolle 2004 Model Free parameters: h,  (3.) (1.) (2.,4.)

European Workshop on Astronomical Molecules, Zwolle 2004 Results 12.2 GHz 6.7 GHz 30 M  (from others) 1000 AU in radius h = 0.39

European Workshop on Astronomical Molecules, Zwolle 2004 The ‘kink’ Velocity Coherence

European Workshop on Astronomical Molecules, Zwolle 2004 Important note IRAM PdB, CS Belloche et al.2002

European Workshop on Astronomical Molecules, Zwolle 2004 MASER vs Thermal emission Advantages: Masers allow to resolve the same linear scales further away 1 1 kpc Fine tracers of dynamics

European Workshop on Astronomical Molecules, Zwolle 2004 Summary Found and modelled a disc in NGC M , 1000 AU radius, h=0.39 Masers behave as thermal emission regarding optical depth Optimal tool to study small linear and dynamical scales at large distances Future: 3D modelling, outliers, satellite lines...

European Workshop on Astronomical Molecules, Zwolle 2004 Thank you