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

2. European Workshop on Astronomical Molecules, Zwolle 2004 Discs in high-mass star-forming regions Zhang et al. 1998 Cesaroni et al. 2000 Shepherd et al. 2001 Sandell et al. 2003

3. European Workshop on Astronomical Molecules, Zwolle 2004 NGC7538-IRS1N: “the” disc Pestalozzi et al. 2004 6.7 GHz Gaume et al. 1995 Minier et al. 1998

4. European Workshop on Astronomical Molecules, Zwolle 2004 The data R.A. / DEC disp. / LOS Vel. Pestalozzi et al. 2001 Minier et al. 1998

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

6. 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

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

8. 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

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

10. European Workshop on Astronomical Molecules, Zwolle 2004 Important note IRAM 04191+1522 PdB, CS Belloche et al.2002

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

12. European Workshop on Astronomical Molecules, Zwolle 2004 Summary Found and modelled a disc in NGC7538 30 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...

13. European Workshop on Astronomical Molecules, Zwolle 2004 Thank you