Imaging simulations of the galactic nucleus with the IBIS gamma-ray telescope on board INTEGRAL

We present imaging simulations of the Galactic Center (GC) observations wit h the Imager on Board Integral Satellite (IBIS). IBIS is a coded mask 20 ke V-10 MeV imaging instrument which will provide unprecedented sensitivity an d angular resolution in the energy range 20-200 keV where the advection dom inated accretion models predict an X-ray emission maximum (in E L-E units) from Sgr A*, the hypothetical massive black hole (BH) in the Galactic Nucle us. The high energy activity from Sgr A* is indeed too low for such a massi ve BH embedded in the dense central regions df the Galaxy and new models in volving energy advection have been recently presented to explain this diffi culty The high sensitivity of IBIS coupled to the planned INTEGRAL GC deep survey shall allow to constrain the models either by the detection of the S gr A* energetic emission or by setting tight upper limits. Based on a simul ation procedure and results of the SIGMA GC survey we calculated the expect ed IBIS sensitivity to such emission. Proper simulation of the IBIS imaging system and image reconstruction of point and diffuse sources of the region were included in the procedure to correctly evaluate statistical and syste matic uncertainties.