Title: Deep Gamma-ray observations of the Galacic Nuclear Region


Proposal ID: 0120277
Subject category: Compact Object
Principal investigator: Goldwurm
Institute: CEA

Abstract

We propose a deep INTEGRAL observation (1000 ksec) of the Nucleus of our Galaxy and of the local (2 degrees) region around it to search for high-energy emission from the radio source SgrA* and to study diffuse hard X-rays and gamma-rays from its close environment. The aim is to study in depth the high energy characteristics of the massive Black Hole of the nucleus and search for the high energy Bremsstrahlung contribution of low-efficiency models (ADAF, Bondi-Hoyle, Disk-Jet) presently used to account for radio and low-energy X-ray emission of Sgr A*. The problem of a central point-like contribution to the observed Galactic Bulge 511 keV line emission will be adressed coupling the high quality imaging data from IBIS and the fine spectral results of SPI. In particular we will search for the soft gamma-ray counterpart of the EGRET source 2EG J1746-2853, located in the very center of the Galaxy and we will test the proposed generation of both annihilating positrons and high energy non-thermal emission from expanding shell of Sgr A East. The Galactic Nucleua is among the most interesting galactic objects in the high energy sky, linking as it does our own Galaxy with AGNs and quasara, and it it one of the most important targets for INTEGRAL. The region will already be observed in the frame of the Core Program. Nevertheless, further exposure of this region is essential to increase the sensitivity sufficiently to adress the issues related to the Galactic Center activity. The nuclear regions will certainly be within IBIS and SPI FOVs during a number of other INTEGRAL observations. The deep study which we propose will be accomplished using a combination of core program time, of serendipitous time when the field is contained within the FOV of other AO-1 observations, and of dedicated observations which we are requesting. We will also perform radio observations at related times in an attempt to observe X/gamma-ray and radio correlated variability from SgrA*