NASA Goddard Space Flight Center
New Mission Concept: Investigation of the Galactic Center in energy range 0.1 - 10 MeV with the Galactic Center Explorer
The European Space Observatory INTEGRAL has been providing excellent results on X-ray and γ-ray astronomy since its launch in 2004. Among the most important results are the spectroscopy and imaging measurements of celestial γ-ray sources, including mapping of 511 keV radiation from the Galactic plane. However the nature of the Galactic Center region 511 keV positron annihilation line is still a mystery. Similarly, the structure and nature of the Galactic Center supermassive black hole and its surroundings, as well as the structure of heavily populated sky regions such as Cygnus and Carina in γ-rays remain unclear. In particular, understanding of the origin of the Fermi Bubbles and of the γ-radiation bulge at the Galactic Center are high on the list of fundamental problems of astrophysics and can possibly solve the enigma of the nature of dark matter. I will present a concept of a potential new-generation γ- ray telescope with the major objectives a) investigate the Galactic Center region 511 keV positron annihilation line by mapping the Galactic Center region with high energy (<1% FWHM) and angular (< 10 arcmin) resolution and with line sensitivity <10-5 ph cm-2 s-1; b) understand the nature of the Galactic Center supermassive black hole environment and surrounding region by creating an intensity map with high spectral (<1% at 1 MeV) and spatial (1' - 10') resolution for the photon energy range 0.1 - 10 MeV; and c) explore Galactic chemical evolution and sites of explosive element synthesis by conducting high-sensitivity measurements of nuclear lines from supernovae 1a and from other objects. GalCenEx will also be able to detect γ-ray bursts and determine their location, contributing to multimessenger astrophysics. The instrument is based on a novel high-energy and position resolution CdZnTe calorimeter, coded aperture mask and heavy-scintillator shield, and can be considered for a NASA Explorer mission.