Hard X-ray view of the past activity of Sgr A☆ in a natural Compton mirror

We report the association of the recently discovered hard X-ray source IGR J17475-2822 with the giant molecular cloud Sgr 132 in the Galactic Center region. The broad band (3-200 keV) spectrum of the source constructed from data of different observatories strongly supports the idea that the X-ray emission of Sgr 132 is Compton scattered and reprocessed radiation emitted in the past by the Sgr A* source. We conclude that 300-400 years ago Sgr A* was a low luminosity (Lapproximate to1.5x10(39) erg s(-1) at 2-200 keV) AGN with a characteristic hard X-ray spectrum (photon index Gammaapproximate to1.8). We estimate the mass and iron abundance of the Sgr B2 scattering gas at 2x10(6) M-circle dot(r/10 pc)(2) and 1.9 solar, respectively (where r is the radius of the cloud).