Hard X-Ray Investigation of the Galactic Center Region with Suzaku

The Galactic center (GC) region has been known to exhibit strong enhancements of hot diffuse plasma, which is characterized by the highly ionized Fe-K fluorescence line. Based on past X-ray observations with Ginga, ASCA, and RXTE, in the Galactic plane or bulge region, a non-thermal emission, so-called the ``hard-tail", has been confirmed to dominate the hard X-ray flux above 10 keV, and an association was found between surface brightnesses of the thermal and non-thermal components despite the completely different emission mechanism. Therefore, it is obviously important to investigate an existence of the hard-tail at GC with the unprecedented sensitivity of the HXD onboard Suzaku. By combining its narrow field-of-view of 30' and X-ray images simultaneously obtained by the XIS below 10 keV, an extensive investigation of spectral and spatial properties of the GC hard X-ray emission can be for the first time realized. We will report on results from seven pointings around GC,

with a total exposure of 300 ks, performed in the performance verification phase of Suzaku. Strong hard X-ray signals were clearly detected in every observation by HXD-PIN in 10-70 keV range with a few tenth mCrab level intensities.