Fe XXV Kα Fe I Kα S XV Kα Strong Fe XXV Kα, S XV Kα, and Fe I Kα  the GCXE consists of High Temperature Plasma (HP), Low Temperature Plasma (LP), and Cold Gas. The GCXE is not integral emission of unresolved X-ray stars. X-ray surface brightness of Fe XXV Kα factor 3-4 of discrepancy Average spectrum of the GCXE (Uchiyama+13) Spatial distribution of the GCXE and stars ( Uchiyama+11) The Suzaku Images of the Galactic Center X-ray Emission (GCXE)

Suzaku and other satellites found time variability of Fe I Kα and hard X-ray from molecular clouds (MCs, e.g. Muno+07, Inui+09, Ponti+10).  X-ray light echoes of past flares of super massive black hole Sgr A * at the center of our Galaxy.  Key information for activity history of Sgr A*. Accurate past light curve of Sgr A* (in time and fluxes) depends on 3-d distribution of the MCs (e.g. Ryu+13). 1 X-ray Reflection Nebula (XRN): Echo of Past Sgr A* Flares Line of sight Positions of XRNe (Ryu+13) Variable XRN Sgr B2 (Nobukawa+11) 700 yr activity history of Sgr A* (Ryu+13)

2-2 Hint of a RP from a Close Vicinity of Sgr A* If Sgr A* was very active about a few 10 5 years ago as is suggested by the GC south plasma, it might also leave a RP at a close vicinity of Sgr A*. Suzaku found a hint of RP near Sgr A* (l = 0°.1, b = -0°.1 ). The plasma also shows a hint of Compton shoulder of the 6.4 keV line. The fitting of a CIE plasma model leaves residuals at ~ 6.7 keV and ~ 6.3 keV. RP model and Compton shoulder of the 6.4 keV line significantly improve the fitting. Suzaku spectrum near Sgr A* (l = 0°.1, b = -0°.1)

New Sciences of the GCXE to be unveiled by ASTRO-H We propose three pointing observations, which play complementary roles. (1) The Sgr A* region is for the study of Sgr A* and its vicinity. (2) The GC East region is the strongest in Fe I Kα (XRN) (“MC1” in Ponti+10). (3) The GC West is the region of pure HP and LP components with no bright XRN. Galactic longitude Fe XXV Kα line imageFe I Kα line image ( 2) GC East (3) GC West SXS FOV HXI FOV 10 pc ( 1) Sgr A* (2) GC East (3) GC West (1) Sgr A* Proposed 3 positions overlaid on Suzaku XIS images o (deg) Galactic longitude

1. Accurate History of Past Sgr A * Flares SXS simulation spectrum of (2) – (3) Compton shoulder of Fe I Kα Fe I Kα Fe I Kβ SXS simulation spectrum of (1) vs.(3) Fe XXV Kα complex Fe XXVI Lyα Suzaku spectrum shows a hint of the Compton shoulder of Fe I Kα. We can obtain pure Fe I Kα spectrum by subtracting (3) GC West data from (2) GC East data. The shape of the Compton shoulder gives 3-D position of the MC. Then we can obtain more accurate light curve of Sgr A*. In a photo-ionized plasma formed by a past Sgr A* flare, the temperature ratio of ionization (kTz) to electron (kTe) should be higher near Sgr A*. We can see the difference of kTz/kTe between (1) Sgr A* and (3) GC West regions. 2. Plasma Diagnostic for Sgr A* Activities Sgr A* region (kTz/kTe = 3.0) GC West (kTz/kTe = 1.5) CIERP kTz/KTe= G ratio (x+y+z)/w 0.70± ± ±0.0 7

3. Non Thermal Emission and a Coming Sgr A* Flare Fe XXVI Lyα1 & Lyα2 100 km/s red shift 50 km/s blue shift 200 km/s broadening SXS simulation spectrum of (1), (2), and (3) SXS & HXI wide-band simulation spectrum from (1) (1) (3) (2) High-quality spectra of the GCXE with SXS/SXI/HXI give us the first opportunity to investigate exact nature of hard X-ray (possibly non-thermal) emission with no energy gap between 0.5 and 50 keV. coming flare of the nearest massive black hole Sgr A* ( Gillesen et al ). Doppler shift of the GCXE lines tell the dynamics of the GC plasma and XRNe. Do they show the same Galactic rotation curves as stars ? 4. Dynamics of the GCXE Plasma and XRNe

5. The GC: a Treasure Box in Astrophysics We have made many “unexpected” discoveries from the GC with Ginga, ASCA, and Suzaku, such as the GCXE, XRNe, RP and etc. The high-quality spectra of ASTRO-H will surely provide new “unexpected” discoveries, because the GC is full of mystery and a treasure box in astrophysics.