New X-ray views of the Galactic center observed with Suzaku

We report the diffuse X-ray emissions from the Sgr A and B regions observed with Suzaku. From the Sgr A region, we found many K-shell transition lines of iron and nickel. The brightest are Kα lines from FeI, FeXXV and FeXXVI at 6.4 keV, 6.7 keV and 6.9 keV. In addition, Kα lines of NiI and NiXXVII, Kβ of FeI, FeXXV and FeXXVI, and Kγ of FeXXV and FeXXVI are detected for the first time. The center energy of Kα of FeXXV favors collisional excitation as the origin for this line emission. The ionization temperature determined from the flux ratio of Kα of FeXXV and FeXXVI is similar to the electron temperature determined from the flux ratio of Kα and Kβ of FeXXV, which are in the range of 5−7 keV. Consequently, the Galactic Center diffuse X-rays (GCDX) are consistent with emission from a plasma nearly in ionization equilibrium. The radio complex Sgr B region also exhibits Kα lines of FeI, FeXXV and FeXXVI. The 6.7 keV line (FeXXV) map exhibits a local excess at (l, b) = (0◦.612, 0◦.01), and could be a new young SNR. The 6.4 keV image is clumpy with local excesses near Sgr B2 and at (l, b) = (0◦.74, − 0◦.09). Like Sgr B2, this latter excess may be another X-ray reflection Nebulae (XRN).