X-Ray Observations of the Sagittarius D H ii Region toward the Galactic Center with Suzaku

Abstract

Abstract We present a Suzaku X-ray study of the Sagittarius D (Sgr$\;$D) H ii region in the Galactic center region. Two 18$^{\prime}$$\times$ 18$^{\prime}$ images by the X-ray Imaging Spectrometer (XIS) encompass the entire Sgr$\;$D complex. Thanks to the low background, XIS discovered two diffuse sources with low surface brightness and obtained their high signal-to-noise ratio spectra. One is associated with the core of the Sgr$\;$D H ii region, arising from a young stellar cluster. The other object is new and reported here for the first time. We also present 3.5 cm and 6.0 cm radio continuum maps of the new source using the 100-m Green Bank Telescope. We conclude that the source is a new supernova remnant (SNR; G1.2$-$0.0) based on: (1) the 0.9$\pm$0.2 keV thermal X-ray spectrum with emission lines from highly ionized atoms; (2) the diffuse nature with an apparent extent of $\sim$10 pc at the Galactic center distance inferred from the X-ray absorption ($\sim$8.5 $\times$ 10$^{22}$cm$^{-2}$); and (3) the nonthermal radio continuum spectral index ($\sim-$0.5). Our discovery of an SNR in the Sgr$\;$D H ii region leads to a revision of the view of this system, which had been considered to be a thermal H ii region and its environment.