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

Abstract

We present a Suzaku X-ray study of the Sagittarius D (Sgr D) HII region in the Galactic center region. Two 18' × 18' 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 HII region, arising from a young stellar cluster. The other object is new and reported here for the first time. We also present 3.5cm and 6.0cm 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±0.2keV thermal X-ray spectrum with emission lines from highly ionized atoms; (2) the diffuse nature with an apparent extent of ∼10pc at the Galactic center distance inferred from the X-ray absorption (∼8.5 × 10²²cm^-2); and (3) the nonthermal radio continuum spectral index ∼-0.5). Our discovery of an SNR in the Sgr D HII region leads to a revision of the view of this system, which had been considered to be a thermal HII region and its environment.