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

TL;DR

This study uses Suzaku X-ray observations to identify a new supernova remnant near the Sagittarius D HII region, revising previous understanding of this complex as solely a thermal HII region.

Contribution

The paper reports the discovery of a new supernova remnant in the Sagittarius D HII region using X-ray and radio data, providing new insights into the region's nature.

Findings

Identification of a new SNR G1.2--0.0 based on X-ray spectra and radio data.

Detection of diffuse X-ray sources associated with the Sgr D region.

Revised understanding of the Sgr D complex as including a supernova remnant.

Abstract

We present a Suzaku X-ray study of the Sagittarius D (Sgr D) HII region in the Galactic center region. Two 18'x18' 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 the young stellar cluster. The other is a new object in the vicinity of the region. 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+/-0.2 keV thermal X-ray spectrum with emission lines from highly ionized atoms; (2) the diffuse nature with an apparent extent of ~10 pc at the Galactic center distance inferred from the X-ray absorption (~8.5x10^{22} cm^{-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.