Suzaku Discovery of Twin Thermal Plasma from the Tornado Nebula

Abstract

The Tornado nebula (G357.7 − 0.1) is a mysterious radio source with a bright “head” and faint “tail” located in the direction of the Galactic center (GC) region. We here report on the discovery of two diffuse X-ray sources at the head and tail of Tornado with the Suzaku satellite. We found emission lines from highly ionized atoms in the two sources. The spectra have been reproduced by an optically thin thermal plasma with a common temperature of 0.6–0.7 keV. The interstellar absorption ( NH ) of these sources are the same, and are slightly larger than that of the GC distance. Since the estimated distance using the NH value is consistent with radio observations of Tornado, these X-ray sources are likely to be associated with the Tornado nebula. The twin-plasma morphology at both ends of Tornado suggests that the system is a bipolar/outflow source.