Suzaku Observation of the RCW86 Northeastern Shell

Abstract

This paper reports on Suzaku results concerning the northeast shell of RCW86. With both spatial and spectral analyses, we separated the X-rays into three distinct components: low ($kT_{\rm e}\sim$0.3keV) and high ($kT_{\rm e}\sim$1.8keV) temperature plasmas and a non-thermal component, and discovered that their spatial distributions are different from each other. The low-temperature plasma is dominated at the east rim, whereas the non-thermal emission is brightest at the northeast rim, which is spatially connected from the east. The high-temperature plasma, found to contain the $\sim$6.42keV line (K$\alpha$ of low-ionized iron), is enhanced at the inward region with respect to the east rim, and has no spatial correlation with the non-thermal X-rays (the northeast). This result suggests that the Fe-K$\alpha$ line originates from Fe-rich ejecta heated by reverse shock. A possible scenario to explain these morphologies and spectra is that a fast-moving blast wave in a thin cavity collided with a dense interstellar medium at the east region very recently. As a result, the reverse shock in this interior decelerated, and arrived at the Fe-rich region of the ejecta and heated it. In the northeast rim, on the other hand, the blast wave is still moving fast, and is accelerating electrons causing them to emit strong synchrotron X-rays.