The Plasma Structure of the Southwestern Region of the Cygnus Loop with the XMM-Newton Observatory

We observed the southwestern region of the Cygnus Loop in two pointings with XMM-Newton. The region observed is called the "blow-out" region, which is extended further in the south. The origin of the "blow out" is not well understood, but it is suggested that there is another supernova remnant here in radio observation. To investigate in detail the structure of this region in X-ray, we divided our fields of view into 33 box regions. The spectra are well fitted by a two-component nonequilibrium ionization model. The emission measure distributions of heavy elements decrease from the inner region to the outer region of the Loop. Then, we also divided our fields of view into 26 annular sectors to examine the radial plasma structure. Judging from the metal abundances obtained, it is consistent that the X-ray emission is of Cygnus Loop origin, and we conclude that the high-kT_e component (~0.4 keV) originates from the ejecta, while the low-kT_e component (~0.2 keV) is derived from the swept-up interstellar medium. The flux of the low-kT_e component is much less than that of high-kT_e component, suggesting that the ISM component is very thin. Also, the relative abundances in the ejecta component show values similar to those obtained from previous observations of the Cygnus Loop. We find no evidence in X-ray that the nature of the "blow-out" region originated from the extra supernova remnant. From the ejecta component, we calculated the masses for various metals and estimated the origin of the Cygnus Loop as a core-collapse explosion rather than a Type Ia supernova.