We present an analysis of the diffuse soft X-ray emission from the nuclear region of M51 combining both XMM-Newton RGS and Chandra data. Most of the RGS spectrum of M51 can be fitted with a thermal model with a temper...We present an analysis of the diffuse soft X-ray emission from the nuclear region of M51 combining both XMM-Newton RGS and Chandra data. Most of the RGS spectrum of M51 can be fitted with a thermal model with a temperature of 0.5 keV except for the O vii triplet, which is forbidden-line dominated. The Fe L-shell lines peak around the southern cloud, where the O viii and N vn Lya lines also peak. In contrast, the peak of the O vii forbidden line is about 10＂ offset from that of the other lines, indicating that it is from a spatially distinct component. The spatial distribution of the O vii triplet mapped by the Chandra data shows that most of the O vii triplet flux is located at faint regions near edges, instead of the southern cloud where other lines peak. This distribution of the O vii triplet is inconsistent with the photoionization model. Other mechanisms that could produce the anomalous O vii triplet, including a recombining plasma and charge exchange X-ray emission, are discussed.展开更多
基金supported by a National Natural Science Foundation of China for Young Scholar Grant (11203032)the Strategic Priority Research Program"The Emergence of Cosmological Structures" of the Chinese Academy of Sciences Grant No.XDB09000000NSFC grant 11333003 (SM)
文摘We present an analysis of the diffuse soft X-ray emission from the nuclear region of M51 combining both XMM-Newton RGS and Chandra data. Most of the RGS spectrum of M51 can be fitted with a thermal model with a temperature of 0.5 keV except for the O vii triplet, which is forbidden-line dominated. The Fe L-shell lines peak around the southern cloud, where the O viii and N vn Lya lines also peak. In contrast, the peak of the O vii forbidden line is about 10＂ offset from that of the other lines, indicating that it is from a spatially distinct component. The spatial distribution of the O vii triplet mapped by the Chandra data shows that most of the O vii triplet flux is located at faint regions near edges, instead of the southern cloud where other lines peak. This distribution of the O vii triplet is inconsistent with the photoionization model. Other mechanisms that could produce the anomalous O vii triplet, including a recombining plasma and charge exchange X-ray emission, are discussed.
