Deconvolution of the X-Ray Emission and Absorption Components in Centaurus A
Deconvolution of the X-Ray Emission and Absorption Components in Centaurus A
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DOI：
10.1086/303510
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发表时间：
1997-01
期刊：
影响因子：
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通讯作者：
T. Turner;I. George;R. Mushotzky;K. Nandra
中科院分区：
文献类型：
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作者：
T. Turner;I. George;R. Mushotzky;K. Nandra
我们介绍了ROSAT HRI和PSPC加ASCA射电星系半人马座A的X射线观测。HRI图像显示，自15年前爱因斯坦观测以来，X射线喷流一直保持恒定的通量，而核通量下降了约60%。PSPC数据允许第一个详细的空间分辨的X射线光谱的核，喷流，并在Cen A的扩散发射。正如预期的那样，原子核的0.1-2 keV光谱被大量吸收。喷流可以用光子指数为Γ ~ 2.3的幂律来描述，尽管不能排除热模型。微弱的扩散发射的存在被证实，延伸到~6千秒差距从核。漫发射的光谱可以被建模为两个“Raymond-Smith”等离子体。低温成分，kT = 0.29 keV，与恒星加热的气体发射一致，而较硬的成分可能代表银河X射线双星系统的贡献;漫射发射的强度在接近银盘的地方增加。这些扩展的组件的识别使得有可能分离的ASCA光谱的核和弥漫的贡献。0.6-10 keV的核能谱很好地用光子指数为Γ ~ 1.96的幂律连续谱模拟，与Seyfert 1星系的“正则”值很好地吻合。40%的核连续谱被约4 × 1023 cm-2的柱密度吸收，59%被约1 × 1023 cm-2的柱密度吸收，1%被接近21 cm的银河系视线柱密度吸收。核吸收的高度与环核分子云相一致，环核分子云的存在是由一些波段的吸收测量所建议的。观测到的铁Kα发射线看起来很宽;最佳拟合的高斯宽度意味着起源于速度约为11，000 km s-1的物质，而等效宽度为114 ± 18 eV。这两个量都与环核吸收材料的起源非常一致。
We present ROSAT HRI and PSPC plus ASCA X-ray observations of the radio galaxy Centaurus A. The HRI image reveals that the X-ray jet has remained constant in flux since the Einstein observation 15 years ago, while the nuclear flux has decreased by ~60%. The PSPC data allows the first detailed spatially resolved X-ray spectroscopy of the nucleus, jet, and diffuse emission in Cen A. The 0.1-2 keV spectrum of the nucleus is heavily absorbed, as expected. The jet can be described by a power law of photon index Γ ~ 2.3, although thermal models cannot be ruled out. The presence of faint diffuse emission is confirmed, extending out to ~6 kpc from the nucleus. The spectrum of the diffuse emission can be modeled as two “Raymond-Smith” plasmas. A low-temperature component, kT = 0.29 keV, is consistent with emission from gas heated by stars, while the harder component may represent the contribution of galactic X-ray binary systems; the diffuse emission increases in intensity close to the galactic disk. The identification of these extended components makes it possible to separate the nuclear and diffuse contributions to the ASCA spectrum. The 0.6-10 keV nuclear spectrum is well modeled by a power-law continuum of photon index Γ ~ 1.96, in good agreement with the “canonical” value for Seyfert 1 galaxies. Forty percent of the nuclear continuum is absorbed by a column density ~4 × 1023 cm-2, 59% is absorbed by a column ~1 × 1023 cm-2, and 1% is absorbed by a value close to the 21 cm Galactic line-of-sight column. The high degree of nuclear absorption is consistent with the circumnuclear molecular clouds whose existence is suggested by absorption measurements in a number of wave bands. The iron Kα emission line observed appears broad; the best-fit Gaussian width implies an origin in material with velocities ~11,000 km s-1, while the equivalent width is 114 ± 18 eV. Both quantities are in good agreement with an origin in the circumnuclear absorbing material.