Chandra X-Ray Observations of NGC 4151
Chandra X-Ray Observations of NGC 4151
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NGC 4151 的钱德拉 X 射线观测
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
P. Ferruit
中科院分区：
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作者：
Y. Yang;A. Wilson;P. Ferruit
我们介绍了钱德拉X射线观测附近的塞弗特1.5星系NGC 4151。这些图像显示了数百秒差距尺度上的扩展软X射线发射，其灵敏度比以前获得的更好。我们表明，硬X射线分量（大于2千电子伏）是空间未解决的。未分辨核源的光谱可以用重吸收（NH 3 × 1022 cm-3）、硬幂律（r 0.3）加上来自幂律（r 2.6）或热（kT 0.6 keV）分量的软发射来描述。高能成分的通量比ASCA在1993年观测到的有所减少，光谱也变得更硬（2000年的Γ ~ 0.3比1993年的Γ ~ 1.5）。软谱和硬谱之间的巨大差异不利于“软过剩”的部分覆盖或散射模型。相反，很可能硬核和软核组件代表本质上不同的X射线源。强核发射线的钱德拉HETGS光谱所看到的检测。还获得了核东北和西南近1 kpc的扩展发射光谱。这些区域的光谱可用热韧致辐射（kT = 0.4- 0.7keV）或幂律（τ = 2.5-3.2）连续谱加三条发射线来描述。在扩展X射线和[O III] λ5007谱线发射之间有很好的相关性。我们讨论了扩展的X射线发射的性质。因为没有扩展的电子散射硬X射线发射，所以可以获得电子散射柱的上限。这个上限对于软X射线是电子散射核辐射来说太低了，除非原子核向扩展区域辐射的软X射线比向地球辐射的强得多，我们认为这种情况不太可能。我们倾向于这样一种观点，即放射X射线的气体在核辐射的作用下被原位加热。一些X射线可能来自热相，它限制了光学上看到的温暖的电离气体，尽管通过原子核的光电离产生的X射线发射也是可能的。一个微弱的，可能是背景的，致密的X射线源位于从核到西南方向的大约沿着延伸的西南X射线和[O III]辐射的延伸部分。
We present Chandra X-ray observations of the nearby Seyfert 1.5 galaxy NGC 4151. The images show the extended soft X-ray emission on the several hundreds of parsec scale with better sensitivity than previously obtained. We show that the hard X-ray component (greater than 2 keV) is spatially unresolved. The spectrum of the unresolved nuclear source may be described by a heavily absorbed (NH ≃ 3 × 1022 cm-3), hard power law (Γ ≃ 0.3) plus soft emission from either a power-law (Γ ≃ 2.6) or a thermal (kT ≃ 0.6 keV) component. The flux of the high-energy component has decreased from that observed by ASCA in 1993, and the spectrum is much harder (Γ ~ 0.3 in 2000 vs. Γ ≃ 1.5 in 1993). The large difference between the soft and hard spectral shapes does not favor the partial covering or scattering model of the "soft excess." Instead, it is likely that the hard and soft nuclear components represent intrinsically different X-ray sources. The stronger nuclear emission lines of those seen by the Chandra HETGS spectrum are detected. Spectra of the extended emission to almost 1 kpc northeast and southwest of the nucleus have also been obtained. The spectra of these regions may be described by either thermal bremsstrahlung (kT ≃ 0.4-0.7 keV) or power-law (Γ ≃ 2.5-3.2) continua plus three emission lines. There is an excellent correlation between the extended X-ray and [O III] λ5007 line emissions. We discuss the nature of the extended X-ray emission. Because there is no extended electron-scattered hard X-ray emission, an upper limit to the electron scattering column can be obtained. This upper limit is much too low for the soft X-rays to be electron-scattered nuclear radiation, unless the nucleus radiates soft X-rays much more strongly toward the extended regions than toward Earth, a situation we consider unlikely. We favor a picture in which the extended X-ray-emitting gas is heated in situ by the nuclear radiation. Some of the X-rays may originate from a hot phase that confines the warm ionized gas seen optically, although X-ray emission produced via photoionization by the nucleus is also likely. A faint, probably background, compact X-ray source lies ≃2.′2 from the nucleus to the southwest, approximately along an extension of the extended southwest X-ray and [O III] emission.