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arXiv 0809.4656astro-ph
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朱雀号对圆规星系的观测

Suzaku Observations of the Circinus galaxy

Y. Yang, A. S. Wilson, G. Matt, Y. Terashima, L. J. Greenhill

摘要:

我们报告朱雀观测活跃,康普顿厚的Circinus星系。观测是用X射线成像光谱仪(XIS)和硬X射线探测器(HXD)获得的。在10 keV以下,核光谱主要是由高柱密度的冷致密气体反射的辐射,而在13 keV以上,辐射是通过约4 x 10^{24} cm^-2的柱密度直接透射的核发射。在0.2- 10 keV波段,XIS谱被Circinus中最亮的非核源(CG X-1)污染了5%,但在5-10 keV波段下降到1%,在更高的能量下可以忽略不计。我们没有发现硬(>12千电子伏)发射的变化的显着证据。用HXD/GSO在50- 100 keV波段2.5σ水平上勉强探测到Circinus。我们用四个分量模拟了3-70 keV波段的XIS+PIN光谱:康普顿透射核发射,反射核发射,软幂律(代表散射核发射,扩展发射和星系中低于几keV的源污染的组合)。发现硬核幂律的光子指数γ_h ~= 1.6,与软幂律非常相似。高能截止为E_C ~= 49 keV。这些结果与BeppoSax的结果一致。这个模型的外推到GSO带显示出良好的协议与GSO的光谱,并支持我们的检测Circinus高达~= 100 keV。

英文摘要:

We report Suzaku observations of the active, Compton-thick Circinus galaxy. Observations were obtained with both the X-ray Imaging spectrometer (XIS) and the Hard X-ray Detector (HXD). Below 10 keV, the nuclear spectrum is dominated by radiation reflected from cold dense gas of high column density, while above 13 keV the radiation is directly transmitted nuclear emission seen through a column density of $~ 4 x 10^{24} cm^-2. In the 0.2--10 keV band, the XIS spectrum is contaminated at 5% level by the brightest off-nuclear source in Circinus (CG X-1), but drops to 1% in the 5-10 keV and is negligible at higher energies. We find no significant evidence for variability in the hard (>12 keV) emission. The Circinus is marginally detected with the HXD/GSO in the 50--100 keV band at 2.5σlevel. We model the 3-70 keV band XIS+PIN spectra with a four components: the Compton transmitted nuclear emission, the reflected nuclear emission, a soft power law (representing a combination of scattered nuclear emission, extended emission and contamination by sources in the galaxy below a few keV). The hard nuclear power-law is found to have a photon index Gamma_h ~= 1.6, very similar to the soft power-law. The high energy cut-off is E_C ~= 49 keV. These results agree with those from BeppoSax. An extrapolation of this model up to the GSO band shows good agreement with the GSO spectrum and supports our detection of the Circinus up to ~= 100keV.

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