A CHANDRA OBSERVATION OF THE NEARBY SCULPTOR GROUP Sd GALAXY NGC 7793
A CHANDRA OBSERVATION OF THE NEARBY SCULPTOR GROUP Sd GALAXY NGC 7793
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钱德拉对附近雕塑家群 Sd 星系 NGC 7793 的观测
DOI：
10.1088/0004-6256/142/1/20
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
C. Lacey
中科院分区：
文献类型：
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作者：
T. Pannuti;E. Schlegel;M. Filipović;J. Payne;R. Petre;I. Harrus;Wayne D. Staggs;C. Lacey
我们利用钱德拉ACIS对附近的雕刻家群Sd星系NGC 7793进行了观测，作为对附近星系超新星遗迹（SNRs）多波长研究的一部分。假设到NGC 7793的距离为3.91 Mpc，探测到的离散x射线源的极限未吸收光度为LX (0.2-10.0 keV)≈3×1036 erg s−1。在~ 3σ或更高的水平上共检测到22个离散源，包括一个超亮x射线源（ULX）。基于多波长比较，我们确定了一个信噪比一致的x射线源，候选微类星体N7793-S26，一个H区和两个前景银河系恒星。我们还发现，与候选射电信噪比R3对应的x射线在其x射线发射中是时变的：因此我们排除了该源是单一信噪比的可能性。在离散源的分布中可以看到明显的不对称性，其中大多数位于该星系的东半部。采用分位数法对所有光源进行光谱特性分析，提取并分析了4个最亮光源（包括ULX）的光谱。我们使用我们测量的通量以及先前爱因斯坦和Röntgensatellit观测测量的通量来搜索检测到的离散源的x射线发射的时间变异性。从这项研究中，确定了三个离散的x射线源是显著可变的。该星系漫射辐射的光谱分析特征是温度为kT = 0.19-0.25 keV。如果不考虑ULX，则离散光源的光度函数的绝对值为Γ =−0.65±0.11。如果包括ULX，则亮度函数对高LX有一个长尾，其拟合斜率为Γ =−0.62±0.2。ULX-less的坡度与NGC 6946和NGC 2403分布的坡度相当，但比IC 5332和M83分布的坡度浅得多。最后，我们对ngc7793的信噪比种群的多波长特性进行了评述。
We conducted a Chandra ACIS observation of the nearby Sculptor Group Sd galaxy NGC 7793 as part of a multiwavelength study of supernova remnants (SNRs) in nearby galaxies. At the assumed distance to NGC 7793 of 3.91 Mpc, the limiting unabsorbed luminosity of the detected discrete X-ray sources is LX (0.2–10.0 keV) ≈3×1036 erg s−1. A total of 22 discrete sources were detected at the ∼3σ level or greater including one ultraluminous X-ray source (ULX). Based on multiwavelength comparisons, we identify X-ray sources coincident with one SNR, the candidate microquasar N7793-S26, one H ii region, and two foreground Galactic stars. We also find that the X-ray counterpart to the candidate radio SNR R3 is time variable in its X-ray emission: we therefore rule out the possibility that this source is a single SNR. A marked asymmetry is seen in the distribution of the discrete sources with the majority lying in the eastern half of this galaxy. All of the sources were analyzed using quantiles to estimate spectral properties and spectra of the four brightest sources (including the ULX) were extracted and analyzed. We searched for time variability in the X-ray emission of the detected discrete sources using our measured fluxes along with fluxes measured from prior Einstein and Röntgensatellit observations. From this study, three discrete X-ray sources are established to be significantly variable. A spectral analysis of the galaxy's diffuse emission is characterized by a temperature of kT = 0.19–0.25 keV. The luminosity function of the discrete sources shows a slope with an absolute value of Γ = −0.65 ± 0.11 if we exclude the ULX. If the ULX is included, the luminosity function has a long tail to high LX with a poor-fitting slope of Γ = −0.62 ± 0.2. The ULX-less slope is comparable to the slopes measured for the distributions of NGC 6946 and NGC 2403 but much shallower than the slopes measured for the distributions of IC 5332 and M83. Lastly, we comment on the multiwavelength properties of the SNR population of NGC 7793.