arXiv 0806.00742008-06astro-ph

用XMM-牛顿法测量M31盘的X射线光谱

An X-ray spectral survey of the disc of M31 with XMM-Newton

L. Shaw Greening, R. Barnard, U. Kolb, C. Tonkin, J. P. Osborne

备注：: accepted by A&A. 24 pages, 6 figures, 7 tables
DOI：: 10.1051/0004-6361/200809864

摘要：

我们提出了一个完整的光谱调查的X射线点源检测在5个XMM-牛顿观测沿长轴的M31，但避免中央隆起，旨在建立该星系的X射线源的人口特征。我们获得了从2002年开始的五次观测中检测到的335个X射线点源的背景扣除光谱和光变曲线。我们还将我们的源列表与早期的X射线调查和无线电，光学和红外目录相关联。拥有超过50个源计数的源单独进行光谱拟合，以创建迄今为止最准确的M31光度函数。基于这些源的光谱拟合与幂律模型，我们观察到一个广泛的最佳拟合光子指数。从这个分布的最佳拟合指数，我们确定了16个强的高质量X射线双星系统的候选人在M31。我们显示了第一个累积光度函数创建的最佳拟合光谱模型，每个源超过50个源计数的光盘M31。累积光度函数在X射线光度LX间隔37.0 \lesssim log LX erg s-1 \lesssim 37.5中显示出显著的、统计上显著的平坦化。这样的特征也可能存在于其他几个星系的X射线族群中，但统计意义要低得多。我们调查了活动星系核的数量，发现在LX ~1.4x1036 erg s-1以上，观测到的粒子数在统计上主要是由M31的点源粒子数构成的。

英文摘要：

We present the results of a complete spectral survey of the X-ray point sources detected in five XMM-Newton observations along the major axis of M31 but avoiding the central bulge, aimed at establishing the population characteristics of X-ray sources in this galaxy. We obtained background subtracted spectra and lightcurves for each of the 335 X-ray point sources detected across the five observations from 2002. We also correlate our source list with those of earlier X-ray surveys and radio, optical and infra-red catalogues. Sources with more than 50 source counts are individually spectrally fit in order to create the most accurate luminosity functions of M31 to date. Based on the spectral fitting of these sources with a power law model, we observe a broad range of best fit photon index. From this distribution of best fit index, we identify 16 strong high mass X-ray binary system candidates in M31. We show the first cumulative luminosity functions created using the best fit spectral model to each source with more than 50 source counts in the disc of M31. The cumulative luminosity functions show a prominent, statistically significant flattening in the X-ray luminosity LX interval 37.0 \lesssim log LX erg s-1 \lesssim 37.5. Such a feature may also be present in the X-ray populations of several other galaxies, but at a much lower statistical significance. We investigate the number of AGN present in our source list and find that above LX ~1.4x1036 erg s-1 the observed population is statistically dominated by the point source population of M31.

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