The XMM-Newton SSC survey of the Galactic plane
The XMM-Newton SSC survey of the Galactic plane
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XMM-牛顿 SSC 银河系巡天
DOI：
10.1051/0004-6361/201220308
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发表时间：
2013
影响因子：
6.5
通讯作者：
Nebot Gómez-Morán A
中科院分区：
文献类型：
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作者：
Nebot Gómez-Morán A
许多不同种类的x射线源对银河系的高能量景观有贡献。虽然最明亮的x射线发射器的性质现在已经相当清楚了，但对低至中等x射线亮度（LX= 1027−34erg s-1）源的研究仍然很少，我们的知识主要基于对局部成员的观察。宽视场和高灵敏度x射线望远镜的出现，如xmm -牛顿，现在提供了在远距离观察这种低到中等x射线群的机会。我们报告了由xmm -牛顿测量科学中心（SSC）进行的银河系平面测量的结果。除了天体物理学目标之外，这次调查的目的是收集低纬度地区已识别的x射线源的代表性样本，以便以后用于统计识别银河系中其他偶然发现的x射线源。该调查是基于26xmm -牛顿观测，在bb| < 20度处获得，分布在银河系经度的大范围内，覆盖总面积为4度2。我们调查的通量极限在软（0.5-2 keV）波段为2 × 10-15erg cm-2s-1，在硬（2 - 12 keV）波段为1 × 10-14erg cm-2s-1。我们总共探测到1319个单独的x射线源。利用光学跟踪观测，再加上与大范围多波长档案目录的相互关联，我们确定了316个x射线源。这构成了在这个通量水平上光谱鉴定的最大的低纬度x射线源群。大多数已确定的x射线源是活跃的日冕，其光谱类型在A-M范围内，最大距离约为1 kpc。已识别的活动恒星的数量随着光谱类型的增加而增加，在k处达到最大值。使用红外颜色，我们将18%的恒星归类为巨星。观察到的ofFX/FV， x射线和红外颜色分布表明，我们的样本主要是年轻（100迈）至中等（600迈）年龄的种群，其中有少量近主序或演化双星。我们还发现了其他有趣的天体，如大变星（d~ 0.6−2 kpc）、低光度大质量恒星（可能属于γ- cas类系统，d~ 1.5−7 kpc）、金牛座T星和赫比格ae星。少数位于银河系最高纬度区域的星系外光源可以用光学方法识别。对于EPIC pn相机观测到的20个场，我们分别在软带和硬带构造了logN(>S)−logScurves。在软波段，大多数源被确定为活动日冕，在x射线通量为2 × 10-14erg cm-2s-1的情况下，恒星的比例从60°增加到0°，增加了约一个数量级。硬带主要由河外源组成，但也有一小部分来自硬星系群，这些硬星系群由cv、HMXB候选星系或γ- cas类系统和一些活跃的日冕组成，这些日冕也在软带中被探测到。亮度大于1 × 10-13erg cm-2s-1的硬光源的表面密度从l= 20°到银河系中心区域（l= 0.9°）急剧增加了一个数量级。
Many different classes of X-ray sources contribute to the Galactic landscape at high energies. Although the nature of the most luminous X-ray emitters is now fairly well understood, the population of low-to-medium X-ray luminosity (LX= 1027−34erg s-1) sources remains much less studied, our knowledge being mostly based on the observation of local members. The advent of wide field and high sensitivity X-ray telescopes such asXMM-Newtonnow offers the opportunity to observe this low-to-mediumLXpopulation at large distances. We report on the results of a Galactic plane survey conducted by theXMM-NewtonSurvey Science Centre (SSC). Beyond its astrophysical goals, this survey aims at gathering a representative sample of identified X-ray sources at low latitude that can be used later on to statistically identify the rest of the serendipitous sources discovered in the Milky Way. The survey is based on 26XMM-Newtonobservations, obtained at |b| < 20 deg, distributed over a large range in Galactic longitudes and covering a summed area of 4 deg2. The flux limit of our survey is 2 × 10-15erg cm-2s-1in the soft (0.5–2 keV) band and 1 × 10-14erg cm-2s-1in the hard (2–12 keV) band. We detect a total of 1319 individual X-ray sources. Using optical follow-up observations supplemented by cross-correlation with a large range of multi-wavelength archival catalogues we identify 316 X-ray sources. This constitutes the largest group of spectroscopically identified low latitude X-ray sources at this flux level. The majority of the identified X-ray sources are active coronae with spectral types in the range A–M at maximum distances of ~1 kpc. The number of identified active starsincreases towards late spectral types, reaching a maximum at K. Using infrared colours we classify 18% of the stars as giants. The observed distributions ofFX/FV, X-ray and infrared colours indicates that our sample is dominated by a young (100 Myr) to intermediate (600 Myr) age population with a small contribution of close main sequence or evolved binaries. We find other interesting objects such as cataclysmic variables (d~ 0.6−2 kpc), low luminosity high mass stars (likely belonging to the class ofγ-Cas-like systems,d~ 1.5−7 kpc), T Tauri and Herbig-Ae stars. A handful of extragalactic sources located in the highest Galactic latitude fields could be optically identified. For the 20 fields observed with the EPIC pn camera, we have constructed logN(>S) − logScurves in the soft and hard bands. In the soft band, the majority of the sources are positively identified with active coronae and the fraction of stars increases by about one order of magnitude fromb= 60° tob= 0° at an X-ray flux of 2 × 10-14erg cm-2s-1. The hard band is dominated by extragalactic sources, but there is a small contribution from a hard Galactic population formed by CVs, HMXB candidates orγ-Cas-like systems and by some active coronae that are also detected in the soft band. Atb= 0° the surface density of hard sources brighter than 1 × 10-13erg cm-2s-1steeply increases by one order of magnitude froml= 20° to the Galactic centre region (l= 0.9°).