X-ray source populations in the Galactic Plane
X-ray source populations in the Galactic Plane
复制标题
银河平面上的 X 射线源群
DOI：
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发表时间：
2004
期刊：
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通讯作者：
D. Helfand
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作者：
A. Hands;R. Warwick;M. Watson;D. Helfand
我们目前的第一个结果，从XMM牛顿银河系平面调查（XGPS）。在该方案的第一阶段，使用了22个点来覆盖银河经度19°和22°之间、纬度±0.6°之间大约3度2的区域。我们总共分辨了400多个点X射线源，在≥ 5σ的显著性下，通量极限为102 × 10 - 14 erg s-1 cm-2（2-10 keV）。这些源表现出非常广泛的光谱硬度，星际吸收被认为是一个主要的影响。在软（0.4- 2keV）带和硬（2-6 keV）带中检测到的源群显示出令人惊讶的小重叠。大多数的软源似乎与相对较近的恒星与活跃的恒星冕有关，从它们与明亮的恒星对应物的高度重合来判断。XGPS在硬X射线波段的测量结果与ASCA和Chandra早期进行的调查结果相结合，揭示了40年通量中低纬度X射线源计数的形式。在10 - 13 erg s-1 cm-2（2-10 keV）以下，河外源似乎占主导地位，而在这个通量阈值以上，主要是银河系源。XMM-牛顿观测到的微弱银河系人口的性质仍然不确定，尽管灾难性的变量和RS CVn系统可能有很大的贡献。XMM-牛顿观测到与银河脊X射线发射（GRXE）相关的2-6 keV波段的银河平面表面亮度增强。银河系源的综合贡献加上河外信号的突破，占观测到的表面亮度的20%。XGPS的结果与钱德拉在银河系平面进行的深层观测所得出的图像一致，即GRXE的大部分是真正弥散的。
We present the first results from the XMM-Newton Galactic Plane Survey (XGPS). In the first phase of the programme, 22 pointings were used to cover a region of approximately 3 deg 2 between 19° and 22° in Galactic longitude and ±0.6° in latitude. In total we have resolved over 400 point X-ray sources, at ≥ 5σ significance, down to a flux limit of ∼2 x 10 -14 erg s -1 cm -2 (2-10 keV). The sources exhibit a very wide range of spectral hardness, with interstellar absorption identified as a major influence. The source populations detected in the soft (0.4-2 keV) band and hard (2-6 keV) band show surprisingly little overlap. The majority of the soft sources appear to be associated with relatively nearby stars with active stellar coronae, judging from their high coincidence with bright stellar counterparts. The combination of the XGPS measurements in the hard X-ray band with the results from earlier surveys carried out by ASCA and Chandra reveals the form of the low-latitude X-ray source counts over 4 decades of flux. It appears that extragalactic sources dominate below ∼10 -13 erg s -1 cm -2 (2-10 keV), with a predominantly Galactic source population present above this flux threshold. The nature of the faint Galactic population observed by XMM-Newton remains uncertain, although cataclysmic variables and RS CVn systems may contribute substantially. XMM-Newton observes an enhanced surface brightness in the Galactic plane in the 2-6 keV band associated with Galactic ridge X-ray emission (GRXE). The integrated contribution of Galactic sources plus the breakthrough of extragalactic signal accounts for up to 20 per cent of the observed surface brightness. The XGPS results are consistent with the picture suggested from a deep Chandra observation in the Galactic plane, namely that the bulk of the GRXE is truly diffuse.