will be inserted by hand later ) X-ray emission from NGC 1808 : more than a complex starburst ⋆
will be inserted by hand later ) X-ray emission from NGC 1808 : more than a complex starburst ⋆
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稍后将手动插入）NGC 1808 发出的 X 射线：不仅仅是复杂的星暴 ⋆
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
K. Weaver
中科院分区：
文献类型：
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作者：
E. J. Bailón;M. Santos;M. Dahlem;M. Ehle;J. Mas;M. Guainazzi;T. Heckman;K. Weaver
早些时候对NGC1808在不同波段(X射线、光学、近红外、无线电)的观测为星暴或塞弗特2核的存在提供了证据。我们给出了多波长XMM-牛顿和钱德拉观测的结果，它们直接证明了与星暴活动有关的热扩散等离子体和非核未分辨点状源以及低光度活动星系核(LLAGN)或超发光X射线源(ULX)的共存。XMM-牛顿的宽带宽表明，NGC1808中未分辨的核源在硬X射线光谱中占主导地位，而在软区(低于1keV)的发射则由与扩展星暴有关的热分量主导。EPIC和RGS数据都提供了一些重元素发射线的可靠探测，不同元素的丰度范围约为0.7Z⊙到2.2Z。但未检测到6.4keV Fe-K-α荧光线发射。对NGC1808核区域的分析使我们能够探测并解开未分辨的核X射线源和恒星爆发区域的贡献，但核的确切性质仍然未知。观测到的NGC1808的光度为L2−10keV=(1.6 1±0.0 6)×10 erg S.我们的OM2 12 nm图像与CTIO4 m望远镜的Hα框架的比较表明，大质量恒星的发射与热电离气体之间有很好的大体对应关系，但在NGC1808的杆端附近有微小的偏差.在XMM-牛顿光谱分析中发现了一个KT为0.1keV的非常软的热谱分量，它很可能来自≃1808星的晕。
Earlier observations of NGC 1808 in various wavebands (X-ray, optical, near-infrared, radio) provided evidence for the existence of either a starburst or a Seyfert 2 nucleus. We here present the results of multiwavelength XMMNewton and Chandra observations, which directly prove the co-existence of thermal diffuse plasma and non-nuclear unresolved point-like sources associated with the starburst activity, along with a Low Luminosity Active Galactic Nucleus (LLAGN) or an Ultra Luminous X-ray source (ULX). The broad bandwidth of XMM-Newton allows us to show that the unresolved nuclear source in NGC1808 dominates the hard X-ray spectrum, while the emission in the soft regime, below 1 keV, is dominated by a thermal component associated to an extended starburst. Both EPIC and RGS data provide reliable detections of a number of emission lines from heavy elements, with abundances ranging from roughly 0.7 to 2.2 Z⊙ for different elements. However, no 6.4 keV Fe Kα fluorescence line emission was detected. The analysis of the nuclear region of NGC1808 allows us to detect and disentangle the contribution of an unresolved nuclear X-ray source and the starburst region, but the exact nature of the nucleus remains unknown. The observed luminosity of NGC1808 is L2−10 keV = (1.61±0.06)×10 erg s. A comparison of our OM 212 nm image with a CTIO 4-m telescope Hα frame shows a good general correspondence between the emission from massive stars and warm ionized gas, with minor deviations near the ends of the bar in NGC1808. An aditional, very soft thermal spectral component with kT≃0.1 keV has been discovered in the XMM-Newton spectral analysis, which most likely originates from the halo of NGC1808.