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arXiv 1106.3435astro-ph.HE
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邻近早型和晚型星系X射线辐射和X/K光度比的未分辨和弥散分量

Unresolved and diffuse components of X-ray emission and X/K luminosity ratios in nearby early-type and late-type galaxies

Akos Bogdan, Marat Gilfanov

摘要:

我们探讨了未解决的X射线发射的性质在一个广泛的样本的星系的所有形态类型的基础上档案钱德拉数据。在去除明亮致密源后,我们研究了未分辨辐射的L_X/L_K光度比,并与太阳邻域值进行了比较。我们的结论是,未解决的排放是由四个主要组成部分,其中三个是已知的:(i)人口的微弱未解决的来源与老恒星星族。在早型星系中,2-10 keV波段的光度与恒星质量成正比,L_X/L_K =(3.1 \pm 0.9)× 10^27 erg/s/L_K,太阳;由于大的分散在气体含量的星系,我们的样本的大小是不够的,以获得可靠的标度律为这一组成部分;(三)人口的未解决的年轻恒星和年轻的恒星物体在晚型星系。它们的2-10 keV波段光度与恒星形成速率成比例关系,L_X/SFR =(1.7 \pm 0.9)× 10^38(erg/s)/(M_sun/yr);(iv)在四个古老的大质量室女座椭圆星系(M49、M60、M84、NGC 4636)中,我们发现了2-10 keV波段的异常高的X射线发射。它的存在以前没有得到承认,其性质也不清楚。虽然它似乎是更强的星系具有较强的ISM组件,它的存在不能解释的温暖ISM光谱的外推。与室女星系团的关联表明,过量的发射可能是由于在一个大质量星系的引力阱中聚集的团内气体。我们正在研究这个和其他可能性。

英文摘要:

We explore the nature of unresolved X-ray emission in a broad sample of galaxies of all morphological types based on archival Chandra data. After removing bright compact sources, we study L_X/L_K luminosity ratios of unresolved emission, and compare them with the Solar neighborhood values. We conclude that unresolved emission is determined by four main components, three of which were known before: (i) The population of faint unresolved sources associated with old stellar population. In early-type galaxies, their 2-10 keV band luminosity scales with the stellar mass with L_X/L_K = (3.1\pm 0.9) x 10^27 erg/s/L_K,sun; (ii) The ISM with kT ~ 0.2-0.8 keV present in galaxies of all types. Because of the large dispersion in the gas content of galaxies, the size of our sample is insufficient to obtain reliable scaling law for this component; (iii) The population of unresolved young stars and young stellar objects in late-type galaxies. Their 2-10 keV band luminosity scales with the star-formation rate with L_X/SFR = (1.7\pm0.9) x 10^38 (erg/s)/(M_sun/yr); (iv) In four old and massive Virgo ellipticals (M49, M60, M84, NGC4636) we find anomalously high X-ray emission in the 2-10 keV band. Its presence has not been recognized before and its nature is unclear. Although it appears to be stronger in galaxies having stronger ISM component, its existence cannot be explained in terms of an extrapolation of the warm ISM spectrum. Association with Virgo cluster of galaxies suggests that the excess emission may be due to intracluster gas accreted in the gravitational well of a massive galaxy. We investigate this and other possibilities.

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