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首页> 外文期刊>The Astrophysical journal >Globular Clusters and X-Ray Point Sources in Centaurus A (NGC 5128)
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Globular Clusters and X-Ray Point Sources in Centaurus A (NGC 5128)

机译:半人马座A中的球状星团和X射线点源(NGC 5128)

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摘要

We detect 353 X-ray point sources, mostly low-mass X-ray binaries (LMXBs), in four Chandra observations of Centaurus A (NGC 5128), the nearest giant early-type galaxy, and correlate this point-source population with the largest available ensemble of confirmed and likely globular clusters (GCs) associated with this galaxy. Of the X-ray sources, 31 are coincident with 30 GCs that are confirmed members of the galaxy by radial velocity measurement (two X-ray sources match one GC within our search radius), while one X-ray source coincides with a GC resolved by Hubble Space Telescope (HST) images. Another 36 X-ray point sources match probable, but spectroscopically unconfirmed, GC candidates. The color distribution of GCs and cluster candidates in Cen A is bimodal, and the probability that a red, metal-rich GC candidate contains an LMXB is at least 1.7 times that of a blue, metal-poor one. If we consider only spectroscopically confirmed GCs, this ratio increases to ~3. We find that LMXBs appear preferentially in more luminous (massive) GCs. These two effects are independent, and the latter is likely a consequence of enhanced dynamical encounter rates in more massive clusters which have, on average, denser cores. The X-ray luminosity functions of the LMXBs found in GCs and of those that are unmatched with GCs reveal similar underlying populations, although there is some indication that fewer X-ray-faint LMXBs are found in GCs than X-ray-bright ones. Our results agree with previous observations of the connection of GCs and LMXBs in early-type galaxies and extend previous work on Cen A.
机译:我们在最近的巨型早期星系Centaurus A(NGC 5128)的四次Chandra观测中检测到353个X射线点源,主要是低质量X射线双星(LMXBs),并将该点源人口与与该星系相关的已确认和可能的球状星团(GC)的最大可用集合。在X射线源中,有31个与30个GC一致,这是通过径向速度测量确定的星系成员(两个X射线源在我们的搜索半径内与一个GC匹配),而一个X射线源与已解析的GC一致由哈勃太空望远镜(HST)拍摄。另外36个X射线点源与可能的,但在光谱上未经证实的GC候选物相匹配。 Cen A中GC和候选簇的颜色分布是双峰的,并且富含金属的红色GC候选物包含LMXB的概率至少是贫金属的蓝色GC的1.7倍。如果仅考虑经光谱确认的GC,则该比率增加到〜3。我们发现LMXB优先出现在更发光(大量)的GC中。这两种效应是独立的,后者可能是平均密度更高的更大质量星团中动态相遇率提高的结果。 GC中发现的LMXB的X射线光度函数以及与GC不匹配的LMXB的X射线光度函数显示出相似的基本种群,尽管有迹象表明在GC中发现的X射线微弱LMXB少于X射线明亮的LMXB。我们的结果与先前关于早期类型星系中GC和LMXB的联系的观察结果相符,并扩展了有关Cen A的先前工作。

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