论文标题
群内低质量X射线二进制的特性
Properties of intra-cluster low-mass X-ray binaries in Fornax globular clusters
论文作者
论文摘要
我们介绍了一项研究，该研究是在Fornax Galaxy群集的中央1 $ deg^2 $中驻留在球状簇（GC）中的低质量X射线二进制组（LMXB）。与以前的研究不同的是，这些研究仅限于单个星系的最内向区域，旨在比较GC-LMXB的集群内群体与宿主星系的特性。我们使用VLT调查望远镜（VST）和Chandra观测值。我们根据有效半径在GCS中识别168个LMXB，并根据其与最近的星系的距离将其分为宿主 - 伴随物体和集群内对象。我们发现了82个群集内GC-LMXB和86个在星系中托管的对象。我们执行高斯混合模型，将种群分为红色和蓝色GC。正如在星系的最内向区域所发现的那样，LMXB也倾向于在群体内空间中以红色和明亮的GC形成。但是，我们发现，红色GC托管LMXB的可能性随着半乳酸的距离而降低，但对于蓝GC种群，它仍然差不多。研究居住在GC中的LMXB的X射线特性时，我们发现X射线光度函数在群体内和宿主 - 宿主 - 盖拉克斯样本之间存在差异：两者都遵循一个幂律为$ \ sim 8.5 \ sim 8.5 \ times 10^{37} $ erg s $ erg s $^{ - 1} $，以前与intra lmxs lmx complase lmxs compluts lmxs compluts lmx complust， GCS中的LMXB。我们检测到两个种群的硬度比率的暂定差异，其中群集内GC-LMXB的光谱似乎比宿主 - 甘拉克斯对象更难。当我们比较红色和蓝色GC-LMXB时，我们发现相同的趋势：蓝色样品的光谱比红色样品的光谱更难。该结果可能表明LMXBS的光谱特性与宿主GC颜色之间存在关系，从而具有金属性。
We present a study of the intra-cluster population of low-mass X-ray binaries (LMXB) residing in globular clusters (GC) in the central 1 $deg^2$ of the Fornax galaxy cluster. Differently from previous studies, which were restricted to the innermost regions of individual galaxies, this work is aimed at comparing the properties of the intra-cluster population of GC-LMXBs with those of the host galaxy. We use VLT Survey Telescope (VST) and Chandra observations. We identify 168 LMXBs residing in GCs and divide it into host-galaxy and intra-cluster objects based on their distance from the nearest galaxy in terms of effective radius. We found 82 intra-cluster GC-LMXBs and 86 objects that are hosted in galaxies. We perform a Gaussian mixture model to divide the population into red and blue GCs. As has been found for the innermost regions of galaxies, LMXBs tend to form in red and bright GCs in intra-cluster space as well. We find, however, that the likelihood of a red GC to host an LMXB decreases with galactocentric distance, but it remains approximately constant for the blue GC population. Investigating the X-ray properties of the LMXBs residing in GCs, we find a difference in the X-ray luminosity function between the intra-cluster and host-galaxy sample: both follow a power-law down to $\sim 8.5\times 10^{37}$ erg s$^{-1}$, which is consistent with field LMXBs for the intra-cluster sample, while the latter agree with previous estimates for LMXBs in GCs. We detect a tentative difference in the hardness ratio of two populations, where the intra-cluster GC-LMXBs appear to have harder spectra than the host-galaxy objects. We find the same trend when we compare red and blue GC-LMXBs: the spectra of the blue sample are harder spectra than those of the red sample. This result could suggest a relation between the spectral properties of LMXBs and the host GC colour and therefore its metallicity.
