热星系团内介质中心丰度的起源- I。来自XMM-牛顿EPIC的个体和平均丰度比
Origin of central abundances in the hot intra-cluster medium - I. Individual and average abundance ratios from XMM-Newton EPIC
摘要：
炽热的星系团内介质（ICM）富含金属，这些金属是由超新星（SNe）爆炸合成的，并随着时间的推移积累到星系团的深引力势阱中。由于X射线中可见的大多数元素都是由Ia型超新星（SNIa）和/或核心坍缩（SNcc）超新星形成的，测量它们的丰度可以为我们提供自恒星形成高峰期（z ~ 2-3）以来数十亿SNe的核合成产物的直接信息。在这项研究中，我们使用EPIC和RGS仪器上XMM-牛顿测量9个元素（O，Ne，Mg，Si，S，Ar，Ca，Fe和Ni）的丰度从44个附近的冷核星系团，集团和椭圆星系的样品。我们发现，Fe丰度在样品上显示出很大的分散性（~20-40%），在0.2 $r_{500}$范围内，特别是0.05 $r_{500}$。与绝对Fe丰度不同，丰度比（X/Fe）在所考虑的温度范围内（~0.6-8 keV）相当均匀，并且具有有限的分散性。除了对系统不确定性进行前所未有的处理外，我们还提供了迄今为止在ICM中测量的最准确的丰度比，包括我们坚定地检测到的Cr/Fe和Mn/Fe（MOS和pn独立>4σ）。我们发现Cr/Fe、Mn/Fe和Ni/Fe与原始太阳值有显著差异。然而，在原太阳丰度的大的不确定性，使我们无法作出强有力的比较本地和集群内的化学富集。我们还注意到，有趣的是，尽管我们的数据集的净曝光时间很大（~4.5 Ms），但在~3.5 keV附近没有看到线发射特征。
英文摘要：
The hot intra-cluster medium (ICM) is rich in metals, which are synthesized by supernovae (SNe) explosions and accumulate over time into the deep gravitational potential well of clusters of galaxies. Since most of the elements visible in X-rays are formed by type Ia (SNIa) and/or core-collapse (SNcc) supernovae, measuring their abundances gives us direct information on the nucleosynthesis products of billions of SNe since the epoch of the star formation peak (z ~ 2-3). In this study, we use the EPIC and RGS instruments onboard XMM-Newton to measure the abundances of 9 elements (O, Ne, Mg, Si, S, Ar, Ca, Fe and Ni) from a sample of 44 nearby cool-core galaxy clusters, groups, and elliptical galaxies. We find that the Fe abundance shows a large scatter (~20-40%) over the sample, within 0.2$r_{500}$ and, especially, 0.05$r_{500}$. Unlike the absolute Fe abundance, the abundance ratios (X/Fe) are quite uniform over the considered temperature range (~0.6-8 keV), and with a limited scatter. In addition to a unprecedented treatment of systematic uncertainties, we provide the most accurate abundance ratios measured so far in the ICM, including Cr/Fe and Mn/Fe that we firmly detect (>4σ with MOS and pn independently). We find that Cr/Fe, Mn/Fe and Ni/Fe, differ significantly from the proto-solar values. However, the large uncertainties in the proto-solar abundances prevent us from making a robust comparison between the local and the intra-cluster chemical enrichments. We also note that, interestingly, and despite the large net exposure time (~4.5 Ms) of our dataset, no line emission feature is seen around ~3.5 keV.
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