An ASCA Study of the Heavy-Element Distribution in Clusters of Galaxies
An ASCA Study of the Heavy-Element Distribution in Clusters of Galaxies
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ASCA 对星系团中重元素分布的研究
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
T. Ponman
中科院分区：
文献类型：
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作者：
A. Finoguenov;L. David;T. Ponman
我们进行了空间分辨X射线光谱研究的一组11个放松星系团观测的ROSAT/PSPC和ASCA/SIS。使用一种方法，它纠正了基于ROSAT图像的ASCA点扩散函数的能量依赖性的影响，我们约束在每个集群中的Ne，Si，S和Fe的空间分布。Ia型和II型超新星的化学产率的理论处方，然后允许确定的Fe富集从这两种类型的超新星作为半径的函数在每个集群。使用文献中的光学测量，我们还确定了铁的质光比（IMLR）分别为铁合成的两种类型的超新星。对于具有最佳光子统计的团簇，我们发现总Fe丰度随半径显著降低，而Si丰度要么是平坦的，要么降低得不太快，导致Si/Fe比随半径增加。这一结果表明，更大的优势II型超新星（SN）富集在大半径的集群。平均而言，在II型SNe内合成的IMLR随着簇内半径的增加而增加，而在Ia型SNe内合成的IMLR减少。在0.4 Rvirial的固定半径下，由II型SNe合成的IMLR在组和簇之间也增加了5倍。这表明，在早期，这些群体排出了多达90%的II型SNe内合成的Fe。所有这些结果都与气体最初被II型SN驱动的星系风加热和富集的情景一致。由于预热气体的高熵，SN II产物仅被微弱地捕获在基团中。然后，引力束缚的气体富含Ia型超新星合成的元素，因为富含气体的星系吸积到星系团上，并在通过星系团核心的过程中通过密度依赖机制（例如，冲压压力烧蚀、星系骚扰等）。我们认为，在丰富的集群外围的高Si/Fe比可能会产生富集II型SNe释放到集群内介质通过银河系恒星暴驱动的风。在星系团中观察到的低S/Fe比表明贫金属星系是SN II产物的主要来源。
We perform a spatially resolved X-ray spectroscopic study of a set of 11 relaxed clusters of galaxies observed by the ROSAT/PSPC and ASCA/SIS. Using a method, which corrects for the energy-dependent effects of the ASCA point-spread function based on ROSAT images, we constrain the spatial distribution of Ne, Si, S, and Fe in each cluster. Theoretical prescriptions for the chemical yields of Types Ia and II supernovae then allow determination of the Fe enrichment from both types of supernovae as a function of radius within each cluster. Using optical measurements from the literature, we also determine the iron mass-to-light ratio (IMLR) separately for Fe synthesized in both types of supernovae. For clusters with the best photon statistics, we find that the total Fe abundance decreases significantly with radius while the Si abundance is either flat or decreases less rapidly, resulting in an increasing Si/Fe ratio with radius. This result indicates a greater predominance of Type II supernova (SN) enrichment at large radii in clusters. On average, the IMLR synthesized within Type II SNe increases with radius within clusters, while the IMLR synthesized within Type Ia SNe decreases. At a fixed radius of 0.4 Rvirial there is also a factor of 5 increase in the IMLR synthesized by Type II SNe between groups and clusters. This suggests that groups expelled as much as 90% of the Fe synthesized within Type II SNe at early times. All of these results are consistent with a scenario in which the gas was initially heated and enriched by Type II SN-driven galactic winds. Because of the high entropy of the preheated gas, SN II products are only weakly captured in groups. Gravitationally bound gas was then enriched with elements synthesized by Type Ia supernovae as gas-rich galaxies accreted onto clusters and were stripped during passage through the cluster core via density-dependent mechanisms (e.g., ram pressure ablation, galaxy harassment, etc.). We suggest that the high Si/Fe ratios in the outskirts of rich clusters may arise from enrichment by Type II SNe released to the intracluster medium via galactic starburst-driven winds. Low S/Fe ratios observed in clusters suggest metal-poor galaxies as a major source of SN II products.