Nonthermal Emission from Accreting and Merging Clusters of Galaxies
Nonthermal Emission from Accreting and Merging Clusters of Galaxies
复制标题
星系团吸积和合并产生的非热辐射
DOI：
10.1086/324030
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
C. Sarazin
中科院分区：
文献类型：
--
作者：
Y. Fujita;C. Sarazin
我们比较了小合并星系团(“吸积”星系团)和大合并星系团(“合并”星系团)的非热辐射。我们将主要合并定义为改变星系团内部暗物质结构的合并；次要合并是所有其他合并。对于聚积的团簇，还计算了团簇中非热辐射的径向分布。相对论电子是通过反康普顿(IC)和同步辐射产生的非热辐射的来源，它被认为是在吸积或合并产生的激波下加速的。根据层次聚类模型，我们估计了典型的增殖率和合并概率。我们预测，在聚积团簇的内部区域，非热辐射在所有频率上都具有平坦的空间分布。对于同步辐射和硬X射线辐射，我们预测星团边缘的辐射会由于吸积而增加。结果表明，聚集团簇和聚并团簇的IC发射的总亮度是相似的。另一方面，前者的同步加速器射电辐射光度比后者小得多。我们发现，在z~0处，大约10%的星系团应该有硬X射线和射电非热发射，这是由于它们最后一次重大合并，与持续吸积导致的合并相当或占主导地位。此外，由于上次合并，20%-40%的星团应该具有显著的EUV排放。我们还对放宽合并标准的情况进行了研究。如果我们将合并的定义扩展到较大的子星系团的质量至少增加其初始质量的10%，则即使在低密度宇宙中，由于合并，大约20%-30%的z0星系团应该具有硬X射线和射电非热发射。我们将结果与观测结果进行了比较。我们发现，观测到的星系团的EUV发射并不归因于吸积。如果在星系团中观察到的漫射射电辐射是通过吸积或合并加速的电子的同步辐射，则星系团的磁场通常只有~0.1μG。一个令人担忧的问题是，这是一个比法拉第旋转测量所暗示的磁场弱得多的磁场。
We compare the nonthermal emission from clusters of galaxies undergoing minor mergers ("accreting" clusters) and major mergers ("merging" clusters). We define major mergers as mergers that change the inner dark matter structure of clusters; minor mergers are all others. For accreting clusters, the radial distribution of the nonthermal emission in the clusters is also calculated. The relativistic electrons, which are the origin of the nonthermal radiation through inverse Compton (IC) and synchrotron emission, are assumed to be accelerated at shocks produced by accretion or mergers. We estimate the typical accretion rate and merger probability according to a hierarchical clustering model. We predict that in the inner region of accreting clusters the nonthermal emission has a flat spatial distribution at all frequencies. For synchrotron and hard X-ray emissions, we predict an increase in the emissions at the cluster edge due to accretion. We show that the total luminosities of IC emission from accreting and merging clusters are similar. On the other hand, the luminosity of synchrotron radio emission of the former is much smaller than that of the latter. We show that about 10% of clusters at z ~ 0 should have hard X-ray and radio nonthermal emissions due to their last major merger that are comparable to or dominate those due to ongoing accretion. Moreover, 20%-40% of clusters should have significant EUV emission due to their last merger. We also investigate the case where the criterion of mergers is relaxed. If we extend the definition of a merger to an increase in the mass of the larger subcluster by at least 10% of its initial mass, about 20%-30% of clusters at z ~ 0 should have hard X-ray and radio nonthermal emissions due to the merger, even in a low-density universe. We compare the results with observations. We find that the observed EUV emission from clusters is not attributed to accretion. If the diffuse radio emission observed in clusters is synchrotron emission from electrons accelerated via accretion or merging, the magnetic fields of clusters are generally as small as ~0.1 μG. One concern is that this is a significantly weaker field than that implied by Faraday rotation measurements.
DOI：
--
发表时间：
2009
期刊：
影响因子：
--
作者：
Iwasa;Y
通讯作者：
Y