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arXiv 0910.0836astro-ph.COastro-ph.HE
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在z~0.84的四向群并合中没有类星体模反馈的证据

No Evidence of Quasar-Mode Feedback in a Four-Way Group Merger at z~0.84

Dale D. Kocevski, Lori M. Lubin, Brian C. Lemaux, Roy R. Gal, Christopher D. Fassnacht, Gordon K. Squires

摘要:

我们报告的结果钱德拉搜索的Cl 0023 +0423四路集团合并在z ~ 0.84内触发核活动的证据。该系统由四个相互作用的星系群在早期阶段的层次团簇形成,因此,提供了一个独特的外观在处理和进化的水平已经在集团环境之前,集群组装。我们提出了在覆盖整个Cl 0023结构的领域中检测到的X射线点源的数量计数,以及这些源与我们广泛的光谱数据库的互相关。无论是红移分布和X射线源的累积计数揭示了很少的证据表明,该系统包含的X射线发光的活动星系核(AGN)超过在现场人口中观察到的。如果在Cl 0023系统中正在进行预处理,我们的观察表明,强大的核活动并不是淬灭恒星形成和驱动Cl 0023星系演化的主要机制。我们推测,这是由于缺乏足够大的核黑洞所需的权力,这样的活动,因为以前的观察发现了一个高晚型的比例在Cl 0023人口。可能只有在星系群和结构演化的后期,当足够大质量的星系(和中心黑洞)已经形成时,但在流体动力学过程剥离它们的气体储存之前,活动星系核驱动的破坏性外流才成为星系群预处理的重要因素。

英文摘要:

We report on the results of a Chandra search for evidence of triggered nuclear activity within the Cl0023+0423 four-way group merger at z ~ 0.84. The system consists of four interacting galaxy groups in the early stages of hierarchical cluster formation and, as such, provides a unique look at the level of processing and evolution already under way in the group environment prior to cluster assembly. We present the number counts of X-ray point sources detected in a field covering the entire Cl0023 structure, as well as a cross-correlation of these sources with our extensive spectroscopic database. Both the redshift distribution and cumulative number counts of X-ray sources reveal little evidence to suggest that the system contains X-ray luminous active galactic nuclei (AGNs) in excess to what is observed in the field population. If preprocessing is under way in the Cl0023 system, our observations suggest that powerful nuclear activity is not the predominant mechanism quenching star formation and driving the evolution of Cl0023 galaxies. We speculate that this is due to a lack of sufficiently massive nuclear black holes required to power such activity, as previous observations have found a high late-type fraction among the Cl0023 population. It may be that disruptive AGN-driven outflows become an important factor in the preprocessing of galaxy populations only during a later stage in the evolution of such groups and structures when sufficiently massive galaxies (and central black holes) have built up, but prior to hydrodynamical processes stripping them of their gas reservoirs.

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