arXiv 1507.059732015-07-21astro-ph.GAastro-ph.HE

星系团的热外流

Hot Outflows in Galaxy Clusters

C. C. Kirkpatrick, B. R. McNamara

备注：: 18 pages, 13 figures, accepted to MNRAS
DOI：: 10.1093/mnras/stv1574

摘要：

本文利用钱德拉X射线天文台（\it Chandra X-ray Observatory）的观测资料，分析了29个星系团热大气的气相金属丰度分布。所有最亮的星系团（BCGs）都拥有由射电AGN产生的X射线空腔系统。我们发现高元素丰度投影优先沿腔的16个集群。富含金属的等离子体显然是随着X射线空洞（气泡）的上升而被提升到20到几百千秒差距之间的高度。发现了上升气体的最大投射高度（“铁半径”）与喷流功率之间的关系，其形式为$R_{\rm Fe} \propto P_{\rm jet}^{0.45}$。据估计，流出速率通常为每年几十个太阳质量，但在最强大的活动星系核中超过了$100 ~\rm M_\odot ~yr^{-1}$。流出速率是冷却速率的10%至20%，因此单独不能抵消冷却流入。然而，热外流有效地重新分配冷却气体，并可能发挥重要作用，在调节恒星形成和活动星系核的活动在BCGs和可能在巨大的椭圆星系。金属丰度分布总体上可能是复杂的，可能是由于富含金属的气体在循环流中返回或在热大气中被吹来吹去。大约有15%的空洞所做的功被用来提升富含金属的气体，这意味着它们的核黑洞的质量至少增加了$\sim 10^7$ M $_\odot$到$10^9$ M $_\odot$。最后，我们表明，热外流可以占广泛的，气相金属丰度分布相比，恒星光剖面的BCGs，我们认为热外流和冷分子气流之间的可能联系，发现在最近的ALMA观测。

英文摘要：

The gas-phase metallicity distribution has been analyzed for the hot atmospheres of 29 galaxy clusters using {\it Chandra X-ray Observatory} observations. All host brightest cluster galaxies (BCGs) with X-ray cavity systems produced by radio AGN. We find high elemental abundances projected preferentially along the cavities of 16 clusters. The metal-rich plasma was apparently lifted out of the BCGs with the rising X-ray cavities (bubbles) to altitudes between twenty and several hundred kiloparsecs. A relationship between the maximum projected altitude of the uplifted gas (the "iron radius") and jet power is found with the form $R_{\rm Fe} \propto P_{\rm jet}^{0.45}$. The estimated outflow rates are typically tens of solar masses per year but exceed $100 ~\rm M_\odot ~yr^{-1}$ in the most powerful AGN. The outflow rates are 10% to 20% of the cooling rates, and thus alone are unable to offset a cooling inflow. Nevertheless, hot outflows effectively redistribute the cooling gas and may play a significant role at regulating star formation and AGN activity in BCGs and presumably in giant elliptical galaxies. The metallicity distribution overall can be complex, perhaps due to metal rich gas returning in circulation flows or being blown around in the hot atmospheres. Roughly 15% of the work done by the cavities is expended lifting the metal-enriched gas, implying their nuclear black holes have increased in mass by at least $\sim 10^7$ M$_\odot$ to $10^9$ M$_\odot$. Finally, we show that hot outflows can account for the broad, gas-phase metallicity distribution compared to the stellar light profiles of BCGs, and we consider a possible connection between hot outflows and cold molecular gas flows discovered in recent ALMA observations.

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