McNamara B R, Nulsen P E J, Wise M W, Rafferty D A, Carilli C, Sarazin C L, Blanton E L
Astrophysical Institute and Department of Physics & Astronomy, Ohio University, Clippinger Laboratories, Athens, Ohio 45701, USA.
Nature. 2005 Jan 6;433(7021):45-7. doi: 10.1038/nature03202.
Most of the baryons in galaxy clusters reside between the galaxies in a hot, tenuous gas. The densest gas in their centres should cool and accrete onto giant central galaxies at rates of 10-1,000 solar masses per year. No viable repository for this gas, such as clouds or new stars, has been found. New X-ray observations, however, have revealed far less cooling below X-ray temperatures than expected, altering the previously accepted picture of cooling flows. As a result, most of the gas must be heated to and maintained at temperatures above approximately 2 keV (ref. 3). The most promising heating mechanism is powerful radio jets emanating from supermassive black holes in the central galaxies of clusters. Here we report the discovery of giant cavities and shock fronts in a distant (z = 0.22) cluster caused by an interaction between a radio source and the hot gas surrounding it. The energy involved is approximately 6 x 10(61) erg, the most powerful radio outburst known. This is enough energy to quench a cooling flow for several Gyr, and to provide approximately 1/3 keV per particle of heat to the surrounding cluster.
星系团中的大多数重子存在于星系之间炽热、稀薄的气体中。其中心最致密的气体应会冷却，并以每年10至1000个太阳质量的速率聚集到巨大的中心星系上。尚未发现这种气体的可行储存库，如云或新恒星。然而，新的X射线观测显示，低于X射线温度的冷却远比预期少，改变了之前被接受的冷却流图景。因此，大部分气体必须被加热到约2千电子伏特以上的温度并维持在该温度（参考文献3）。最有前景的加热机制是来自星系团中心星系中超大质量黑洞的强大射电喷流。在此我们报告在一个遥远（红移z = 0.22）的星系团中发现了由射电源与其周围热气体相互作用导致的巨大空洞和激波前沿。所涉及的能量约为6×10⁶¹尔格，是已知最强大的射电爆发。这一能量足以抑制冷却流数十亿年，并为周围星系团的每个粒子提供约1/3千电子伏特的热量。
