Chandra、XMM和GMRT数据揭示的HCG 62星系群中的空洞和激波
Cavities and shocks in the galaxy group HCG 62 as revealed by Chandra, XMM and GMRT data
摘要：
我们报告的钱德拉，XMM-牛顿和新的GMRT数据的X射线明亮的紧凑的星系群HCG 62，这是已知的少数几个群体之一，拥有清晰的，小的X射线腔的内部区域的分析结果。这是正在进行的18组X射线/低频射电研究的一部分，最初选择的高质量X射线数据和AGN/热气相互作用的证据。在更高的频率（1.4 GHz），HCG 62腔系统显示出最小的无线电发射，但在235 MHz和610 MHz的新GMRT观测清楚地检测到对应于腔的无线电波瓣的扩展低频发射。通过X射线和低频射电观测的协同作用，我们比较和讨论了气体和射电源的形态，光度和压力。我们发现，无线电源是辐射效率低，与无线电光度的比率$\sim 10^{-4}$的机械腔功率，和波瓣的无线电压力是约一个数量级低于周围的热气体的X射线压力。由于钱德拉表面亮度和温度分布的高空间分辨率，我们还确定了位于36千秒差距的冲击波阵面的西南部的组中心，靠近南部的射电瓣，马赫数$\sim 1.5$和总功率约一个数量级高于腔功率。正如温度图所示，这样的冲击可能加热了南部地区的气体。这个冲击波也可以解释在铁丰度图中所看到的弧形富集气体区域，因为这可能是由其前部附近的非麦克斯韦电子分布产生的。
英文摘要：
We report on the results of an analysis of Chandra, XMM-Newton and new GMRT data of the X-ray bright compact group of galaxies HCG 62, which is one of the few groups known to possess clear, small X-ray cavities in the inner regions. This is part of an ongoing X-ray/low-frequency radio study of 18 groups, initially chosen for the availability of good-quality X-ray data and evidence for AGN/hot gas interaction. At higher frequency (1.4 GHz), the HCG 62 cavity system shows minimal if any radio emission, but the new GMRT observations at 235 MHz and 610 MHz clearly detect extended low-frequency emission from radio lobes corresponding to the cavities. By means of the synergy of X-ray and low-frequency radio observations, we compare and discuss the morphology, luminosity and pressure of the gas and of the radio source. We find that the radio source is radiatively inefficient, with a ratio of radio luminosity to mechanical cavity power of $\sim 10^{-4}$, and that the radio pressure of the lobes is about one order of magnitude lower than the X-ray pressure of the surrounding thermal gas. Thanks to the high spatial resolution of the Chandra surface brightness and temperature profiles, we also identify a shock front located at 36 kpc to the south-west of the group center, close to the southern radio lobe, with a Mach number $\sim 1.5$ and a total power which is about one order of magnitude higher than the cavity power. Such a shock may have heated the gas in the southern region, as indicated by the temperature map. The shock may also explain the arc-like region of enriched gas seen in the iron abundance map, as this may be produced by a non-Maxwellian electron distribution near its front.
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