天鹅座A II的多波长研究。遗迹反喷流的X射线逆康普顿辐射和喷流占空比的影响
Multiwavelength study of Cygnus A II. X-ray inverse-Compton emission from a relic counterjet and implications for jet duty-cycles
摘要：
强大的射电星系和类星体，如原型天鹅座A的占空比知之甚少。逆康普顿散射宇宙微波背景（ICCMB）光子的X射线观测比同步辐射的射电观测探测更低的洛伦兹因子粒子。对较近和较远的叶瓣进行比较研究，它们之间的距离为10秒kpc，因此光的旅行时间为10秒几千年，在生命周期的研究中产生了额外的时间分辨率。我们共同添加了所有存档的Chandra ACIS-I数据，并提供了天鹅座A的深度200 k图像。这张深层图像揭示了来自反喷流的X射线发射的存在，反喷流即从地球后退的喷流，与前一次喷流活动有关。非热X射线发射，我们解释为ICCMB辐射。没有任何可辨别的X射线发射与喷流向地球。我们的结论是：（1）来自遗迹喷流的辐射，表明喷流活动的前一幕，发生在当前喷流活动之前，表现为同步辐射。(2)天鹅座A的遗迹反喷流发射出X射线，而遗迹接近喷流时却没有发射出X射线，这使得连续的喷流活动之间的时间间隔大约为10^6年。(3)射流的横向膨胀导致膨胀损失，这将能量分布转移到较低的能量。(4)假设电子由于绝热膨胀而冷却，则所需的磁场强度基本上小于均分磁场强度。(5)相对论性粒子在当前喷流中的分布有一个很高的最小洛伦兹因子，大约为10 ^3，它是从这个活跃星系的中心核喷射出来的。节录。
英文摘要：
The duty-cycle of powerful radio galaxies and quasars such as the prototype Cygnus A is poorly understood. X-ray observations of inverse-Compton scattered Cosmic Microwave Background (ICCMB) photons probe lower Lorentz-factor particles than radio observations of synchrotron emission. Comparative studies of the nearer and further lobes, separated by many 10s of kpc and thus 10s of thousands of years in light-travel time, yield additional temporal resolution in studies of the lifecycles. We have co-added all archival Chandra ACIS-I data and present a deep 200 ks image of Cygnus A. This deep image reveals the presence of X-ray emission from a counterjet i.e. a jet receding from Earth and related to a previous episode of jet activity. The non-thermal X-ray emission, we interpret as ICCMB radiation. There is an absence of any discernible X-ray emission associated with a jet flowing towards Earth. We conclude that: (1) The emission from a relic jet, indicates a previous episode of jet activity, that took place earlier than the current jet activity appearing as synchrotron radio emission. (2) The presence of X-ray emission from a relic counterjet of Cygnus A and the absence of X-ray emission associated with any relic approaching jet constrains the timescale between successive episodes of jet activity to ~10^6 years. (3) Transverse expansion of the jet causes expansion losses which shifts the energy distribution to lower energies. (4) Assuming the electrons cooled due to adiabatic expansion, the required magnetic field strength is substantially smaller than the equipartition magnetic field strength. (5) A high minimum Lorentz factor for the distribution of relativistic particles in the current jet, of a few 10^3, is ejected from the central nucleus of this active galaxy. Abridged.
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