射电活动星系核相对论性束流Doppler因子的决定(I)3C273  

The Determination of the Doppler Factor of Relativistic Beaming in Active Galactic Nuclei. (I) Application to 3C 273

作　　者：王春成[1,2,3] 周又元[1,2,3] 王挺贵[1,2,3] 

机构地区：[1]中国科技大学天体物理中心 [2]中国科学院宇宙线和高能天体物理开放实验室 [3]中国科学院射电天文开放实验室

出　　处：《天体物理学报》1998年第2期117-127,共11页

基　　金：国家自然科学基金

摘　　要：目前决定射电活动星系核Ｄｏｐｐｌｅｒ因子δ的方法，主要是用均匀球状源模型的同步自康普顿机制（ＳＳＣ）关联射电和Ｘ射线（或光学）波段各一点的流量来定出δ．观测表明，此方法有较大的不足．本文发展了一种新方法，一方面将ＳＳＣ机制推广到非均匀情况，另一方面是用谱拟合代替点计算．我们首次用这种方法对３Ｃ２７３的Ｄｏｐｐｌｅｒ因子进行了推算．计算结果表明，３Ｃ２７３的多普勒因子δ～３１３．在假设喷流中非均匀成分和喷流整体的运动速度相同时，得到相对论性束流运动方向与视向的夹角θ～１５°．根据δ定出源的内禀亮温度约为５０×１０１０Ｋ，缓解了“康普顿灾变”的困难．由于非均匀模型比均匀模型更接近射电活动星系核中心致密子源的真实物理图象，有关参数由３Ｃ２７３的同时性和准同时性多波段观测定出，观测结果对ＳＳＣ机制提供了较好的支持，故理论和观测相符，由此确定的多普勒因子是更可信的．he principal method to determine the Doppler factor of radioloud AGNs is to connect one radio flux and one Xray(or optical) flux within the SSC frame of the homogeneous sphere model. Various observations, however, reveal serious problems with this method. In this paper, we develop a new method to derive the Doppler factor. On the one hand, we extend the SSC mechanism to the inhomogeneous case. On the other hand and more importantly, we substitute “point flux calculation”by spectral fit. Applying our new method to the brightest quasar in the sky, we find that Doppler factor of 3C 273 is around 313 Assuming that the inhomogeneous components move as fast as the bulk motion of the jet, we get the angle between the line of sight and the bulk velocity of relativistic beaming to be about 15 degrees. The intrinsic brightness temperature derived from theDoppler factor is nearly 50 ×1010 K, which relaxes the difficulty of the “Compton Catastrophe”.As we can see, the inhomogeneous model better matches the nature of the compact subsource in the central region of radioloud AGNs than the homogeneous hypothesis does. At the same time, the relevant parameters of our model calculation are determined through the simultaneous and quasisimultaneous multiwaveband observations of 3C 273 Moreover, we find good support to the SSC mechanism from the observations. Agreement between theory and observations allows us to believe that the Doppler factor derived here is better than most previous values. Our method will be an improved way to determine theDoppler factor.

关 键 词：多谱勒因子 喷流 类星体 射电星系核 束流 

分 类 号：P158[天文地球—天文学] P162.5