3C345 VLBI核心的可能的视超光速运动

ON A POSSIBLE SUPERLUMINAL MOTION OF THE VLBI CORE IN THE QUASAR 3C345

对类星体3C345的最新VLBI观测表明,节点C_6和C_7在向西北方向作视运动,这与节点C_4在1981—1984期间的视运动大致上平行.观测到的节点C_6和节点C_7的这种视运动是与钱善瑎所提出的"核心运动模型"所作出的预测的结果相符合的.本文利用现有关于3C345的所有VLBI观测数据,用比较严格的方法,定出了3C345的VLBI核心的南北方向视运动曲线和各个节点的视运动所沿的共同轨道的形式.结果表明,3C345的VLBI核心的南北方向视运动是振荡式的(见图4),导出的最大视运动速度为(0.10—0.15)mas/yr(即2c或3c,H_0=100公里·秒^(-1)·百万秒差距^(-1)).在1993年之前,对节点C_6和节点C_7的视轨道的VLBI监测,对于检验这个模型具有决定性的意义.非常希望对VLBI核心用VLBI相位参考技术来进行视运动的直接测定.

The most recent VLBI observation of the quasar 3C345 shows that the apparent motions of knots C_6 and C_7 were north- westwards and approximately paralleled to the apparent motion of knot C_4 during the period (1981—1984). This kind of apparent motion of C_6 and C_7 is consistent with the predictions of the core motion model' proposed by Qian(1991). In this paper a more precise method is used to derive the apparent motion of the core in the south north direction and the common path of the intrinsic motion of the knots. The apparent motion derived for the core is oscillatory (see fig. 4) and the maximal apparent speed is about 0.10—0.15mas/yr (or 2-3c, H_0=100 km sec^(-1) Moe^(-1)). For testing the model VLBI observations of knots C_6 and C_7 in the nearfuture (before 1993) would be crucial. Direct measurements of the core positions by VLBI phase-referencing technique would be most desirable.