The Two Mini-lobes of the CSO OQ208 - VLBI Observations at 5 GHz and 8.4 GHz
We present the results of VLBI observations at 5 GHz and 8.4 GHz of the compact symmetric object (CSO) OQ208. Images taken on four epochs at 5 GHz and one at 8.4 GHz show that the parsec radio structure of the source consists of two mini-lobes, both of them are resolved into two hot-spots. We note that the component D is stronger than the component C in the south-west region at 5 GHz, indicating that component D is less free-free absorbed than C at low frequency. On the basis of the separation of components A and D, a proper motion of 0.032 ± 0.02 mas yr-1 between the two mini-lobes is estimated. This value is about half the previous estimates based on the separation of components A and C with 8.4 GHz VLBI data. The reason for the decrease in the expansion velocity is discussed.
作 者： Wei-Hua Wang Xiao-Yu Hong Tao An 作者单位： Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030;National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 刊 名： 天体物理学报(英文版) ISTIC SCI 英文刊名： CHINESE JOURNAL OF ASTRONOMY AND ASTROPHYSICS 年，卷(期)： 2003 3(6) 分类号： P14 关键词： galaxies: individual (Mkn 668 OQ208) - galaxies: active