标题： 一种估计活动星系核喷流中频率依赖核心偏移的新方法 显示英文标题

标题： A new method for estimating frequency-dependent core shifts in active galactic nucleus jets

摘要： 我们讨论通过甚长基线干涉测量(VLBI)观测到的活动星系核核心区域的不透明性，并描述了一种从单天线观测到的耀斑频率依赖时间延迟中推导VLBI核心频率依赖偏移的新方法。 将该方法应用于类星体3C 345的核心偏移，显示直接从VLBI观测中测量的核心偏移与使用所提出方法从总通量密度中的耀斑推导出的结果之间有非常好的一致性。 耀斑的频率依赖时间延迟可用于推导喷流的物理参数，例如从VLBI核心到喷流基部的距离以及核心区域的磁场。 我们对3C 345的估计表明核心磁场约为0.1 G，1 pc处的磁场约为0.4 G。 显示英文摘要

摘要： We discuss the opacity in the core regions of active galactic nuclei observed with Very Long Baseline Interferometry (VLBI), and describe a new method for deriving the frequency-dependent shifts of the VLBI core from the frequency-dependent time lags of flares observed with single-dish observations. Application of the method to the core shifts of the quasar 3C 345 shows a very good agreement between the core shifts directly measured from VLBI observations and derived from flares in the total flux density using the proposed method. The frequency-dependent time lags of flares can be used to derive physical parameters of the jets, such as distance from the VLBI core to the base of the jet and the magnetic fields in the core region. Our estimates for 3C 345 indicate core magnetic fields ~0.1 G and magnetic field at 1 pc ~0.4 G.