The milliarcsecond structure of highly variable radio sources
Citations Over TimeTop 13% of 1992 papers
Abstract
We define a new sample of core-dominated extragalactic sources: those whose flux density has exceeded 4.5 Jy at 8 GHz at any epoch. This Variable Source Sample has 41 members. We have begun a program of VLBI studies of those members of the Variable Source Sample which are not otherwise being observed. In this paper we show first-epoch maps 12 of the 13 new objects. We discuss the morphologies and "scale lengths" (analogous to e-folding lengths) of sources in the complete Variable Source Sample to the extent these quantities are known, and compare them to the sources in the complete flux-limited sample of Pearson & Readhead (1988). We also discuss the ratio of X-ray to radio luminosities of sources in the Variable Source Sample. Our principal results are the following: 1. The morphologies of the Variable Source Sample and Pearson-Readhead sources are similar. 2. We confirm the Pearson-Readhead result that the distribution of position angle differences between milliarcsecond and arcsecond scales shows peaks at 0^deg^ and 90^deg^. 3. In our VLBI images, the "scale lengths" of Variable Source Sample and Pearson-Readhead sources are all smaller than about 120 pc. Compact Steep Spectrum sources have the largest scale length; BL Lac objects have much smaller scale lengths. 4. BL Lac objects have significantly higher ratios of X-ray to radio luminosities than the quasars in the Variable Source Sample.