Milli-Arcsecond Morphology and Structural Changes in a \\Complete Sample of Radio Sources
Session 44 -- Radio Galaxies, Jets and Disks
Display presentation, Wednesday, 9:20-6:30, Pauley Room

## [44.08] Milli-Arcsecond Morphology and Structural Changes in a \\Complete Sample of Radio Sources

T.J. Pearson, A.C.S. Readhead (Caltech), P.D. Barthel (University of Groningen), J.E. Conway (NRAO), S.T. Myers (Caltech)

We have conducted a VLBI survey of a complete, flux-density--limited sample of 65~extragalactic radio sources, selected at 5~GHz, in order to study their morphology and to look for superluminal motion and other structural changes. First-epoch images of 37 sources were published by Pearson \& Readhead (1988, ApJ, 328, 114). Here we present 5-GHz images, with a resolution $\sim 1$~milliarcsec, taken at three epochs spread over 9 years for each of 25 sources.

The majority of the sources have an asymmetric, core-jet morphology. Several of these are superluminal sources in which an emission feature moves outward along the jet at $v_{\rm app} > c$ (e.g., 0850+581, 1642+690, 1928+738, BL~Lac, 3C~216, 3C~345). Several other sources with similar morphology, however, show no changes in relative positions of subcomponents, although subcomponent flux densities do change (e.g., 0711+356, 1652+398, 1823+568).

We draw attention to a new class of compact symmetric'' objects with double or triple morphology (e.g., 0108+388, 0710+439, 2352+495). We have placed limits $< c$ on relative motion of components in these sources, and they show little if any evidence for relativistic beaming. The central engine appears to lie midway between two lobes $\sim 100$~pc apart.

The sample also includes some compact steep-spectrum sources and other sources that are difficult to classify.