Evolution of Radio Sources

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10. Evolution of Radio Sources  

We heard several new results on the growth and evolution of radio sources. Compact Symmetric Objects (CSO's: Readhead et al., these Proceedings; Taylor, Readhead, & Pearson, these Proceedings) appear to be candidates for the long-sought precursors of FR II sources. They show signs of intrinsic asymmetries on parsec scales (and also exemplify the exquisite difficulty of finding the true radio nuclei of small sources in the presence of free-free absorption).  Studying proper motions  on both sides of the nucleus in double-jetted CSO's may also allow more reliable estimates of speeds and orientations  in small-scale jets (Pearson, these Proceedings). At another extreme, Scheuer (these Proceedings) showed that the lobes of FR II sources with prominent jets may exhibit the jet-related length asymmetry expected for mildly relativistic advance-but, if so, at speeds less than those naïvely inferred from synchrotron aging. Whether or not one trusts aging calculations-see Rudnick & Katz-Stone (these Proceedings) and Eilek (these Proceedings) for reasons why one might not-the small size of the asymmetry in Scheuer's data puts a lower bound on source lifetimes.

Alan Bridle
Wed Apr 10 10:19:46 EDT 1996