Inferences from Superluminal Motion Statistics

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Session 100 -- AGN: Unified Picture
Oral presentation, Friday, January 14, 2:15-3:45, Crystal Forum Room (Crystal City Marriott)

[100.03] Inferences from Superluminal Motion Statistics

R.C. Vermeulen, M.H. Cohen (Caltech)

We present an up-to-date compilation of internal proper motion measurements. We demonstrate how their statistics, and those of future large homogeneous samples, may be used to infer the distribution of Lorentz $\gamma$ factors, and how superluminal motion statistics may impact AGN unification studies. The current data are derived from inhoogeneous ovbservations, but none-the-less suggest that there is either a wide spread of $\gamma$s in quasars, or that there are separate bulk and pattern $\gamma$s, or both; the simplest model, without separate pattern velocities, and identical or similar $\gamma$ in all quasars, is now ruled out.

There is a well-defined upper envelope in the $\mu$-$z$ diagram, as indeed predicted by beaming models. Its shape currently suggests that either the universe is closed, or the Lorentz factors increase with redshift. Second-epoch observations of the Caltech-Jodrell VLBI survey are in progress. They will allow a detailed study of the distribution of Lorentz factors in narrow redshift bins, from which evolution of $\gamma$ on parsec scales, if any, will be apparent. Thereafter, intercomparison of the statistics between redshift bins will allow q$_{0}$ to be constrained.

Friday program listing