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Session 112 - Radio Galaxies and Jets: VLBI.
Oral session, Thursday, January 18
1st Floor, La Villita Assembly Building

[112.04] Observations and Simulations of Parsec Scale Jets in Active Galactic Nuclei

A. J. Mioduszewski, P. A. Hughes (U. Michigan), D. C. Gabuzda (Lebedev Physical Inst), H. D. Aller (U. Michigan)

A study of parsec scale structure of AGN using both observations and simulations is presented. Very Long Baseline Polarimetry (VLBP) images at 2.8 cm of several QSOs and one BL Lac object have been made and analyzed at 2 epochs. The 2 epochs are separated by 15 months and most of the objects show significant evolution in that time. We present a study of the evolution of jet structures in total and polarized flux and discuss the evolution and kinematics of components and their relation to the magnetic field direction given by the polarization data. To explore the relationship between parsec scale jet structure evolution and integrated flux variations, the appearance of knots are correlated with the more frequently sampled integrated total intensity and polarized light curves obtained by the University of Michigan Radio Observatory (UMRAO).

We present a series of simulated maps showing the appearance in total intensity of flows computed using a recently developed relativistic hydrodynamic code (Duncan amp; Hughes 1994: ApJ, 436, L119). We find that relativistic flows subject to strong perturbations exhibit a density structure consisting of a series of nested bow shocks, and that this structure is evident in the intensity maps for large viewing angles. However, for viewing angles <30^\circ, differential Doppler boosting leads to a series of axial knots of emission, similar to the pattern exhibited by many VLBI sources. A set of time evolved images of the perturbed jet have been made and total fluxes computed so a light curves at different frequencies are created and compared to the UMRAO light curves of AGN. The simulated light curve exhibits structures that are associated with the onset and merging of perturbations but do not reflect the periodic nature of the perturbations.

Program listing for Thursday