AAS 201st Meeting, January, 2003
Session 114. Quasars
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[114.20] The Implications of Helical Patterns in 3C120

R. C. Walker (NRAO), P. E. Hardee (Univ. of Alabama)

Ongoing monitoring observations with the VLBA at 1.7 GHz show a pattern and motions that suggest that the internal jet structure is helical with a long wavelength (Walker et al 2001, Ap. J. 556, 772). The pattern is stationary or slowly moving with features moving through it at superluminal speeds. Physical theory and numerical simulation of jets show that helical patterns are an expected result in many circumstances as a result of instabilities. The wavelength and pattern speed of such structures are related to the internal sound speed and Lorentz factor and to the external sound speed. The 3C120 pattern suggests that the jet lies in a relatively cool medium. The internal jet structure expected from the theory suggests that the pattern will have a wider opening angle than the trajectories of individual particles. This helps avoid a requirement for extreme conditions when interpreting the appearance of the jet in terms of relativistic beaming. This poster will draw heavily on results from the above reference but includes two new observations and some new theoretical results.

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