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Session 104 - Radio Galaxies, Radio Observations of AGN Jets & Outflows.
Display session, Saturday, January 10
Exhibit Hall,

[104.11] HST Optical Polarimetry and Spectral Mapping of the M87 Jet

E. S. Perlman, J. Biretta, W. Sparks, F. D. Macchetto (STScI)

We present the results of HST WFPC2 observations of the M87 jet in the optical and near-infrared. In several regions extremely high polarizations are seen (\gtrsim 50%), approaching the theoretical maximum possible for synchrotron radiation emitted by a coherent magnetic field. A large amount of correspondence is seen when comparing the resultant polarized flux and position angle maps to recent 15 GHz polarimetry data taken with the VLA. The direction of the magnetic field is largely parallel to the jet, except in the ``shock-like'' knots (upstream parts of HST-1, D, A, and C), where it becomes perpendicular to the jet. But unlike in the radio, the magnetic field also turns from parallel to perpendicular to the jet at the downstream ends of the inner knots (D, E, and F). Also unlike in the radio, the most heavily polarized portion of the jet (>60the precursor region. Comparison of contemporaneous F555W and F814W WFPC observations has revealed that the optical spectral index of some of the areas which contain and generate superluminal components have much harder spectra than other, less active regions of the jet. This last result is similar to what is found in the radio for the superluminal regions of blazar jets. We discuss the implications of these findings for the energetics and structure of synchrotron jets.

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Program listing for Saturday