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Session 22 - Radio - Loud AGN & Extragalactic Jets.
Display session, Wednesday, January 07
Exhibit Hall,
The alignment of optical emission along the axis of radio emission in high redshift radio galaxies is now a common phenomenon. In many cases this aligned component can be shown to be significantly polarized, a result that has led to models for the emission that employ scattering of light emitted from the AGN. Both electron scattering and dust scattering have been proposed, and both mechanisms have positive and negative attributes. One aspect of dust scattering that has not been explored previously is the response of the dust grains to the passage of the strong shock associated with the radio source. The scattering medium must be distributed over many tens of kiloparsecs, and it must survive for a time comparable to the age of the radio source. Analogs with emission line conditions suggest that the dust is contained in gas clouds of high density contrast and small filling factors embedded in a more diffuse medium. The survival of dust grains in such an environment after the passage of a 10,000 km/s shock associated with the radio jet is calculated for a wide range of parameters. It is found that for almost all cloud configurations the grains are destroyed by sputtering processes in a time much less than the minimum radio source lifetime of 10 million years. Thus polarization due to an in situ population of grains seems somewhat problematic. Two alternate methods for grain production are explored.
