The Alignment Effect at Low Redshift

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Session 122 -- AGN: Accretion Disks, Tori and Gas
Oral presentation, Saturday, January 15, 2:15-3:45, Salon IV Room (Crystal Gateway)

[122.06] The Alignment Effect at Low Redshift

A. Dey (UC Berkeley), W. van Breugel (IGPP)

Distant radio galaxies (z$>$1) have spatially extended, multi-component UV ($\lambda_{rest} < 4000$\AA) continua which are preferentially aligned with the major axis of their associated radio source. Although various physical processes have been suggested to explain this alignment effect, the high-redshift radio galaxies are optically faint and hence discriminating between these processes is very difficult. Therefore, we conducted an optical and near-UV continuum imaging survey of 44 low-redshift radio galaxies (0.08$<$z$<$0.1) in order to search for nearby (bright) cases of aligned extended UV continuum in order to select a sample for a detailed study.

We report the results of our survey and compare the properties of the aligned UV continua seen in our low-redshift sample to those seen in the high-redshift radio galaxies. We have discovered spatially extended UV continuum emission that is distributed along the radio axis in approximately 30\% of the radio galaxies in our sample. Our spectroscopic and polarimetric observations of the UV continua in these low-redshift radio galaxies reveal that the UV continuum emission is due to a variety of processes. These observations indicate that the aligned UV continua in most cases are nonstellar in origin. If the aligned UV continua in distant radio galaxies are also dominated by nonstellar processes, the ages of these objects that have been deduced from stellar population modeling of the broad-band spectral energy distributions have been significantly underestimated.

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