An extreme rotation measure in the high-redshift radio galaxy PKS B0529–549

Creators: Broderick, J. W.; de Breuck, C.; Hunstead, R. W.; Seymour, N.

Abstract

We present the results of a radio polarimetric study of the high-redshift radio galaxy PKS B0529−549 (z= 2.575), based on high-resolution 12-mm and 3-cm images obtained with the Australia Telescope Compact Array. The source is found to have a rest-frame Faraday rotation measure of −9600 rad m^(−2), the largest seen thus far in the environment of a z > 2 radio galaxy. In addition, the rest-frame Faraday dispersion in the screen responsible for the rotation is calculated to be 5800 rad m^(−2), implying rotation measures as large as −15 400 rad m^(−2). Using supporting near-infrared (near-IR) imaging from the Very Large Telescope, we suggest that the rotation measure originates in the Lyα halo surrounding the host galaxy, and estimate the magnetic field strength to be ~10 μG. We also present a new optical spectrum of PKS B0529−549 obtained with the New Technology Telescope, and propose that the emission-line ratios are best described by a photoionization model. Furthermore, the host galaxy is found to exhibit both hot dust emission at 8.0 μm and significant internal visual extinction (~1.6 mag), as inferred from Spitzer Space Telescope near/mid-IR imaging.

Additional Information

© 2007 The Authors. Journal compilation © 2007 RAS. Accepted 2006 December 5. Received 2006 December 1; in original form 2006 October 6. JWB acknowledges the receipt of both an Australian Postgraduate Award and a Denison Merit Award. RWH acknowledges support from the Australian Research Council. We thank Bryan Gaensler, Montse Villar-Martın, Andrew Humphrey and Elaine Sadler for valuable discussions, and the anonymous referee for helpful suggestions. The ATCA is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by the CSIRO. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the NASA and the National Science Foundation.

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