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Date and Time of the Query: 2019-04-22 T13:23:59 PDT
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For refcode 2009ApJ...707..114F:
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Copyright by American Astronomical Society. Reproduced by permission
2009ApJ...707..114F Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A Feain, I. J.; Ekers, R. D.; Murphy, T.; Gaensler, B. M.; Macquart, J.-P.; Norris, R. P.; Cornwell, T. J.; Johnston-Hollitt, M.; Ott, J.; Middelberg, E. Abstract. We present the results of an Australia Telescope Compact Array 1.4 GHz spectropolarimetric aperture synthesis survey of 34 deg^2^ centered on Centaurus A-NGC 5128. A catalog of 1005 extragalactic compact radio sources in the field to a continuum flux density of 3 mJy beam^--1^ is provided along with a table of Faraday rotation measures (RMs) and linear polarized intensities for the 28% of sources with high signal to noise in linear polarization. We use the ensemble of 281 background polarized sources as line-of-sight probes of the structure of the giant radio lobes of Centaurus A. This is the first time such a method has been applied to radio galaxy lobes and we explain how it differs from the conventional methods that are often complicated by depth and beam depolarization effects. Assuming a magnetic field strength in the lobes of 1.3 B_1_ {mu}G, where B_1_ = 1 is implied by equipartition between magnetic fields and relativistic particles, the upper limit we derive on the maximum possible difference between the average RM of 121 sources behind Centaurus A and the average RM of the 160 sources along sightlines outside Centaurus A implies an upper limit on the volume-averaged thermal plasma density in the giant radio lobes of <n_e_ > < 5 x 10^--5^ B ^--1^_1_ cm^--3^. We use an RM structure function analysis and report the detection of a turbulent RM signal, with rms {sigma}_RM_ = 17 rad m^--2^ and scale size 0fdg3, associated with the southern giant lobe. We cannot verify whether this signal arises from turbulent structure throughout the lobe or only in a thin skin (or sheath) around the edge, although we favor the latter. The RM signal is modeled as possibly arising from a thin skin with a thermal plasma density equivalent to the Centaurus intragroup medium density and a coherent magnetic field that reverses its sign on a spatial scale of 20 kpc. For a thermal density of n_1_ 10^--3^ cm^--3^, the skin magnetic field strength is 0.8 n ^--1^_1_ {mu}G. Key words: galaxies: individual: Centaurus A NGC 5128, techniques: interferometric, techniques: polarimetric
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