Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A
MetadataShow full item record
We present the results of an Australia Telescope Compact Array 1.4 GHz spectropolarimetric aperture synthesis survey of 34 deg2 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 1.3B1 G, where B1 = 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 (ne) <5 x 10-5B-11 cm-3. We use an RM structure function analysis and report the detection of a turbulent RM signal, with rms sRM = 17 rad m-2 and scale size 0.3, 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 n1 10-3 cm-3, the skin magnetic field strength is 0.8 n-1 1 G.
Copyright © 2009 The American Astronomical Society ("AAS")-[The Astrophysical Journal (ApJ) Feain, I., 2009 ApJS 707 (1), 114-125.]
Showing items related by title, author, creator and subject.
O'Sullivan, S.; Feain, I.; McClure-Griffiths, N.; Ekers, Ronald; Carretti, E.; Robishaw, T.; Mao, S.; Gaensler, B.; Bland-Hawthorn, J.; Stawarz (2013)We present a Faraday rotation measure (RM) study of the diffuse, polarized, radio emission from the giant lobes of the nearest radio galaxy, Centaurus A. After removal of the smooth Galactic foreground RM component, using ...
Saripalli, L.; Subrahmanyan, R.; Thorat, K.; Ekers, Ronald; Hunstead, R.; Johnston, H.; Sadler, E. (2012)Based on the Australia Telescope Low Brightness Survey (ATLBS) we present a sample of extended radio sources and derive morphological properties of faint radio sources. 119 radio galaxies form the ATLBS-Extended Source ...
McKinley, B.; Briggs, F.; Gaensler, B.; Feain, I.; BERNARDI, G.; Wayth, Randall; Johnston-Hollitt, M.; Offringa, A.; ARCUS, Wayne; Barnes, D.; Bowman, J.; Bunton, J.; Capallo, R.; Corey, B.; Deshpande, A.; Desouza, L.; Emrich, David; Goeke, R.; Greenhill, L.; Hazelton, B.; Herne, David; Hewitt, J.; KAPLAN, D.; Kasper, J.; Kincaid, B.; Koenig, R.; Kratzenberg, E.; Lonsdale, C.; Lynch, Mervyn; McWHIRTER, S.; Mitchell, D.; Morales, M.; Morgan, E.; Oberoi, D.; Ord, Stephen; Pathikulangara, J.; Prabu, T.; Remillard, R.; Rogers, A.; Roshi, A.; Salah, J.; Sault, R.; UDAYA SHANKAR, N.; Srivani, K.; Stevens, J.; Subrahmanyan, R.; Tingay, Steven; Waterson, Mark; Webster, R.; Whitney, A.; Williams, Andrew; Williams, C.; Wyithe, J. (2013)We present new wide-field observations of Centaurus A (Cen A) and the surrounding regionat 118MHz with the Murchison Widefield Array (MWA) 32-tile prototype, with which weinvestigate the spectral-index distribution of Cen ...