Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A
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 ta...
| Main Authors: | , , , , , , , , , |
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| Format: | Journal Article |
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The American Astronomical Society
2009
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| Subjects: | |
| Online Access: | http://hdl.handle.net/20.500.11937/12762 |
| _version_ | 1848748167166689280 |
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| author | Feain, I. Ekers, R. Murphy, T. Gaensler, B. Macquart, Jean-pierre Norris, R. Cornwell, T. Johnston-Hollitt, M. Ott, J. Middelburg, E. |
| author_facet | Feain, I. Ekers, R. Murphy, T. Gaensler, B. Macquart, Jean-pierre Norris, R. Cornwell, T. Johnston-Hollitt, M. Ott, J. Middelburg, E. |
| author_sort | Feain, I. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | 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. |
| first_indexed | 2025-11-14T07:00:44Z |
| format | Journal Article |
| id | curtin-20.500.11937-12762 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T07:00:44Z |
| publishDate | 2009 |
| publisher | The American Astronomical Society |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-127622023-02-22T06:24:23Z Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A Feain, I. Ekers, R. Murphy, T. Gaensler, B. Macquart, Jean-pierre Norris, R. Cornwell, T. Johnston-Hollitt, M. Ott, J. Middelburg, E. galaxies individual (Centaurus A NGC 5128) techniques polarimetric interferometric techniques 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. 2009 Journal Article http://hdl.handle.net/20.500.11937/12762 10.1088/0004-637X/707/1/114 The American Astronomical Society unknown |
| spellingShingle | galaxies individual (Centaurus A NGC 5128) techniques polarimetric interferometric techniques Feain, I. Ekers, R. Murphy, T. Gaensler, B. Macquart, Jean-pierre Norris, R. Cornwell, T. Johnston-Hollitt, M. Ott, J. Middelburg, E. Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A |
| title | Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A |
| title_full | Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A |
| title_fullStr | Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A |
| title_full_unstemmed | Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A |
| title_short | Faraday Rotation Structure on Kiloparsec Scales in the Radio Lobes of Centaurus A |
| title_sort | faraday rotation structure on kiloparsec scales in the radio lobes of centaurus a |
| topic | galaxies individual (Centaurus A NGC 5128) techniques polarimetric interferometric techniques |
| url | http://hdl.handle.net/20.500.11937/12762 |