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Magnetic fields in barred galaxies IV. NGC 1097 and NGC 1365

Lookup NU author(s): Dr Andrew Fletcher, Professor Anvar Shukurov, Andrew Snodin, Professor Dmitry Sokoloff, Dr Vladimir Shoutenkov

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Abstract

We present λ3.5 cm and λ6.2 cm radio continuum maps in total and polarized intensity of the barred galaxies NGC 1097 (at 2″-15″ resolution) and NGC 1365 (at 9″-25″ resolution). A previously unknown radio galaxy southwest of NGC 1097 is reported. Apart from a smooth faint envelope and a bright central region, both galaxies exhibit radio ridges roughly overlapping with the massive dust lanes in the bar region. The contrast in total intensity across the radio ridges is compatible with compression and shear of an isotropic random magnetic field, where the gas density compression ratio is approximately equal to 4 and the cosmic ray density is constant across the ridges. The contrast in polarized intensity is significantly smaller than that expected from compression and shearing of the regular magnetic field; this could be the result of decoupling of the regular field from the dense molecular clouds. The regular field in the ridge is probably strong enough to reduce significantly shear in the diffuse gas (to which it is coupled) and hence to reduce magnetic field amplification by shearing. This contributes to the misalignment of the observed field orientation with respect to the velocity vectors of the dense gas. Our observations, for the first time, indicate that magnetic forces can control the flow of the diffuse interstellar gas at kiloparsec scales. The total radio intensity reaches its maximum in the circumnuclear starburst regions, where the equipartition field strength is about 60 μG, amongst the strongest fields detected in spiral galaxies so far. The regular field in the inner region has a spiral shape with large pitch angle, indicating the action of a dynamo. Magnetic stress leads to mass inflow towards the centre, sufficient to feed the active nucleus in NGC 1097. - We detected diffuse X-ray emission, possibly forming a halo of hot gas around NGC 1097. © ESO 2005.


Publication metadata

Author(s): Beck R, Fletcher A, Shukurov A, Snodin A, Sokoloff DD, Ehle M, Moss D, Shoutenkov V

Publication type: Article

Publication status: Published

Journal: Astronomy and Astrophysics

Year: 2005

Volume: 444

Issue: 3

Pages: 739-765

Print publication date: 01/12/2005

ISSN (print): 0004-6361

ISSN (electronic): 1432-0746

Publisher: EDP Sciences

URL: http://dx.doi.org/10.1051/0004-6361:20053556

DOI: 10.1051/0004-6361:20053556


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