2002/08/08 by M. Soida, R. Beck, M. Urbanik +1 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20021100
published as Astron.Astrophys. 394 (2002) 47-58 · 12 pages, 14 figures, A&A accepted
arxiv created 2002/08/08 · openalex publication_date 2002/10/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We present three-frequency VLA observations of the flocculent spiral galaxy NGC 4414 made in order to study the magnetic field structure in absence of strong density wave flows. NGC 4414 shows a regular spiral pattern of observed polarization -vectors with a radial component comparable in strength to the azimuthal one. The average pitch angle of the magnetic field is about 20°, similar to galaxies with a well-defined spiral pattern. This provides support for field generation by a turbulent dynamo without significant “contamination” from streaming motions in spiral arms. While the stellar light is very axisymmetric, the magnetic field structure shows a clear asymmetry with a stronger regular field and a smaller magnetic pitch angle in the northern disk. Extremely strong Faraday rotation is measured in the southern part of the disk, becoming Faraday thick at 6 cm. The distribution of Faraday rotation suggests a mixture of axisymmetric and higher-mode magnetic fields. The strong Faraday effects in the southern region suggest a much thicker magnetoionic disk and a higher content of diffuse ionized gas than in the northern disk portion. An elongation of the 20 cm total power emission is also seen towards the South. Although NGC 4414 is currently an isolated spiral, the asymmetries in the polarized radio emission may be sensitive tracers of previous encounters, including weak interactions which would chiefly affect the diffuse gas component without generating obvious long-term perturbations in the optical structure.