J. Knapik

Jagiellonian University, Cracovia, Lesser Poland Voivodeship, Poland

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Publications (4)10.17 Total impact

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    ABSTRACT: We performed a high-sensitivity search for galaxy-scale magnetic fields by radio polarimetry at 10.45 GHz and 4.85 GHz with the Effelsberg 100 m radio telescope, accompanied by Hα imaging, for the two Local Group irregular galaxies IC 10 and NGC 6822. Their star-forming bodies are small and rotate slowly. IC 10 is known to have a very high star-forming activity, resembling blue compact dwarfs, while NGC 6822 has a low overall star-formation level. Despite very different current star formation rates, our Hα imaging revealed a large web of diffuse Hα filaments and shells in both IC 10 and NGC 6822. Some of them extend far away from the galaxy's main body. The total power emission of both objects shows bright peaks either at the positions of optically strong star-forming clumps (IC 10) or individual H Ii regions or supernova remnants (NGC 6822). However, in both cases we detect a smoothly distributed, extended component. In IC 10 we found clear evidence for the presence of a diffuse, mostly random magnetic field of =~ 14 mu G strength, probably generated by a fluctuation dynamo. One of the Hα -emitting filaments appears to be associated with enhanced magnetic fields. We also rediscuss the reddening of IC 10 and its implications for its distance. In the case of NGC 6822 we found only very weak evidence for nonthermal emission, except perhaps for some regions associated with local gas compression. We detect in both galaxies small spots of polarized emission, indicative of regular fields ( =~ 3 mu G), at least partly associated with local compressional phenomena.
    Astronomy and Astrophysics 07/2003; · 5.08 Impact Factor
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    01/2001; 230:171-172.
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    ABSTRACT: Two flocculent galaxies NGC 3521 and NGC 5055 has been observed at 10.55GHz with the Effelsberg 100m telescope. In both cases polarized emission reveals substantial radial component of regular magnetic field - similar to that in grand-designed spirals. Comparison with H_alpha distribution obtained at Lowell Observatory is presented. Polarization models discussed, support modern non-standard dynamo concepts for magnetic field generation in galaxies.
    Astronomy and Astrophysics 10/2000; · 5.08 Impact Factor
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    ABSTRACT: Traditional views considered usually the galactic magnetic field perfectly frozen into the gas while the interstellar turbulence can only randomize the field structure. In the last decade polarization studies of nearby spirals gave evidence that turbulent motions may generate regular magnetic fields, which itself are only partly tied to the gas. As a result of our recent observations we found clear evidence for dynamo action without contamination from spiral arm flows. We present also examples of magnetic fields probably decoupled from bulk gas motions. We definitely prove the existence of regular magnetic fields in an irregular galaxy, which supports non-standard dynamo theories, like the buoyancy dynamo.
    11/1999; -1:18-27.

Publication Stats

32 Citations
10.17 Total Impact Points

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Institutions

  • 2003
    • Jagiellonian University
      Cracovia, Lesser Poland Voivodeship, Poland
  • 2001
    • Ruhr-Universität Bochum
      Bochum, North Rhine-Westphalia, Germany