Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989a%26a...217...17k&link_type=abstract
Astronomy and Astrophysics, Vol. 217, NO.1/2 JUN(II), P. 17, 1989
Astronomy and Astrophysics
Astrophysics
109
Scientific paper
We present new high-resolution observations of the total and linearly polarized emission of M81 at λ20cm obtained with the VLA. Even at this low frequency we found a high degree of linear polarization of 47+/-3% in the southwestern interarm region. Hence, the degree of uniformity B_u_/B_t_ in this region is as high as 0.8+/-0.2. Depolarization considerations could remove the ambiguity of the rotation measure (RM) between λ20cm and λ6.3cm in this region. The RM analysis to determine the large-scale magnetic field structure in the disk of spiral galaxies is extended to derive the pitch angle and the location of the neutral line in the case of a bisymmetric spiral magnetic field structure (BSS). We show, for the first time, that the azimuthal RM distribution is clearly double-periodical between 6kpc and 12kpc radius. This gives strong evidence for a BSS magnetic field structure in M81 as generated by an αω-dynamo with mode m=1. From the amplitude, the zerolevel and the phases of the two RM distributions we could conclusively derive a mean pitch angle {PSI}_0_ of the magnetic field spiral of -18^deg^+/-6^deg^. There are indications that {PSI}_0_ increases with radius. For the above value of {PHI}_0_ we found that the neutral lines are located approximately in the interarm regions. The high degree of uniformity in the southwestern interarm region indicates that the uniform magnetic field generated and/or maintained by the dynamo is less disturbed in the interarm region. Alternatively, the αω-dynamo may work more effectively just in the interarm region due to density waves which modify the shear motion in a galaxy.
Beck Rainer
Hummel Evi
Krause Marita
No associations
LandOfFree
The Magnetic Field Structures in Two Nearby Spiral Galaxies - Part Two - the Bisymmetric Spiral Magnetic Field in M81 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Magnetic Field Structures in Two Nearby Spiral Galaxies - Part Two - the Bisymmetric Spiral Magnetic Field in M81, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Magnetic Field Structures in Two Nearby Spiral Galaxies - Part Two - the Bisymmetric Spiral Magnetic Field in M81 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1849040