Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-02-09
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
22 pages, 12 figures, accepted for publication in Astronomy and Astrophysics, final copy-edited version
Scientific paper
A sample of large northern Spitzer Infrared Nearby Galaxies Survey (SINGS) galaxies was recently observed with the Westerbork Synthesis Radio Telescope (WSRT) at 1300-1760 MHz. In Paper II of this series, we described sensitive observations of the linearly polarized radio continuum emission in this WSRT-SINGS galaxy sample. Here we explore the systematic patterns of azimuthal modulation of both the Faraday depth and the polarized intensity and their variation with galaxy inclination. A self-consistent and fully general model for both the locations of net polarized emissivity at 1-2 GHz frequencies and the global magnetic field topology of nearby galaxies emerges. Net polarized emissivity is concentrated into two zones located above and below the galaxy mid-plane, with the back-side zone suffering substantial depolarization (by a factor of 4-5) relative to the front-side zone in its propagation through the turbulent mid-plane. The field topology, which characterizes the thick-disk emission zone is in all cases an axisymmetric spiral with a quadrupole dependence on height above the mid-plane. The front-side emission is affected by only mild dispersion (10's of rad/m2) from the thermal plasma in the galaxy halo, while the back-side emission is affected by additional strong dispersion (100's of rad/m2) from an axisymmetric spiral field in the galaxy mid-plane. The field topology in the upper halo of galaxies is a mix of two distinct types: a simple extension of the axisymmetric spiral quadrupole field of the thick disk and a radially directed dipole field. The dipole component might be a manifestation of (1) a circumnuclear, bipolar outflow, (2) an in situ generated dipole field, or (3) evidence of a non-stationary global halo.
Beck Rainer
Braun Robert
Heald George
No associations
LandOfFree
The Westerbork SINGS survey III. Global magnetic field topology 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 Westerbork SINGS survey III. Global magnetic field topology, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Westerbork SINGS survey III. Global magnetic field topology will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-124251