Radio emission in a random magnetic field: radio halos and the
structure of the magnetic field in the Coma cluster
Peter C. Tribble
CITA, 60 St. George Street, Toronto M5S 1A1, Canada
Accepted 1991 June 27. Received 1991 June 25; in original form 1991
April 16.
Abstract
Models of cluster radio halos have been constructed allowing for
a random magnetic field. The resulting halo is far from smooth, both in
intensity and polarization. The magnetic field must therefore be
tangled on sufficiently small scales to reduce intensity fluctuations
to observed levels. The smoothness of the inner regions of the radio
halo in the Coma cluster, with fluctuations at about the 5% level at
1 arcmin resolution, indicates that the outer scale of magnetic field
fluctuations is less than 15 kpc. Similar considerations indicate that
less than 10% of the total halo emission can be due to galactic wakes
and demonstrate that the halo emission and the magnetic field are
spread throught the whole volume of the cluster and are not localized
with a small filling factor. In the simplest models the fractional
polarization should be similar to the fluctuation level, although the
polarization can be substantially decreased if the field has a high
degree of symmetry.
Contents:
- Introduction
- Radio emission in a random magnetic field
- Models
- Comparison with the Coma radio halo
- Galactic Wakes
- Relation to Rotation measure and polarization
data
- Conclusions
This article appeared in Monthly Notices of the Royal Astronomical
Society, vol 253, pp. 147-152 (1991). Copyright Royal
Astronomical Society.
Unfortunately I don't have the original images that appeared in the
paper still online here, so the figures aren't included. Given time, I
may remedy this, but in the meantime there's just a bit of TeX garbage
where the figures are supposed to go. Sorry about that.
___________________________________
Peter Tribble, peter.tribble@gmail.com