Issue |
A&A
Volume 403, Number 3, June I 2003
|
|
---|---|---|
Page(s) | 1045 - 1057 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20030464 | |
Published online | 23 May 2003 |
Characteristics of the structure in the Galactic polarized radio background at 350 MHz
1
Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
2
ASTRON, PO Box 2, 7990 AA Dwingeloo, The Netherlands e-mail: ger@astron.nl
3
Kapteyn Institute, PO Box 800, 9700 AV Groningen, The Netherlands
Corresponding author: M. Haverkorn, mhaverkorn@cfa.harvard.edu
Received:
16
December
2002
Accepted:
21
March
2003
Angular power spectra and structure functions of the Stokes parameters
Q and U and polarized intensity P are derived from three sets
of radio polarimetric observations. Two of the observed fields have
been studied at multiple frequencies, allowing determination of power
spectra and structure functions of rotation measure RM as well. The
third field extends over a large part of the northern sky, so that the
variation of the power spectra over Galactic latitude and longitude
can be studied. The power spectra of Q and U are steeper than
those of P, probably because a foreground Faraday screen creates
extra structure in Q and U, but not in P. The extra structure in
Q and U occurs on large scales, and therefore causes a steeper
spectrum. The derived slope of the power spectrum of P is the
multipole spectral index , and is consistent with earlier
estimates. The multipole spectral index
decreases with
Galactic latitude (i.e. the spectrum becomes flatter), but is
consistent with a constant value over Galactic longitude. Power
spectra of the rotation measure RM show a spectral index
, while the structure function of RM is
approximately flat. The structure function is flatter than earlier
estimates from polarized extragalactic sources, which could be due to
the fact that extragalactic source RM probes the complete line of
sight through the Galaxy, whereas as a result of depolarization
diffuse radio polarization only probes the nearby ISM.
Key words: magnetic fields / polarization / techniques: polarimetric / ISM: magnetic fields / ISM: structure / radio continuum: ISM
© ESO, 2003
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