Statistical Properties of Galactic Starlight Polarization
P. Fosalba, A. Lazarian, S. Prunet, J. A. Tauber;
ApJ, 2002, 564, 762
ABSTRACT:We present a statistical analysis of Galactic interstellar polarization from the largest compilation available of starlight data.
The data
comprises ~9300 stars, of which we have selected ~5500 for our analysis.
We find a
nearly linear growth of mean polarization degree with extinction.
The
amplitude of this correlation shows that interstellar grains are not fully
aligned with the Galactic magnetic field, which can be interpreted as the
effect of a large random component of the field.
In agreement with earlier
studies of more limited scope, we estimate the ratio of the uniform to the random
plane-of-the-sky components of the magnetic field to be
Bu/Br~0.8.
Moreover, a clear correlation exists between polarization degree and
polarization angle that provides evidence that the magnetic field geometry follows
Galactic structures on large scales.
The angular power spectrum
Cl of the starlight polarization degree for Galactic plane data
(|b|<10deg) is consistent with a power law, Cl~l-1.5
(where l~180deg/&thetas; is the multipole order), for all
angular scales &thetas;>~10'.
An investigation of sparse
and inhomogeneous sampling of the data shows that the starlight data
analyzed traces an underlying polarized continuum that has the same
power-spectrum slope, Cl~l-1.5.
Our findings suggest that
starlight data can be safely used for the modeling of Galactic polarized
continuum emission at other wavelengths.
KEYWORDS: ism: dust, extinction, galaxies: structure, galaxy: stellar content, ism: magnetic fields, methods: statistical, polarization
PERSOKEY:statistical analysis, polarisation, extinction, optical, ,
CODE: fosalba2002