# Alignment of Quasar Polarizations 0507274

1. Oct 31, 2005

### CarlB

Mapping extreme-scale alignments of quasar polarization vectors

Accepted by Astronomy & Astrophysics; 19 pages, 17 figures. Include Table A1 which will be available via CDS

D. Hutsemekers, R. Cabanac, H. Lamy, D. Sluse

Based on a new sample of 355 quasars with significant optical polarization and using complementary statistical methods, we confirm that quasar polarization vectors are not randomly oriented over the sky with a probability often in excess of 99.9%. The polarization vectors appear coherently oriented or aligned over huge (~ 1 Gpc) regions of the sky located at both low (z ~ 0.5) and high (z ~ 1.5) redshifts and characterized by different preferred directions of the quasar polarization. In fact, there seems to exist a regular alternance along the line of sight of regions of randomly and aligned polarization vectors with a typical comoving length scale of 1.5 Gpc. Furthermore, the mean polarization angle $\bar{\theta}$ appears to rotate with redshift at the rate of ~ 30\degr per Gpc. The symmetry of the the $\bar{\theta}$ -z relation is mirror-like, the mean polarization angle rotating clockwise with increasing redshift in North Galactic hemisphere and counter-clockwise in the South Galactic one. These characteristics make the alignment effect difficult to explain in terms of local mechanisms, namely a contamination by interstellar polarization in our Galaxy. While interpretations like a global rotation of the Universe can potentially explain the effect, the properties we observe qualitatively correspond to the dichroism and birefringence predicted by photon-pseudoscalar oscillation within a magnetic field. Interestingly, the alignment effect seems to be prominent along an axis not far from preferred directions tentatively identified in the CMB maps. Although many questions and more particularly the interpretation of the effect remain open, alignments of quasar polarization vectors appear as a promising new way to probe the Universe and its dark components at extremely large scales.
http://arxiv.org/abs/astro-ph/0507274

Interesting. Any comments? It appears to have initially been rejected by Arxiv, then accepted 60 days later. A theoretical paper referenced is here:

The Dynamical Mixing of Light and Pseudoscalar Fields

Sudeep Das, Pankaj Jain, John P. Ralston, Rajib Saha

We solve the general problem of mixing of electromagnetic and scalar or pseudoscalar fields coupled by axion-type interactions ${\cal L}_{int} =g_{\phi} \phi \epsilon_{\mu \nu \a \b}F^{\mu \nu}F^{\a \b}$. The problem depends on several dimensionful scales, including the magnitude and direction of background magnetic field, the pseudoscalar mass, plasma frequency, propagation frequency, wave number, and finally the pseudoscalar coupling. We apply the results to the first consistent calculations of the mixing of light propagating in a background magnetic field of varying direction, which shows a great variety of fascinating resonant and polarization effects.
http://arxiv.org/abs/hep-ph/0410006

Carl

Last edited: Oct 31, 2005