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| Paper: |
Large-Scale Alignments of Quasar Polarization Vectors: Evidence
at Cosmological Scales for Very Light Pseudoscalar Particles Mixing
with Photons ? |
| Volume: |
449, Astronomical Polarimetry 2008: Science from Small to Large Telescopes |
| Page: |
441 |
| Authors: |
Hutsemékers, D.; Payez, A.; Cabanac, R.; Lamy, H.; Sluse, D.; Borguet, B.; Cudell, J. |
| Abstract: |
Based on a sample of 355 quasars with significant optical
polarization, we found that quasar polarization vectors are not
randomly oriented over the sky as naturally expected. The probability
that the observed distribution of polarization angles is due to chance
is lower than 0.1%. The polarization vectors of the light from
quasars are aligned although the sources span huge regions of the sky
(∼ 1 Gpc). Groups of quasars located along similar lines of sight
but at different redshifts (typically z ≈ 0.5 and z ≈ 1.5)
are characterized by different preferred directions of
polarization. These characteristics make the observed alignment effect
difficult to explain in terms of a local contamination by interstellar
polarization in our Galaxy. Interpreted in terms of a
cosmological-size effect, we show that the dichroism and birefringence
predicted by a mixing between photons and very light pseudoscalar
particles within a magnetic field can qualitatively reproduce the
observations. We find that circular polarization measurements could
help constrain this mechanism. |
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