The RoboPol optical polarization survey of gamma-ray - loud blazars

Abstract

We present first results from RoboPol, a novel-design optical polarimeter operating at the Skinakas Observatory in Crete. The data, taken during the May - June 2013 commissioning of the instrument, constitute a single-epoch linear polarization survey of a sample of gamma-ray - loud blazars, defined according to unbiased and objective selection criteria, easily reproducible in simulations, as well as a comparison sample of, otherwise similar, gamma-ray - quiet blazars. As such, the results of this survey are appropriate for both phenomenological population studies and for tests of theoretical population models. We have measured polarization fractions as low as $0.015$ down to $R$ magnitude of 17 and as low as $0.035$ down to 18 magnitude. The hypothesis that the polarization fractions of gamma-ray - loud and gamma-ray - quiet blazars are drawn from the same distribution is rejected at the $10^{-3}$ level. We therefore conclude that gamma-ray - loud and gamma-ray - quiet sources have different optical polarization properties. This is the first time this statistical difference is demonstrated in optical wavelengths. The polarization fraction distributions of both samples are well-described by exponential distributions with averages of $⟨p⟩=6.4_{-0.8}^{+0.9}\times 10^{-2}$ for gamma-ray--loud blazars, and $⟨p⟩=3.2_{-1.1}^{+2.0}\times 10^{-2}$ for gamma-ray--quiet blazars. The most probable value for the difference of the means is $3.4_{-2.0}^{+1.5}\times 10^{-2}$. The distribution of polarization angles is statistically consistent with being uniform.

14 pages, 6 figures, accepted by MNRAS. ASCII versions of Tables 2 and 3 are available as ancillary files with this submission

References in corpus (6)

• The Second-Generation Guide Star Catalog: Description and Properties
• A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279
• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• Placing Confidence Limits on Polarization Measurements
• CLASH-VLT: Constraints on the Dark Matter Equation of State from Accurate Measurements of Galaxy Cluster Mass Profiles
• The Relation between Radio Polarization and Gamma-ray Emission in AGN Jets

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