Systematic Study of Gamma-Ray-Bright Blazars With Optical Polarization and Gamma-Ray Variability

Abstract

Blazars are highly variable active galactic nuclei which emit radiation at all wavelengths from radio to gamma-rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies and it also varies dramatically. The polarization of blazars is of interest for understanding the origin, confinement, and propagation of jets. However, even though numerous measurements have been performed, the mechanisms behind jet creation, composition and variability are still debated.We performed simultaneous gamma-ray and optical photopolarimetry observations of 45 blazars between Jul. 2008 and Dec. 2014 to investigate the mechanisms of variability and search for a basic relation between the several subclasses of blazars. We identify a correlation between the maximum degree of optical linear polarization and the gamma-ray luminosity or the ratio of gamma-ray to optical fluxes. Since the maximum polarization degree depends on the condition of the magnetic field (chaotic or ordered), this result implies a systematic difference in the intrinsic alignment of magnetic fields in pc-scale relativistic jets between different types blazars (FSRQs vs. BL Lacs), and consequently between different types of radio galaxies (FR Is vs. FR IIs).

Optical Polarimetry and Radio Observations of PKS1510-089 between 2009 and 2013

“…The 2009 long term PA rotation event was monitored by different authors [9][10][11]13,18]. We could minimize the gaps between the observation and assume that the angle rotated by the smallest difference, as we shown in a schematic view in Figure 3.…”

Polarimetric Monitoring of Jets with Kanata Telescope

“…The variability amplitudes of gamma-rays and optical flares in 3C 279 also differed from those in 3C 454.3. In [6], we discuss the origin of these differences among several types of blazars. Figure 2 shows the distribution of variability indices of polarization degree calculated separately for each source.…”

“…Forty-five AGNs were monitored daily for 6.5 years, beginning in 2008. Details of the observations and analyses are described in [6]. We selected gamma-ray bright blazars detected by Fermi-Large Area Telescope (LAT) instruments to obtain simultaneous observations in the optical and gamma-ray bands.…”

“…was tested using the block Bootstrap method (details of this method are described in Appendix A, [6]). In contrast, 3C 279 showed no clear correlation between optical flux and polarization degree (see [6]). The variability amplitudes of gamma-rays and optical flares in 3C 279 also differed from those in 3C 454.3.…”

“…The significance of the correlation (95% C.L.) was tested using the block Bootstrap method (details of this method are described in Appendix A, [6]). In contrast, 3C 279 showed no clear correlation between optical flux and polarization degree (see [6]).…”