J/ApJ/833/77 gamma-ray bright blazars optical polarization (Itoh+, 2016) ================================================================================ Systematic study of gamma-ray bright blazars with optical polarization and gamma-ray variability. Itoh R., Nalewajko K., Fukazawa Y., Uemura M., Tanaka Y.T., Kawabata K.S., Madejski G.M., Schinzel F..K., Kanda Y., Shiki K., Akitaya H., Kawabata M., Moritani Y., Nakaoka T., Ohsugi T., Sasada M., Takaki K., Takata K., Ui T., Yamanaka M., Yoshida M. =2016ApJ...833...77I (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Active gal. nuclei ; BL Lac objects ; Polarization ; Photometry Keywords: BL Lacertae objects: general - galaxies: jets - gamma rays: galaxies - polarization Abstract: Blazars are highly variable active galactic nuclei that 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 2008 July and 2014 December 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 parsec-scale relativistic jets between different types of blazars (flat-spectrum radio quasars vs. BL Lacs) and consequently between different types of radio galaxies (FR I versus FR II). Description: We performed optical and near-infrared imaging polarimetry of 42 AGNs between 2008 August and 2014 December with the 1.5m diameter Kanata telescope. We used two instruments attached to the Kanata telescope: the Triple Range Imager and SPECtrograph (TRISPEC) and the Hiroshima One-shot Wide-field Polarimeter (HOWPol). TRISPEC was attached to the Cassegrain focus of the Kanata telescope from 2006 to 2011, and it has a CCD and two InSb arrays, enabling photopolarimetric observations in one optical and two near-infrared bands simultaneously. HOWPol is installed at the Nasmyth focus of the Kanata telescope and has been in operation since 2009. We performed V-, J-, and Ks-band photometry and polarimetry observations of each target from 2008 July to 2010 February using TRISPEC and performed the V- and RC-band photometry and polarimetry observations from 2008 July to 2010 February using HOWPol. Each observing sequence consisted of successive exposures at four position angles of a half-wave plate of 0{deg}, 45{deg}, 22.5{deg}, and 67.5{deg}. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file ident.dat 117 45 List of studied stars phot/V/* . 44 V-band photometry of individual objects phot/R/* . 36 R-band photometry of individual objects phot/J/* . 34 J-band photometry of individual objects phot/Ks/* . 34 Ks-band photometry of individual objects PD/V/* . 37 V-band polarization degree of individual objects PD/R/* . 27 R-band polarization degree of individual objects PA/R/* . 27 R-band polarization angle of individual objects PA/V/* . 37 V-band polarization angle of individual objects -------------------------------------------------------------------------------- See also: J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015) Byte-by-byte Description of file: ident.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 12 A12 --- Name Blazar ID in the form Kanata-BL-NN 14- 30 A17 --- 3FGL Fermi-LAT 3FGL name (3FGL JHHMM.m+DDMM) 32- 45 A14 --- CptName Counterpart name 47- 48 I2 h RAh Right ascension (J2000.0) 50- 51 I2 min RAm Right ascension (J2000.0) 53- 56 F4.1 s RAs Right ascension (J2000.0) 58 A1 --- DE- Declination (J2000.0) 59- 60 I2 deg DEd Declination (J2000.0) 62- 63 I2 arcmin DEm Declination (J2000.0) 65- 68 F4.1 arcsec DEs Declination (J2000.0) 70- 75 A6 --- photV phot/V when Johnson V photometry (1) 77- 82 A6 --- photR phot/R when R Cousins photometry (1) 84- 89 A6 --- photJ phot/J when J Johnson photometry (1) 91- 97 A7 --- photKs phot/Ks when Ks Johnson photometry (1) 99-102 A4 --- PDV PD/V when V polarisation degree (1) 104-107 A4 --- PDR PD/R when R polarisation degree (1) 109-112 A4 --- PAV PA/V when V polarisation angle (1) 114-117 A4 --- PAR PA/R when R polarisation angle (1) -------------------------------------------------------------------------------- Note (1): All files in the subdirectories are named Kanata-BL-NN.dat -------------------------------------------------------------------------------- Byte-by-byte Description of file: phot/V/* phot/R/* phot/J/* phot/Ks/* -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 F8.2 d MJD Modified Julian Day 10- 15 F6.3 mag mag Magnitude in filter 17- 21 F5.3 mag e_mag Uncertainty of magnitude -------------------------------------------------------------------------------- Byte-by-byte Description of file: PD/V/* PD/R/* -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 F8.2 d MJD Modified Julian Day 10- 13 F4.1 % Pold Porarization degree 15- 18 F4.1 % e_Pold Uncertainty of polarization degree -------------------------------------------------------------------------------- Byte-by-byte Description of file: PA/V/* PA/V/* -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 F8.2 d MJD Modified Julian Day 10- 14 F5.1 deg Pola Polarization angle 16- 20 F5.1 deg e_Pola Uncertainty of polarization angle -------------------------------------------------------------------------------- Acknowledgements: Any presentation of the scientific analysis or usage of the data from the photopolarimetric catalog of blazars should include the appropriate reference(s) to Kanata paper(s). Ryosuke Itoh, itoh(at)hp.phys.titech.ac.jp, itohryosuke(at)gmail.com ================================================================================ (End) R. Itoh [Tokyo Institute of Technology], P. Vannier [CDS] 09-Dec-2016