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.
<Astrophys. J. 833, 77 (2016)>
=2016ApJ...833...77I 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°, 45°, 22.5°, and
67.5°.
File Summary:
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FileName Lrecl Records Explanations
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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
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See also:
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
Byte-by-byte Description of file: ident.dat
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Bytes Format Units Label Explanations
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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)
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Note (1): All files in the subdirectories are named Kanata-BL-NN.dat
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Byte-by-byte Description of file: phot/V/* phot/R/* phot/J/* phot/Ks/*
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: PD/V/* PD/R/*
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: PA/V/* PA/V/*
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Bytes Format Units Label Explanations
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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
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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