J/MNRAS/442/1693 Gamma-ray-loud blazars optical polarization (Pavlidou+, 2014)
The RoboPol optical polarization survey of gamma-ray-loud blazars. Pavlidou V., Angelakis E., Myserlis I., Blinov D., King O.G., Papadakis I., Tassis K., Hovatta T., Pazderska B., Paleologou E., Balokovic M., Feiler R., Fuhrmann L., Khodade P., Kus A., Kylafis N., Modi D., Panopoulou G., Papamastorakis I., Pazderski E., Pearson T.J., Rajarshi C., Ramaprakash A., Readhead A.C.S., Reig P., Zensus J.A. <Mon. Not. R. Astron. Soc., 442, 1693-1705 (2014)> =2014MNRAS.442.1693P 2014MNRAS.442.1693P
ADC_Keywords: QSOs ; Gamma rays ; Polarization Keywords: polarization - galaxies: active - galaxies: jets - galaxies: nuclei Abstract: We present first results from RoboPol, a novel-design optical polarimeter operating at the Skinakas Observatory in Crete. The data, taken during the 2013 May-June 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 Rmag of 17 and as low as 0.035 down to 18mag. 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 3σ 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=6.4+0.9-0.8x10-2 for gamma-ray-loud blazars, and
=3.2+2.0-1.1x10-2 for gamma-ray-quiet blazars. The most probable value for the difference of the means is 3.4+1.5-2.0x10-2. The distribution of polarization angles is statistically consistent with being uniform. Description: In 2013 June, RoboPol performed an optopolarimetric survey of a sample of gamma-ray-loud blazars, results from which are presented in this paper. All of our sources (including the control sample) are monitored twice a week at 15GHz by the Owens Valley Radio Observatory (OVRO) 40-m telescope blazar monitoring programme. 28 of them are also monitored at 30GHz by the Torun 32-m telescope. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 83 104 Photometric and polarization results of the RoboPol 2013 June optical polarization survey of γ-ray-loud blazars and the γ-ray-quiet control sample sources table3.dat 149 104 Additional archival information for the 89 high-quality sources as well as the control sample ones -------------------------------------------------------------------------------- See also: J/ApJS/175/97 : CGRaBS: survey of γ-ray blazar candidates (Healey+, 2008) J/ApJ/715/429 : First Fermi-LAT AGN catalog (1LAC) (Abdo+, 2010) J/ApJ/743/171 : The 2LAC catalog (Ackermann+, 2011) J/ApJS/194/29 : Observations of blazars at 15GHz (Richards+, 2011) J/ApJ/748/49 : Optical spectroscopy of 1LAC broad-line blazars (Shaw+, 2012) J/ApJ/764/135 : Spectroscopic redshifts of BL Lac objects (Shaw+, 2013) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 14 A14 --- Name RoboPol ID ("RBPL" stands for "RoboPol") 16- 19 F4.1 mag Rmag ?=- R magnitude 21- 24 F4.2 mag e_Rmag ?=- rms uncertainty on Rmag 26- 30 F5.3 % P Polarisation 32- 36 F5.3 % e_P rms uncertainty on P 38- 42 F5.1 deg PA [-92/82] Polarisation angle (1) 44- 48 F5.1 deg e_PA [0.4/198] rms uncertainty on PA (2) 50- 60 A11 --- r_Rmag Origin of photometry 62- 71 A10 "date" ObsDate.F First observation date 72 A1 --- --- [,] 74- 83 A10 "date" ObsDate.L Last observation date -------------------------------------------------------------------------------- Note (1): Note that the polarization angle been corrected for instrumental rotation of 2.31±0.34° as discussed in 'pipeline' paper. Note (2): The error in the instrumental rotation is accounted for in the final error estimate through formal error propagation. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 14 A14 --- Name RoboPol ID ("RBPL" stands for "RoboPol") 16- 37 A22 --- OName A common survey name 39- 40 I2 h RAh Right ascension (J2000) 42- 43 I2 min RAm Right ascension (J2000) 45- 48 F4.1 s RAs Right ascension (J2000) 50 A1 --- DE- Declination sign (J2000) 51- 52 I2 deg DEd Declination (J2000) 54- 55 I2 arcmin DEm Declination (J2000) 57- 60 F4.1 arcsec DEs Declination (J2000) 62- 66 F5.3 --- z [0.01/3.4]?=- Redshift 68 I1 --- r_z ?=- Reference for the redshift (5) 70- 72 A3 --- Cl BZCAT Class as of November 14, 2013 (3) 74- 81 A8 --- Prog Other monitoring programs (4) 82- 88 F7.4 Jy S15 [0.01/29]?=- Flux density at 15GHz averaged over June-August 2013 90- 95 F6.4 Jy e_S15 ?=- rms uncertainty on S15 97-101 F5.3 --- m [0/0.5]?=- Intrinsic modulation index as computed by Richards et al. 2011 (J/ApJS/194/29) 103-107 F5.3 --- e_m ?=- Error on m (lower value) 109-113 F5.3 --- E_m ?=- Error on m (upper value) 115-125 E11.6 ct/cm2/s Fgam ?=- Flux of γ photons above 100MeV 127-131 F5.3 --- Gamma [1.6/3]?=- Spectral index Γ as given in the 2FGL 133-137 F5.3 --- e_Gamma [0.008/0.24]?=- rms uncertainty on Gamma 139-147 F9.3 --- VI [12/14190]?=- Variability index, as given in the 2FGL 149 I1 --- H [0/1] Flag indicating whether the source is in CGRaBS (Healey et al. 2008, J/ApJS/175/97) -------------------------------------------------------------------------------- Note (3): BZCAT Classes are: BZB = BL Lac objects BZ? = BL Lac candidates BZQ = flat-spectrum radio quasars BZU = blazars of uncertain type Note (4): Other monitoring programs codes as follows: O = OVRO 15GHz T = Torun 30GHz F1 = F-GAMMA monitoring before June 2009 F2 = F-GAMMA monitoring after June 2009 Note (5): Redshift references as follows: 1 = Shaw et al., 2013ApJ...764..135S 2013ApJ...764..135S, Cat. J/ApJ/764/135, Spectroscopy of BL Lacs 2 = Shaw et al., 2012ApJ...748...49S 2012ApJ...748...49S, Cat. J/ApJ/748/49, Spectroscopy of 1LAC broad line quasars 3 = Ackermann et al., 2011ApJ...743..171A 2011ApJ...743..171A, Cat. J/ApJ/743/171, The Second Catalog of AGN Detected by the Fermi LAT 4 = Abdo et al., 2010ApJ...715..429A 2010ApJ...715..429A, Cat. J/ApJ/715/429, The First Catalog of AGN Detected by the Fermi LAT 5 = Healey et al., 2008ApJS..175...97H 2008ApJS..175...97H, Cat. J/ApJS/175/97, Candidate Gamma-Ray Blazar Survey 6 = M. Shaw, personal comm. with JLR, circa Aug 2011. -------------------------------------------------------------------------------- History: From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Mar-2015
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