TY - JOUR

T1 - Estimating the distribution of rest-frame time-scales for blazar jets

T2 - a statistical approach

AU - Liodakis, I.

AU - Blinov, D.

AU - Papadakis, I.

AU - Pavlidou, V.

PY - 2017/3

Y1 - 2017/3

N2 - In any flux-density limited sample of blazars, the distribution of the time-scale modulation factor Delta t ' / Delta t, which quantifies the change in observed time-scales compared to the rest-frame ones due to redshift and relativistic compression follows an exponential distribution with a mean depending on the flux limit of the sample. In this work, we produce the mathematical formalism that allows us to use this information in order to uncover the underlining rest-frame probability density function of measurable time-scales of blazar jets. We extensively test our proposed methodology using a simulated Flat Spectrum Radio Quasar population with a 1.5 Jy flux-density limit in the simple case (where all blazars share the same intrinsic time-scale), in order to identify limits of applicability and potential biases due to observational systematics and sample selection. We find that for monitoring with time intervals between observations longer than similar to 30 per cent of the intrinsic time-scale under investigation the method loses its ability to produce robust results. For time intervals of similar to 3 per cent of the intrinsic time-scale, the error of the method is as low as 1 per cent in recovering the intrinsic rest-frame time-scale. We applied our method to rotations of the optical polarization angle of blazars observed by RoboPol. We found that the intrinsic time-scales of the longest duration rotation event in each blazar follows a narrow distribution, well described by a normal distribution with mean 87 d and standard deviation 5 d. We discuss possible interpretations of this result.

AB - In any flux-density limited sample of blazars, the distribution of the time-scale modulation factor Delta t ' / Delta t, which quantifies the change in observed time-scales compared to the rest-frame ones due to redshift and relativistic compression follows an exponential distribution with a mean depending on the flux limit of the sample. In this work, we produce the mathematical formalism that allows us to use this information in order to uncover the underlining rest-frame probability density function of measurable time-scales of blazar jets. We extensively test our proposed methodology using a simulated Flat Spectrum Radio Quasar population with a 1.5 Jy flux-density limit in the simple case (where all blazars share the same intrinsic time-scale), in order to identify limits of applicability and potential biases due to observational systematics and sample selection. We find that for monitoring with time intervals between observations longer than similar to 30 per cent of the intrinsic time-scale under investigation the method loses its ability to produce robust results. For time intervals of similar to 3 per cent of the intrinsic time-scale, the error of the method is as low as 1 per cent in recovering the intrinsic rest-frame time-scale. We applied our method to rotations of the optical polarization angle of blazars observed by RoboPol. We found that the intrinsic time-scales of the longest duration rotation event in each blazar follows a narrow distribution, well described by a normal distribution with mean 87 d and standard deviation 5 d. We discuss possible interpretations of this result.

KW - relativistic processes

KW - methods: statistical

KW - galaxies: active

KW - galaxies: jets

KW - ACTIVE GALACTIC NUCLEI

KW - OPTICAL POLARIZATION-PLANE

KW - COMPACT RADIO-SOURCES

KW - GAMMA-RAY ACTIVITY

KW - LORENTZ FACTORS

KW - BL-LACERTAE

KW - POPULATION STATISTICS

KW - LUMINOSITY FUNCTIONS

KW - SUPERLUMINAL MOTION

KW - DECELERATING FLOWS

U2 - 10.1093/mnras/stw3038

DO - 10.1093/mnras/stw3038

M3 - статья

VL - 465

SP - 4783

EP - 4794

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -