Mon. Not. R. Astron. Soc., 441, 1899-1909 (2014/July-1)
Detection of significant cm to sub-mm band radio and γ-ray correlated variability in Fermi bright blazars.
FUHRMANN L., LARSSON S., CHIANG J., ANGELAKIS E., ZENSUS J.A., NESTORAS I., KRICHBAUM T.P., UNGERECHTS H., SIEVERS A., PAVLIDOU V., READHEAD A.C.S., MAX-MOERBECK W. and PEARSON T.J.
Abstract (from CDS):
The exact location of the γ-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11cm to 0.8mm wavelength, F-GAMMA programme) and γ-ray (0.1-300GeV) ∼ 3.5yr light curves of 54 Fermi-bright blazars. We perform a source stacking analysis and estimate significances and chance correlations using mixed source correlations. Our results reveal: (i) the first highly significant multiband radio and γ-ray correlations (radio lagging γ rays) when averaging over the whole sample, (ii) average time delays (source frame: 76±23 to 7±9d), systematically decreasing from cm to mm/sub-mm bands with a frequency dependence τr, γ(ν) ∝ ν-1, in good agreement with jet opacity dominated by synchrotron self-absorption, (iii) a bulk γ-ray production region typically located within/upstream of the 3mm core region (τ3mm, γ = 12±8d), (iv) mean distances between the region of γ-ray peak emission and the radio `τ = 1 photosphere' decreasing from 9.8±3.0pc (11cm) to 0.9±1.1pc (2mm) and 1.4±0.8pc (0.8mm), (v) 3mm/γ-ray correlations in nine individual sources at a significance level where one is expected by chance (probability: 4x10–6), (vi) opacity and `time lag core shift' estimates for quasar 3C 454.3 providing a lower limit for the distance of the bulk γ-ray production region from the supermassive black hole (SMBH) of ∼ 0.8-1.6pc, i.e. at the outer edge of the broad-line region (BLR) or beyond. A 3mm τ = 1 surface at ∼ 2-3pc from the jet base (i.e. well outside the `canonical BLR') finally suggests that BLR material extends to several parsec distances from the SMBH.
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)
galaxies: active - galaxies: jets - galaxies: nuclei - quasars: general - gamma-rays: galaxies - radio continuum: galaxies
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<Available at CDS (J/MNRAS/441/1899): table2.dat>
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