Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars
2014 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 441, no 3, 1899-1909 p.Article in journal (Refereed) Published
The exact location of the gamma-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 (11 cm to 0.8 mm wavelength, F-GAMMA programme) and gamma-ray (0.1-300 GeV) similar to 3.5 yr 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. gamma-ray correlations (radio lagging gamma rays) when averaging over the whole sample, (ii) average time delays (source frame: 76 +/- 23 to 7 +/- 9 d), systematically decreasing from cm to mm/sub-mm bands with a frequency dependence tau(r,gamma)(v) proportional to v(-1), in good agreement with jet opacity dominated by synchrotron self-absorption, (iii) a bulk gamma-ray production region typically located within/upstream of the 3 mm core region (tau(3mm),(gamma) = 12 +/- 8 d), (iv) mean distances between the region of. gamma-ray peak emission and the radio 'tau = 1 photosphere' decreasing from 9.8 +/- 3.0 pc (11 cm) to 0.9 +/- 1.1 pc (2 mm) and 1.4 +/- 0.8 pc (0.8 mm), (v) 3 mm/gamma-ray correlations in nine individual sources at a significance level where one is expected by chance (probability: 4 x 10(-6)), (vi) opacity and 'time lag core shift' estimates for quasar 3C 454.3 providing a lower limit for the distance of the bulk gamma-ray production region from the supermassive black hole (SMBH) of similar to 0.8-1.6 pc, i.e. at the outer edge of the broad-line region (BLR) or beyond. A 3 mm tau = 1 surface at similar to 2-3 pc from the jet base (i.e. well outside the 'canonical BLR') finally suggests that BLR material extends to several parsec distances from the SMBH.
Place, publisher, year, edition, pages
2014. Vol. 441, no 3, 1899-1909 p.
galaxies: active, galaxies: jets, galaxies: nuclei, quasars: general, gammarays: galaxies, radio continuum: galaxies
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-106588DOI: 10.1093/mnras/stu540ISI: 000338763600005OAI: oai:DiVA.org:su-106588DiVA: diva2:737842