Six years of Fermi-LAT and multi-wavelength monitoring of the broad-line radio galaxy 3C 120: Jet dissipation at sub-parsec scales from the central engine

Y. T. Tanaka, A. Doi, Y. Inoue, C. C. Cheung, L. Stawarz, Y. Fukazawa, M. A. Gurwell, M. Tahara, J. Kataoka, R. Itoh

    研究成果: Article査読

    16 被引用数 (Scopus)

    抄録

    We present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240-56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the γ-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a γ-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ∼0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the γ rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. We also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.

    本文言語English
    論文番号L18
    ページ(範囲)1-6
    ページ数6
    ジャーナルAstrophysical Journal Letters
    799
    2
    DOI
    出版ステータスPublished - 2015 2月 1

    ASJC Scopus subject areas

    • 天文学と天体物理学
    • 宇宙惑星科学

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