Relativistic Plasma as the Dominant Source of the Optical Continuum Emission in the Broad-Line Radio Galaxy 3C 120

• Published in: The Astrophysical journal Vol. 715; no. 1; pp. 355 - 361
• Main Authors: León-Tavares, J, Lobanov, A. P, Chavushyan, V. H, Arshakian, T. G, Doroshenko, V. T, Sergeev, S. G, Efimov, Y. S, Nazarov, S. V
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 20-05-2010; IOP
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; COSMIC RADIO SOURCES; Earth, ocean, space; EMISSION; Exact sciences and technology; GALAXIES; INTERFEROMETRY; IONIZATION; PLASMA; RADIO GALAXIES; RELATIVISTIC PLASMA; SEYFERT GALAXIES; Radio galaxies; galaxies: jets; acceleration of particles; Particle acceleration; galaxies: individual (3C 120); Continuum; Active galaxies; Relativistic plasma; Light emission; galaxies: active; Cosmic radio sources; Jets; radio continuum: galaxies
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/715/1/355

We report a relation between radio emission in the inner jet of the Seyfert galaxy 3C 120 and optical continuum emission in this galaxy. Combining the optical variability data with multi-epoch high-resolution very long baseline interferometry observations reveals that an optical flare rises when a superluminal component emerges into the jet, and its maxima is related to the passage of such component through the location of a stationary feature at a distance of {approx}1.3 pc from the jet origin. This indicates that a significant fraction of the optical continuum produced in 3C 120 is non-thermal, and it can ionize material in a sub-relativistic wind or outflow. We discuss implications of this finding for the ionization and structure of the broad emission line region, as well as for the use of broad emission lines for determining black hole masses in radio-loud active galactic nucleus.