A CO molecular gas wind 340 pc away from the Seyfert 2 nucleus in ESO 420-G13 probes an elusive radio jet^⋆

¹ Istituto di Astrofisica e Planetologia Spaziali (INAF–IAPS), Via Fosso del Cavaliere 100, 00133 Roma, Italy
e-mail: j.a.fernandez.ontiveros@gmail.com, juan.fernandez@inaf.it
² National Observatory of Athens (NOA), Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS), 15236 Athens, Greece
³ Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁴ Universidad de La Laguna (ULL), Dpto. Astrofísica, Avd. Astrofísico Fco. Sánchez s/n, 38206 La Laguna, Tenerife, Spain
⁵ Department of Astrophysics, Astronomy & Mechanics, Faculty of Physics, National and Kapodistrian University of Athens, Panepistimiopolis Zografou 15784, Greece
⁶ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
⁷ Astronomy Division, University of California, Los Angeles, CA 90095-1547, USA
⁸ Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
⁹ Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir, Km 4, 28850 Torrejón de Ardoz, Madrid, Spain
¹⁰ Observatoire de Paris, LERMA, College de France, CNRS, PSL Univ., Sorbonne University, UPMC, Paris, France
¹¹ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Observatory, 439 92 Onsala, Sweden
¹² Departamento de Astronomía, Universidad de Concepción, Concepción, Chile
¹³ National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁴ Department of Astronomy, School of Science, Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588, Japan
¹⁵ Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
¹⁶ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
¹⁷ Dirección de Formación General, Facultad de Educación y Cs. Sociales, Universidad Andres Bello, Sede Concepción, autopista Concepción-Talcahuano 7100, Talcahuano, Chile

Received: 22 August 2019
Accepted: 30 October 2019

Abstract

A prominent jet-driven outflow of CO(2–1) molecular gas is found along the kinematic minor axis of the Seyfert 2 galaxy ESO 420-G13, at a distance of 340–600 pc from the nucleus. The wind morphology resembles the characteristic funnel shape, formed by a highly collimated filamentary emission at the base, and likely traces the jet propagation through a tenuous medium, until a bifurcation point at 440 pc. Here the jet hits a dense molecular core and shatters, dispersing the molecular gas into several clumps and filaments within the expansion cone. We also trace the jet in ionised gas within the inner ≲340 pc using the [Ne II]_12.8 μm line emission, where the molecular gas follows a circular rotation pattern. The wind outflow carries a mass of ∼8 × 10⁶ M_⊙ at an average wind projected speed of ∼160 km s⁻¹, which implies a mass outflow rate of ∼14 M_⊙ yr⁻¹. Based on the structure of the outflow and the budget of energy and momentum, we discard radiation pressure from the active nucleus, star formation, and supernovae as possible launching mechanisms. ESO 420-G13 is the second case after NGC 1377 where a previously unknown jet is revealed through its interaction with the interstellar medium, suggesting that unknown jets in feeble radio nuclei might be more common than expected. Two possible jet-cloud configurations are discussed to explain an outflow at this distance from the AGN. The outflowing gas will likely not escape, thus a delay in the star formation rather than quenching is expected from this interaction, while the feedback effect would be confined within the central few hundred parsecs of the galaxy.