MICONIC: JWST/MIRI MRS reveals a fast ionized gas outflow in the central region of Centaurus A

¹ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain
² Telespazio UK for the European Space Agency (ESA), ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Spain
³ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis bd Arago, 75014 Paris, France
⁴ Institut Universitaire de France, Ministère de l’Enseignement Supérieur et de la Recherche, 1 rue Descartes, 75231 Paris Cedex 05, France
⁵ European Space Agency, c/o Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, USA
⁶ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill Edinburgh, EH9 3HJ, Scotland, UK
⁷ Observatorio Astronómico Nacional (OAN-IGN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
⁸ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium
⁹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁰ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torrejón de Ardoz, 28850, Madrid, Spain
¹¹ I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
¹² Max-Planck-Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, D-53121 Bonn, Germany
¹³ Department of Astronomy, Stockholm University, The Oskar Klein Centre, AlbaNova, SE-106 91 Stockholm, Sweden
¹⁴ LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS, 92190 Meudon, France
¹⁵ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁶ Centre for Extragalactic Astronomy, Durham University, South Road, Durham DH1 3LE, UK
¹⁷ Dept. of Astrophysics, University of Vienna, Türkenschanzstr. 17, A-1180 Vienna, Austria
¹⁸ ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
¹⁹ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-Sur-Yvette, France

^⋆ Corresponding author: aalonso@cab.inta-csic.es

Received: 28 March 2025
Accepted: 27 May 2025

Abstract

We present a kinematical study of the ionized and molecular gas in the central region (∼7–14″∼100–200 pc) of the nearby radio galaxy Centaurus A (Cen A). We used JWST/MIRI MRS ∼5−28 μm observations taken as part of the Mid-Infrared Characterization of Nearby Iconic galaxy Centers (MICONIC) of the MIRI European Consortium. The two gas phases present contrasting morphologies and kinematics in Cen A. The brightest emission from the ionized gas, traced with a range of ionization potential (IP) lines analyzed here (from [Fe II] to [Ne VI]), is extended along the direction of the radio jet. We also detected emission from low IP emission lines and H₂ transitions in the galaxy disk region mapped with MRS. Both gas phases present rotational motions in the disk but also complex kinematics. The MRS observations reveal several ionized gas kinematical features that are consistent with simulation predictions of a jet-driven bubble and outflow interacting with the galaxy interstellar medium. These include broad components in the nuclear line profiles (σ∼600 km s⁻¹ in [Ar II] and [Ne III]), high velocities (reaching approximately +1000, −1400 km s⁻¹) confined within the nuclear region, velocities of hundreds of kilometers per second in several directions in the central 2″, and enhanced velocity dispersions perpendicular to the radio jet. Moreover, we find evidence of shock excitation in the nuclear region of Cen A based on mid-infrared line ratios. We compared the ionized gas mass outflow rate with Cen A's active galactic nucleus (AGN) luminosity and radio jet power and demonstrate that both mechanisms provide sufficient energy to launch the outflow. The noncircular motions observed in the mid-infrared H₂ lines can be reproduced with either a warped rotating disk model or a radial component. The latter might be to related to gas streamers detected in cold molecular gas. Notably, there is no clear indication of a fast nuclear H₂ outflow in Cen A, only a weak blueshifted component in the line profiles. This could be due to a relatively low nuclear warm H₂ column density and/or the limited geometrical coupling of Cen A's inner radio jet with the circumnuclear disk of the galaxy.